In this presentation, I am planning to talk about several MEMS/Microfluidic-based approaches for the rapid and reproducible construction of hydrogel microstructure. Hydrogels are attractive materials because of its excellent deformability, biocompatibility, and the ability to be chemically-modified. They are thus very useful for various biomedical applications including implantable monitoring and tissue engineering.
Fluorescent hydrogels hold great promise for in vivo continuous glucose monitoring with wireless transdermal transmission and long-lasting activity. We synthesized a highly-sensitive fluorescent monomer, and then fabricated injectable-sized fluorescent polyacrylamide hydrogel beads and fibers with high uniformity and high throughput. We find that the fluorescent beads provide sufficient intensity to transdermally monitor glucose concentrations in vivo.
Large-scale 3D tissue architectures that mimic microscopic tissue structures in vivo are very important for not only in tissue engineering but also drug development without animal experiments. We demonstrated a construction method of 3D tissue structures by using cell beads and cell fibers. To prepare the cellular beads, we used an axisymmetric flow focusing device (AFFD) that allows us to encapsulate HepG2 cells within monodisperse collagen beads. We then seeded 3T3 cells on the surface of the collagen beads. Finally HepG2 and 3T3 cells were successfully made contact with each other. Moreover, by putting these capsules in a 3D chamber and incubating them, we successfully established complicated and milli-sized 3D structures. We believe that altering the shape can be possible as simple as changing the mold, and will try to combine multiple types of cells to create more complex system that functions as a living organism. As the cell fibers, a cell-encapsulating core-shell hydrogel fiber was produced in a double coaxial laminar flow microfluidic device. When with myocytes, endothelial, and nerve cells, they showed the contractile motion of the myocyte cell fiber, the tube formation of the endothelial cell fibers and the synaptic connections of the nerve cell fiber, respectively. By reeling, weaving and folding the fibers using microfluidic handling, higher-order assembly of fiber-shaped 3D cellular constructs can be performed. Moreover, the fiber encapsulating beta-cells is used for the implantation of diabetic mice, and succeeded in normalizing the blood glucose level.
References
Yun Jung Heo , Hideaki Shibata , Teru Okitsu , Tetsuro Kawanishi, and Shoji Takeuchi: Long-term in vivo glucose monitoring using fluorescent hydrogel fibers, Proc. Natl. Acad. Sci. USA, vol. 108(33), pp. 13399-13403, 2011
Hideaki Shibata, Yun Jung Heo, Teru Okitsu, Yukiko Matsunaga, Tetsuro Kawanishi, and Shoji Takeuchi: Injectable hydrogel microbeads for fluorescence-based continuous glucose monitoring, Proc. Natl. Acad. Sci. USA, vol. 107, no. 42, pp. 17894-17898, 2010
Hiroaki Onoe, Teru Okitsu, Akane Itou, Midori Kato-Negishi, Riho Gojo, Daisuke Kiriya, Koji Sato, Shigenori Mirua, Shintaroh Iwanaga, Kaori Kuribayashi-Shigetomi, Yukiko Matsunaga, Yuto Shimoyama, and Shoji Takeuchi: Metre-long Cellular Microfibres Exhibiting Tissue Morphologies and Functions, Nature Materials, vol.12, pp. 584-590, 2013

Electrospinning is a popular technique for making nanofibrous tissue engineering scaffolds. After cell incorporation, the cell-scaffold construct can be used to regenerate various human body tissues/organs. However, owing to the normally dense structures of electrospun scaffolds, cells can only be seeded in 2D on scaffold surface using the post-electrospinning cell seeding approach. For putting cells in 3D and directly inside electrospun scaffolds, we designed and investigated a facile method by combining cell seeding with scaffold fabrication. In this method, cell electrospraying was performed concurrently with electrospinning of the scaffold, placing cell-encapsulated microspheres into the matrix of nanofibrous scaffold, and the subsequent immersion treatment dissolved the shell of microspheres, releasing the cells for the cell-laden scaffold. In our experiments, a dual-source dual power setup was employed for conducting concurrent cell electrospraying and electrospinning. For cell electrospraying, a coaxial device was used. A cell suspension of human umbilical vein endothelial cells (HUVECs) and a gelatin/alginate blend solution were fed into the inner and outer concentric tubes, respectively. Crosslinked, core-shell structured microspheres containing HUVECs could be dissolved by immersing them in a cell culture medium, releasing the cells. The microsphere structure and cell viability of both encapsulated cells and released cells were studied using SEM, live/dead staining assessment assisted by fluorescent microscopy and laser scanning confocal microscopy. The optimal condition for cell electrospraying was investigated by modulating major processing parameters (composition of polymer blend, applied voltage, flow rate, etc.). For electrospinning, emulsions were made using PLGA solutions and vascular endothelial growth factor (VEGF)-containing PBS (or PBS alone). They were subsequently electrospun to make nanofibrous scaffolds with or without VEGF incorporation. Various experiments were conducted for studying the morphological and structural properties of nanofibrous scaffold, as well as the release behavior of VEGF. When concurrent cell electrospraying and emulsion electrospinning was performed, bioactive and cell-laden scaffolds were fabricated. The post-electrospinning immersion treatment could release encapsulated cells in the nanofibrous scaffolds. Furthermore, the space left by the dissolved microspheres provided the room for subsequent cell proliferation and infiltration. Cell culture experiments and comparative studies were then performed for evaluating cell functions in scaffolds with or without VEGF incorporation. Results indicated that cell proliferation and cell infiltration were enhanced in VEGF-loaded scaffolds. This new fabrication method can lead to breakthroughs in developing electrospun scaffolds for the regeneration of complex human body tissues.

Cell encapsulation in hydrogel microparticles have been investigated for decades in various bioengineering applications including tissue engineering, and cell therapy. However, most of the time, the cells are encapsulated randomly in whatever material that forms the microparticles, most commonly alginate. The lack of control over the spatial organizations of the cells and the extracellular environment within the microparticles significantly limits for advanced applications. Here we report a novel, multi-fluidic cell microencapsulation approach where 1 or more types of cells are encapsulated in pre-assigned compartments in the microparticles with controlled extracellular matrix. These microparticles can be produced with controllable and nearly monondispersed sizes at rates of over 10,000 microparticles per min and therefore provide a promising platform for high throughput applications. We demonstrated the utilization of these extracellular matrix-supported microparticles for 3D culturing of cells that typically require specific microenvironment to survive such as human umbilical vein endothelial cells (HUVECs) and small intestine stem cells. By taking advantage of the confinement effect, we also showed robust and scalable productions of size-controlled multicellular microtissues. Lastly, to demonstrate the broad applications of these microparticles, we performed proof-of-concept studies on three different co-culture systems including cell segregations under 3D confined space, the supporting role of stromal cells in hepatocyte functions and the paracrine cell signaling in aggregation of endothelial cells, all in a high throughput manner.

A common strategy for the creation of functions in polymeric materials is the targeted combination of different polymers or polymers with inorganic components and the design of the interface between the phases [1]. Hereby the different components can be physically mixed or joined. Alternatively they can be covalently linked.
Several examples for the design of functions are presented, each illustrating a different concept to gain a function. The multivalent binding of polyglycerols on micro porous polyetherimide membranes combines a separation capability with hemocompatibility [2]. The covalent integration of nanoparticles as netpoints in a polymer network matrix enables a magneto sensitive reversible movement of the resulting hybrid material [3]. The pore morphology of polymeric foams strongly influences their shape-memory capability [4]. The internal geometry of a magnetic, active phase in a polymer matrix results in a triple shape effect, whereby the series of the shape changes can be determined by the applied stimulus [5].
The fundamental principles demonstrated in these material systems might stimulate further research in the field of multifunctional materials.
[1] M. Behl, M. Razzaq, A. Lendlein, Adv. Mater. 2010, 22, 3388-3410.
[2] A.T. Neffe, M. von Ruesten-Lange, S. Braune, K. Lützow, T. Roch, K. Richau, A. Krüger, T. Becherer, A.F. Thünemann, F. Jung, R.
Haag, A. Lendlein, J. Mater Chem B, 2014, 2, 3626-3635.
[3] M.Y. Razzaq, M. Behl, K. Kratz, A. Lendlein, Adv. Mater. 2013, 25, 5730-5733.
[4] T. Sauter, K. Kratz, A. Lendlein, Macromol. Chem. Phys. 2013, 214 (11), 1184-1188.
[5] M.Y. Razzaq, M. Behl, K. Kratz, A. Lendlein, Adv. Mater. 2013, 25, 5514-5518.

There is currently no effective treatment strategy following traumatic injury to the peripheral nervous system (PNS) in either partial or full loss of extremity function. Recent work has demonstrated neural recording and electrical stimulation devices that allow for neural-motor control of prosthetic limbs. However, much improvement is required to reach the resolution of neural interfacing needed for physiological functionality. In addition to neural interfacing, tissue engineering strategies are potential means to restore functionality after traumatic injury to the PNS. However, current interventions are years from being effective in the clinic. Therefore, our goal is to engineer material platforms that both promote nerve regeneration and provide an electrical interface for prosthetic integration that is clinically relevant now.
To date, the influence of nerve channel geometry and dimensions of sub-200 mu;m scale on neural regeneration has been poorly investigated due to material processing. For interfacing with either the motor or sensory axons of the PNS, geometric constraints may provide a means for selectively regenerating axons to intimately interface electrodes with sensory or motor nerve fibers, respectively. Furthermore, topography robustly influences the orientation and length of neural growth. However, no technique currently exists to fabricate mu;m topography features on the interior surface of nerve guidance channels without the inclusion of films or rolling.
Herein, we present a new method for engineering polymeric nerve guidance channels with intrinsic topography or recording electrodes. Utilizing a thermal drawing process (TDP), macro-scale preforms of biocompatible polyetherimide were made with rectangular and cylindrical channels. Topographical features or electrodes composed of conductive polyethylene were machined and added to the preforms. TDP reduced the cross-sectional dimensions by up to 200 times while maintaining the original geometries. Rectangular, rectangular with microgrooves, and cyclindrical neural growth channels with dimensions 30-200 mu;m were evaluated in vitro for their influence on neurite outgrowth from primary dorsal root ganglia (DRGs). Total distance of neurite outgrowth into the channel as well as the orientation of neurite extension and cell nuclei within the channel were measured with respect to the geometry and dimensions of the growth channel. Preliminary data suggests that narrower channels (40-60 mu;m) enhance the orientation of DRG outgrowth compared to larger channels (>100 mu;m), but very limited growth is observed in small channels (<40 mu;m). However, inclusion of microgrooves within the large channel increases neurite orientation. These results demonstrate our ability to utilize the TDP to design new polymeric nerve guidance channels as a strategy for PNS regeneration and neural interfacing.

In comparison to neutral linear polymers, functional and architecturally complex (i.e., non-linear) polymers offer distinct opportunities for enhancing the properties and performance of therapeutic proteins. However, understanding how to harness these parameters is challenging, and studies that capitalize on them in vivo are scarce. This presentation will cover this important topic with emphasis on two types of therapeutic proteins: ones for which long circulation in the bloodstream is desired, and ones for which retention and/or stabilization in the gastrointestinal tract is desired.
We will first present how the modification of an enzyme with a polymer of appropriate architecture can impart exceptionally low immunogenicity (e.g., generation/recognition of antibodies in vivo), with a commensurably low loss of therapeutic activity.[1,2] Secondly, we will also discuss how the modification of an enzyme with a polymer bearing appropriate functional groups can promote its stability (and thus therapeutic activity) at different locations in the gastrointestinal tract. Furthermore, functional polymers that interact with mucin will be shown to promote retention in the upper part of the gastrointestinal tract, and thus enhance the therapeutic activity of enzymes at this location.[3] Overall, the importance of the findings will be framed with context to selected relevant diseases that stand to benefit most from the presented concepts. This work was supported by the Swiss National Science Foundation (310030_135732) and the Sassella Stiftung.
[1] Liu, Tirino, Radivojevic, Phillips, Gibson, Leroux, Gauthier. Advanced Functional Materials. 2013, 23, 2007
[2] Liu, Johansen, Zabel, Leroux, Gauthier. Submitted
[3] Fuhrmann, Grotzky, Lukicacute;, Matoori, Yu, Luciani, Walde, Schlüter, Gauthier, Leroux. Nature Chemistry, 2013, 5, 582

Nanostructured materials have been used as substrates for sensitive cellular or biomolecule recognition due to their high surface-area to volume ratio and biocompatibility. Whereas the deposition of these nanomaterials on surfaces is often irreversible, the analysis of the isolated biological samples is often limited to on-device microscopic imaging and spectroscopy applications. Therefore, biodegradable nanostructure substrates will facilitate the recovery of cells or biomolecules for downstream analysis (e.g., DNA, RNA, or proteomic analysis) and cell culture. Here, we describe a biodegradable nanostructured coating that allows for either temperature-responsive or mechano-sensitive degradation. The ultrathin coating (135.2 nm ± 8.6 nm) was formed by a layer-by-layer (LBL) deposition of biotinylated gelatin and neutravidin. Nanoroughness on the coating (30.7 nm ± 6.1 nm) was achieved by the incorporation of 70 nm streptavidin nanoparticles that were physisorbed directly on the gelatin coating. Temperature degradation of the applied coating to a glass or PDMS surface was achieved by raising the temperature to 370C; allowing their complete removal after 10 min. For local degradation of the coating, a normal force was applied through a frequency-controlled 80 µm microtip to dislodge partial regions of the coating, mimicking thixotropic hydrogel behaviors.
To demonstrate the biocompatibility and extremely sensitivity of the nanocoating, we used it for circulating tumor cells (CTCs) isolation and recovery. CTCs are extremely rare cells present in the blood stream of metastatic cancer patients (1 CTC per 10⁹ blood cells) and their isolation and processing constitutes a technological challenge. We incorporated the nanocoating on our microfluidic ^HBCTC-Chip¹ with tumor-cell specific antibodies at its surface (anti-EpCAM, anti-EGFR, anti-HER2). The clinical value of the nanocoating-microfluidic system was established when CTCs were detected in 87.5 % of patients with metastatic breast and lung cancer. The temperature degradation mechanisms of the nanocoating allowed recovery of 98.3 % ± 3.5 % of target cells with viabilities up to 92.03 % ± 4.5 %. Additionally, the frequency-controlled microtip allowed the recovery of individual CTCs from cancer patients that were analyzed for the presence of driver mutations in the PIK3CA (H1047R) and EGFR (exon 19 deletion and L858R) oncogenes.
In summary, our nanoscale, reversible biomaterial would enable and/or improve downstream assays through the release of any surface (e.g. beads, glass surfaces) that was initially employed to selectively isolate cells, proteins or DNA from a biological specimen.
References
1 Stott, S. L. et al. Isolation of circulating tumor cells using a microvortex-generating herringbone-chip. Proceedings of the National Academy of Sciences107, 18392-18397, doi:10.1073/pnas.1012539107 (2010).

Polymers containing metal centers are attracting increasing attention as they offer access to new functional macromolecular and supramolecular materials with interesting properties. Our group has developed ring-opening polymerization routes from strained precursors to form metallopolymers such as polymetallocenes with high molecular weights that allows easy processing. Well-defined architectures (e.g. block copolymers) are available through living polymerization processes, including a remarkable recently developed photocontrolled method. This talk will focus on recent efforts to use these metallopolymers to create, for example, photonic crystal devices with applications in displays, and self-assembled supramolecular materials in the form of thin films, which can be used in nanolithographic applications and catalysis. A new approach termed living crystallization-driven self-assembly offers a powerful new route to controlled structures
References:
1. G.R. Whittell, M.D. Hager, U.S. Schubert, I. Manners Nature Materials2011, 10, 176.

Hydrogel microparticles or microgels have been demonstrated to be useful in a variety of biological applications such as tumor targeting[1,2], bioresponsive microlenses[3], and in non-fouling coatings[4]. Microgels are made up of hydrophilic polymer chains that are lightly cross-linked. Microgels conjugated to dyes are excellent candidates for photoacoustic (PA) imaging due to the opportunities for structural versatility, their tunable biocompatibility and biodegradability and most importantly, their potential to generate high intensity PA signals through multivalent display of dye molecules.
The PA effect relates to the generation of acoustic waves by absorption of electromagnetic energy. PA imaging is thus a technique that combines the advantages of optical and ultrasonic imaging. Through its ability to provide optical-absorption contrasts as opposed to contrasts in mechanical properties which are unable to detect anomalies like early stage tumors, it offers a distinct advantage over pure ultrasonic imaging. At the same time, due to the fact that ultrasound scattering is weaker compared to optical scattering in biological tissues, the high spatial resolution of ultrasound beyond depths greater than 1 mm is maintained, which is difficult to achieve through pure optical imaging methodologies.
The microgels utilized in this project are primarily synthesized from the monomer N-Isopropylmethacrylamide (NIPMAm). During the synthesis, a co-monomer, N-(3-Aminopropyl)methacrylamide hydrochloride (APMA) is introduced in order to provide functional handles in the form of amine groups to the microgels, which facilitate the attachment of dye molecules using suitable conjugation techniques. The dyes utilized for conjugation to microgels in this project are Malachite Green (MG) and Rose Bengal (RB). MG has a high molar extinction coefficient and a low quantum yield, which is advantageous for PA, while RB provides the opportunity for modulation using a secondary laser, in order to improve the signal to noise ratio. PA signals have successfully been generated from the microgel-dye constructs by incorporating them into tissue phantoms made from alginate. The constructs have also been characterized with respect to their profile and size and are found to be spherical with a hydrodynamic diameter of around 850 nm. Because degradation properties are a critical design consideration for in vivo imaging agents, future studies will utilize degradable microgels for generating PA signals and will analyze the effect of microgel degradation on PA signals. An additional goal will involve the investigation of cell viability in the presence of dye conjugated microgels.
1. Dickerson, E.B., et al., BMC CANCER, 2010. 10.
2. Nayak, S., et al., J AM CHEM SOC, 2004. 126(33): p. 10258-10259.
3. Hendrickson, G.R., et al., SOFT MATTER, 2009. 5(1): p. 29-35.
4. Bridges, A.W., et al., BIOMATERIALS, 2008. 29(35): p. 4605-4615.

Phosphate-based inorganic-organic hybrid nanomaterials are presented that consist of the inorganic cation [ZrO]²⁺ and functional organic anion with a phosphate group. These nanomaterials are easily accessible by a water-based synthesis. They can be promising optical marker or drug containers for application in medicine and molecular biology.
Fluorescent nanoparticles
Optical imaging has emerged as a powerful modality for visualizing whole organisms or single cells (e.g. tumor cells) in life science [1]. In particular for in vivo application, new biocompatible contrast agents are required.
As a first example of a new class of inorganic-organic hybrid nanomaterials, ZrO(FMN) (FMN: flavin mononucleotide) shows high biocompatibility and high cell uptake [2]. The dye anion is responsible for bright green emission of the nanoparticles under UV and blue-light excitation.
This concept is extended to blue and red emission: ZrO(PUFP) (PUFP: phenylumbellipherone phosphate) and ZrO(RP) (RP: resorufin phosphate) [3]. Moreover, an alternative for green emission is presented: ZrO(MFP) (MFP: methylfluorescein phosphate).
Nanoparticles as drug delivery systems
In contrast to systemic drug administration, nanoparticular drug delivery systems can effectively reduce side-effects. Different material concepts are known for drug delivery with nanoparticles. Drugs are attached on the surface (e.g., Au, SiO₂) or encapsulated in matrix materials (e.g., polymers, liposomes, CNTs, SiO₂).
In order to obtain drug-loaded phosphate-based inorganic-organic hybrids, phosphate ester prodrugs are used [5]. These nanoparticles can be loaded with up to 70 wt-% of drugs against inflammation, bacterial infection, rheumatism, arthritis, multiple sclerosis or cancer. The respective drug is delivered within several hours or days under physiological conditions.
Both properties fluorescence and drug delivery can be combined to bimodal hybrid nanomaterials that can be used for diagnosis and therapy, simultaneously.
[1] J. G. Fujimoto, D. Farkas, Biomedical Optical Imaging, Oxford University Press, Oxford, 2009.
[2] M. Roming, H. Lünsdorf, K. E. J. Dittmar, C. Feldmann, Angew. Chem. Int. Ed.2010, 49, 632-637.
[3] J. G. Heck, C. Feldmann, in preparation.
[4] M. Roming, C. Feldmann, Solid State Sci., 2011, 13, 508-512.
[5] Heck, Poszlig;, Reichardt, Napp, Alves, Stühmer, Feldmann, patent application2014 DE 102014004512.9.

We introduce that multifunctional solvent-free colloidal fluids with highly integrated functionalities can be fabricated using layer-by-layer (LbL) assembly.
To prepare multifunctional colloidal fluids, oleic acid (OA)-stabilized magnetic nanoparticles (i.e., OA-Fe₃O₄ NPs) and CdSe@ZnS quantum dots (OA-QDs) were synthesized in nonpolar solvent. After the functional nanoparticles were synthesized, amine-functionalized dendrimers (NH₂-dendrimer) and OA-Fe₃O₄ NPs were alternately adsorbed onto 600 nm-sized silica colloids (i.e., SiO₂/ (NH₂-dendrimer/ OA-Fe₃O₄ NPs)_n) via ligand exchange-induced LbL assembly in organic media. Although multilayer-coated colloids were prepared in organic media, the colloids with an outermost NH₂-dendrimer layer (i.e., SiO₂/ (NH₂-dendrimer / OA-Fe₃O₄ NPs)_n/ NH₂-dendrimer) were highly miscible in aqueous media. This characteristic arose due to the amine protonation of the dendrimers, which induced electrostatic repulsions between neighboring positively charged colloids in aqueous media and thus prevented colloidal aggregation. Electrostatic LbL-assembled (anionic polyelectrolyte (PSS)/ cationic IL-SH-QDs)_n multilayers were then sequentially deposited onto the outermost NH₂-dendrimer layer of magnetic colloids. To disperse QDs in aqueous media, OA-QDs dispersed in toluene were phase-transferred to thiol-functionalized imidazolium-type ionic liquid (IL-SH) media. These multifunctional colloids coated with an outermost layer of the IL-SH-QDs (i.e., SiO₂/ (NH₂-dendrimer / OA-Fe₃O₄ NPs)₃/ NH₂-dendrimer/ (PSS/ IL-SH-QDs)₃) were precipitated by centrifugation to remove the aqueous media and were subsequently redispersed in IL-SH host media. Imidazolium-type ionic liquids have been reported to exist as a supramolecular structure of cations and anions linked together by weak interactions. So, IL-SH-QDs-encapsulated nanocomposite colloids can effectively participate in IL-SH media without any phase segregation.
These resulting colloidal fluids exhibit superparmagnetism, photoluminescence, ionic conduction as well as liquid-like behavior without addition of any solvent. Particularly, mixtures of photoluminescent colloidal fluids with and without OA-Fe₃O₄ NPs behaved effectively as magneto-optically separable colloidal fluids.
We believe that our approach can provide a basis for exploiting multifunctional colloidal fluids with liquid-like behavior at room temperature, because various functionalities can be highly integrated into colloids via LbL assembly at the single particle level.

Magnetic resonance imaging (MRI) as a non-invasive diagnostic technique can provide anatomically detailed images of living bodies at the cellular and molecular levels in real time with excellent spatial resolution. However, since this technique suffers from low detection sensitivity, contrast agents are needed to help detect and characterize pathological abnormalities. Paramagnetic contrast agents assist in enhancing the image contrast by reducing the longitudinal relaxation time (T1) of surrounding water protons, which appear brighter in the T1-weighted MR image. Among contrast agents, gadolinium (III)-chelated complexes, such as gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA), can improve imaging contrast due to strong dipolar interactions with water nuclei protons, and are the most widely used complexes in clinical diagnosis. However, individual gadolinium ions generate low signal enhancement and show toxicity caused by poor gastrointestinal absorption.Therefore, considerable effort has been devoted both to enhance the signal and minimize the toxicity of gadolinium compound loaded-nanoparticles. Furthermore, activatable, i.e. stimuli-responsive, contrast agents help to detect biological activity by generating a signal in response to specific environmental variations in biological systems. Especially, MRI contrast agents show high MR signals in cancer-specific physiological conditions, such as acidic conditions, which leads to effective cancer diagnoses without overdosage of contrast agents. Herein, we present a novel strategy to formulate pH-sensitive gadolinium-based MRI contrast agents capable of increasing MR signals in cancer-specific environments, such as acidic conditions. Py-Gd nanoparticles are prepared by coating Pyrene-Gadolinium (Py-Gd), a complex of gadolinium with pyrenyl molecules, with pyrenyl PEG using a nano-emulsion method. These particles show superior T1 MR signal in acidic conditions compared with neutral conditions. Furthermore, the particles exhibit biocompatibility and MR contrast effects though in vitro/in vivo studies. From these results, we confirm that Py-Gd nanoparticles have the potential to be applied for accurate cancer diagnosis and therapy.

Recently, considerable demands on nanostructured materials such as fibers, particles, rods, tubes, and disks have been emerged for a variety of applications including optoelectronics, multimodal imaging, and nanomedicine. In particular, nanoparticles fabricated from conjugated polymers with unique properties, such as high fluorescence, excellent photostability, good biocompatibility, and low cytotoxicity have provided new fluorescent probes for sensing and cellular imaging with proper surface modifications. The surface modification of conjugated polymer dots (CPdots) is known to be important in biology-related studies because the colloidal stability of CPdots in aqueous solution is a primary concern. We demonstrate a new, versatile CPdot material for the analysis of a specific protein. Some experiments were involved in using graphene oxide (GO) was used as an effective quencher, in hybridization with other shape of materials for sensory applications. Several types of nanohybrids of conjugated polymer dot will be presented in detail.

The colloidal stability and biological susceptibility of nanoparticles (NPs) can be significantly regulated by their surface modification. The magnetic-plasmonic NPs could be used in various biological fields because of their dual functionalities. By modifying the surfaces of the NPs with functional ligand molecules, the NPs can be used as magneto-optical tags for cells. To demonstrate this, we used poly-L#8209;Lysine with thiol and Lactose moieties (PLL-SH-Lac) as surface modifier. It proves to be advantageous over other ligands in terms of biocompatibility and capability of functionalization. On the other hand, we synthesized FeCo@Ag core-shell NPs as magnetic-plasmonic NPs. Then, the surfaces of the NPs were modified with PLL-SH-Lac via SH groups. HepG2 cells have lactose receptors and thus, PLL-SH-Lac modified NPs can be selectively conjugated with the cells through specific interaction between lactose moieties in PLL-SH-Lac and lactose receptors on cell surface. To enhance the specific interaction, minimizing the non-specific electrostatic interactions, we tuned the charge of the PLL-SH-Lac by replacing amino groups with carboxylic groups. To avoid charge repulsion between cell membrane and PLL-SH-Lac modified FeCo@Ag NPs due to carboxylic group, we changed the input ratio of Lactose, carboxyl groups and thiol groups. By tailoring these parameters we can obtain desirable PLL-SH-Lac FeCo@Ag NPs-Cell attachment which can be characterized by techniques like confocal laser scanning microscopy and dark field microscopy. The cell attachment can be further extended to magnetic-cell separation of cancerous cell line from normal cell line.

There is an apparent competition between electronic performance and mechanical compliance in semiconducting polymers. This talk describes two studies toward the design, synthesis, and characterization of high-performance semiconducting polymers that are also elastomers. The first study examines a series of poly(3-alkylthiophene)s (P3ATs), the most well known example of materials in which mechanical compliance and electronic performance have been observed to be in competition. P3ATs with longer alkyl side chains (n ge; 8) have high elasticity and ductility, but poor electronic performance (as manifested in photovoltaic efficiency in blends with fullerenes); P3ATs with shorter chains (n le; 6) exhibit the opposite characteristics. A series of four polymer films in which the average length of the side chain is n = 7 is tested using mechanical, spectroscopic, microscopic, and photovoltaic device-based measurements to determine whether or not it is possible, in principle, to maximize both mechanical and electronic performance in a single organic semiconductor (the “best of both worlds”). The four polymer samples are (1) a physical blend of equal parts P3HT and P3OT (P3HT:P3OT, n = 6 and n = 8); (2) a block copolymer (P3HT-b-P3OT); (3) a random copolymer (P3HT-co-P3OT); and (4) poly(3-heptylthiophene) (P3HpT, n = 7). The tensile moduli obtained by mechanical buckling correlate well with spectroscopic evidence (using the weakly interacting H-aggregate model) of a well-ordered microstructure of the polymers. The block copolymer was the stiffest of the hybrid samples (680 ± 180 MPa), while P3HpT exhibited maximum compliance (70 ± 10 MPa) and power conversion efficiency in a 1:1 blend with the fullerene PC₆₁BM using stretchable electrodes (PCE = 2.16 ± 0.17%) that was similar to that of P3HT:PC₆₁BM. P3HpT is an rare example of a semiconducting thermoplastic elastomer. The second study involves the use of randomly incorporated conjugated monomers into the backbone of a low-bandgap polymer. This approach—random segmentation—reduces the modulus (by reducing the structural order) while leaving the electronic performance intact. The results of these experiments may permit the design of organic semiconductors with improved mechanical and electronic properties for mechanically robust and stretchable applications.

Tremendous efforts on treating malfunctioning body parts using artificial material has been made to provide better clinical-aesthetical results for both medical personnel and patient&’s experience. These materials are becoming more sophisticated with biocompatibility and functionalities in the medical and tissue engineering fields. As a biocompatible tissue engineering material, mussel adhesive protein (MAP) drew attentions because it can readily deliver various functions, such as cell adhesion and proliferation, through its adhesiveness to conventional polymer scaffolds. To further exploit MAP as a functional tissue engineering biomaterial, a chimeric protein of MAP and silica-binding peptide (SBP), R5-fp-151, was designed and produced in Escherichia coli. The SBP originated from diatoms can promote the silica precipitation in mild conditions. Silica promotes and stimulates osteoblast cells to up-regulate multiple gene markers critically associated with bone regeneration, such as synthesis in collagen type 1. Thus, we investigated electrospun R5-fp-151 scaffold chimeric for its potential as a bone regeneration biomaterial.

Mechanical behaviors of LbL polyelectrolyte composites (PECs) are directly influenced by both assembly and testing conditions (e.g., pH, ionic strength or IS). To understand the interplay between the mechanics of PECs and environment conditions, we studied the swelling and corresponding mechanical behaviors of LbL assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) 70-bilayer PECs using Atomic Force Microscopy(AFM)-based methods. Positively charged PAH (M_w~15k, Sigma-Aldrich) and negatively charged PAA (M_w~50k, Polysciences) were assembled on freshly Piranha solution-treated glass substrates at pH 7.5 and 3.5, respectively (IS = 10^-2M based on repeating unit of the polyelectrolytes) using a Carl Zeiss HMS programmable slide stainer. We measured the film modulus via AFM-based nanoindentation using a microspherical tip (R = 12.5 µm, k = 0.2 N/m) and a Dimension Icon AFM (Bruker-Nano) at various IS (0.01 - 1.0M NaCl) and pH (5.5 to 2.0). Effective indentation modulus, E_ind, was calculated from the indentation force-depth curves based on linear elastic Hertz model. In addition, we measured the film thickness, t_f, at corresponding pH and IS by selective film removal. The thickness measurement was done by either contact mode AFM imaging when t_f <10µm, or our recently developed height difference measurement method combining the AFM step motor and height sensor when t_f>10µm. At each IS, the film swells at a certain pH prior to its dissolution. The dissolution pH of PAH/PAA varies with IS due to the dependence of local pK_a on bath IS. At 0.1M and 1.0M IS swelling is accompanied with E_ind decrease from 2.8±0.5MPa and 2.9±0.6MPa to 35.0±1.6kPa and 9.2±1.9kPa, respectively (mean±SEM, n ge; 8 locations each state). This ~10²-10³× decrease highlights the impacts of the ionic cross-link density on PEC mechanics and in drastic contrast to the entropic elasticity prediction. At pH 5.5, when both PAH and PAA are highly charged, t_f increases from 2.6±0.1 µm with IS 1M to 7.7±0.5µm with IS 0.01M, together with an increase in E_ind (2.9±0.6MPa at 1M compared to 4.2±0.7MPa at 0.01M), instead of a decrease. This IS dependence highlighted the impacts of reduction in local chain stiffness due to Debye screening and likely decrease in effective ionic cross-link charge density due to doping by free ions at higher IS. At the near dissolution pH, E_ind was ~ 200× higher at 0.01 M than 1.0 M, which can be attributed to the presence of stronger electrostatic double layer repulsion from net positive charges at lower IS. Our ongoing studies are investigating the time-dependent mechanics of PECs governed by the reversible ionic cross-links and fluid flow using AFM-based nanorheometer and creeping tests. The goal of this study is to understand the molecular factors that govern the stimulus-tailorable, time-dependent mechanics that can benefit an array of mechanics-oriented applications.

Stretchable and flexible electronics are considered important for the next generation wearable devices. Several recent studies have experimentally demonstrated electronic devices on stretchable substrates [Science 327, 1603 (2010); Nat Commun 4, 1543 (2013)]. However, development of a stretchable conductor is critical for the interconnection of these devices to form complex circuits [Nat Commun 3, 977 (2012)]. This problem is exacerbated because of the limited inherent stretchability of common interconnect metals such as copper and aluminum. In this work, we present a lateral spring design for fabricating stretchable copper conductors. These copper conductors, with polymer backing, are observed to have a total stretchability of 800%, or 8 times their original lateral length.
For the fabrication of the stretchable copper conductors, we used bulk silicon <100> as a starting substrate. A sacrificial layer of amorphous silicon (1 mu;m) was deposited on the oxidized silicon substrates using PECVD. The wafers were then spin-coated with polyimide (4 mu;m) and cured at 350 °C for 50 minutes. We then deposited aluminum thin film (200 nm) as a hard mask, using sputtering process, for PI etch. The PI layer was etched using oxygen plasma at 60 °C followed by copper seed layer deposition (200 nm) for electroplating of copper. A photoresist based soft mask was used to pattern the electrochemical deposition of copper (4 mu;m). The seed layer was then etched using argon plasma RIE. The devices were finally released using a XeF₂ gas based selective and isotropic etching of amorphous silicon sacrificial layer. The released samples were tested for mechanical performance and the resistance was characterized under stress and after multiple stress cycles.
Stress-strain characteristics for the stretchable conductors showed a standard, non-linear behavior typically shown by hyperelastic materials [Rubber Chem Tech 79, 835 (2006)]. The yield point was obtained as 110 MPa. The stretch at yield point was observed to be 780%; however, this strain was not reversible. We observed that the elastic limit of strain for this conductor design was 600%. Further, it was observed that the resistance of the conductors only changed by 1-2% on application of strain up to 600% (within the elastic limit). The resistance was observed to approach a particular value, and remain constant after hundred cycles of strain within the elastic limit.
In conclusion, we report a stretchable and flexible copper conductor with excellent mechanical and electrical characteristics fabricated using CMOS compatible materials and processes. The conductor can stretch up to 8 times its original length and resistance of the conductor is found to be almost invariant with applied lateral strain. As a device demonstration, the conductors have been used as interconnects for metal heating pads in the design of a stretchable, foldable, wirelessly controllable thermal patch.

High speed electronics are critical for many advanced applications. Making such devices mechanically flexible offers significant advantages compared to their rigid counterparts, promoting folding, ease of storage, and conformity to any kind of platform. There is a wide spectrum of electronics applications where high-speed operations and mechanical flexibility are simultaneously needed, such as high-speed and wireless communications, and remote sensing. Fast flexible electronics offer superior performance and application advantages, however to date, there is no cost-effective flexible process exhibiting high budget compatibility and ultra-large-scale integration compatibility. One of the widespread techniques for the fabrication of fast flexible electronics is through the transfer technique, relying on the use of silicon-on-insulator (SOI) wafers for releasing silicon nanomembranes (SiNMs) [Adv. Funct. Mater. 21, 3029 (2011)]. However, this technique offers three major drawbacks: (i) temperature constraint of plastic substrates: limitation for high budget processes, (ii) incompatibility for ultra-large-scale integration, and (iii) high expense and wastage of the full SOI wafer after release. Previously, we have reported a novel cost-effective technique for releasing thin silicon sheets from low-cost bulk monocrystalline (100) wafers [MRS Fall Meeting 2012]. In this work, we adapt this process for the release of single-crystal high-speed metal-oxide-semiconductor field-effect transistors (MOSFETs). We use state-of-the-art high-k/metal gate stack, using atomic layer deposition Al₂O₃ and highly doped polysilicon. The process is continued by creating an array of etch holes across the wafer and etching down the silicon substrate using the BOSCH process. Finally, a thin flexible silicon sheet with fabricated devices on top is released by exposing the wafer to xenon difluoride (XeFe₂) isotropic etchant. The flexible high-speed transistors display outstanding mechanical flexibility and transparency properties, showing a correlation between transmittance percentages and etch holes size. Radio-frequency (RF) electrical characterization is performed in order to illustrate the ultra-fast frequency response of the flexible high-speed MOSFETs through the determination of the cut-off frequency f_t and maximum frequency f_max. Such excellent mechanical flexibility enables these devices to be used in various unique applications, providing a promising route to flexible digital circuits for applications requiring ultra fast performances that cannot be satisfied with low-mobility organic semiconductors, or other costly flexible processes, incompatible with the state-of-the-art microfabrication processes. Thus, through this work, we were able to demonstrate and address three of the key components in modern devices and integrated circuits (ICs): performance, functionality, and cost, all together with the benefit of flexibility.

Porous coordination polymers (PCPs), also referred to as metal-organic frameworks, are 3D supramolecular polymers formed by dative bonding between multitopic organic ligands and metal ions or oxo-clusters. PCPs may be considered the material counterparts to molecular coordination compounds such as complexes, cages, and metal-organic polyhedra. While frequently treated as static after synthesis, recent investigations have discovered that, especially when in contact with solution, PCPs are dynamic, transformable entities, subject to the substitution reactions common to their molecular counterparts. We report here our recent discoveries in the ligand exchange dynamics of the Zn(2-methylimidazolate)₂ PCP, also known as ZIF-8, including the first evidence for competitive dissociative and associative ligand substitution mechanisms in this class of materials. We discuss the fundamentals and consequences of these ligand exchange reactions in PCPs, and how conditions, such as the solvent, may be chosen to direct a desired aim. Finally, we emphasize how knowledge of the ligand dynamics of PCPs may be applied to design new functional or hybrid materials through our study of host-guest materials for catalysis, by encapsulating molecular catalysts in the pores of PCPs.

Combined systems of semiconducting polymers and aqueous electrolytes are emerging as a new frontier of organic electronics, with many promising applications in neuroscience, biomedicine and photoelectrochemical cells. A detailed characterization of the effect of direct, prolonged contact with water in working conditions, typically upon visible light illumination, is thus urgently needed. Here, we first report a detailed study of processes occurring in thin films of regio-regular poly(3-hexylthiophene) (rr-P3HT), the election material for such applications, exposed to different environmental conditions. We demonstrate that the contact with saline solutions is not worst than contact with open air: in both situations the reversible formation of a charge transfer complex between polymer and molecular oxygen is the main phenomenon, enhanced by visible light illumination. Experimental data and theoretical modeling provide an insightful picture of the complex formation, as a precursor of photo-activated doping, and first unambiguously identify its spectral signature by means of vibrational spectroscopy techniques. In addition, Second Harmonic Generation spectroscopy, optoelectronic measurements (e.g., photocurrent, photovoltage, surface capacitance, cyclic voltammetry) and Atomic Force Microscopy studies contribute to draw a comprehensive picture of the phenomena occurring at the complex rr-P3HT/electrolyte interphase. In perspective, this work fully validates use of semiconducting polymers in contact with electrolytes, and represents a useful basis for applications both in organic bioelectronics and in organic-based photoelectrochemical cells.

Patterning functional materials is a central challenge across many fields of science. Despite the fact that there are hundreds of commercially available photoresists, the functional diversity amongst these materials is severely limited. In most applications, the photoresist serves the sole purpose of a sacrificial mask or mold; very rarely is the resist material incorporated as a structural element or chemically functional interface. The ability to generate new kinds of chemically functional materials directly via photolithography would enable a host of new applications, for example in microelectromechanical systems (MEMS), microfluidics, patterned biomaterials and artificial optical materials. We recently reported a negative tone photoresist using a photoactivated olefin metathesis catalyst, which can be quickly prepared in a one-pot synthesis from commercially available starting materials.[1]
Olefin metathesis is a robust synthetic methodology that has led to new polymeric materials with many applications, such as drug delivery, organic electronics, and photonic crystals. We recently developed a method of patterning using a ruthenium photocatalyst, PhotoLithographic Olefin Metathesis Polymerization (PLOMP). In this procedure, a latent metathesis catalyst is activated by light to react with the olefins in the surrounding environment. We demonstrate a negative tone resist by using the photocatalyst to crosslink a difunctional ROMP monomer within a matrix of linear polymer. The versatility of ruthenium-mediated olefin metathesis can now be utilized to photopattern a variety of functional materials via PLOMP, advancing the field of photoinitiated olefin metathesis from a curiosity to materials science applicable to mass microfabrication.
These olefin-rich solutions are competent UV photoresists, at both 254 nm and 352 nm. Under 254 nm irradiation, we were able to cure 1-2 micron thick films in 60 to 90 seconds using a benchtop 8-watt lamp. Functional diversity has been incorporated into PLOMP resists in a number of ways, including copolymerization of functional monomers into the linear polymer, and through the introduction of additives into the resist solution. We have successfully incorporated a variety of functional groups into the resist material, including esters, acids, ethers, amines and isocyanates. As well, we have demonstrated direct write lithography to generate 3D nanostructures with unique chemical functionality. We anticipate that PLOMP will enable the development of directly patterned micro- and nanostructures with chemical, mechanical and optical functionality not currently available with existing fabrication techniques.
[1] Weitekamp, R. A.; Atwater, H. A.; Grubbs, R. H. J. Am. Chem. Soc.2013, 135, 16817-16820.

Micro- and nano-particles are now cornerstones of a broad span of nanotechnologies with important applications in various applications ranging from paints and coatings to cosmetics and medicine. Such applications demand access to (1) a wide range of useful materials from which these particles are produced, (2) internal architectures that could enable different functionalities, and (3) size ranges. Although it seems surprising and counter-intuitive, the standard process of optical fiber drawing that produces extended lengths of uniform fiber can contribute to solving this long-standing challenge. Over the past few years, an in-fiber particle fabrication method has been developed that relies on a surface tension-driven fluid instability - the Plateau-Rayleigh capillary instability (PRI) [1,2]. Thermal treatment of a multimaterial core/cladding fiber induces the PRI at the heterogeneous interfaces along the whole fiber length, causing the initially intact core to break up into a periodic necklace of uniformly-sized spherical particles held stationary and isolated from each other in a sacrificial polymer matrix. This novel fabrication strategy has shown to be suitable for producing particles from a broad spectrum of polymers and glasses in a multiplicity of structures and with diameters spanning the range from 1 mm (visible to the naked eye) down to 20 nm (the size of a single virus).
The amount of particles produced by this method is dependent on how many cores may be stacked in a single fiber and how fast the fiber can be drawn from its parent preform. While certain applications in medicine might require only grams or less of particles, other applications require much larger quantities - potentially tons, as in the case of nanoparticles used in producing paints and coatings. We show here that fiber spinning machines (Made by Hills, Inc., Florida) that can generate fibers with complex cross sectional geometries at a rate of thousands of pounds of material per hour may be exploited to produce multimaterial fibers in which the PRI is reliably reproduced - similarly to those observed in thermally drawn fibers. Furthermore, the complex fiber structures that can be produced through fiber spinning facilitate the large-scale fabrication of structured functionalized particles. We demonstrate this by producing multimaterial core-shell fluorescing particles and discuss the possibility of extending this work to include much more complex particle geometries.
[1] J. J. Kaufman, G. Tao, S. Shabahang, E.-H. Banaei, D. S. Deng, X. Liang, S. G. Johnson, Y. Fink, and A. F. Abouraddy, “Structured spheres generated by an in-fibre fluid instability,” Nature 487, 463 (2012).
[2] J. J. Kaufman, R. Ottman, G. Tao, S. Shabahang, E.-H. Banaei, X. Liang, S. G. Johnson, Y. Fink, R. Chakrabarti, and A. F. Abouraddy, “In-fiber production of polymeric particles for biosensing and encapsulation,” Proc. Natl. Acad. Science (USA) 110, 15549 (2013).

Controlling the nanoscale morphology of π-conjugated polymers is an attractive strategy to optimize their properties in optoelectronic applications. The self-assembly of rod-coil block copolymers offers a wealth of nanoscale structures both in solution and in thin films, promising the functionality of semiconducting polymers married to the tunability of flexible insulating polymers. While self-assembled linear multiblock copolymers containing conjugated segments have been prepared and applied to devices and sensors, more complex architectures have not been explored. Towards this end, we have investigated the design and synthesis of miktoarm H-shaped pentablock copolymers containing a semiconducting polymer core. We anticipate that this novel architecture will permit access to complex nanoscale morphologies with increased control over the orientation and geometry of the rod-type block.
To access the H-shaped polymer, we developed an “in-out” graft approach using ring-opening metathesis polymerization to and from norbornene end-capped poly(3-hexyl)thiophene with narrowly dispersed molecular weight. The norbornene end-capped P3HT is prepared by click chemistry. The flexible polynorbornene blocks were designed to favor microphase separation and aid characterization. An advantage of this "in-out" method using ROMP is its synthetic versatility. The resulting H-shaped polymers self-assemble in solution and in thin films, as observed by SAXS, DLS, and TEM. Properties of these materials, as well as composites with carbon nanotubes, will be discussed.

Metallized polyimide polymer films are of interest owing to their wide scope of applications including adaptive optical mirrors, solar dynamic power generation, radiation shielding and thermal control coatings.¹ Palladium-based polyimide films have proven to be unique in terms of thermal reduction, photochemistry and nanoparticulate distribution within the polymer matrix. A nanoscale surface-metallized Pd polymer is made by thermally curing Pd polyamic acid films at 300°C. When Pd polyamic acid is exposed to lamp radiation for 15 hours prior to curing, an additional nanoscale metallic interlayer is created within the surface-metallized polyimide matrix. These etalon type films have the ability to transform electromagnetic radiation into mechanical energy.² Possible applications of these etalon type films include natural laser cavities, narrow band pass filters and microelectromechanical (MEMS) switches.²
Whilst previous efforts have produced metallic interlayer in 15 hours, an excimer laser reduces this time to 4 minutes.³ As presented here, an additional development involves passing the laser beam through a beam homogenizer. As a result, large swathes of uniform irradiation areas have been created. Transmission electron microscopy (TEM) of the cross section of the irradiated films reveals fluence dependent interlayer depths of 200nm to 800nm. Ongoing studies are directed towards understanding the mechanism of surface metallic layer formation, metallic interlayer formation, and metal nanoparticulate transport within the polymer matrix. In addition to Pd, surface metallization and interlayer formation using other metals is discussed. Preliminary results with a femtosecond laser show that a metal interlayer can be formed with less than 10 seconds of exposure time and are also presented.
1) Mackenzie, A.; Cravey, R. L.; Dudley, K. L.; Fralick, D. T.; Miner, G. A.; Stoakley, D. M. Fabrication and Electromagnetic Characterization of Novel Self-Metallized Thin Films, NASA Langley Research Centre, 2003.
2) Gaddy, G. A.; Locke, E. P.; Miller, M. E.; Broughton, R; Albrecht-Schmitt, T. E.; Mills, G. Photoinduced, Controlled Generation of Palladium Crystallite Structures in Polyimide Films. J. Phys. Chem. B 2004, 108, 17378-17383.
3) Miner, G. A.; Stoakley, D. M.; Gaddy, G. A.; Koplitz, B. D.; Simpson, S. M.; Lynch, M. F.; Ruffner, S. C. Laser-induced fabrication of metallic interlayers and patterns in polyimide films, United States Patent 7,758,927 B2, 2010.

Poly(L-lactic acid) (PLLA) is one of the most popular biodegradable polymers with biocompatibility and has gained biomedical attention as biomaterials for three-dimensional scaffolds of tissue engineering and drug delivery system. In this study, we synthesized PLLA based amphiphilic diblock copolymers and investigated the surface properties and wettability of the copolymers. Nanofibers of PLLA based diblock copolymers were also fabricated for the applications of tissue engineering scaffold.
We selected polyacrylate which has carboxyl groups for hydrophilic block segments. Diblock copolymers, polyacrylate-block-poly(L-lactic acid)s (PAA-b-PLLAs), were synthesized as follows. Macroinitiator PtBA-OH was synthesized from tert-butyl acrylate by ATRP method using a bifunctional initiator having OH group. Molecular weights (M_n) of PtBA-OH increased linearly in proportion to the reaction time of ATRP. The polydispersity index (PDI) remained as low as 1.2 up to 60% monomer conversion. L-Lactide was polymerized from PtBA-OH macroinitiators in the presence of Sn(Oct)₂ to obtain PtBA-b-PLLAs. M_n and unit ratios of PtBA-b-PLLAs were controllable by the ratio of OH end group of PtBA-OH and L-lactide. M_ns of PtBA-b-PLLA were in the range of 33,200 to 88,800 which were determined by GPC, and the unit molar ratios (PLLA : PtBA) calculated by ¹H NMR were in the range of 1 : 1.3 to 1 : 4.6. PAA-b-PLLA was prepared by deprotecting the tert-butyl acrylate groups of PtBA-b-PLLA by using trifluoroacetic acid. The obtained polymers were characterized by using FT-IR, GPC, ¹H NMR, and optical rotation measurements. Complete deprotection was confirmed by the disappearance of tert-butyl group by ¹H NMR. Thin films of the PAA-b-PLLAs were prepared by casting 1% (w/v) solution onto glass slides. Since PAA-b-PLLA is insoluble in any single solvent, mixed solvent of chloroform and methanol was used for the cast solvent. Wettability of the cast films was controllable by the ratio of the PAA content of PAA-b-PLLA and the ratio of chloroform and methanol. The surface morphology of the thin films was analyzed by atomic force microscopy (AFM). The AFM phase images revealed that morphology of PAA-b-PLLA depended on the solvents ratio.
In order to create porous scaffolds for soft tissue engineering, PtBA-b-PLLA and PAA-b-PLLA fibers were prepared by electrospinning technique. PtBA-b-PLLA was dissolved in trifluoroethanol to obtain viscous solution, and PAA-b-PLLA was dissolved in chloroform and methanol mixed solvents. The obtained highly viscous solutions were electrospun at a high input voltage of 30 kV to create nanofibers. The scanning electron microscopy results showed that the obtained nano-fiber membranes have a porous structure suitable for cell adhesion and growth. Wettability of nanofiber membranes varied depending on PAA content of the diblock copolymers and the methanol content of the mixed solvents.

On the development of flexible electronics, a highly flexible nonvolatile memory, which is an important circuit component for the portability, is necessary. However, the flexibility of existing nonvolatile memory has been limited, e.g. the smallest radius into which can be bent has been millimeters range, due to the difficulty in maintaining memory properties while bending. Here we propose the ultra flexible resistive nonvolatile memory using Ag-decorated cellulose nanofiber paper (CNP). Cellulose is renewable and the most abundant biomass on earth, and is a raw material of commercial paper. CNP is made of chemically treated 4 nm cellulose nanofibers with 3-4 nm width and has outstanding properties including a high tensile strength and a low thermal expansion coefficient. The Ag-decorated CNP devices showed the stable nonvolatile memory effects with 6 orders of ON/OFF resistance ratio and the small standard deviation of switching voltage distribution. The memory performance of CNP devices can be maintained without any degradation when being bent down to the radius of 350 mu;m, [1] which is the smallest value compared to those of existing flexible nonvolatile memories. Thus the present device using abundant and mechanically flexible CNP offers a highly flexible nonvolatile memory for portable flexible electronics.
[1] Scientific Reportsin press (2014)

The development of flexible electronic skins with high sensitivities and multimodal sensing capabilities is drawing great interest due to the potential applications in wearable electronics, prosthetic limbs, robotic skins, and remote surgery. In particular, piezoresistive composite elastomers have been regarded as key components in electronic skins due to the low-cost and simple fabrication process, high flexibility and scalability. However, relatively poor sensitivity, low response time, and signal drifts with temperature still need to be overcome. Herein, we introduce a novel design of flexible electronic skins based on interlocked system of carbon nanotube composite elastomer films that contain microdome shaped arrays. These designs provide an enhanced change in contact area on various external forces and enable to minimize a viscoelastic property, leading to giant tunneling piezoresistance and thus high sensitivity and rapid response/relaxation times. We show that dimensions of surface microstructures such as diameter, pitch of periodic structures, and shape of microstructure strongly affect the piezoresistance. Finally, we demonstrate wearable electronic skins which can detect minute environmental changes in real-time and simultaneously resolve multidirectional forces. In addition, the electronic skin can sensitively monitor human breathing flows and voice vibrations, which should find applications in human-health monitoring systems.

Shape memory polymers (SMP) are a new class of novel biomaterials that can undergo shape change upon exposure to external stimuli (light, heat, pH, magnetic field, etc.). Thermally-induced and light-induced SMP are promising functional materials for biomedical applications such as surgical sutures and cardiovascular stents. Biomedical applications often require outstanding biodegradability and biocompatibility, however, biodegradable light-induced shape-memory polymers are not currently available. In this study, modified poly(ε-caprolactone) (PCL) tri-block copolymers were synthesized through ring opening polymerization. The photoreactive cinnamoyl moieties were incorporated into the semi-crystalline copolymers to make the UV-light crosslinking networks. Furthermore, a nanocomposite containing gold nanoparticles (AuNPs) and the SMP was fabricated to introduce light-responsive shape memory behavior using the surface plasmon resonance of AuNP to induce the photothermal effect. The polymer microstructures were confirmed by NMR, and the thermal properties of the polymer networks were characterized by TGA and DSC. The shape memory behavior was quantitatively investigated by cyclic thermomechanical tests using DMA. The shape transition of the nanocomposite from a spiral coil to a flat film was visually demonstrated for the potential cardiovascular stent application. Of novel significance, a rapid 3D prototype device that mimics helical blood flow in the aorta was fabricated and used to test the in-vitro biodegradation of the SMPs. Mass loss, molecular weight decrease and the mechanical properties were measured with time and compared to that using a standard test method for accessing in-vitro biodegradation of polymers - ASTM F1635-11.

Our research aims to develop shape memory assisted self-healing polymers comprising of core-shell nanocapsules, of poly(urea-formaldehyde) (PUF), with bisphenol-A-diglycidyl ether (DGEBA) core, bis-amine hardener and a thermo-responsive shape memory polymer. 100nm spherical capsules were synthesized via an in-situ oil-in-water miniemulsion polymerization process using sodium dodecyl sulfate and poly(ethylene-maleic-anhydride) (EMA) and as surfactant and co-surfactant respectively. The particle size and distribution, as well as surface morphology, were determined by Dynamic Light Scattering (DLS) and Scanning Electron Microscope (SEM), respectively. The chemical structures were confirmed by H¹ Nuclear Magnetic Resonance (H¹-NMR) and Fourier Transform Infrared Spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray Spectroscopy (EDS), both of X-ray level technology, mainly for measurement of atom dispersion, were also used to determine the % loading of the catalyst with the capsules core. Self-healing efficacy was determined by adding hardeners into the polymer matrix, composed of bulk polymer, primer and nanocapsules, under various temperatures. Relative self-healing efficiency was then accessed using SEM images and Dynamic Mechanical Analysis (DMA) in to determine the complex modulus before and after the healing stage.

Controlling drug release kinetics is of great significance as the efficacy and toxicity of the local therapeutics depend largely on the release kinetics. Over the past few decades, considerable advances have been made in controllable delivery systems aimed at maintaining an adequate drug concentration in the blood or in target tissues at a desired value. Among them, stimuli-responsive nanomaterials are of interest, as they enable well-regulated release kinetics by the programmable stimuli applied. Although different stimuli have been investigated to fabricate responsive systems, developing delivery systems with multi-tunable release kinetics remains a scientific challenge. Based on the unique chemical and biological properties of selenium element, selenium-containing polymers have attracted increasing interest as drug delivery vehicles and artificial enzymes.^1,2 In contrast to the vast emerging research with regard to selenium-containing polymers, the occurrence of tellurium in biopolymers is poorly explored. Tellurium containing organic compounds have been investigated as mimics of glutathione peroxidase, which plays an important role in protecting cells from oxidative stress. Besides, tellurium-containing compounds are reported to be less toxic than selenium counterparts.³ Although some tellurium-containing drugs are already under investigation or clinical trials, little attention has been paid to the possibility of introducing tellurium into bio-polymers. This report is to highlight a novel tellurium-containing polymer, which possesses the ability to deliver platinum based drug with ligand-regulated release kinetics for different time span.⁴ Tellurium was introduced to water soluble polymers for the first time as drug delivery vehicles. The coordination chemistry between platinum and tellurium was designed to enable the load of platinum based drug. Through the competitive coordination of biomolecules, the drugs could be released in a controlled manner. Furthermore, the release process showed a ligand regulated manner, in which the release kinetics could be modulated by different competitive ligands. As a result, the goal of enhanced delivery efficiency and fewer side effects may be achieved. Additionally, other metal containing drugs could potentially also benefit from this approach. Considering that other polyamine and S-donor ligand can also take part in the competitive coordination, its in-vivo release may be greatly enhanced. We believe that tellurium-containing polymers may provide new components for future biomedical nanotechnologies. References (1) Xu, H.; Cao, W.; Zhang, X. Acc. Chem. Res.2013, 46, 1647-1658. (2) Cao, W.; Zhang, X.; Miao, X.; Yang, Z.; Xu, H. Angew. Chem., Int. Ed.2013, 52, 6233-6237. (3) Engman, L. Acc. Chem. Res.1985, 18, 274-279. (4) Cao, W.; Gu, Y.; Meineck, M.; Li, T.; Xu, H. J. Am. Chem. Soc.2014, 136, 5132-5137.

The advantage of magnetic resonance imaging (MRI) is mainly the direct visualization of the physico-chemical processes occurring during the polymer dissolution in real time. Nowadays, polymeric matrices are widely used in different types of industries. One of the common uses of such polymers is in pharmaceutical industry. Hydrophilic polymeric materials are excellent matrices for sustained release formulations. Therefore it is desirable to describe the polymer swelling, and to find a correlation between swelling kinetics and active pharmaceutical ingredient (API) release.
The aim of this study was to measure the dissolution kinetics of polymeric matrices with the different ratio of hydrophilic and lipophilic components, utilizing MRI technology. For this purpose, six different matrices, in forms of tablets, were prepared. In addition, especially for the experiment in MRI magnet, flow through cell and tablet holder were designed and manufactured by 3D printing technology. The experiments were performed under specific conditions i.e. phosphate buffer saline pH 6 as a medium, medium temperature - 37°C, the flow rate of medium - 4 ml/min, the time of experiment 4- 8 hours. To improve the visibility of the erosion front, composite magnetic nanoparticles SiO_2/FeO_x as a MRI contrast agent were used. Each matrix was measured three times and the thickness of gel layer was evaluated in three different regions.
To sum up, MRI turned out to be suitable imaging method for polymer swelling quantification. For the future measurements, the effect of different additives on the polymer swelling kinetics will be evaluated. The results from the whole research should lead to the database of matrix components and conditions of technological processes and their effects on the dissolution profile of API. Such database would notably simplify the formulation of dosage forms with the desired drug release.

Temperature-responsive hydrogels have attracted considerable attention due to their potential biomedical applications or sensors. In this work we aim to study effect of Hofmeister series on the temperature -induced volume change of multilayer-based hydrogels composed of poly(N-vinylcaprolactam) (PVCL). The PVCL hydrogels were derived from hydrogen-bonded poly(vinylcaprolactam)-co-(aminopropyl)methacrylamide)/poly(methacrylic acid) (PVCL/PMAA) multilayer films cross-linked with glutaraldehyde. We found that the presence of SO₄^2-, H₂PO4^macr; and Cl^macr; decreased the phase transition temperature of PVCL hydrogel and suppressed its temperature-induced volume transitions due to decrease in LCST of the polymer. Br^macr; had no significant effect on the film properties at any investigated concentrations. In contrast, hydrogel swelling was increased in the presence of iodide at high concentration of ions; however, the shrinkage of the film was steadily decreasing with increasing of I^- concentration. Layer of gold nanoparticles was introduced into the hydrogel as optical markers to visualize swelling/shrinking behavior in the presence of ions. We believe that our findings provide new prospects for understanding the effect of Hofmeister anions on confined thin non-ionic polymeric hydrogels.

Liquid crystalline elastomers (LCEs) are polymeric networks that combine the elasticity of rubbers with the molecular orientability of low molar mass liquid crystals, which allows for their reversible deformation by external stimuli, such as temperature changes, magnetic or electric fields, or light irradiation. Additionally, when LCEs are mechanically deformed the network&’s constituent mesogenic molecules rearrange affecting the internal orientation causing fluctuations in physical properties. As such they are ideal candidates for applications in actuation, sensing, and smart substrates. Incorporation of external fillers with special features (e.g. sensitivity to light irradiation or electric fields) produces more efficient LCEs with responses to a wider range of stimuli. In this work, we report the preparation of magnetic sensitized poly(methylhydrosiloxane)-based nematic LCEs by incorporation of iron oxide nanoparticles with loadings of up to 0.5 wt.%, and their thermal, mechanical and magneto-mechanical characterization by differential scanning calorimetry, temperature-driven expansion/contraction experiments, extensional tests, and magnetic-driven actuation experiments. Both the glass and nematic-to-isotropic transition temperatures decrease to the same extent with particle addition. The reversible expansion upon cooling from 100°C to ambient temperature was reduced from 54% for the neat elastomer to 17% for the 0.5 wt% composite. Meanwhile, reversible contractions of up to 24% were observed with the application of alternating magnetic fields (AMFs) of up to ~48kA/m at 300 kHz. We confirmed that the contractions are due to temperature increase caused by heat dissipation from the nanoparticles. Finally, we were able to demonstrate that the inclusion of magnetic nanoparticles yields LCEs with adjustable thermo- and magneto-mechanical properties that can be tailored by changing the amount of particles embedded in the elastomeric matrix.

Poly(N-isopropylacrylamide) (PNIPAAm) is an ubiquitous stimuli-responsive material and has been used in many novel applications. In the present work, one of the facile methods of improving the pore size and response behavior of PNIPAAm based hydrogels has been studied, and its thermal and mechanical properties have been quantified and further compared with low porosity and slower responsive PNIPAAm hydrogels by utilizing different characterization techniques. Furthermore, in order to alter the transition temperature, both the faster and slower hydrogels were subjected to different qualities of media by introducing a co-solvent (methanol) and an anionic surfactant (sodium dodecyl sulfate). The alteration of the transition temperature, changes in the enthalpy release, and difference in the mechanical properties due to such addition were studied. The work enhances the present knowledge of both fast responsive and conventional PNIPAAm based hydrogels and promotes them to be more extensively utilized as multifunctional, advanced materials.

Dielectric elastomers exhibit high transverse and axial strain when subjected to an applied electric field. This electrically-driven actuation can be harnessed in a wide range of potential applications including artificial muscles, interactive touch-screen devices, deformable lens, and other optical devices. The realization of such devices is often limited by poor breakdown strength, high remnant strains, and inadequate repeatability of actuation. We recently fabricated and characterized a new class of multilayer dielectric elastomer films comprising alternating layers of two different polymers, at least one of which is an elastomer. The films discussed here contain THV (a PVDF terpolymer) and poly(Ethylene Octene) [EO] elastomer. The multilayer structure provides improved dielectric and electromechanical performance relative to monolithic films of THV or EO. These properties are controlled by the composition and the layer structure. For example, increasing the concentration of the elastomeric EO component increases the maximum axial strain (s_z). Layering EO with THV also increases the breakdown strength (E_B ~ 300 V/mu;m) relative to monolithic EO (E_B ~ 150 V/mu;m) or THV (E_B ~ 245 V/mu;m) control films. This enhancement in breakdown strength is consistent with a barrier effect that is also observed in multilayer polymer capacitor films. The increase in breakdown strength allows 512-layer 75 vol% EO / 25 vol% THV films to achieve maximum axial strains of s_z ~ 4%, higher than can be attained by either EO or THV films alone. In addition, layering reduces remnant strain and electromechanical hysteresis by limiting the effective field within the THV layers. The 75% EO/ 25% THV films show robust operational longevity with little loss in axial strain when subjected to repeated actuation at E_max = 250 V/mu;m (producing s_z = 2.2%). Under these conditions, we observe 3,000 consecutive actuation cycles with no electrical breakdown. In comparison, single component EO control films undergo electrical breakdown at this field and THV control films survive only a few hundred actuation cycles under these conditions. Finally, the effects of repeated actuation on the film structure were studied using dual beam Focused Ion Beam (FIB) / Scanning Electron Microscopy (SEM). This technique allows us to image the layer structure of both ‘as fabricated&’ films and those subjected to repeated actuation under an applied field. FIB/SEM is also used to image the layer structure after electrical breakdown, providing insight into breakdown mechanisms in multilayered elastomer films.

This research focuses on developing solid particles to serve as potential alternative dispersants in oil drilling, cleaning, and recovery. Here, we synthesized multifunctional microgel particles, containing both acrylic acid (AA) and N-[3-(dimethylamino)propyl] methacrylamide (DMAPMA), in a primarily N-isopropylacrylamide (NIPAm) network via surfactant free precipitation polymerization. These ionic microgel particles exhibit large size transition behaviors to environmental stimuli such as pH and temperature which, if needed, can be tuned to exhibit varying parabolic swelling/deswelling behaviors in response to pH. More importantly, we have investigated the use of these functionalized microgel particles for controlled adsorption and release of active species such as dioctyl sodium sulfocsuccinate (DOSS) and Triton X-100, into and from, the polyampholyte particles as a function of pH to engineer the viscoelasticity of oil-water interfaces.

Thermo-responsive hydrogels such as poly-N-isopropylacrylamide (PNIPAM) exhibit reversible swelling/shrinking properties, making them ideal candidates for controlled release applications such as drug delivery [1]. For practical applications, remote triggering of the hydrogels is desired, which is realized by heating magnetic nanoparticles/hydrogels composites by exposing them to external alternating radiofrequency (RF) magnetic field [2]. Literature survey shows that a detailed study of phase transitions in PNIPAM using remote heating of magnetite nanoparticles is absent. In this work, we present a systematic study on the factors that influence the lower critical solution temperature (LCST) of PNIPAM hydrogels during their RF heating using Fe₃O₄ nanoparticles. Preliminary studies showed the highest specific absorption rate (SAR) for 15 nm sized Fe₃O₄ nanoparticles, which monotonically decreased as the nanoparticle sizes increased to 20-30 nm. A series of PNIPAM solutions with varying concentrations of Fe₃O₄ nanoparticles were prepared and characterized using transmission electron microscopy, dynamic light scattering (DLS) and Raman spectroscopy. In-situ transmission measurements were used to determine the LCST of PNIPAM under various aqueous concentrations with dispersed Fe₃O₄ nanoparticles. A systematic decrease in the LCST from 34 0C to 31 0C was observed as the concentration of PNIPAM was increased from 0.2 wt. % to 1.2 wt. %, keeping the concentration of Fe₃O₄ nanoparticles constant. On the other hand, varying the concentrations of the nanoparticles did not drastically affect the LCSTs of PNIPAM solutions. However, increasing the basicity of the PNIPAM solutions by adding adjusted KOH pellets, showed a pronounced lowering of the LCST by 2-3 0C at all PNIPAM concentrations. The controlled remote tuning of the LCST in PNIPAM using Fe₃O₄ nanoparticles as reported here provides valuable information towards using these thermo-responsive polymers for targeted and controlled release in drug delivery. Detailed analysis of the optimized SAR of Fe₃O₄ nanoparticles and LCST of PNIPAM solutions will be presented and discussed for future applications.
[1]. D. Schmaljohann, Adv. Drug Delivery Rev., 2006, 58, 1655-1670.
[2]. L. B. Chen, F. Zhang and C. C. Wang, Small, 2009, 5, 621-628.

Mono-domain liquid crystal elastomers (LCEs) are new materials uniquely suitable for artificial muscles, as they undergo large reversible uniaxial shape changes, with strains of 20-500% and stresses of 10-100 kPa, falling exactly into the dynamic range of a muscle. LCEs exhibit little to no fatigue over thousands of actuation cycles. Their practical use has been limited, however, owing to the difficulty of synthesizing components and achieving consistent alignment during crosslinking across the whole material, and often a high nematic-isotropic phase transition temperature. The most widely-studied method for LC alignment involves mechanical stretching of the material during one of two crosslinking steps, which makes fabrication difficult to control and lending itself mainly to samples that can be easily grasped (with sizes of the order of mm). In this article, we describe a method of adapting the LCE synthesis to micro-scale objects, achieving monodomain alignment with a single crosslinking step, and lowering the cycling temperature. LCE precursor droplets are embedded in, and then stretched in a polymer matrix at high temperature. Confinement of the uniaxially stretched droplets maintains the alignment achieved during stretching, and allows us to eliminate one of the crosslinking steps and the variability associated with it. Adding a co-monomer during the polymerization leads to a lower nematic-to-isotropic transition temperature to 58 ^oC, significantly expanding the range of potential applications for these micro-muscles. We demonstrate reversible thermal switching of the micro-muscles in line with the largest strain changes observed for side-chain LCEs, and a DSC characterization of the material phase transitions. The method demonstrates the parallel fabrication of many micro-scale &’actuators&’, and is amenable to further scale-up and manufacturing.

We report on poly(methacryic acid) (PMAA) porous hydrogel microparticles of cubical and spherical shape which combine pH-triggered volume and size changes with controlled redox-degradation. Cubical and spherical hydrogels are obtained on porous sacrificial templates after cross-linking of PMAA layers within hydrogen-bonded multilayers of (PMAA/polyvinylpyrrolidone) (PMAA/PVPON) with cystamine and dissolving sacrificial inorganic cores. The produced hydrogels are able to maintain their three-dimensional structures in dry state. The swelling of multilayer hydrogel microparticles is controlled via reaction time with cystamine and its concentration. The disulfide links enable hydrogels with redox response and provide a rapid degradation of the hydrogels in the presence of cellular concentration of glutathione. The hydrogel particles take up doxorubicin and release it at lower pH values or upon particle degradation. We also discuss the stimuli-triggered doxorubicin release and shape-dependent cellular uptake of the cubical and spherical hydrogels. The hydrogel dually responsive particles presented in this work demonstrate a new approach to efficiently transport drug into cell and overcome drug resistance by rapid drug releasing and shape-regulated internalization.

Marine biofouling, the unwanted colonization micro-organisms in seawater, cost the shipping industry an estimated $60B annually. In this research, the anti-fouling properties of surface structured hydrogels are investigated along with the influence of autonomous external triggers (e.g. temperature or shear stress. The aim is to control the properties of the coatings in a responsive manner in order to reduce biofouling under all circumstances. The novel combination of using a thermo responsive hydrogel with a relief structure, that can be switched to change its properties, shows excellent potential as an anti-fouling coating for ships.
Surface relief structures are known to possess anti-fouling properties, if they are the right length scale for the specific organism. Unfortunately these structures can be easily damaged, specifically during cleaning. For this is would be preferred to switch the coating to a flat state during this process. Moreover, most organisms prefer either a hydrophilic or a hydrophobic surface, so making an anti-fouling coating only hydrophilic or only hydrophobic would not be sufficient. However it has been shown that if the surface energy of the surface changes (hydrophilic to hydrophobic or vice versa) the organisms detach.
The hydrogel coatings are based on a thermal responsive poly(N-Isopropylacrylamide) (PNIPAm) polymer. PNIPAm exhibits a lower critical solution temperature (LCST) at which the polymer changes from an extended chain conformation into a collapsed chain. This feature allows reversible switching from a swollen state (hydrophilic) to a collapsed state (hydrophobic).
Surface relief structures are made by photoembossing. To this end, the polymer film is illuminated with UV light through a contact mask to activate a photoinitiator in the illuminated areas. Subsequently, the polymer film is heated above its glass transition temperature to mobilize the monomers. The monomers will diffuse to the illuminated areas due to polymerization induced diffusion, which also locally increases in the height of the polymer film at the illuminated areas. A multifunctional monomer is used and, therefore, a high crosslink density is generated in the illuminated areas.
We have shown that relief structures with a pitch between 5-500 µm can be generated. The relief structures switch to a (close to) flat state at temperatures below the LCST. It is also shown that this switching is reversible and that it is accompanied by a significant change in surface energy. Therefore we believe that the used hydrogel coating will be a promising alternative for current anti-fouling coatings.

Bidirectional shape-memory polymer networks have been introduced recently as materials capable of a reversible active movement.^{1, 2} The bidirectional shape-memory effect (rbSME) was realized in polymer networks providing crystallizable domains, which were capable to act as actuator domains (AD) and as shifting-geometry determining domains (SGDs). This morphology could be achieved by polymer networks providing two different type of domains with distinct T_ms or by semi-crystalline networks having a broad melting range (ΔT_m). In the latter case the assignment to the ADs and SGDs can be made by a thermomechanical programing procedure.¹ Here, we explored whether polymer networks with a broad ΔT_m could be realized by copolymerization of ε-caprolactone based oligomers of different M_w to enable a tailorable rbSME around body temperature. Two series of copolymer networks (cPCLBA) of the mixture of PCL with different weight contents of n-butyl acrylate (BA) were synthesized via photo polymerization. The first series of polymer networks cPCL(2, 16)BA contained a mixture of PCL with M_w of 2 kDa and 16 kDa, while the second series networks of cPCL(3, 4, 8)BA included a mixture of chain lengths of 3, 4, and 8 kDa. Differential scanning calorimetry (DSC) revealed a broad ΔT_m for both series networks ranging from -10 °C to 50 °C for networks cPCL(2, 16)BA and from -5 °C to 45 °C for networks cPCL(3, 4, 8)BA. In both systems an increase of the BA weight content decreased the degree of crystallinity. The rbSME of two networks of cPCLBA with 25 wt% BA having the highest degree of crystallinity were quantified in cyclic thermomechanical experiments, which consisted of a one-step initial programming by stretching to ε_prog = 40% at 60 °C cooling to T_low = 0 °C and heating to the separation temperature (T_sep) again. In the subsequent reversibility cycles the reversible strains (ε_rev) were investigated as a function of T_sep ranging from 31 °C to 40 °C. The network cPCL(2, 16)BA exhibited ε_rev ranging from 1% to 6%, while the network cPCL(3, 4, 8)BA provided the ε_rev from 4% to 16% under the same conditions, which were attributed to the contribution of the crystallization kinetics for the different chain lengths of PCL in networks. Such networks having tunable rbSME around body temperature would be candidates for potential applications such as smart implants and medical instruments.
References
1. M. Behl, K. Kratz, U. Noechel, T. Sauter and A. Lendlein, Proceedings of the National Academy of Sciences U.S.A., 2013, 110 (31), 12555-12559.
2. M. Behl, K. Kratz, J. Zotzmann, U. Nöchel and A. Lendlein, Advanced Materials, 2013, 25, 4466-4469.

We have designed a novel class of nanocomposite hydrogel inks suitable for 4D printing. Akin to biological systems, such as plants, these structures undergo controlled swelling and shrinkage to realize complex, time-dependent changes in shape upon printing. By combining a multimaterial 3D printer and stimuli-responsive inks, highly programmable, shape-changing hydrogel structures can be patterned. These biomimetic composites may find potential application as biomedical devices, tissue engineering scaffolds, smart textiles, and well beyond.

Regenerative medicine has been pointed one of the most promising field for the treatment of several human diseases, with special attention on the development of biomaterials with similar properties of the human living tissues. Amongst the endeavors to develop new biomaterials, the injectable thermally-responsive polymers have been showed as an interesting material in several studies, inasmuch as they can be applied in minimally invasive surgeries and used in the repairing of spinal cord injuries, cartilage and others. For these applications, the new material must be biocompatible, moldable, with suitable mechanical properties, biodegradable and adhesive. Combining these characteristics, the poly(N-vinylcaprolactam) (PNVCL) has attracted great attention mainly because it is a thermosensitive smart polymer and undergoes a coil-globule transition in aqueous solution at specific temperature (lower critical solution temperature, LCST), as well as it is non-toxic and biocompatible. Aiming to improve the bioproperties, a promising quest is the development of nanocomposites (NC&’s), which can associate the polymer features with the mechanical strength of bioactive ceramics, like mesoporous silica nanofibers, which could improve the mechanical properties and control the delivery process. In face of that, this study pursues to provide some highlights by the study of PNVCL-SiO₂ biocomposites. Hence, in this research, hybrid mesoporous SiO₂ fibers were synthesized by one-pot sol-gel technique and modified with the (3-aminopropyl)triethoxysilane coupling agent. Scanning electron microscopy images showed SiO₂ nanofibers with narrow size distribution and well-defined shapes with dimensions (width and length) about 60 nm and 300 nm respectively, whilst the X-ray diffraction and transmission electron microscopy images revealed nanoparticles with long range ordering of the pores in a hexagonal mesostructure. Because of that, these fibers are an interesting candidate for drug encapsulation and release. The NC&’s were prepared by in situ polymerization of NVCL monomer and SiO₂ nanofibers (1%w/w) with a radical initiator (70 ^oC/4 h in dimethyl sulfoxide). The monomer polymerization could be proved by nuclear magnetic resonance (¹³C,¹H), infrared and Raman spectroscopies. The LCST behaviors were determined using UV-Vis transmission measurements of samples with 1% w/w in aqueous solution and revealed similar values for both polymer and nanocomposites (35°C) (although the PNVCL exhibited a faster decline during the time). Besides, the differential scanning calorimeter analysis showed an increase of 12°C in the glass transition temperature for the NC (compared with the PNVCL), which infers a reduction in polymeric chains mobility. These results evidence the mesoporous silica nanofibers can change the thermal properties of NC&’s and retain the thermo-response of the pure polymer, which are substantial features for drug delivery and injectable polymers applications.

Hydrogels are a sort of soft matter usually formed by cross-linked hydrophilic oligomers. Depending on the molecular weight between cross link points, hydrogels exhibit ability to absorb a given amount of water and swell. The properties of a hydrogel are usually determined by the chemical properties of their constituent macromolecules. However, a group of hydrogels, called “smart hydrogels,” changes properties in response to environmental changes or external stimuli. Poly-N-isopropylacrylamide (PNIPAm ) is a responsive hydrogel which have attracted considerable attention in construction of smart hydrogels because is hydrophilic, temperature and PH-responsive and can be highly programmable. Polyhedral oligosisquioxane (POSS) are nanoscale sized molecules decorated with organic groups thus being soluble in an organic polymer matrix. The incorporation of POSS into PNIPAm&’s backbone produces hybrid hydrogels where no chemical crosslink was needed. That is, the bulkiness of POSS prevents large scale chain movements (i.e., reptation) and therefore generates physical crosslinks and hydrogel behavior. Moreover, the nanosilicate cages endow the hydrogel with improved mechanical properties, yet temperature response is still maintained. Therefore, POSS tunes the elastic modulus, swelling behavior and lower critical solution temperature of POSS-PNIPAm hydrogels.

Ultra-drawn high molecular weight polymer films can potentially have very high in-plane thermal conductivity which would enable the use of polymers in a variety of thermal management applications, like electronics packaging, flexible electronics and heat exchanger systems. However, the measurement of in-plane thermal conductivity is very challenging due to the small heat flow through small cross-sectional area of thin films and large radiation and convection heat loss from surfaces. Several established methods do exist, like 3omega; method, general electro-thermal method, AC calorimetry method, transient thermal grating, or microbridge. However, these methods are either for solid films deposited on a substrate, or require smooth surface or complicate nanofabrication. In this work, we developed a system based on the Angstrom method, which was originally used to measure thermal conductivity of rod-like or thick slab materials, to measure the in-plane thermal conductivity of freestanding film like the ultra-high molecular weight polyethylene (UHMWPE) film with different draw ratios. There are three thin wires in parallel: one copper wire as a heater and two thermocouple wires with conjunction bead in center as two temperature sensors. The freestanding film is suspended upon the three wires. By applying a modulated current or voltage to the copper wire heater, a temperature wave is formed on the heater and transport along the in-plane direction of the film. The two thermocouples detect the temperature waves with different amplitudes and phases at different positions, which are used to obtain the thermal conductivity of the films. Measurements on plastic wrap, cover glass, stainless steel, Al foil, stretched paraffin film and ultra-drawn UHMWPE film are demonstrated. More discussions will be presented including sensitivity on temperature amplitude ratio and time lag, uncertainty from the thermocouple, air conduction and convection and radiation among wires. This work is supported by DOE DE-EE0005756.

Various way of catalysis using photo or electro-catalysts such as TiO₂, ZnO, and MoS₂ etc. have been researched for a long time to remove the organic contaminants most efficiently in the aqueous system. However, in order to apply these catalysts to the practical industry or some parts of human life, using light or electricity as fundamental source of power is inevitable to activate them, which makes limitation in an absence of light or in cost, respectively.
Here, we demonstrated the catalytic activity of various catalysts hybridized with piezoelectric potential inducing PVDF-TrFE polymer, which can play a role of the power source by itself while mechanically bending, so as to drive the catalysis possible in an absent of the light without any electrical power supply. In our experimental bending test, TiO₂-P25/PVDF-TrFE showed the decomposition of the Rhodamine B (commonly used as organic contaminants) perfectly in 6 hours in dark system and even more, the catalytic efficiency was 33% higher than photo-catalytic one using UV-light (365nm) at the same conditions.
The finding of this novel strategic method could be a new trend for practical and powerful applications in water purification system.

Nature has provided great inspirations for the development of artificial soft materials (e.g., hydrogels) that produce complex 3D structures. Current strategies in synthesizing self-shaping hydrogels mainly focus on inherently encoding hydrogels with information that enables the generation of one or few types of shapes in response to stimuli^[1,2]. However, these encoded hydrogels can only take limited (usually less than three) types of shapes. We have developed a chemically uniform 2D hybrid hydrogel sheet that can take almost unlimited arbitrary 3D shapes. Our strategy relies on the modulation of localized planar stresses induced by the localized photothermal heating of the hydrogel sheet upon the irradiation of near infrared (NIR) light. The hybrid hydrogel sheet is made from thermo-responsive poly(N-isopropyl acrylamide) hydrogel with silver nanoparticles (AgNPs) embedded inside. The irradiation of the hybrid hydrogel sheet with NIR light induces localized heating arising from the photothermal effect of AgNPs, thus controlling shape transformations of the hydrogel sheet. By properly adjusting the exposure area of the hydrogel, we have achieved multiple 3D shapes from one single hydrogel sheet. Representative shapes include such as helical (right and left helixes), saddle-like, boat-like, and hoof-like structures. SEM, TEM, UV-VIS, FTIR and photothermal imaging techniques are used to characterize our composite hydrogel. Computer simulation was performed to understand the heat dissipation within the hydrogel and the resulting mechanical deformation of the hydrogel sheet. We expect that our hydrogel may find applications in such as soft actuators, artificial muscles, and drug delivery.
[1] H. Therien-Aubin, Z. L. Wu, Z. H. Nie, E. Kumacheva, J. Am. Chem. Soc.2013, 135, 4834minus;4839.
[2] Z. L. Wu, M. Moshe, J. Greener, H. Therien-Aubin, Z. H. Nie, E. Sharon, E. Kumacheva, Nat.Commun.2013, 4, 1586.

Conductive hearing loss (CHL) due to the disarticulation of the ossicular chain may result from skull fracture, aseptic necrosis during acute otitis media, or the erosive action of cholesteatoma in chronic otitis media. In the United States, cholesteatoma alone advances to severe CHL in approximately 3 children per 100,000 annually. The incidence of the disorder increases with age, reaching as high as 13 individuals per 100,000. The loss of middle ear function at a young age, even when it is limited to one ear, can produce irreversible deficits in hearing and language. The ossicular chain is reconstructed by placing a titanium prosthesis across the gap between the remaining ossicles. In lieu of quantitative feedback, however, the surgeon is forced to rely on “feel.” Even in experienced hands, this intuitive approach leads to sub-optimal outcomes in over 30% of middle ear surgeries. The persistence of significant CHL is further exacerbated by a shortage of surgeons who feel insufficiently experienced to offer consistent surgical results.
Here, we introduce a smart implant that can predict the efficiency of middle ear transmission to ensure the optimal positioning of middle ear prosthetics to overcome CHL with greater consistency. This new technology is based on the recent discovery of an auditory force sensor (AFS) that can be seamlessly integrated with existing middle ear prostheses. The AFS is created from a polymeric piezoelectric composite material with transduction properties that accommodate the precise measurement of the middle ear transfer function. We envision that target specifications for each metric will provide immediate feedback during surgical placement to standardize technical performance and outcomes. The major innovation of this technology is its ability to measure frequency-specific transmission across the reconstructed middle ear making it possible to adjust prosthesis placement and mechanics until functional capacity is optimized.

Supramolecular block copolymers, SBCPs, which are the supramolecular analog of covalently-bonded block copolymers, consist of individual polymer blocks connected by non-covalent bonds. Most of the research concerning supramolecular block copolymers has focused on hydrogen bonding or metal-ligand coordination for the supramolecular bonds. Ionic bonds, however, are stronger and less-directional compared to other physical interactions, and Coulombic interactions ionic interactions are easily tunable through the choice of anion (e.g. sulfonate vs. carboxylate) and cation (e.g. primary or secondary amine, quaternary ammonium). Yet the use of ionic bonds to build block copolymer structures had been relatively small.
This paper describes the synthesis of a polystyrene-polyisobutylene supramolecular multiblock copolymer (SMBCP) formed by ionic bonds between two telechelic oligomers, α,omega;-sulfonated polystyrene, HO₃S-PS-SO₃H (sPSs), and α,omega;-amino-polyisobutylene, H₂N-PIB-NH₂ (nPIBn). The sPSs and nPIBn telechelic oligomers were synthesized by RAFT and cationic polymerization, respectively.¹ Ionic bonds formed due to proton transfer from the sulfonic acid groups to the amine groups. The oligomeric building blocks were immiscible and individually had poor mechanical properties, but the resulting SMBCP formed free-standing flexible films with a highly ordered lamellar structure. The SMBCP exhibited a modulus of 90 MPa, a yield point at 4% strain and toughness of 15 MJ/m³.
The ionic bonds and the block structure persisted to the decomposition temperature of the ion pairs at high temperature, i.e. ~195°C. A reversible order-disorder transition occurred between 190°C and 210°C,. The SMBCP melt was viscoelastic and shear-thinning at high non-linear strains, but the viscosity and elasticity completely recovered when the strain was reduced to within the linear response region.
This SMBCP prepared demonstrates the efficacy of simple, strong ionic interactions for constructing supramolecular block copolymers. This work also showed that sulfonated telechelics may be prepared by RAFT polymerization, which is much simpler than the more conventional anionic polymerization usually used for such telechelic polymers.
Acknowledgment. This work was supported by grants from the Chemical, Bioengineering, Environmental and Transport Systems Program (CBET-1066517), the Polymer Program (DMR-1309853) of the National Science Foundation, the U.S. Army Research Office under grant no. W911NF-07-1-0452 Ionic Liquids in Electro-Active Devices (ILEAD) MURI and the Nanotechnology Institute under grant no. NTI 1001-03, .and the Office of Naval Research and Northrop Grummund (Award No. N00014-07-1057).
1. Zhang, L.; Kucera, L. R.; Ummadisetty, S.; Nykaza, J. R.; Elabd, Y. A.; Sotrey, R. F.; Cavicchi, K. A.; Weiss, R. A. Macromolecules, in press.

A challenge in stimuli-sensitive hydrogels e.g. shape-memory hydrogels (SMHGs) is their dimensional stability during and after the shape shifting. We explored, whether active hydrogels can be designed by incorporating cyrstallizable oligomeric side chains into hydrophilic polymer networks based on N-vinyl-2-pyrrolidone (NVP) crosslinked with oligo(ethylene glycol)dimethacrylate (OEGDMA, M_n = 370 gmiddot;mol^-1). Monofunctionalized oligo(omega;-pentadecalactone) (OPDL, M_n = 2,900 gmiddot;mol^-1, T_m = 89 °C) or monofunctional oligotetrahydrofuran (OTHF, M_n = 7,400 gmiddot;mol^-1, T_m = 29 °C) were selected to provide the grafted oligomeric chains aggregating to form switching domains.^[1,2] In this way the swelling capacity of the DSHGs was almost independent from temperature. Furthermore, the transition temperature Tshy;_trans of the DSHGs depended on the oligomer selected and especially in the case of the OTHF was a function of the Mshy;_n of the oligomers. An initial biological evaluation revealed these DSHGs biocompatible. In conclusion these DSHGs display an interesting material platform for the design of biocompatible, stimuli-sensitive materials capable of on demand shape changes.
References
[1] M. Balk, M. Behl, U. Nöchel, A. Lendlein, Macromol. Mater. Eng.2012, 12, 1184-1192.
[2] M. Balk, M. Behl, U. Nöchel, A. Lendlein, Macromol. Symp.2014, in print.

The synthesis of biologically-inspired macromolecules with defined sequence, narrow dispersity, unique structural and self-assembly properties has large potential ranging from biomedical applications such as nanocarriers for medical therapeutics, to non-biological nanotechnology applications such as DNA-template scaffolds.
Here we report our work that uses a unique DNA polymerase, terminal deoxynucleotidyl transferase (TdT), to polymerize high molecular weight polynucleotides with versatile functionalities. This is achieved by using specific oligonucleotide initiators and incorporating functionalized nucleotides into the growing polynucleotide chains. By controlling the combination of initiator and the choice of nucleotides, we are able to create various polynucleotide architectures, including homo-polynucleotides, co-polynucleotides and diblock co-polynucleotides. The range of polynucleotide architectures can be harnessed to induce polynucleotide self-assembly into multifunctional micellar structures in solution or into network structures on surfaces.
In solution, by tuning the relative length of hydrophilic to hydrophobic block lengths in solution, we are able to manipulate the micellar morphologies from star-like to crew-cut micelles. On surface, we employ DNA&’s inherent molecular recognition fidelity to create oriented, supramolecular polynucleotide networks on surfaces that will be utilized as DNA scaffolds (1nm in width) for metal nanowire formation over a large area (1 × 1 cm²). We will also report on the reaction kinetics of our polymerization approach, which follows that of a controlled condensation polymerization.

Sequence-defined polymers, epitomized in nature by polypeptides and poly(nucleic acids), are polymers composed of a multiplicity of monomers, each monomer distinguished from another by having a different side chain, and the various monomers are sequenced into a polymer in a predetermined order. These are distinguished from random copolymers. In nature, sequence-defined polymers create biomaterials, encode information, perform biocatalysis, participate in molecular recognition, and shuttle species across membranes. To date the vast majority of synthetic sequence-defined polymers are either laboratory examples of the natural sequence-defined biopolymers, or close analogs based on similar structural units and bond-forming reactions. For example, peptides, pseudopeptides, and peptoids all rely on amino acid structures and peptide bonds.
In this presentation we will introduce and describe a new class of synthetic sequence-defined polymers whose architecture does not involve peptide bonds. The chemistry behind the architecture provides facile approaches for the incorporation of side-chains as "R-groups" into the monomer structures, such that diverse monomers can be produced. These monomer structures can be assembled into polymer chains in predetermined order to create sequence-defined polymers. The synthesis can be carried out either 1) using protected monomers appended to a growing polymer chain, deprotecting the terminus of the chain before each monomer addition, or 2) assembled by a submonomer synthesis approach that does not require monomer protection or deprotection steps. We will describe the results of three polymer synthesis methods using these R-group substituted monomers: 1) batch synthesis of homopolymers, 2) solution phase synthesis by addition of one monomer at a time using deprotection steps, and 3) a solid phase method using a submonomer approach to create sequence-defined polymers.
In addition, we will show the results of molecular simulations of these new types of structures, which illustrate conformational order due to hydrogen bonding and other interactions that are suggestive of protein secondary structure. It is anticipated that side-chain functionality, self-organizing conformations, and intermolecular self-assembly of these sequence-defined soft polymer materials will lead to biomimetic functionality and applications.

Materials with bio-inspired attributes are excellent candidates for the development of new technologies. Manifested by the ability to respond to stimuli, bio-inspired properties not only extend materials lifetime, but may also minimize environmental footprint. Among particularly impressive properties of bio-inspired materials that recently received significant attention is the ability to self-repair. Recent studies have utilized a variety of non-covalent and covalent chemistries that have led to self-healing polymers. The main challenge is to generate polymer networks that exhibit high glass transition temperature (Tg) with remote self-repairing, triggered by electromagnetic radiation, electric and/or magnetic fields, and environmental/atmospheric changes. This presentation will focus on the recent advances in utilization of coordination chemistries in which catalysts may play a dual role; (1) catalyze crosslinking reactions forming thermosetting networks and (2) serve as self-repairing components. Covalent incorporation of chemically modified polysaccharides into crosslinked polyurethanes offers another opportunity. Upon mechanical damage, followed by UV light exposure, these networks exhibit self-repairing properties. Furthermore, when monosaccharide moieties are crosslinked, self-repairing is achieved in the presence of atmospheric carbon dioxide and water. Unlike plants, these networks require no photo-initiated reactions, thus are capable of repairs in darkness under atmospheric conditions. Physico-chemical processes responsible for this unique self-repair process involve physical diffusion of cleaved network components to damaged area, which lead to the formation of carbonate and urethane linkages.

This work investigates the design of self-healing materials combining supramolecular chemistry and the chemistry of epoxides. Supramolecular rubbers described so far, incorporating a large number of physical cross-links through cooperative hydrogen bonds display interesting self-healing properties. However, whenever these materials are not chemically crosslinked, they have only a limited solvent and creep resistance and when physical crosslinks are replaced by chemical ones, the self-healing ability decreases.^[1-3]
The idea of the work presented here is to devise a convergent chemical platform permitting to increase the number of chemical crosslinks in a controlled way without changing the concentration of H-bonding groups, in order to keep a high self-healing ability. To this end, the key point is to vary the average functionality of monomers by combining bifunctional and tetrafunctional epoxy resins.
Starting from a single reactive prepolymer, functionalized in a first step with a defined number of H-bonding groups, we prepared a series of networks. A range of formulations, presenting different ratios of diepoxide and tetraepoxide is presented; the curing process as well as the thermo-mechanical properties of the cured materials were investigated. The occurrence of gelation was studied through solubility test and rheological analysis and compared to theoretical predictions. In addition, the self-healing efficiency was evaluated by means of tensile tests on virgin and after-cut materials.
The introduction of the tetrafunctional epoxide is observed to give rise to gelled materials and to increase the rigidity and tensile strength of the systems whereas the glass transition temperature, T_g remains almost constant. High self-healing efficiencies were observed for all materials, complete recovery after 24 hour of self-healing was obtained for crosslinked materials combining a high density of H-bonding group and low gel fraction.
[1] D. Montarnal, F. Tournilhac, M. Hidalgo, J.-L. Couturier and L. Leibler, J. Am. Chem. Soc., 131, 7966 (2009)
[2] D. Montarnal, F. Tournilhac, M. Hidalgo and L. Leibler, J. Polym. Sci. A: Polym. Chem.,48, 1133 (2010)
[3] S.P. Khor , R.J. Varley, S.Z. Shen, Q. Yuan, J. Appl. Polym. Sci.128, 3743-3750 (2013)

Self-healing materials have the ability to repair or prevent further damage autonomously, where and when it occurs. A successful strategy for designing self-healing materials relies on microencapsulation of liquid healing agents which are dispersed throughout a bulk polymer or coating. Here we explore the use of electrospun core-shell fibers to sequester healing chemistry for protective coatings. In coaxial electrospinning, two immiscible liquids are pumped through the inner (self-protective core) and outer (polymer shell wall) coaxial needles. A high voltage is applied on the needle tips to electrostatically draw out core-shell fibers (submicron size in diameter).
We have developed a polysiloxane based coating for steel containing two types of core-shell fibers. Fiber type A contains a stoichiometric mixture of low molecular weight silanol terminated poly(dimethylsiloxane) (PDMS) with a poly(diethoxysiloxane) crosslinker and fiber type B contains a crosslinking initiator, with the polymer shell of poly(vinyl alcohol) for both fiber types. The electrospun fiber layers are then sprayed with a silicone conformal coating to bind the fibers to the steel substrate to produce a conformal coating. When the coating is mechanically damaged, the two fiber types release their liquid core materials to fill the damaged region, crosslink, and restore the protective coating layer. Characterization of fibers and coating include SEM, TEM, confocal fluorescence microscopy, and FTIR. Development of new coatings synthesized by core-shell electrospinning will provide corrosion protection to metals, thus increasing material lifetime and performance.

The regeneration of damaged tissue is common in biological systems. Vascular networks enable the regrowth of living structures by supplying nutrients and oxygen to cells near the injury. Although synthetic vascular materials have been developed to achieve self-healing, early work focused mainly on rebonding internal cracks and did not demonstrate the ability to regenerate lost mass. Large, open damage volumes are problematic for vascular systems because healing agents can “bleed out” from the damaged region due to forces such as gravity and surface tension.
Here, we present a microvascular polymer that restores large-scale damage in a process inspired by biological regeneration. Two adjacent vascular networks contain separate components of a novel 2-part healing chemistry. Damage-induced rupture of the vascular networks triggers delivery of a two-part healing chemistry to the damage site where mixing occurs. Mixing initiates two chemical reactions that progress at different timescales. The first reaction causes rapid gelation (~30 s) of the liquid healing agent and aids in retention of healing agents within the damage volume. Healing agents fill the damage volume by an accretive process where liquids are deposited onto the gel scaffold in cycles until the damage volume is recovered. A second polymerization reaction occurs on a much longer timescale (hours) and converts the soft gel into a structural polymer to restore the material&’s original mechanical performance.
We investigate the effects of healing agent delivery, sample configuration, surface energy, and vascular density on the maximum fill size of damage in thin epoxy sheets. Through careful selection of sample design and delivery schedule, we achieve a maximum recoverable diameter of 11.2 mm for through-thickness cylindrical defects. The performance of our system constitutes a 196% increase in recovered damage area over non-gelling controls.

Thin-film pressure sensors based on elastomers have required either foams or microstructuring. Solid films of elastomer have not been used due to low sensitivities mostly due to relatively high moduli on the order of megapascals. However, solid elastomeric films are more easily incorporated into electronics, are more scalable and can be transparent. Here, we demonstrate elastomers with Young&’s moduli on the order of 1 kPa while maintaining elastic recovery. Typically, materials with kPa moduli are viscoelastic. Within a pressure sensor, a viscoelastic material will have a substantial hysteresis and will recover from pressure slowly and incompletely. Off-stoichiometry thiol-click chemistry with thiol-functionalized polydimethylsilane (PDMS) and vinyl-terminated PDMS oligomers is used to form elastomers with low crosslink densities and long, flexible side chains. These side chains plasticize the elastomer, leading to a much smaller Young&’s modulus and helping to maintain the elastic behavior. These elastomers are transparent, ultrasoft, and have little to no hysteresis in compression cycles, indicating mostly elastic behavior.
Pressure sensors using these elastomers are made by depositing electrodes onto films with thicknesses below 100 nanometers. The thin films are made by diluting the PDMS oligomers into a good solvent and rod coating the solutions onto glass. The resulting pressure sensors act as variable resistors. With the application of pressure and voltage, the film is compressed and current flows between the electrodes. For 2 mm x 2 mm pressure sensing pixels and an applied voltage of 1V, the current increases from a picoamp baseline to 10&’s of picoamps to nanoamps depending on the electrode design and the amount of applied pressure from 1 g to 1 kg of force. This range of sensitivity matches that of finger pressure, which makes these sensors suitable for pressure-sensitive touchscreens. These pressure sensors are incorporated into a matrix-addressable array by using a transistor array with the variable resistors in series with the drain and the drain current is measured. When using transparent electrodes, these arrays are transparent, low-power, highly sensitive and have high 2-dimensional spatial resolution. This allows these pressure sensor arrays to be used in many applications including pressure-sensitive, multi-touch touchscreens.

Mechanoresponsive polymers hold great technological potential in drug delivery, ‘smart&’ optical systems and microelectromechanical systems. Unfortunately, limitations include (i) hysteresis and fatigue - e.g. when the response involves large-scale molecular rearrangements, as is the case with order-to-disorder transitions, critical phase transitions, or melting and glass transitions, or (ii) the need for high-energy photons that are damaging and/or too readily attenuated - e.g. when the response is a cis-trans isomerization of stilbene or azobenzene moieties triggered by ultraviolet light.
Recently, a new class of polymers that contains the unit of dibenzocyclooctadiene (DBCOD), a flexible cyclooctane group connecting two rigid phenyl rings, can generate an anomalous giant mechanical contraction, -2300 ppm/K.¹ More impressively, this giant contraction is completely reversible in response to low-energy heating or NIR photons. The unique advantages of the material include:
Low energy: It requires less than one-third of the energy needed for the photoisomerization of azobenzene and thus enables remote NIR actuation for biological applications;
Completely reversible: No signs of fatigue or failure have been observed after extended cycling. This is in stark contrast to conventional systems that employ melting, glass transitions, or order-to-disorder transitions (e.g. liquid crystals);
High output: Due to the deep penetration of low-energy NIR stimulation, the entire depth of a sample can be stimulated, thus has the potential to deliver considerably higher conversion efficiency and greater mechanical energy output.
Mechanical characterization, calorimetry, spectroscopic analysis and density-functional theory calculations all point to a conformational change of the DBCOD moiety, from the thermodynamic global energy minimum (twist-boat) to a local minimum (chair), as the origin of this abnormally large thermal strain.
Incorporation of few-walled carbon nanotubes (FWCNTs) into the films increases the mechanical stiffness twofold, and dramatically increases the NIR-induced contraction strain up to a factor of nearly 24 at the optimal FWCNT concentration of ~ 3 wt%.²
The DBCOD-containing polymers offer a new pathway to create macromolecular switches and motors, and to design novel systems for thermal energy storage and conversion as well as zero thermal expansion polymers.
[1] X. Shen, C. Viney, E.R. Johnson, C.C. Wang and J.Q. Lu. Nature Chemistry 5, 1035-1041 (2013).
[2] X. Shen, C. Viney, C.C. Wang and J.Q. Lu. Adv. Funct. Mater. 24, 77-85 (2014).

The elastic and dielectric properties of poly-n-isopropyl-acrylamide (PNIPAM) polymer network can be modified due to the volumetric phase transition induced by the change in its temperature. PNIPAM based polymer network contains 95-99% of water and is therefore ideally suited for the design of underwater acoustic meta-material systems. The volumetric phase transition in PNIPAM is abrupt and occurs within 1^OC change in temperature around 32-34 ^OC. The temperature change in the polymer can be induced by an external stimulus, which can be through physical contact such as thermal or electrical stimulation [1]. Non-evasive mode of external stimulation such as magnetic [2], optical [3] or electromagnetic (EM) mode is more attractive due to its adiabatic process of heat transfer in the hydrogel. The external stimulation can be made efficient by incorporating magnetic or dielectric nanoparticles into the polymer network. The alternate way is to control the frequency and power of the stimulating source to optimize the dissipation within the polymer network.
Our objective was to control acoustic wave-propagation through a medium using EM stimulus. Direct measurement shows that the velocity of the ultrasonic waves through the polymer is slower than its velocity through water [4]. It results in a difference in wave propagation through the polymer below and above the phase transition temperature [4]. The dielectric properties of the PNIPAM have also been measured to optimize the response of the polymer to the electromagnetic radiation. Based on the fundamental elastic response of PNIPAM to EM waves, we have fabricated periodic phononic crystal (PhC) structures with transmission bandwidth in the ultrasonic frequency range for potential biomedical application. The PhC structures are embedded with the hydrogel PNIPAM network and can be controlled using EM stimuli such as infrared (IR) or radio-frequency (RF) radiation. The absorption of far-IR light by the polymer results in volumetric phase transition in the PNIPAM matrix. Ultrasonic transducers were used under water as source and receiver for the appropriate impedance matching of the hydrogel filled PhC structures. By controlling the concentration of the polymer in the hydrogel network and the dimension of the PhC structure, the efficiency of the remotely modulated structure can be controlled. We demonstrate IR light stimulated ultrasonic filters with a modulation depth of 95%. [5] The novel polymer based PhC structure opens up a new class of acousto-optic device for ultrasonic applications.
[1] B. Garner, T. Cai, Z. Hu., A. Neogi, Optics Exp. 16, 19410 (2008)
[2] S. Ghosh, Y. Chao, T. Cai, Z. Hu, A. Neogi, J. Phys. D: Appl. Phys. 42, 135501 (2009).
[3] B. Garner, T. Cai, M. Kim, Z. Hu, A. Neogi, Appl. Phy. Exp., 2, 075001 (2009).
[4] E. Walker, D. Reyes, A. Krokhin, A. Neogi, Ultrasonics, 54, 1337 (2014)
[5] E. Walker, D. Reyes, A. Krokhin, A. Neogi, Appl. Phys. Lett. (2014) [In press]

Ionic Polymer actuators are a class of soft material which produces large impressive bending displacement under low voltage.
Their soft mechanical properties make them the candidate of choice for delicate manipulations of fragile objects or in mechanically sensitive medium (biomedical and bio-mimicking devices).
Memory and physical movement are the leading characteristics of intelligent behaviour in living systems. Recent developments in polymer actuators have achieved reversible muscle-like movements with a variety of mechanisms and stimuli.¹ One way to make them “smarter” is to incorporate memory of environmental history and previous actuator states into the material itself.
In 2010, T. Xie² showed that a multi-temperature shape memory effect (SME) is present in single broad glass transition in Nafion, and J. Rossiter et al.³ showed in 2012 that this effect is still present in IPMCs. Adapting the synthesis of the IPMCs to get thinner electrodes, we have been able to combine high elongation programing multi-temperature shape memory effect with the ionic actuation functions of IPMCs.⁴ Studying these properties, we discovered what we called electro mechanical memory.
Electro-mechanical memory material is an actuator whose ionic actuation response can be tuned or completely switched off by a mechanical programming, in a reversible fashion. This material combines functionalities of ionic actuators with those of a shape memory polymer. As shown if the figure 1, the temperature memory effect can also be used to store at two different temperatures two different shapes and actuation responses.
The material is capable of bending motions at low voltage, shape-memory actuation to 100 % strain for programming/recovery in the 60-110°C temperature range. The ionic actuation amplitude decreases linearly with strain up to 70 %, and completely switches off for strain ge; 100%. The effect is reversible, however, and ionic actuation is restored upon shape-memory recovery of the material to strains le; 100%.
The incorporation of a large shape memory effect in ionic actuators will lead to the fabrication of smarter life-like materials and devices. It will also be shown briefly that combining these technologies can be realized with a large class of materials.
References
1. R. H. Baughmann, T. Mirfakhrai, and J. D. W. Madden, Mater. Today, 2007, 10, 30-38.
2. T. Xie, Nature, 2010, 464, 267-70
3. J. Rossiter, K. Takashima, and T. Mukai, Smart Mater. Struct., 2012, 21, 112002.
4. A. Khaldi, J.A. Elliott, S.K. Smoukov, Electro-Mechanical Actuator with Muscle Memory, (under review)

CO₂-sensitive polymers are stimuli-responsive materials that behaves as tunable self-assembling, phase transition manipulated by CO₂. The regulation process have great advantages, since it only involves CO₂ and inert gases, without the introduction of other impurities. We have synthesized an amidine-containing block copolymer and prepared a type of CO₂-responsive polymeric vesicles, which can reversibly self-expand and self-contract under CO₂ stimulation¹. We exploited a novel polymer bionanoreactor by tuning CO₂ concentration in polymer solution, duo to the vesicular membrane permeability can be modulated in a broad range. The vesicles act as nanoseparator in order to sieve different sized nanoparticles or guest molecules. They can be applied in nanoreactors to compartmentalize different enzymatic catalytic reactions². We prepared the CO₂-responsive polymer poly(N,N-diethylaminoethylmethacrylate) modified magnetic nanoparticles (Fe₃O₄@dye/SiO₂-PDEAEMA) to realize the reversible adsorption/release of protein just by bubbling CO₂ and N₂ alternately³. We have also develop the smart nanostructured membranes capable of switching oil/water wettability using CO₂ as a green trigger via electrospinning.
References
[1] Q.Yan, R. Zhou, C.K. Fu, H.J. Zhang, Y.W. Yin, and J. Y.Yuan, Angew. Chem. Int. Ed. 50, 4923 (2011).
[2] Q.Yan, J. B.Wang, Y. W. Yin, and J. Y. Yuan, Angew. Chem. Int. Ed. 52, 5070 (2013)
[3] J. Guo, N.J. Wang, J.J. Wu, Q.Q.Ye, C. Zhang, X.H. Xing, and J.Y.Yuan, J. Mater. Chem. B, 2, 437 (2014)

Reducing anthropogenic carbon dioxide emissions is a major issue faced by many scientists today. Technologies aim at capturing CO₂, followed by sequestration or utilization. A key step for both sequestration and utilization approaches of CO₂ is controlled capture, storage and release. Here we report an efficient way of controlled capture and release of carbon dioxide using nature-inspired, cheap, abundant and non-toxic pigments, namely Quinacridone and Indigo. Electrochemically reduced electrodes with ~100nm-thick pigment films are capable of forming a Pigmentmiddot;carbonate salt in an organic electrolyte environment. Captured CO₂ can be released by electrochemical oxidation, or by heating. The uptake efficiency i.e. the amount of captured CO₂ in mmol per gram of capturing agent, was found to be 4.6mmol/g [1]. This value is among the highest reported uptake efficiency for any CO₂ capture technology. The energy efficiency of the capture/release cycle is 15 kJ/mol CO₂. One of the greatest advantages of the process is operation at room temperature. For comparison, the state-of-the-art aqueous amine industrial capture process has an uptake efficiency of ~8 mmol/g with process steps involving heating to >100 °C. We further report on synthetic manipulation of indigo and quinacridone pigments to obtain novel materials capable of efficient and improved long-term stable operation.
[1] D. H. Apaydin, E. D. G#322;owacki, E. Portenkirchner, N. S. Sariciftci Angew.Chem.Int.Ed.
2014 DOI: 10.1002/anie.201403618

The emerging field of CD_r polymers (polymers capable of Continuous Depolymerization mediated by a reaction based detection unit) represents a unique opportunity to develop materials that provide an amplified response to specific stimuli. The design of CD_r polymers features a thermodynamically unstable polymer capped with a stabilizing functionality chosen specifically to respond to a specific chemical or physical signal (i.e., the reaction based detection unit). When the signal of interest cleaves the bond between the polymer and the reaction based detection unit, the resulting species continuously and completely depolymerizes from head-to-tail. Thus, a single reaction between the signal and the detection units leads to the release of tens, hundreds, or even thousands of monomers, which can result in a massive change in properties if the polymer is incorporated into a material. The inherent amplification in the depolymerization mechanism of this class of polymer has the potential to drastically increase the rate of response in stimuli-responsive materials, as well as allowing for the development of plastics that are easily recycled.
Poly(phthalaldehyde) (PPA) and derivatives are a class of CD_r polymers that depolymerize to monomer completely in seconds to minutes in a variety of environments as a result of its exceptionally low ceiling temperature (T_c = -40 °C). This presentation will focus on the development of PPA and derivatives as CD_r polymers capable of providing an amplified response in a variety of settings. Specifically, we will describe the use of these polymers in responsive materials such as microcapsules and as reagents that provide an amplified and selective response in a quantitative analytical assay.

Responsive and reversibly actuating surfaces are intrinsic to natural systems and become a key requirement for advanced artificial materials and devices. Such dynamic “smart” materials found promising applications in biomedicine, microfluidics, microactuation systems, tissue engineering, sensors and optics.^1,2 Recently, we have developed reversible actuation of surface structures by combining a rigid, passive “bone” structural elements (e.g. polymer microposts) with a soft, active “muscle” component (stimuli responsive hydrogels).³ The swelling and contraction of the hydrogel upon application of various stimuli (pH, temperature) introduce forces on the microstructures and result in their fast and reversible reorientation from tilted to perpendicular to the surface. In this work, we present a novel dynamic hybrid system comprise of “skeletal” microstructures partially embedded into temperature responsive hydrogel loaded with gold nanorods (AuNR). AuNRs exhibit strong plasmon absorption tunable at near IR region and capable of efficient light to heat conversion upon irradiation at their resonance wavelength. Accordingly, the reversible actuation of microstructures can be achieved by alternating irradiation with near IR light through photothermally induced volume transition of the thermoresponsive hydrogel. This design allows remotely controlled spatiotemporal mechanical actuation of microstructured surfaces on sub-second timescales. The synthetic versatility and biocompatibility of these hybrid systems can find important applications in biomedical applications (cell stimulation), transport, and microfluidics and will lead to wide application in many other hydrogel systems for fabrication of smart dynamically responsive materials.
1. R.Geryak, V. V. Tsukruk, Soft Matter, 2014, 10, 1246-1263.
2. A.Grinthala, J. Aizenberg, Chem. Soc. Rev., 2013, 42, 7072-7085.
3. P. Kim, L. D. Zarzar, X. He, A. Grinthal, J. Aizenberg, Curr. Opin. Solid State Mater. Sci.,2011, 15, 236-245.

Catalysis is among the most important applications within the field of nanoscience [1]. The large surface area of nanoparticles qualifies them naturally to act either as heterogeneous promoters for catalytic reactions or as a support for homogeneous catalysts. Especially magnetic nanoparticles are meant to overcome the most tantalizing drawback in homogeneous catalysis, i.e. reliable separation and recycling of often toxic and expensive transition metal complexes for more sustainability in catalysis. Thus, they simultaneously comply with economical and ecological requirements [2].
We have synthesized highly ferromagnetic, thermoresponsive nanomagnets with a graphene coated cobalt metal core to which amphiphilic, thermoresponsive N-isopropylacrylamide (NIPAM) polymer branches were covalently attached [3]. This novel hybrid material could be further modified with a Pd-phosphine complex to catalyze Suzuki-Miyaura cross-coupling reactions. The heterogenized metal-complex acted as a ‘self-separating&’ catalyst. Thermally triggered switching of poly-NIPAM coated C/Co-nanoparticles in typical biphasic water/toluene reaction systems allowed for a temperature- controlled shift of the catalyst from the aqueous to organic phase and vice versa. This enabled the catalyst to switch in the organic layer at reaction temperature and to return into the aqueous layer once the reaction mixture was cooled (ambient temperature; magnetic removal and reuse of the catalyst). The immobilized catalyst was recycled from the aqueous phase by taking advantage of the magnetic cores and reused in ten iterative reaction cycles.
[1] A. Schaetz, O. Reiser, W.J. Stark, Chem. Eur. J., 2010, 16, 8950.
[2] R. N. Grass, E. K. Athanassiou, W. J. Stark, Angew. Chem., 2007, 119, 4996.
[3] M. Zeltner, A. Schaetz, M.L. Hefti, W.J. Stark, J. Mater. Chem., 2011, 21, 2991

Recent advances in the processing and understanding of neural data has led to a pressure for improvements in materials that are able to chronically interface with soft neural tissue. Traditional electrodes including those patterned on silicon or polyimide, are stiff enough for insertion. However, these materials are grossly mismatched in terms of modulus when compared to the tissues they stimulate and record from. Shape memory polymers (SMPs) have proven a more compatible substrate, leading to neural prosthetics that can both insert reliably while softening considerably after some time in vivo. A challenge with these systems however is the chronic lifespan of these devices, due to the hydrolytic instability of previously used constituent monomers. Now using a rigid aliphatic dithiol, a chronically stable substrate that exhibits the shape memory effect is described for use as an ultrasoft long-term or permanent platform for neural electrodes. A trifunctional thiol, tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate (TMICN), is substituted for an equivalently rigid dithiol, tricyclodecane dithiol (TCDDT), and added to a trifunctional alkene, 1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO). 2,2-Dimethoxy-2-phenylacetophenone (DMPA) was used as a photoinitiator to catalyze the thiol-ene ‘click&’ reaction between the comonomers. Using this system, an order of magnitude drop in rubbery modulus is shown from the 10MPa to 1MPa regime, allowing for substrates which more closely resemble the stiffness of the penetrated tissue. In addition to the modulus drop, the aliphatic nature of the dithiol allows for a decreased swelling of the overall network when tested in physiologic conditions (1x PBS, 37°C). Most importantly, due to the removal of the ester linkages in the main chain of the polymer, no hydrolytic degradation was observed in the network under accelerated aging conditions, leading to chronically stable electrode substrates. These results show the ultra-softening nature of the polymer composition TCDDT TATATO and the possibility of using this network as a substrate which more closely matches the stiffness of the physiology with which it interacts. Overall, these polymers show promise as a reliable substrate for neural interfaces which can maximize insertion success while minimizing scar-formation in vivo long-term.

Recently, materials that can convert electrical energy into mechanical work have drawn great attention. Applications in robotics, tactile or optical displays and microelectrochemical systems are currently investigated. Likewise, interest in actuators devices is increasing toward applications where low voltage and low weight properties are required. One way to achieve such prerequisites is to combine the mechanical and electronic properties of carbon nanotubes (CNTs) with the stability and conductivity of ionic liquids. Indeed, the CNTs can be dispersed in ionic liquids to form hybrid composites also named bucky gels, thanks to the non-covalent (π-π stacking and cation-π) interactions. These composites possess good electronic properties but often require the use of a polymeric support (such as PDVF) in order to enhance their mechanical and processability properties and to be eventually used, for example, in soft actuating applications. Many studies have been dedicated to understand and optimize the interactions between the ionic liquid and carbon nanotubes and their mechanical behavior (strain) in actuators devices.
However, up to now, only a few articles have proposed the use of poly(ionic liquid)s (PIL) as an alternative to ionic liquids for hybrid composites with carbon nanotubes Indeed, to the best of our knowledge, no studies were done on real actuating devices. To further understand the interaction between poly(ionic liquid)s and carbon nanotubes, we have investigated a series of composites. First, we prepared the poly(ionic liquid)s polymers by free-radical polymerization of the vinyl-imidazolium moiety. Then, we have focused our attention on the mechanical, thermal, electronic and 3-D organization properties of the resulting composites. Characterization techniques such as DSC, TGA, FTIR, RAMAN, SEM, XRD and XPS were used to provide us valuable fundamental information on the composites materials. As a second part of the study, we have investigated the effect of using cross-linked ionic polymers on the properties of the carbon nanotubes composites as well as using different counter ions (Br^-, BF₄^-, (CF₃SO₂)₂NH^-) while keeping the same imidazolium ring.
Finally, for the last part of this study, we focused our attention on testing the polymer-CNTs composites previously prepared as electrodes in actuators devices using the following 3 layers configuration: composite/PVDF:PIL/composite. Mechanical properties, displacement and force measurements will be shown and compared with standard systems (ionic liquids/carbon nanotubes composites) previously reported.

The search for smart materials, that respond to external stimuli by changes in shape or size, has recently attracted considerable attention from the material research community.
In addition to the obvious attractiveness of such studies in basic science, smart materials have many potential applications, including serving as key building blocks for production of new sensors, micro-robots, micro-pumps and actuators.
Some years ago, de Gennes proposed to use nematic liquid crystalline elastomers (LCEs) as artificial muscles(1). The idea was to make use of a conformational change of the polymer backbone at the nematic-to-isotropic phase transition as the motor for a macroscopic and reversible contraction. Based on de Gennes&’s idea, several thermo and photo-responsive nematic LCEs have been produced(2).
Making use of a soft lithography approach called replica molding, we succeeded in creating micron-sized responsive pillars made of nematic side-on LCEs and nematic main-chain LCEs(3,4). Using similar approaches, we have now developed microstructured nematic LCE surfaces with stimuli-dependent roughness, inducing switchable wetting properties(5,6).
Recent results will be presented related to these responsive surfaces, as well as the development of new nematic monomers and elastomers with low transition temperatures.
(1)P.-G. de Gennes, C. R. Acad. Sci. Paris, 281b, 101 (1975) ; C. R. Acad. Sci. Paris IIb, 324, 343 (1997).
(2)C. Ohm, M. Brehmer, R. Zentel, Adv. Mater., 22, 3366 (2010).
(3)A. Buguin et al., J. Am. Chem. Soc., 128, 1088 (2006).
(4)H. Yang et al., J. Am. Chem. Soc., 131, 15000 (2009).
(5)Z. L. Wu et al., Adv. Funct. Mater., 23, 3070 (2013).
(6)Z. L. Wu et al., ACS Appl. Mater. Interfaces, 5, 7485 (2013).

Silica encapsulation of various biological and non-biological systems has been shown to incorporate favorable characteristics such as improved thermal stability while maintaining native functionality. Additionally, the discovery of polypeptides, proteins and polyamines that allow for the formation of silica under ambient temperature and pH has afforded the possibility of facile encapsulation of enzymes, polypeptides and other biological systems. We have designed, synthesized and characterized amphiphilic, micelle-forming elastin-like polypeptide (ELP) constructs that contain silaffin (R5) peptide domains at the micellar coronae and facilitate the designed polycondensation of silica around the self-assembled micelle. We show that the addition of the ~2 kDa R5 silaffin peptide creates a template-dependent micellar core for silica formation, resulting in near-monodisperse hybrid silica-ELP nanoparticles; in addition, these particles are not observed when the silaffin domains are not present or when the ELP-R5 constructs are not self-assembled into micelles. These nanoparticles are characterized using electron microscopy, and light and x-ray scattering techniques to explore the effect of ELP chain length, precursor concentration and reaction kinetics. In addition, we demonstrate the conjugation and encapsulation of fluorescent and hydrophobic small molecules within the particle cores towards application in drug delivery systems .

Engineering scaffolds based on hybrid multifunctional biodegradable polymers and biomatrix proteins are in high demand due to their ease of processability, tunable mechanical properties, modifiable degradation times, biocompatibility, and bioactive regenerative properties. Among the various methods to recreate fibro-prorous scaffolds with nano/microfeatures of the extracellular matrix (ECM) morphology, electrospinning has gained considerable attention as a facile technique to fabricate seamless tubular 3D conduit of various diameters and lengths for vascular tissue engineering applications. Accordingly, tubular grafts were fabricated from blends of polycaprolactone (PCL) and poliglecaprone (PGC) polymers and coated with a novel human biomatrix gel (HuBiogeltrade;). Poliglecaprone (PGC), a copolymer made of randomly segmented PCL and PGA, has higher mechanical properties and a shorter degradation period (60% reduction in mechanical strength within 3-4weeks as a suture) compared to PCL. Being a relatively durable polymer, PCL can provide enhanced viscoelasticity and prevent the early collapse of 3D tubular structure which in turn may inhibit the tissue-regeneration.Hubiogeltrade; is a unique collagenous biogel comprised of collagens, laminin, and proteoglycans. Multifunctional scaffolds from polymer blends and biomatrix proteins provide the necessary biomechanics and biological functions for tissue regeneration. Two crosslinking agents, a natural crosslinker namely genipin (Gp) and another carbodimide reagent namely 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), were used for further stabilizing the biomatrix and the effect of crosslinking was evaluated for structural, morphological, mechanical properties using SEM, IR, DSC and DMA. SEM images and fiber diameter distrubution showed fiber size between 0.2 µm to 1 µm with the majority of fiber diameters being under 500 nm, indicating upper range of protein fiber-sizes ( for example, collagen fibers are in the range of 50 to 500 nm diameters). Coating did not affect the graft mechanics but increased its hydrophilicity. Overall data showed that PCL/PGC blends with 3:1 composition (coated with HuBiogel) exhibited mechanical properties comparable to those of human native arteries (tensile stregnth of 1-2 MPa and tensile moduclus of 9-12 MPa). Studies on crosslink density, stability of biomatrix up on crosslinking in physiological medium, and in vitro cell-growth using human endothelial cells and smooth muscle cells are underway. "This research is supported by the NSF Research Experiences for Undergraduates (REU)-site program under DMR-1058974”

Our aim has been to design cyto- and biocompatible, biopolymer based hydrogels for soft tissue applications. Thus, injectable hyaluronan-based (HA) hydrogels were created. Injectable hydrogels are widely used as scaffolds for tissue engineering, as cell encapsulation vehicles and in drug delivery due to their favorable properties, e.g. tissue-like water content, efficient mass transfer, easily manipulated physical properties and ability to homogeneously encapsulate cells. In this study we created two injectable hydrogel types consisting of aldehyde-modified hyaluronan and hydrazide-modified poly (vinyl alcohol) or aldehyde- and hydrazide-modified hyaluronan using hydrazone chemistry. With highly selective, quick and mild hydrazone chemistry we can form covalently crosslinked hydrogels by mixing the components together. Hyaluronan is widely used in tissue engineering due to its favorable tissue like properties. Poly (vinyl alcohol) (PVA) was used to combine the mechanical properties of synthetic polymer with biomimetic properties of biopolymer.
The chemical structures and degree of substitution (DS %) of modified polymer components were confirmed using FTIR and ¹H-NMR spectroscopy. HA-PVA and HA-HA hydrogels were formed by combining two polymer components with different DS %, polymer concentration and polymer molecular weight (M_w). Mechanical (compressive test) and rheological (oscillation test) properties, degree of swelling, diffusion (fluorescence recovery after photobleaching, FRAP), biodegradation with hyaluronidase and structure (FTIR) were analyzed. Clear differences were seen between hydrogels. As expected, with higher polymer concentration and higher DS % (more crosslinked structure), the degree of swelling was lower and mechanical (Young&’s modulus, E) and rheological (Storage modulus G&’ and Loss modulus G&’&’) properties were higher. The gelation time increased from seconds to minutes when polymer concentration was lower. Diffusion using FRAP was tested with 20, 150, 500 and 2000 kDa dextrans. A clear difference between different dextran sizes with all gels was seen. Smaller particles diffused faster and larger slower. Not all samples showed total recovery, which meant that the pore sizes were too small for the larger dextran particles or there were traps inside the gel. Also, the diffusion coefficient can be determined with this method. All hydrogels were shown to be biodegradable with hyaluronidase. All HA-HA hydrogels behaved like softer HA-PVA hydrogels. The cell viability of these hydrogels were confirmed with neural cells.
To conclude, the properties of hyaluronan-based hydrogels can be altered using different DS %, polymer concentration and polymer molecular weight. These hydrogels showed properties suitable for soft tissue applications and the incorporation of microparticles with drug is also possible.

Ice accretion is a serious safety hazard for aircrafts, power lines, motor vehicles, marine structures, communication towers and wind turbines. Any humid environment at subzero temperatures will promote ice accretion, making the problem a global concern. The most common methods of ice removal are extremely energy intensive. Mechanical removal, electro-mechanical expulsion, thermal removal and chemical removal are the industrial standards of today. Each method involves either imputing enough force to break off any accreted ice, or imputing enough energy to melt the ice. There exists a strong need to develop ice-phobic surfaces, i.e. surfaces that shed accreted ice with little or no external energy input.
Decreasing the surface energy has been shown to correlate strongly with lowering the adhesion strength of ice with a given surface. However, the lowest possible surface free energy (a dense CF₃ film) gives a theoretical lower limit to ice adhesion around 150 kPa. For reference, flat aluminum has an ice adhesion strength >1000 kPa. The practical icing applications listed above require much lower adhesion strengths to freely shed accreted ice, which necessitates circumventing this lower limit to create truly ice-phobic surfaces.
In this work, we develop new fundamentals for understanding and designing truly ice-phobic surfaces and coatings. We show how controlling the crosslink density and volume of unreactive, entangled chains of a polymer matrix allows for the design of surfaces with negligible ice adhesion. These new understandings allow us to create surfaces that display ice adhesion strengths as low as 5 kPa, a 30-fold decrease from the theoretical minimum and a 300% improvement over any other reported system. By repeatedly icing and de-icing the surface, we demonstrate the durability and practical applicability of our icephobic surfaces. Moreover, we demonstrate the universal applicability of our findings across several material systems. We also show results from outdoor testing over the winter months of 2013-14, highlighting the practical and real-world applicability of our surfaces.
Superhydrophobic surfaces, i.e. Lotus leaf mimicing surfaces where water simply rolls off without wetting the texture, have gained wide attention in recent years. In the literature, superhydrophobic surfaces are often claimed to reduce ice adhesion by lowering the areal fraction of ice in contact with the surface. However, over time water condenses within the pores of the surface, mitigating any positive effects, and raising the ice adhesion dramatically. Based on our newfound understanding, we&’ve also created the first ever ice-phobic AND superhydrophobic surfaces. These self-cleaning surfaces, where water rolls off with essentially no tilt angle, display ice adhesion strengths as low as 25 kPa, even in the fully wetted state.

Biopolymer-based hydrogels possess great potential for tissue engineering applications due to their intrinsic biocompatibility and viscoelastic properties. The weak mechanical properties and low bioactivity, however, limit their application for hard tissue engineering. Bioactive glass (BG) particles have been added to hydrogels to improve their bioactivity, but they commonly form brittle and non-homogeneous structures. In this study, sol-gel technique was used to prepare homogeneous mixture of BG and gelatin. These constructs were fabricated using simultaneous crosslinking of gelatin with genipin, and the formation of BG network using an aqueous solution of tetraethyl orthosilicate (TEOS). The effects of temperature and concentration of each compound on gelation time and physicochemical properties of hydrogels were assessed. Gelatin was not integrated into the BG network structure when the sol-gel process was conducted at room temperature due to the faster gelation rate of gelatin compared to BG. The homogenous mixture of gelatin and BG, however, was formed due to chemical crosslinking of gelatin at 37 °C in the presence of genipin. Increasing the concentration of genipin from 0.1 wt% to 0.5 wt% decreased swelling ratio of hydrogels 4 fold and reduced the gelation time from 2 h to 1 h. Addition of more than 20 v% TEOS to gelatin solution simultaneously formed a brittle structure. However, a solid hydrogel was formed when 15 v% TEOS was added to 10 wt% gelatin solution contained 0.25 wt% genipin. This construct was still water absorbent with 5 fold less swelling ratio compared to pure gelatin at the same composition. The results of this study demonstrated that sol-gel method was an efficient technique for the fabrication of uniform mixtures of a biopolymer and BG for the preparation of bioactive hydrogels that can be used for different biomedical applications such as low load bearing bone regeneration.

Nanosized titania has emerged as an important material for several advanced technologies including energy harvesting (i.e., photovoltaics) and the photocatlytic degradation of organic pollutants in water, air, and on surfaces. In this research, TiO₂ materials were biomimetically synthesized, utilizing peptides/polymers (e.g. polyethylene imine (PEI), protamine, and lysozyme) to initiate and mediate the precipitation of titania from an aqueous Ti-containing precursor (e.g. TiBALDH or TiOCl₂). Biomimetic approaches for creating TiO₂ represent an attractive alternative to traditional high temperature (> 500°C) synthesis methods, as biomimetically generated titania contains functional organic constituents that are incompatible with high temperature processing. Unfortunately, biomimetic mineralization techniques typically produce amorphous or poorly-crystalline titania materials or require specialized, recombinantly produced proteins to produce highly-crystalline rutile or anatase TiO₂. In this study, we have investigated the devitrification of biomimetically synthesized titania materials under relatively mild conditions that mimic natural microbial environments. This processing route yielded bio-hybrid /nano TiO₂ materials that displayed photocatalytic activity exceeding that of commercially available titania photocatalyst (Aeroxide P25). Furthermore, the production of highly-crystalline titania under such benign conditions is advantageous, as the organic component of the bio-hybrid material is preserved and available for further functionalization. Indeed, the chlorination of these organic constituents yields halamine compounds that provide potent antimicrobial activity to the material system, independent of illumination conditions.

Gelatin is derived from a component of the extracellular matrix (ECM). Therefore, materials based on gelatin are interesting candidates for biomedical applications. Crosslinking of gelatin is an option to tailor its properties. First, gelatin can be functionalized with a small molecule, e.g. glycidyl methacrylate (GMA), whereby the introduced double bonds can react chemoselectively in a subsequent reaction to form networks. Thereby the degree of functionalization is better controllable and a higher reactivity can be achieved by introducing fast reacting functional groups compared to a direct crosslinking of gelatin with a bifunctional crosslinker. GMA-functionalized gelatin has already shown to allow crosslinking by photopolymerization^[1] and metathesis.^[2] Here, we report on a comprehensive characterization of GMA-gelatin and its network formation by a Michael addition using oligo(ethylene glycol) of varied chain length as crosslinker.
Gelatin was functionalized on 94 mol% of the free amino groups, which could be shown by NMR studies and a photometric assay based on the reaction of trinitrobenzene sulfonic acid with the remaining free amino groups of lysine in gelatin determining the degree of functionalization. This furthermore showed that GMA was not introduced on free hydroxyl groups. Hydrogel networks formed under variation of crosslinker chain length and concentration were characterized by thermo gravimetric analysis, wide angle X-ray scattering, volumetric swelling studies, differential scanning calorimetry (DSC), tensile tests and rheology. NMR and IR investigations proved the reaction of the double bonds of the methacrylate groups with the crosslinker. The gel content of the hydrogels (68#8209;77%) was independent of the gelatin concentration used for the network formation (5-20 wt%). Varying the chain length of the crosslinker results in a tailorable swelling capacity with a volumetric degree of swelling between 1000-3000 vol%, depending on the hydrogel composition, while mechanical properties similar to soft-tissue were obtained with storage moduli between 0.2-23.8 kPa. The covalent crosslinking suppressed the self-organization of gelatin-chains to single and triple helices with overall helical content below 5%. In order to study the behavior of the materials in the body, in vitro degradation studies in phosphate buffer saline at 37 °C were performed showing the complete degradation of the hydrogels after 5-7 days depending on the chain length of the crosslinker. The water uptake increased from 1000 to 44000 wt% during degradation, while the mechanical strength decreased by two orders of magnitude, attributed to the cleavage of the crosslinker by degradation of the connected ester bonds at the GMA junctions, which was proved by sodium dodecyl sulfate polyacrylamide gel electrophoresis and DSC measurements.
[1] B. F. Pierce, et al. Macromol. Biosci. 2012, 12, 484-493.
[2] A.T. Neffe, et al. PAT J.2014, accepted.

Cardiovascular disease remains a leading cause of death worldwide. Due to the limited regenerative capacity of heart tissue, development of adequate cardiac regeneration strategy has emerged as an attractive approach. Designing biomimetic materials to support the approach will be essential to the overall therapeutic success. Here, we demonstrated virus engineering strategies for cardiovascular regeneration by exploiting its physical and biological structural features. The multiple aspects of the natural cardiac microenvironment could be emulated in our designed virus. We modified virus to express angiogenic factor (Thymosin β4) and integrin binding peptide (RGD), and then micro patterned them to enhance extracellular topography and stiffness to guide human CPC (cardiac progenitor cells) and EPC (endothelial progenitor cells) alignment. The enhanced survival and mobilization capacity of cardiac and endothelial progenitor cells and enhanced vessel formation by our engineered virus was observed when cells were cultured on the virus matrices. Micro patterning of our engineered virus shows that cellular shapes and their functions were successfully dictated by our engineered virus. Our designed virus functionalized with various ligands and growth factors and by modulating physical and mechanical properties can be used as a convenient cardiac tissue engineering platforms, providing therapeutic potential in heart regenerative medicine. [This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2013R1A1A3008484) and by a grant of the Korean Health Technology R&D Project, Ministry of Health & Welfare (HI13C1256), Republic of Korea]

Evolution of tough pathogens that resist existing antibiotics targeting these pathogens has become one of the greatest challenges in health care. Inspired by the structures of bacteria-invading viruses and antimicrobial peptides, we hypothesize that in addition to a balance of amphiphilicity and electropositivity, the nanoscale architecture is another important factor that defines the selectivity and efficiency of membrane-active antimicrobial agent. Here we study the structure-activity relationship of a series of polymer molecular brushes (PMBs) with well-defined structures that mimic spherical and rod-shaped viruses. Our preliminary data confirm that PMBs can be designed to exhibit high activity and double selectivity, suggesting that nanoscale architecture is an important design parameter. We attribute this enhanced activity and selectivity to the spatially-defined, multivalent interactions enabled by PMBs to remodel cell membranes, as suggested by our synchrotron small angle x-ray scattering and confocal microscopic studies. Since not all bacteria are harmful, and infectious bacteria often coexist with blood cells, selectivity among different types of bacteria and blood cells as revealed in our PMB designs is of great significance to the development of polymer-based antibiotics.

Marine mussels utilize multiple bidentate complexes formed by Fe(III) and DOPA in mussel adhesive protein (fp-1) to reinforce tough and elastic byssal fibers as a specialized underwater adhesive aid. In this study, mussel-inspired electrospun nanofibers were fabricated using recombinant mussel adhesive protein (rfp-1), Fe(III)-DOPA complexes, and polycaprolactone. The mechanical properties of the fabricated nanofibers were reinforced by the Fe(III)-DOPA complex found in fp-1, which is a key component of the naturally occurring high-performance mussel fiber coating. Experimental results show that the stoichiometry of Fe(III)-DOPA complexes in the nanofibers could be controlled by buffer pH conditions and the stiffness of the nanofiber mat increased linearly with the concentration of the Fe(III)-DOPA complexes, as monitored by resonance Raman spectroscopy. This suggests the potential of Fe(III)-DOPA complexation as an effective strategy for enhancing the mechanical properties of nanofibrous biomedical materials.

Superior mechanical properties allow silkworm silk fibroin to be applied in diverse fields. However, silkworm silk&’s lack of biological functions and relatively poor biodegradation has hindered its wide use in tissue engineering. In this study, we improved bulk-scale adhesive ability as well as micro-scale adhesiveness to cells and various biomolecules by blending silk fibroin (SF) with RGD peptide-fused recombinant mussel adhesive protein (MAP-RGD). Based on high protein productivity and simple addition of MAP-RGD, silkworm silk was able to acquire much enhanced adhesion, proliferation, and spreading of mammalian cells. Adhesive silk fiber also showed better attachment of biomolecules, including carbohydrate and protein compared to SF without MAP-RGD. MAP-RGD-blended SF material also demonstrated improved hydrophilicity, swelling, and biodegradability without notable hampering of the original mechanical properties of SF. Simple blending strategy can expand silk&’s application as an adhesive substitute composite material with improved biological functions.

Bio-mimic polymers derived from biological origins are attractive materials for the preparation of biocompatible surfaces. Polymers based on protein or peptide, sugar, and lipid structures have shown great potential in the preparation of biocompatible hydrogels, drug delivery carriers, and tissue scaffolds. Among them, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), which mimics the head group of phosphatidylcholine (PC), showed exceptional hemocompatibility, antiprotein adsorption activity, and antithrombotic activity.
Lipid bilayers in biomembranes consist of diverse phospholipids, including phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) with various compositions according to the cell and tissue type.
Inspired by the outstanding biocompatibility of PC-based polymers, we synthesized phospholipid-mimic polymers, poly(2-methacryloyloxyethyl phosphoric acid) (PMPA), poly(2-methacryloyloxyethyl phosphorylethanolamine) (PMPE), and poly(2-methacryloyloxyethyl phosphorylserine) (PMPS), with head groups other than the phosphocholine moieties, PA, PE, and PS head groups, respectively. Each biomembrane-mimic polymer was successfully synthesized by atom transfer radical polymerization (ATRP). The molecular weight distributions of PMPA, PMPE, and PMPS were analyzed by gel permeation chromatography (GPC) in vitro cytotoxicity was also examined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assay.
Considering phospholipid compositions in cell membranes vary between organs, tissues, cells, and even cellular organelles, the biomembrane-mimic polymers based on diverse phospholipid head groups can be a potential platform for the preparation of cell- or tissue-specific surfaces with both biocompatibility and bioactivity, which are difficult to be obtained by only PC-based polymers for biomedical applications.

Poly(3,4-alkylenedioxythiophenes) have been extensively explored as materials for biomedical implants such as biosensors, tissue engineering scaffolds and microelectronic devices. Considerable efforts have been made to incorporate bioactivity into the conducting polymers for their long term performance and efficacy in devices. However, there remains an unmet need for developing functionalized conducting polymers that can be modified with biomolecules to improve the interface between the hard electrode and soft tissue. Here we report modifications of EDOT (3,4-ethylenedioxythiophene) and ProDOT (3,4-proplylenedioxythiophene)-based conducting polymers using two different surface chemistries. A carboxylic acid functional group was used to modify the PEDOT films with laminin-based YIGSR peptides whereas a terminal alkene group was used to modify the PProDOT films with fibronectin-based RGD peptides. The peptides were coupled to the PEDOT and PProDOT films via amide coupling and thiol-ene click chemistry protocols, respectively. The films were characterized via XPS and FTIR spectroscopy to confirm the presence of the peptide. Cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS) was performed on the unmodified and modified films to determine the effect of chemically coupling the peptide on the electronic behavior of the films. The chemical modification of the films did not alter the electronic behavior of the films significantly. Future work will be focused on determining the impact of peptide coupling on the interaction of cells with these films.

Development of sequence-defined or structurally-precise polymers as
high-performance materials is a major challenge in materials science. In
this work, we report a facile synthesis platform to produce monodisperse and
stereochemically precise nucleotidomimetic polymers. Based on a top-down
approach, we are able to precisely incorporate a wide-variety of functional
group modifications in a simple two-step process. First, we utilize the
natural ability of DNA polymerase to enzymatically incorporate
chemically-modified monomers (e.g., C5-dibenzocyclooctyl dUTP) in a
template-directed fashion. Second, we employ copper-free click chemistry to
integrate the desired chemical functionality at precise locations along the
polymer chain. In this way, we produced a variety of branched DNA
homopolymer and heteropolymer architectures including 3-arm star, symmetric H, and
block-brush. Overall, this synthetic strategy allows for the systematic
variation of oligomer length, stoichiometry, concentration, and
environmental conditions to rapidly explore nucleotidomimetic polymer phase
behavior for materials discovery.

In this study, we synthesized amphiphilic block copolymers containing catechol groups and organic solvent dispersive metal nanoparticles were prepared by using the catechol groups of the block copolymer as reduction agents. It is well known that amphiphilic block copolymer micelles have been used as microreractors for preparation of metal nanoparticles. Metal nanoparticles were prepared by loading metal ions into hydrophilic moieties in block copolymer micelles followed by adding reduction agents. Size of nanoparticles can be controlled by changing sizes of hydrophilic part of block copolymer. The nanoparticle can disperse independently owing to stabilizing the metal nanoparticles with block copolymers. However, interaction between nanoparticles and block-copolymers are usually weak, the metal nanoparticles are easy to aggregate with mixing hydrophilic solvents, increasing temperature, and so on. Thus, simple ways to synthesize more stable dispersion of metal nanoparticles stabilized with block-copolymers have been required.
Catechol groups, which are present in the adhesive protein of mussel, show high adhesion property for a wide variety of materials. Moreover, catechol groups can act as reduction agents by oxidation reaction from catechol to quinone. From this reason, block copolymers having catechol moieties can realize a one-step and automatic synthesis of organic solvent dispersed metal nanoparticles.
Amphiphilic block copolymers were prepared from styrene and 3, 4-dimethoxystyrene by the reversible addition-fragmentation chain transfer (RAFT) polymerization technique. Methoxy groups were deprotected to hydroxy groups by boron tribromide. Chemical structures and molecular weights of synthesized blockc copolymers were determined by using a nuclear magnetic resonance and a gel permeation chromatography. Metal nanoparticles were synthesized with mixing deprotected polymer and metal salt in a mixed solution of chloroform, N, N-dimethylformamide, and water at room temperature. Nanoparticles were observed by using a transmission electron microscope, and dispersion stability was measured by UV-visible absorption spectra. In the case of silver ion mixed, nanoparticles of Ag were successfully synthesized. The nanoparticle was stably dispersed in hydrophobic solution, such as chloroform, and average diameter was around 8 ~10 nm. The dispersion stability of nanoparticles was affected from copolymerization ratio. Gold nanoparticles were also successfully synthesized by same procedures, and stably dispersed in organic solvents.
We successfully synthesized metal nanoparticles in a single step by using amphiphilic block copolymers having catechol moieties as reduction agents at room temperature. From the result, we suggested a useful preparation method of organic-solvent-dispersible metal nanoparticles.

Monomer of 2-(3-(6-Methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido)ethyl methacrylate (SCMHBMA) with 2-ureido-4[1H]-pyrimidone (UPy) group and monomer of N-acryloyl 6-aminocaproic acid (A6ACA) with alkyl group were synthesized. Novel quadruple hydrogen-bonding supramolecular network polymer was polymerized from the two monomers. The structures of monomers and polymer were characterized by infrared spectrum (IR), hydrogen nuclear magnetic resonance (¹H-NMR) and mass spectrum. ¹H-NMR and IR results verified that quadruple hydrogen-bonds existed between the molecular chains of the supramolecular polymer. Thermal properties were investigated by differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). The supramolecular polymer behaves like elastic polymers with a high rubber plateau and a low melting temperature, which is favorable for low temperature processing. The product has good toughness and mechanical properties.

Temperature-triggered formation of nanostructures with distinct biological activity offers opportunities in selective modification of matrices and in drug delivery. Toward these ends, diblock polymers comprising poly(diethylene glycol methyl ether methacrylate) (PDEGMEMA) were conjugated to the C-terminus of a triple helix-forming collagen-like peptide (CLP) with the sequence (GPO)₇GG. The ability of the CLP domain to maintain its triple helix conformation after conjugation with the polymer was confirmed via circular dichroism (CD). Dynamic light scattering (DLS) measurements suggested the diblock conjugate underwent a reversible temperature-induced transition from solution to nanoparticles with a diameter around 100 nm. While the LCST of the PDEGMEMA was 18 °C, the diblock exhibited a transition temperature of 32 °C when dissolved in PBS buffer, and 37 °C when dissolved in deionized water. Transmission electron microscopy (TEM) suggested the formation of well-defined vesicles above the transition temperature, while no supramolecular assemblies were observed at room temperature. A PEG-CLP diblock, as a negative control, did not show assembly behavior at any temperature investigated, indicating the self-assembly of PDEGMEMA-CLP diblock was triggered by the collapse of the thermoresponsive domain above its LCST. The incorporation of CLP domains in these nanostructures offers opportunities for the selective targeting of collagen-containing matrices in vitro and in vivo.

Recently, tremendous progress has been made in directed assembly of nanoscale building blocks by viewing entire NPs modified with various linkers (i.e., polymers, proteins, or DNAs) as molecular mimics. This strategy is opening new research frontiers in nanoscience and nanotechnology. Here we present a new strategy to fabricate supracolloidal molecules with well-defined valence via concurrent assembly of binary metallic NPs decorated with oppositely charged block copolymers (BCPs). The assembly of binary mixtures generated highly monodipersed dimer (AB), trimer (AB₂), and tetramers (AB₃) with high purity by controlling the length of polymers, size of NPs, and feed ratio of binary NPs. Our experimental and computational studies indicate that the nanostructures arise from the delicate interplay between the dimension match of the binary NPs, the charge density of BCP chains, and molecular weight of BCPs. More interestingly, this assembly approach constitutes a unique “self-limiting” assembly mechanism, that is, the neutralization of overall charges limits the further addition of NPs to the assembled supracolloids, arising from the flexibility of polymer tethers. The ability to construct multi-component assemblies with defined valence represents a promising step in the self-assembly of structurally complex functional materials.

Although nature extensively uses hydration force and ionic interaction to control the geometry (e.g., secondary.tertiary/quaternary structures) and dynamics (e.e., self-organization) of proteins, the use of similar forces to control the behavior of small molecules is less explored and more difficult. Here we report the design and characterization of a novel zwitterionic molecule that adopts the folded structure in organic solvent under soluable state through ionic interaction. Being hydrated in water, this molecule unfolds as self-assembling buliding blocks of supramolecular nanofibrils. By tuning the hydation force, transition among multiple self-assembled structures are achieved.

We investigate the cooperative folding behaviors of comb-like macromolecules containing helical polypeptide side-chains. While the helix-to-coil transition of linear helical polypeptides (e.g., poly(ε-benzyloxycarbonyl-L-lysine) (PZLL)) can be predicted by the Schellman-Zimm-Bragg model, the folding of helical polypeptide chains in the comb macromolecules (e.g., polynorbornene-g-poly(ε-benzyloxycarbonyl-L-lysine) (PN-g-PZLL)) cannot be accurately described by the existing models. A positive folding cooperativity was observed in PN-g-PZLL, presumably due to the formation of helical bundles between grafted PZLL. Nuclear Overhauser enhancement spectroscopy (NOESY) was used to reveal the side-chain interactions within the comb macromolecules in solution. The intermolecular interactions and morphology of these comb macromolecules in bulk and in thin films have also been investigated using wide angle X-ray scattering (WAXS) and infrared spectroscopy (IR).

Recently, we demonstrated that filamentous supramolecular structures can be assembled from polypeptide-grafted macromolecules and nanoparticles via a cooperative supramolecular polymerization process. We are interested in finding a regulation mechanism by which the slow supramolecular polymerization process may be accelerated. To achieve this goal, we investigate a series of chemical reactions that can modify the interactions between the macromolecules and nanoparticles in-situ and subsequently affect their self-assembly in solution. By modulating the interactions between the macromolecular subunits in solution, different supramolecular structures (e.g., filaments and thin membranes) were obtained and the polymerization rates can be regulated. The electrostatic interactions between the macromolecular subunits may play an important role in determining the supramolecular structures at equilibrium and the kinetics of their formation.

Recently, Ru complexes have attracted great attention in photo-catalysis and photocurrent generation under visible light irradiation. In this research, we synthesized terpyridine (tpy) ligand and Ru(tpy)₂ containing self-assembled polymer films on ITO and glass substrates and investigated their photocurrent efficiency. We tested Fe, Zn, Co, Cu, Ni metals which can coordinate with the tpy ligand to synthesize self-assembled polymer films. Especially using Cu, the film growth rate was the fastest due to the higher metal-ligand binding energy which was confirmed by UV-vis spectrometry. In the photocurrent experiment, Zn, Fe and Co self-assembled polymer films exhibited higher efficiency when compared to Cu and Ni. Furthermore, we confirmed with CV that this tendency is related the redox potentials of metal and Ru complexes. We conclude that the metal-ligand interaction plays an important role not only in generating self-assembled films, but also in enhancing photocurrent efficiencies

Ordered microporous polymer structures have potential application in catalysis, surface engineering and optoelectronics. Breath Figure Technique (BFT) is a simple and cost effective water based self-assembly method of patterning a polymer thin film into ordered microporous structures. In this study BFT was applied to a series of commercial conjugated polymer: polythiophene derivatives with varying side chain length. An in-depth study of processing parameters has been carried with the aim of controlling the morphology of the honeycomb film over large, PV relevant areas. Optical and Opto-electronic properties of such patterned films and their effect of morpholgy are studied using SEM, X-ray scattering, AFM, Fluorescence Lifetime Imaging (FLIM) and Spectroscopy Methods [1]. Blends of these polymers with a fullerene derivative, PCBM, were also subjected to BFT and characterized with similar methods to asses their potential use as active layers in PV solar cells.
Reference:
1. Tsai et al. “Structural dynamics and charge transfer via complexation with fullerene in large area conjugated polymer honeycomb thin films” Chemistry of Materials, vol. 23, no. 3, pp. 759-761, Feb. 2011.

Electrospinning is an interesting process for producing various functional non-woven fibers with average diameters in the range of micro to nanometers. The driving force for the interest in this technique is the possibility to produce inorganic and polymeric fibers with several potential applications. In this method is possible to incorporate other materials into electrospun nanofibers, such as conjugated polymers, to yield the nanofibers optical and electronic properties aiming at fabricating optoelectronic devices or sensors. Therefore, in this work PMMA/MEH-PPV nanofibers were obtained by electrospinning. Initially we investigated the influence of the solvent and the polymer concentration on electrospinning of PMMA. After determining the best conditions, 0.1% MEH-PPV was added in order to obtain fluorescent nanofibers. The obtained nanofibers were characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), confocal microscopy and photoluminescence spectroscopy. The SEM images showed that irrespective of the solvent, an increase in polymer concentration resulted in an increase of average fiber diameter with less possibility of bead formation. Addition of a cationic surfactant, dodecyltrimethylammonium chloride (CTAB), improved the solution spinnability, leading to nanofibers with good morphology, small diameters and controlled size. The optical characterizations showed that MEH-PPV was effectively impregnated into the PMMA fibers without phase separation, and that the fluorescent property was preserved after fiber electrospinning. The results presented here demonstrate the ability of the electrospinning approach to obtain fluorescent PMMA/MEH-PPV nanofibers with potential for optical applications, including optical devices and chemical sensors.
Acknowledgements: We thank financial support from FAPESP (Proc. 2013/23880-3), CNPq, CAPES, MCTI and EMBRAPA from Brazil.

Supramolecular chirality generated from self-assembled small molecules, dendrimers and polymers have been attracting a large amount of attention because of their unique chiroptical properties and their potential applicability for display, optical filter, memory, sensor and so on. We demonstrate a new strategy to create a secondary chirality-based circular polarizing polymer film. The secondary chirality was enhanced by the chirally-oriented structures of the self-assembled chromophore in polymer matrix.
In this work, the pyrene-functionalized L-gutamide (g-Pyr) as a low-molecular organogelator was selected because this compound can form a gel in various organic meida through the formation of well-developed#12288;nano-fibrous aggregates showing extremely large circular dichroism (CD). The g-Pyr assembly-incorporated poly(ethylene-co-vinyl acetate) (EVA) film was prepared by a casting method from the organic solution. The chiroptical properties of the g-Pyr/EVA films were evaluated by UV-vis, CD and fluorescence spectroscopies. The CD spectra of the g-Pyr/EVA film exhibit the extremely large positive Cotton effect at the absorption band around 325 - 370 nm. This result indicates that the g-Pyr formed chirally ordered assembly in an EVA film. The CD signal was assigned by pyrenyl moieties with an R-chiral stacking form. Interestingly, when the polymer film was annealed above 90 #730;C for 10 min, the CD signal was changed from positive to negative. On the other hand, the absorption spectra of the g-Pyr/EVA film showed no significant change after thermal treatment. These results indicate that the thermal treatment promotes the drastic change of chiral orientation keeping the π-stacking among the pyrenyl moieties. In our presentation, we will discuss the detail chiroptical properties and circular polarizing properties of the g-Pyr/EVA films in various conditions.

Nanotechnology is considered the basis for production of micrometric and nanometric three-dimensional inorganic structures by biotemplates. Biological systems have been used to construct hybrid mesostructures. Areas as biomimetic and bio-inspired engineering have studied structured inorganic system integrated with organic materials. More and more nanotechnology researchers have found in these biological structures a useful model to overcome their challenges of design and manufacturing, since the potential use of these materials with complex morphologies linked to its high reproducibility and morphological control put these materials in a prominent position in the materials engineering. In this way, we present a facile route to construct inorganic-organic hybrid mesostructures. Herein, microtubules with self-assembled gold nanoparticles were prepared using the fungi Xylaria sp as biotemplate and colloidal dispersion of gold nanoparticles by Turkevich Method. Inocula of the fungi Xylaria sp were added in an Erlenmeyer flask containing three different media: Czapeck (CZA), Czapeck with yeast extract (CZALEV) and Potato-Dextrose medium (PD), well-establish media in the literature. The medium was removed after two weeks to adding 100 mL of the noble-metal colloidal dispersion. Gold nanoparticles were characterized by X-ray diffraction (XRD), UV-Vis spectroscopy and scanning electron microscopy (SEM) and, the microtubules, by scanning electron microscopy (SEM). The diffractogram of the noble-metal nanoparticles confirmed the face-centered cubic structure. The plasmom band in 528 nm showed the characteristic region of gold nanoparticles. The average size of gold nanoparticles, calculated by SEM showed average size of 20 nm. According to the SEM images, gold nanoparticles were presented in the hyphae in the three different media. However, the hyphae that presented more quantity of gold nanoparticles were those cultivated in CZA medium. In this medium, there are macronutrients specific for fungi. Yeast and potato present in CZALEV and PB media promotes the self-assembled nanoparticles in these components which causes the low presence of the nanoparticles in the hyphae. Therefore, it is possible to construct microtubules with gold nanoparticles with controlled size using biotemplate by varying the culture media.
[1]Li, Z,; Chung, S. W.; Nam, J. M.; Ginger, D. S.; Mirkin, C. A. “Living templates for the hierarchical assembly of gold nanoparticles” Angew. Chem. Int. Ed., 42, 2003, 2306-2309.
[2]Benyus, J. M. "Biomimicry: Innovation Inspired by Nature", Nature Publishing Group, 1997.
[3]Cobley, C. M.;J Chen,J. Y.; Cho, E. C.; Wang, L. V.; Xia, Y. N. Chem. Soc. Rev. 40 (1), 2011, 44-56.
[4]Bigall, N. C.; Reitzig, M.; Naumann, W.; Simon, P.; van Pee, P. S.; Eychmuller, A. Angew. Chem. Int. Ed., 47, 2008, 7876-7879.

The preparation and characterization of a dynamic optical filter comprised of polymer cholesteric liquid crystal (CLC) microparticles dispersed in a nematic liquid crystal host will be detailed. CLCs self-organize into periodic helical structures that selectively reflect circularly polarized light of the same handedness as the twist within the helical superstructures. Selective reflection of light from the periodic structure results in a transmission notch / reflection peak in the electromagnetic spectrum at a spectral location determined by the periodicity. These structures exhibit classic viewing angle dependent color (i.e., iridescence). CLC microparticles of various compositions, sizes, and shapes were produced and incorporated into a variety of nematic liquid crystal (NLC) hosts whose average director orientation could be controlled by an applied electric field. Changes to the orientation of the CLC microparticle (and thus color) were induced by application of an electric field to the dispersions. Examinations exploring field strength, temporal dynamics, and color changes were explored. To optimize the optical properties of the CLC materials, the microparticle production method provided control of two parallel boundary conditions. Controlled boundary conditions reduce defect-generated scattering in the particles, and provided a novel means to control the orientation of particles when incorporated into dynamic (e.g., switchable and tunable) nematic liquid crystal-based optical devices (e.g., optical filters, switchable ‘smart windows&’, transflective displays).

The peppermint fragrance as core material was encapsulated by polyurea as shell material which was made through the interfacial polymerization of 4,4&’-diphenylmethane diisocyanate(MDI) and hexamethylene diamine(HMDA)in miniemulsion. The preparation technique was studied through a series of single factor and orthogonal analysis. The nanocapsules were tested and characterized by dynamic light scattering(DLS), scanning electron microscopy(SEM),transmission electron microscopy(TEM) Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and thermal gravimetric analysis(TGA). We investigated the factors which influence the particle size distribution of peppermint fragrance nanocapsules, such as the dosage of fragrance, the dosage of dispersant, stirring / homogenizing rate, ultrasonic power and time, monomer ratio and so on. We obtained the optimum conditions for the preparation of peppermint fragrance nanocapsules. The average size of the peppermint fragrance nanocapsules is 122.7nm with the polydispersity index(PDI)of 0.185. The nanocapsules demonstrate a good thermal stability at a high temperatures and protection of the fragrance against release.

Metal organic frameworks (MOFs) are a class of microporous coordination polymers comprised of metal ions interconnected through a network of organic linkers. Zeolitic imidazolate frameworks (ZIFs), a subclass of MOFs, exhibit potential for biomedical imaging and therapeutics delivery. ZIF-90 is of particular interest because combines high structural and chemical stability with linker aldehyde groups that enable covalent bonding of dyes and therapeutic agents. Here, we describe a surfactant-based approach for synthesizing and isolating ZIF nanoparticles (NPs) that allows exquisite control over particle size and morphology. A matrix of reaction conditions established how growth mechanisms are affected by temperature, reaction time, and surfactant chemistry. Our results show that tunable particle sizes between 20-600 nm are achievable with lozenge, rod, and spherical morphologies. ZIF-90 NPs were labeled with fluorescent dyes for in vitro cell studies using CHO-K1 cells. Uptake as high as 100 µg/mL is attainable, with negligible impact on cell viability.

Nanogels have recently emerged as promising materials for the delivery of a wide range of therapeutic molecules due to their advantageous hydrophilic structures. This work describes the preparation of novel, multifunctional, lipid-coated polymer nanogels that were crosslinked by photo-triggered Michael-type reaction via the use of liposome templates. The photo-sensitive gelation and temporal control of the crosslinking reaction were confirmed by oscillatory rheology experiments of bulk hydrogels, and the production of nanogels was confirmed via dynamic light scattering and transmission electron microscopy. The surface functionality of the lipid-coated nanogels was demonstrated by surface modification with a reactive fluorescent dye. These multifunctional lipid-coated nanogels, given the mild preparation conditions, ease of size control, and versatility of the chemical linkages used as cross-links, have significant potential for use in polymeric nanoparticulate drug delivery systems.

In this work, PEDOT:PSS solution was mixed with second solvent such as DMSO and EG to enhance electrical conductivity and the solution was electro spun to make nanofibers web that can be used for electrical and/or chemical sensors. The weight of the second solvent and polymer concentration were changed to find an optimum conditions. The prepared nanofibers webs were annealed for various temperatures and times. The electrical conductivity for each sample was measured and the characterization by using Raman spectroscopy and XPS. Acknowledgement: This work was supported by the Small and Medium Business Administration in 2014 (No. S2090919).

Microfluidic method is used to fabricate microfibers for some medical applications such as vaccine or drug delivery. This study is divided into experimental and numerical parts. Some microfibers made of Gelatin and Gelatin/PCL are fabricated. SEM images of the fiber surface and cross section are provided. In the numerical area, the channel is modeled using COMSOL software. The cross section obtained from the numerical work has a good agreement with the experimental results. Additionally, the results illustrate that the cross section of the microfibers made with microfluidic approach is not necessarily round. Finally, it can be shown that with a change in the inlet of the microchannel, the fiber that passing through the channel will have a hole and is called “Hollow Fiber.” It can be concluded that microfluidics is a useful method for pharmaceutical applications such as vaccine and drug delivery. Pharmaceutical industry can be greatly beneficial by using microfluidic assays in various drug development stages, from target screening, toxicity studies in preclinical evaluations, diagnostics in clinical trials, drug formulation and manufacturing process optimization.

Recently, the heat problem of the electronic devices such as high-power device, LED, and semiconductor elements have become seriously because of the change to higher performance, higher functionality and the miniaturization. Although various techniques for heat releasing have been developed, more effective method heat from the devices have been requested. As one of heat releasing techniques, the method using the thermal conductive plate with an electrical insulation property is utilized. For this purpose, the many approaches using various kinds of thermal conductive inorganic materials have been examined. However, a large amount of fillers must generally, be used in a plate, in order to achieve thermal highly conductive efficiency. We introduce a novel approach to fabricate the thermal highly conductive plate. Our concept is as follows: (1) core/shell composite microbeads are prepared using boron nitride nanopartilces as a shell and cellulose as a core (2) their core/shell composite microbeads is incorporated into an insulating resin as filler (3) thermal conductive pathways are efficiently formed by contacts among shells of composite spherical microbeads in an insulating resin. In this study, cellulose/boron nitride core/shell microbeads were prepared using viscose phase separation method. The thermal conductive plates using cellulose/boron nitride core/shell microbeads as fillers fabricated by the compression molding. The thermal conductivity of the obtained thermal conductive plates showed 5.2 Wm^-1K^-1, although boron nitride crystal contained only around 27.5 wt% in the plate. In addition, the thermal conductivity of the obtained thermal conductive plates increased to 7.8 Wm^-1K^-1, in the case of 44.5 wt% of boron nitride crystal content. The fabricated thermal conductive plates showed several times more efficient in a thermal conductivity than that obtained naked boron nitride. As results, thermal highly conductivity and cost minimization were derived. This indicates that favorable thermal conductive pathways are formed in an insulating resin.

Electrospinning is employed to prepare conductive polypyrrole (PPy) nanofibers with uniform morphology and good mechanical strength. In the present work, we have developed a way to electrospinning PPy solution with carrier into ultrafine fibers. Soluble PPy (1%, 3% e 5%) was synthesized with dimethylformamide (DMF) as dopant and then applied to electrospinning with or without poly(butylene adipate-co-terephthalate) (PBAT) as carrier. The electrospinning process is done based on different potential source using a 12KV capable of forming the well-known Taylor cone which facilitates the formation of fibers. To prepare the solution we use the probe for better dispersion of PBAT / Ppy.We used scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX) and differential scanning calorimetry (DSC) analyses to characterize homogeneously PBAT/PPy blends. and four-probe method characterized the morphology, chemical composition, vitreous transition and conductivity of the produced nanofibers. This new composite nanobiomaterial is very attractive to bone regenerative medicine. The results of these experiments will allow us to have a better understanding of PPy electrospun nanofibers and will permit the design of effective electrodes in the brain machine interfaces biomedical devices.

One approach to creating organic/inorganic composite materials is via direct encapsulation of pre-synthesized nanoparticles (NPs) into a polymer host material.¹ This technique is less than ideal, however, since control over the dispersion of the NPs is difficult. We are interested in creating composite materials by synthesizing the NPs in situ from metal ions that are uniformly distributed across the polymer matrix. Our current approach is to create multifunctional polymers with both metal-binding groups and π-electron deficient/rich aromatic groups. The polymer serves as a solid organic host material, the metal ion binding domain allows for pre-organization of metallic NP precursors, and the π-π stacking domain is added to control organization and assembly of the polymer. We have synthesized such multifunctional polymers using a 1,3,5-triazine core with 2,2':6',2''-terpyridine for metal ion binding. By further modification of the triazine core with pyrene or naphthalene derivatives we created two different multifunctional polymers which mix to form strong π-π stacks between electron rich and electron deficient aromatic systems. These polymers then assemble and preorganize metal ions inside the polymer matrix. We have shown that reduction of the mixture of multifunctional metallopolymers gives in situ formation of metallic nanoparticles inside the organic matrix. Future work will focus on development of multifunctional polymers with different types of self-organization to control size and shape of the formed metallic nanonaparticles.
(1) Ghosh, K.; Maiti, S. N. J. Appl. Polym. Sci.1996, 60, 323-331.

In order to obtain polyvinyl alcohol nanocomposites, the raw polymer, polyvinyl alcohol (purchased from Sigma Aldrich) was dissolved in distilled water. Powder of titanium oxide nanoparticles (anatase nanoparticles with particle sizes ranging between 18 and 30 nm from Nanostructured and Amorphous Materials, Inc.) have been dispersed in distilled water by sonication (500 W, one hour) in order to obtain a homogeneous mixture. The solution and the mixture were then mixed together and sonicated at 500 mW for 100 minutes. The as obtained suspension was deposited on glass substrates and the water has been removed by heating in a vacuum oven at 70 ^oC for about 12 hours. The complete water removal was confirmed by TGA studies.
Polyurea formaldehyde microcapsules filled with dicyclopentadiene have been synthesized, as described elsewhere. In order to add self-healing capabilities to polyvinyl alcohol nanocomposites, a series of samples labelled as PVA-TiO₂-SH has been prepared. The samples belonging to this series consisted of the polymeric matrix (PVA), loaded with the nanofiller (TiO₂), first generation Grubbs catalyst, and polyurea formaldehyde microcapsules filled with dicyclopentadiene. This series contain all the components required to ignite the self-healing process.
Another series of samples labelled as PVA-TiO₂-NH contained the polymeric matrix (PVA), loaded with the nanofiller (TiO₂), and polyurea formaldehyde microcapsules filled with dicyclopentadiene. This series does not contain the Grubbs catalyst and accordingly does not exhibit self-healing capabilities.
TGA tests have been done on samples from both series and confirmed that water has been completely removed. Raman spectra confirmed the presence of DCPD in microcapsules and in both series. The mechanical properties of the as prepared films (both PVA-TiO₂-SH and PVA-TiO₂-NH) have been tested by dynamical mechanical analysis (DMA), at various temperature in the range 25 ^oC to 50 ^oC. First DMA tests inspected the stress-strain dependence and provided the elongation at break, tensile strength, and Young modulus for both series. The second DMA tests aimed at a better understanding of the fatigue and on the effect of self-healing on fatigue by including a set of 20 very slow mechanical cycles on both PVA-TiO₂-SH and PVA-TiO₂-NH. The effect of temperature on the self-healing capabilities is reported. Optical and microscopy studies of both PVA-TiO₂-SH and PVA-TiO₂-NH, before and after mechanical tests are presented.

Fibre-reinforced thermoset polymers have seen an increasing development in the last decades, thanks to their stiffness and load-bearing properties as well as low density. In addition, since they are heterogeneous by nature, the introduction of complementary functionalities, such as the ability to sense deformations, or self repair damage can be envisaged. Extrinsic capsule-based healing systems for composite structures are based on the introduction of microcapsules which, upon an intra-matrix damage event, break and release the healing agent to the crack plane. Many different encapsulated healing agents were explored in the past years. The healing efficiency is usually assessed by comparing a given mechanical property of the virgin material (which contains the healing agent) to the same one after damaging and healing events.
In the present work, we investigated and compared the healing capability of a glass fibre-reinforced epoxy by using two different healing agents, both dispersed within the matrix phase in the form of 150-250 mu;m spheres. In both cases, the healing system is introduced in the material by functionalising the glass fibre-preform (through manual dispersion) prior to Vacuum Assisted Resin Infusion Moulding (VARIM) processing.
In the first case, the healing agent is a polar organic solvent, EPA (contained in fragile polymeric spherical shells); the agent, being released when a crack passes through the capsule, is able to swell the matrix by diffusion, thus bringing the crack faces in close contact, and to enable the reaction of residual resin and hardener functionalities of the under-cured matrix.
In the second case, the healing material is a thermoplastic polymer with a low melting temperature, PCL (about 60°C), introduced in the composite in the form of solid microspheres. When a crack passes through the microspheres and the material is heated above 60°C, the melt thermoplastic is able to flow into the crack volume and fill it. Once the composite is cooled down, the crack is filled of solid thermoplastic material and new interfaces with the epoxy are established.
We show here results obtained by testing the composites with Double Cantilever Beam (DCB) experiments, and assessing the healing efficiency by comparing the slopes of the elastic stress-displacement part of the curve as well as the fracture toughness. It is observed that the first system is better suited to heal neat resins and is not adapted for a composite, i.e. in the presence of reinforcing fibres, because those constitute a hindrance for the swelling. However, for the same testing conditions, better results are obtained with the second system, although the need to heat up the material in order to induce the healing makes the system less autonomous.

Wheat gluten (WG) is a natural biodegradable protein polymer having great potential to substitute for conventional plastics. However, due to a lack of intermolecular covalent bonds and chain entanglements between gluten molecules, WG based materials are quite brittle and have high water absorption, which can cause premature brittle failure and softening by absorbing moisture. Appropriate modifications could mitigate these problems. Normally, blending with plasticizers (e.g. glycerol, sorbitol) or crosslinking with small molecules (e.g. aldehyde, diisocyanate) are used, but neither can solve these two problems well or simultaneously. Improved ductility is generally achieved at large expense of modulus and strength, or vice versa, which often makes materials unusable. However, modification with anhydride functional rubbery macromolecular crosslinker effectively reduces water absorption and improves mechanical properties.
The present work uses a macromolecular crosslinker, polymethyl acrylate-co-maleic anhydride (PMA-MA), which has great elasticity and high anhydride reactivity to amine and hydroxyl groups in the WG. The PMA-MA copolymer is synthesized through free radical polymerization at molar ratios of 95/5, 90/10 and 80/20. WG and PMA-MA is blended at a ratio of 80/20 (wt:wt), which was previously shown to be the best blending ratio for WG blends with other polymers. Phase separation is observed in the new blends via DSC, with two T_g observed: a weak transition for the PMA-MA phase (25^oC) and a strong transition for the WG phase (180^oC). The blends&’ two T_g are higher than T_g of the blends constituents, PMA-MA (15 ^oC) and WG (175 ^oC), illustrating crosslinking between the anhydride of PMA-MA and amines and hydroxyls in WG. The transition for the PMA-MA phase becomes weaker as the MA fraction in the copolymer increases, and becomes indistinct for the case with 80/20 molar ratio copolymer. Flexural testing indicates PMA-MA modified WG exhibits dramatically increased stress, strain, toughness and reduced water absorption. With addition of 20wt% PMA-MA (90/10), the blend&’s properties are improved as much as 100%, 480% and 1000% on strength, strain and toughness, respectively; and only slightly decrease of modulus from 4GPa to 2.9GPa. Meanwhile, the water absorption ratio is reduced to 52% from 120%.
In conclusion, through modification by PMA-MA functional macromolecular cross-linker, WG&’s mechanical properties are dramatically improved to a level above widely used polystyrene and approaches aerospace grade epoxy, making WG&’s application as biodegradable plastics more promising.

Among the family of carbon-based systems, graphene is one of the youngest members alongside diamond, graphite, fullerenes and carbon nanotubes. There is a significant interest in carbon-based nanomaterials as supercapacitor electrodes owing to their lighter weight, higher electrical conductivity and specific surface area. Moreover, supercapacitors store energy by forming a double layer of electrolyte ions on the surface of conductive electrodes. There is large number of interesting possibilities in creating new designs for such energy storage devices if the carbon-based electrodes can be tailored and engineered to fit new functionalities (i.e. higher stored energy) by forming composites with polymer, for instance. In this work, we present the synthesis of in-situ oxidative polymerization transforming pyrrole to polypyrrole in the presence of functionalized graphene sheets producing high-quality novel 2D hybrids / composites as advanced electrochemical platforms/electrodes for energy storage and conversion. The obtained functional materials are investigated by means of electrochemical and in-situ Raman spectroscopic methods in terms of cyclic voltammetry (CV) with scan rate, electrochemical impedance spectroscopy (ac EIS) determining specific capacitance and resistance, charge-discharge cycling with varying concentration ratio of graphene/pyrrole and charge transfer dynamics by monitoring Raman spectroscopy bands as a function of applied electrochemical bias. The synergistic surface and interfacial interaction due to structural conjugation between the p-type polypyrrole on the surface of negatively charged carboxylated functionalized graphene sheets is anticipated to result in higher charge storage capacity than those of graphene-only or polymer-only films. It is the higher electrical conductivity of p-doped polypyrrole and higher surface area of carboxylated functionalized graphenes promote higher charge accumulation in these (super)capacitors. These results are complemented with AFM and TEM combined with electron diffraction structural techniques to establish property-structure relationship. We also report the optimization of the relative concentrations of carboxylated functionalized graphene in the polypyrrole matrix to maximize the compositions&’ specific capacitance. The work is supported by the author's start-up (SG) and NSF-KY EPSCoR (EPS-0814194 and 3048108525-l4-046) grants.

The refractive index (n) of a material is one of the most important factors in determining its suitability for optical applications, which often require a high n value in conjunction with a high transparency. Nowhere is this more evident than in the demands imposed by the industrial production of solar cells, LEDs, OLEDs, optical lenses and filters, anti-reflection films, and optical adhesives. For fabrication of the high refractive index materials, two methods have been developed and proven successful. The one is the synthesis of special polymers, which contains heavy atoms such as sulfur and halogen. The other is the blending of metal oxide nanoparticles (NPs) such as TiO₂ and ZrO₂ into conventional polymers. However, these two methods have weak point in transparency, complexes fabrication process and cost. To solve these problems, we established a new method for facile fabrication of high refractive index material that is based on simple blending of polymer and heteropoly acid of tungsten oxide (WO₃), such as 12-tungstophosphoric acid (H₃PW₁₂O₄₀: PW12) and 12-tungstosilicic acid (H₄SiW₁₂O₄₀: SiW12). The hybrid of polymer and heteropoly acid was obtained by casting method from poly(methyl methacrylate) (PMMA) and PW12 dissolved ethyl acetate solution. The obtained hybrid film showed high transparency between 0 wt% and 90 wt% of PW12 weight fraction in the hybrid. With increase the n value from 1.4881 to 1.7544 was observed with increasing the weight fraction of PW12 in the hybrid. In the case of poly(hydroxyethyl methaclylate) (PHEMA) and SiW12 hybrids also showed significant increase of n value from 1.5053 (PHEMA) to 1.7810. In the presentation, the hybridization mechanism of polymer and heteropoly acids and mechanical properties of hybrids would be discussed.

Poly(L-lactic acid) possess exceptional properties such as biocompatibility and biodegradability. These properties have facilitated their properties in biomedical applications as sutures and tissue engineering scaffolds. In order to create suitable biocompatible materials for various tissue engineering applications, it is important to be able to understand protein adsorption and cell adhesion behaviors on the material surfaces. It is known that the nanoscale distribution of adsorbed proteins affects cell adhesion behaviors. In this study, we synthesized PLLA based diblock copolymers which self-assemble and generate a variety of nanostructured morphology and investigated the relationship between the surface properties of the polymers and protein adsorption, cell adhesion behaviors. We selected poly(fluorostyrene), which has high polar groups and shows high hydrophobicity for one of the block segment. Diblock copolymers, poly(L-lactic acid)-b-poly(fluorostyrene), were synthesized by the combination of controlled ring-opening polymerization using aluminium isopropoxide and living radical polymerization. PLLA rich polymers were synthesized via the ATRP process using copper bromide, and PFS rich polymers were synthesized via the RAFT process. Molecular weights and unit ratios of the diblock copolymers were controlled by catalytic content and the polymerization time. The obtained polymers were characterized by using FT-IR, GPC, ¹H NMR, and DSC. The DSC results of the diblock copolymers showed the glass transition of both the block units, suggesting that both the block units of the diblock copolymers are immiscible. The thin films of the diblock copolymers were prepared by spin-coating 1 % (w/v) chloroform solution onto glass slides. The surface morphology of the thin films was analyzed by atomic force microscopy (AFM). The AFM phase images revealed that the diblock copolymers formed a microphase-separated structure ; dots, lamellae, and cylinders, varying with the composition ratios and the PFS block lengths. The domain size ranges from 20 nm to 60 nm in diameter. In addition, the surface modification was taken by alkaline etching. AFM height images of the etched films showed porous structures formed by the removal of the PLLA unit. The influence of the surface morphologies on physicochemical properties was investigated by contact angle measurements and cell adhesion rate measurements using MC3T3-E1 cells. The contact angle of PLLA-b-PFSs before etching were 3 0 to 16 0 higher than that of PLLA. While the cell adhesion rate calculated after 5 h cultivation of PLLA was 100 %, those of PLLA-b-PFSs before etching were depressed to 82 to 51% with an increase in the contact angle. Moreover, PLLA-b-PFSs after etching showed higher water- repellency than PLLA and lower cell adhesion ratio. These results indicated that varying the unit ratio of the diblock copolymers definitely influence protein adsorption and cell adhesion behaviors.

We have designed an ABA type block copolymer (BCP) where the middle block can be utilized to conjugate biologically relevant moieties such as an oligopeptide. The copolymer consists of a majority of poly(methacrylic acid) as the A block and a minority of poly(2-hydroxyethyl methacrylate) as the central B block. By incorporating the peptide into the middle block, we create a peptide cluster in the block copolymer architecture, which is a potential factor in regulating cell-polymer interfacing. With this design, we synthesized a high molecular weight poly(methacrylic acid)-block-poly(2-hydroxyethyl methacrylate)-block-poly(methacrylic acid) ABA block copolymer via sequential anionic polymerization.
In order to couple the peptide with the synthesized BCP, we have developed a post-polymerization modification route involving thiol-acrylate Michael addition. We show that thiol-acrylate Michael addition is a versatile chemical reaction to conjugate highly functional peptide onto a middle B block which is hindered by extremely long outer A blocks. As other types of coupling reactions may have drawbacks including residual metal traces which must be avoided for biological systems, or short radical lifetimes which may prevent successful functionalization to high molecular weight polymers. In contrast, the Michael addition has relatively mild reaction conditions and by-product formation can be also minimized. More importantly, it is possible to minimize possible side reactions which can be caused by highly functional reactants and accordingly to achieve high conversion. By optimizing the reaction conditions, we successfully modified the block copolymer with the peptide sequence Tyr-Gly-Arg-Gly-Asp (YGRGD). We further tested cell viability on these block copolymers, showing the feasibility of their application for cell-polymer interfacing.

Polythiophenes and their derivatives are known for their semiconductor behavior and high environment stability at elevated temperatures. However, its poor mechanic properties and biodegradability limits their applications. The application of conducting polymers at the interface between biology and electronics has been found to be useful for the development of implants for tissue engineering and nerve regeneration, mechanical actuators (artificial muscles) and sensors. Blends of polythiophenes (PT) and polythiophenes derivatives with the biocompatible thermoplastic polymer, such as poly(hidroxybutyrate-co-valerate) (PHBV), can improve the thermo, mechanical and biocompatibility performance of these materials. PT/PHBV blends are candidates for biological application such scaffold for tissue engineering applications. In addition, conducting polymers are biocompatible materials able to stimulate cell attachment, proliferation and regeneration through electrical signals in which the dopant agents embedded in the material play an important role. In work, were prepare poly(3-ethyl-thiophene acetate)/PHBV blends scaffolds to be employed tissue regeneration. The poly(3-ethyl-thiophene acetate) (PTAcEt) was synthesized by Sugimoto method. The polymerization of the monomer was made by FeCl₃ chemical oxidation, in chloroform and N₂ atmosphere by 24h. PTAcEt/PHBV blends were prepared by solution method. Films of the blends were prepared in four different weight ratios of PTAcEt, for 2, 4, 8 and 12 % (w/w). The materials were characterized by FT-IR, UV-Vis, Fluorescence Spectroscopy, thermal analysis DSC and TGA. The colorimetric method using 3-(4,5-dimethylthiazol-2-yl) 2,5-Diphenyl bromide Tetrazoilium (MTT) were used to assess the cell viability of the blends. The cell viability assay was conducted with cells of mouse embryo fibroblast (MEF) with polymerization yield of 41%. The final product of the polymerization was confirmed by the FT-IR spectra. The vanish of the band around 736 cm^-1, visible in the monomers spectrum, and the arising of another band around 830 cm^-1 in the polymer&’s spectrum occur due to the formation 2.5 bonds in the thiophene ring. The UV-Vis analysis of the films show that the PHBV matrix do not contributes with the absorbance at this region and, for the blend film, show an increase of the absorbance due concentration increase of PTAcEt in the blends. In the thermal analysis, a curve of pure PHBV showed two melting peaks (160°C and 174°C). With the increase of PTAcEt amount in the PHBV matrix, both of the melting peaks became wider and shifted to lower temperatures. The increase tendency of first and second melting points with increase of PTAcHex amount, suggests an increase in the crystallinity of the blends. The biological assay shows that PTAcEt/PHBV blends are not cytotoxic to the cells growing. The MTT assay shows that blends with 4% of PTAcEt present greater cell viability than the pure PHBV.

Enzymatic synthesis of polyaniline is a mild synthetic route that has been studied in the last 20 years. Several oxidoreductases have been used in the synthesis of poyaniline, and many modifications in the reaction media have been already studied. In this work, we developed a new synthetic method based on an enzymatic-cascade reaction using the mixture glucose oxidase/horseradish peroxidase. An enzymatic cascade reaction is a succession of enzymatic reactions in which the product of a reaction is consumed in the next one. Enzymatic-cascade reactions are very common in the metabolic routes, but have been barely employed in chemical synthesis due to their complexity, as compared with single-step enzymatic reactions. In order to control the structure of the polyaniline, aniline and aniline-sulfonic acid, were polymerized in presence of several biologically relevant polyelectrolytes, such as deoxyribonucleic acid, chitosan, and chondroitin sulfate. The resulting polyaniline was compared with that synthesized from well-known poly(sodium styrene sulfonate) and polydiallyldimethylammonium chloride. The synthesis was conducted in presence of a mixture of glucose-oxidase/horseradish peroxidase. These two enzymes have been used independently to synthesize polyaniline, but here, we proposed a cascade method to minimize the presence of hydrogen peroxide in the reaction media. The reaction was initiated by adding glucose to the reaction media containing the monomers and the enzymes. Glucose oxidase catalyzed the oxidation of glucose to gluconolactone with the in situ production of hydrogen peroxide. The polymers were characterized by several spectroscopic techniques, such as Fourier transformed infrared, UV-visible, and X-ray photoelectron spectroscopy. In addition, the reactions were monitored by changes in the open circuit potential, and impedance of the solution. As a proof of concept, polypyrrole was also synthesized using a cascade reaction. This synthetic route opens the possibilities to use sugar and atmospheric oxygen as oxidizer for the enzymatic-cascade synthesis of polymers.

The development of biocompatible substrates has often focused on the design of polymeric materials which are non-toxic, have controllable degradation, and are able to be modified for bio-signaling or drug release. However, an oft neglected parameter, modulus, is integral to the development of chronically viable implantable biomedical devices in soft tissue due to the potential for tissue damage by the device post-implantation. Controllable modulus, high for implantation and low in vivo, is an excellent way to control native tissue response. Relatively speaking, the modulus of a material is controlled by the density between crosslinks. By decreasing the number of crosslinks we can effectively decrease the rubbery modulus of the material in vivo, however, decreasing the crosslink density also tends to decrease the glass transition of the material, often making it rubbery, leading to dimensional instability, and making it unusable by surgeons. By increasing the rigidity of the monomer constituents in the polymer network we can effectively decrease the rubbery modulus of a material while retaining a desirably high glass transition temperature, allowing ease of surgeon implantation. Herein we describe the design, synthesis and materials properties of a range of rigid thiol monomers, their materials properties when incorporated into thiol-ene networks and their use in biomedical devices.

Mixed metal oxides (MMOs) are promising materials for use in insertion batteries and supercapacitors, but performance is strongly dependent on the architecture of these materials. Cooperative assembly with block copolymers provide one facile route to control the morphology at the nanoscale, but sol-gel processing of such materials can be challenging due to the requisite requirements over condensation rates to prevent precipitation of one of the components. Moreover, the simultaneous formation of the ordered structure and the condensed network impedes the ability to orient and align the mesostructure. To overcome these challenges, a citric acid mediated approach is used wherein the mesoporous MMO is synthesized through the thermally induced formation of a carbonate intermediate. This approach enables additional processing to modulate the ordered mesostructure templated by the block copolymer, poly(ethylene glycol-methacrylate)-block-poly(butyl acrylate) in this case. We demonstrate that this approach can generate highly ordered mesoporous MMOs using nickel and cobalt nitrate as a model system.The whole compositional spectra from pure mesoporous nickel oxide to pure cobalt oxide can be obtained with this approach with average pore size ranging between 14-16 nm based on AFM micrographs. The templated porous architecture of multi-component oxides can allow for enhanced cycling stability and high rate capacity (> 900 mAh/g at 200 mA/g) when used as anodes in lithium ion battery.

Cellulose nanocrystals (CNCs) have emerged as a new class of renewable material for various applications due to their remarkable properties and commercialization prospect. The relative low density, expected low cost, non-toxic character, uniform nanosize distribution, high aspect ratios, high surface area, thermal properties and high modulus of elasticity make CNCs attractive nanomaterials that recently prompted the industrial production of CNCs in North America. While previous works focused mainly on the use of CNCs as reinforcing agent for biocomposites, there has been an emerging interest in using modified CNCs for biomedical applications. In this present work, we report the synthesis, characterization and cytotoxicity studies of novel cationic surface modified CNC derivatives. The negative surface of CNC was rendered positive after grafting with cationic polymers via surface-initiated living radical polymerization method. The modified CNCs were characterized by both spectroscopic and microscopic techniques. Cationic nature of the modified CNCs was further confirmed by gold deposition on the surface of CNCs. Their cytotoxicity effects were evaluated using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay in two cell lines such as mouse macrophages (J774.A1) and human breast cancer (MCF7). This colorimetric assay is based on the conversion of MTT into formazan crystals (blue) by living cells, indicating mitochondrial activity, which is related to the number of viable cells. We found that only one of the modified CNCs caused significant decreased in J774.A1 cell viability (50%), at the highest concentration tested (100 µg/mL). However this concentration is well above of what would be applicable for biomedical purposes. MCF7 cells were not affected by any of the compounds at any concentration. The modified cationic CNCs were found to be non-toxic at physiological concentrations and thus offer great promises as novel platforms for use in a variety of bio-inspired applications.

Cationization of materials is an important area of research since cellular delivery of DNA, proteins and other macromolecules is a challenge due to the repulsive electrostatic forces. In this work, various nanocarriers, namely rosette nanotubes (biocompatible nanomaterials generated from the self-assembly of a bio-inspired bicycle, featuring the hydrogen bonding arrays of guanine and cytosine) and peptides with tunable properties such as size, charge and functional groups were synthesized and characterized by microscopy, dynamic light scattering and zeta potential measurements. These cationic nanomaterials have low toxicity and were found to bind with plasmid DNA via electrostatic interactions. It was found that some rosette nanotubes interact with plasmid DNA, as observed by atomic force microscopy. Some of these nanomaterials were labeled with a fluorescent dye and complexed with plasmid DNA at physiological conditions. The resulting complexes were successfully and reproducibly internalized with isolated cells, as evidenced by green fluorescence.

Amyloid fibrils tend to be deposited on tissues, which are closely related to many degenerative disorders such as Alzheimer&’s and Parkinson's diseases. Measurement of the surface potential of amyloid fibrils is practically important in studying the related mechanism of their formation that is governed by electrostatic interaction between amyloidogenic proteins. Kelvin probe force microscopy (KPFM) enables us to characterize the morphological and surface potential properties of the amyloid fibrils. To the best of our knowledge, it has not yet been fully elucidated to measure the surface potential of regrown amyloid fibrils made of amyloid fragments deconstructed by well-defined ultrasonic energy. We observed that regrown fibrils became thicker than the original fibrils in radial direction, so does their surface potential. Meanwhile, the surface potential density of the regrown fibrils is very similar to that of original fibrils. These results will help to shed light on intensive understanding of the physical property changes in the regrowth process of amyloid fragments.

The large, reversible actuation of main-chain liquid crystal elastomers (MC-LCE) has been widely reported. The most common synthetic technique utilized is based on the pioneering approach, first reported by Finkelmann, where a partially crosslinked polydomain gel is mechanically aligned and the crosslinking is completed in the aligned state^. Spatially complex alignment is difficult to achieve, however, with this technique in-part due to the delicate, mechanical nature of the process. Here, we report a system of nematic MC-LCEs that is designed to be synthesized in a cell with the order of the LCE defined by photoaligned surfaces. A two-step reaction is employed; first, a near-stoichiometric mixture of mesogenic diacrylate and primary amine is filled into a surface aligned cell and is oligomerized by the step-growth Michael Addition in the aligned state. Subsequently the resulting linear oligomers are crosslinked through free-radical polymerization of remaining acrylate groups forming a lightly crosslinked network. Polarizing optical microscopy and differential scanning calorimetry are used to investigate the isotropic-nematic transition behavior of the oligomer and paranematic-nematic transition behavior of the elastomer. Spontaneous thermomechanical actuation is observed, with certain compositions demonstrating an elongation of greater than 60% on cooling through the paranematic-nematic transition temperature. Control of actuation strain is demonstrated through control of network structure and order. Utilizing a point-by-point alignment technique, arbitrary director patterns, and as such actuation strains, are achievable. Planar and twisted nematic director orientation can be controlled with sub-100 mu;m spatial resolution. The resulting elastomers can form complex origami-inspired structures including a Miura-Ori inspired actuator capable of a 5x reduction in area on heating or exposure to solvents. Patterning arrays of topological defects leads to the introduction of points of Gaussian curvature; the resulting actuators are capable of stroke greater than 40 mm/mm and work capacities of greater than 2 J/kg.

Shape memory polymers (SMPs) are those polymers capable of being fixed in a temporary shape and recovered to their original shape by triggering them with various stimuli, including heat, water, or light. Here, we seek an SMP suitable for deployment in the body with a triggering temperature between 37 and 50 0C, which would biodegrade over a period of 6 months to a year, and which possess good mechanical and shape memory properties. An SMP with such properties would have diverse applications in minimally invasive surgery, spanning drainage stents to hernia meshes, yet existing materials largely fall short of achieving all of the requirements in one composition. To address this need, we have designed a multiblock polyurethane whose shape memory recovery derives from a relatively low-melting hardblock and whose shape fixing comes from a semicrystalline copolymer soft block. Thus, polyols featuring poly(ethylene glycol) (PEG) as a central initiator and various proportions of biocompatible lactone and glycolide monomers have been prepared and then polymerized to multiblock polyurethane form using POSS diol as a chain extender and hexamethylene diisocyanate as the urethane linker. Here, POSS stands for the polyhedral oligosilsesquioxane hybrid moiety featuring known biocompatibility a desirably low (ca. 120 °C) melting point in polyurethane form so as to minimize pre-degradation during melt processing. By controlling the architecture of the diol, particularly the mole percentage of PEG, the properties of the material could be controlled. Each synthesis was followed by detailed molecular characterizations in including proton NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) for mechanical properties. Shape memory experiments performed to determine fixing and recovery ratios of the polymers. We prepared polyols to feature narrow molecular weights between 11 kDa and 14 kDa and melting transitions between 52 and 55 0C. This melting transition could be lowered to 37 0C simply through incorporation of glycolide at low levels, which we postulate breaks up the lactone-based crystals. The resulting polyurethanes were found to feature two melting transitions: a lower temperature transition corresponding to that of the polyol and ranging from 35 to 55 °C and a higher melting transition associated with the POSS-based hard block at 120 0C. These transitions are used for setting the temporary and permanent shapes, respectively. We observed with DMA that an excellent rubbery plateau exists between the two melting points, a characteristic needed for good shape memory properties. Indeed, all of the materials reveal good shape memory properties, and we will report the shape fixing and recovery ratios. Initial findings on degradation behavior will be reported, as well.

We explore shape memory polymer (SMP) and surface microstructuring to develop reusable stamps that exhibit very strong adhesion (> 30 atmospheric pressure) and extremely high adhesion reversibility (strong to weak adhesion ratio of > 10⁴). These stamps are utilized for the purpose of transfer printing that allows for the creation of complex three-dimensional (3D) microstructures and devices which incorporate both 2D and 3D components. Current transfer printing methods mainly rely on the kinetically controlled adhesion of elastomeric stamps made of polydimethylsiloxane (PDMS) which inherently places practical limits on the size, shape, and materials of the constituent parts for assembled 3D microstructures. Specifically, the limited adhesion strength and time-dependent nature of elastomeric stamps requires parts to be 2D. By taking advantage of the thermally-controlled shape memory properties of our SMP stamps, we can deterministically assemble 3D devices from 2D and 3D micro-scale building blocks which are impractical to manipulate with traditional transfer printing methods. These SMP stamps are specifically designed to exhibit dramatic changes in elastic modulus with high shape-fixity factors at a convenient glass transition temperature (T_g). By heating and cooling the SMP stamps during critical stages of operation, extremely strong dry adhesive force may be established and then, through the intelligent use of surface microstructuring, may be reduced dramatically to facilitate release. The combination of superior, time-independent adhesive strength and reversibility enables the development of new classes of heterogeneous micro-devices which were previously not possible through traditional monolithic microfabrication or elastomeric stamp-based transfer printing techniques.

Thermally-induced shape-memory effects in polymers under stress free conditions are typically limited to one way effects. Here we introduce crosslinked polymer networks comprising crystallizable domains, which are capable of a reversible, bidirectional shape-memory effects (rbSME). After application of a specific thermomechanical treatment such polymers can repetitively shift under stress-free conditions between two defined shapes A and B upon alternate heating and cooling, whereby different shape shifting geometries can be programmed and reshaped.
In this study the rbSME properties of a multiphase copolyesterurethane network named PPD-PCL comprising two distinct melting transitions which was prepared from star-shaped oligo(omega;-pentadacalactone)tetrol (PPD) and oligo(ε-caprolactone)triol (PCL) precursors as well as a crosslinked poly[ethylene-co-(vinyl acetate)] cPEVA and a copolymer network cPCLBA, containing crystallizable PCL domains and amorphous poly(n-butylacrylate) domains, were explored by cyclic thermomechanical tests. Such tests consisted of a programming module followed by repetitive stress-free heating cooling cycles, where the rdSME capability was quantified by the characteristic reversible strain and the switching temperatures T_act(A→B) and T_act(B→A). In addition in situ small angle X-ray scattering (SAXS) investigations were conducted to explore the nano structural changes during rbSME.
Excellent rbSME properties with high reversible strains ranging from 8% to 21% could be implemented in all three crosslinked polymer networks comprising crystallizable actuation domains. In situ X-ray investigations could further demonstrate that the macroscopic shape changes of the explored polymer systems are correlated with reversible nano structural changes of the crystallizable actuation domains. In a multi-cyclic experiment with more than 250 cycles it could be demonstrated that the rbSME performance of cPEVA was not affected by the number of applied reversibility cycles, which qualifies such materials for actuator applications.
References
Behl, M.; Kratz, K.; Zotzmann, J.; Noechel, U.; Lendlein, A., Reversible Bidirectional Shape-Memory Polymers, Advanced Materials, 25:32 (2013) 4466-4469
Behl, M.; Kratz, K.; Noechel, U.; Sauter, T.; Lendlein, A., Temperature-memory polymer actuators,Proceedings of the National Academy of Sciences, 110 (2013) 12555-12559

Polyphenols are ubiquitous in nature serving a variety of functions including mechanical adhesion, structural support, pigmentation, radiation protection, and chemical defense. One of the most prominent features of this class of biomolecules is their ability to adhere at solid-liquid interfaces. Exploiting their inherent adhesive properties, we have engineered a method to form thin adherent polymerized films on substrates immersed in solutions of biological polyphenols. This talk will emphasize the use of polyphenol coatings for targeting and therapeutic applications of gold nanorods. Deposition of a conformal thin polyphenol coating was observed upon incubation of CTAB stabilized nanorods in an alkaline solution of polyphenols. The polyphenol coating formed from this process is several nanometers in thickness and serves as a primer for further surface functionalization of the nanorods. In one case, the polyphenol coating is further coated with silver and targeted toward bacteria using a surface bound antibody, whereupon plasmonic heating of the nanorod was exploited to kill bacterial cells. In another application, antibody to MUC1 was conjugated to the polyphenol coated nanorods and used to target and photoablate MUC1 positive cancer cells. Polyphenol coatings represent a versatile and facile approach to surface functionalization of nanomaterials for a variety of medical and nonmedical applications.

Creating an effective anti-fouling surface that response to a broad spectrum of foulants remains a major technical goal. Such surfaces are valuable in applications ranging from biomedical devices to coatings used in a variety of environments, particularly marine applications. We have recently developed polymers that use sequence controlled oligopeptides attached to block copolymers as model segments in our study of the importance of composition and architecture in surface active coatings. In this study we used natural and unnatural amino acids to build up sequences of preselected architecture and attached them to polystyrene-block-polydimethylsiloxane blocks copolymers employing thiol-ene “click” chemistry. Peptide chemistry permits essentially any sequence to be produced from available amino acids. Natural hydrophobic and hydrophilic amino acids and unnatural amino acids containing either PEG, hydrocarbon or fluorocarbon segments were investigated. The sequences were selected to enable combinations of polar and non-polar units based on our observation that "ambiguous" surfaces of mixed polar units provide strong settlement resistance and excellent fouling release against a wide range of species. These materials were created in part to understand critical length scales involved in the effective ambiguous surface. In addition we are investigating the incorporation of zwitterion units, known to further enhance fouling release as well as the fluorinated groups which favor surface segregation of associated units. These surfaces were tested against protein settlement, and fouling by marine organisms such as Ulva Linsa (released from non-polar surfaces) and Navicula (released from polar surfaces). Surface analysis included contact angle measurements, and surface sensitive methods such as XPS and NEXAFS. These studies have shown the importance of sequence control in anti-fouling behavior and the ability of even small quantities of fluorinated units to very effectively draw the surface-active unit to the surface region.

Several applications of polymer-based materials require the fabrication of a hybrid interface between polymer thin films and inorganic substrates like silicon wafers. The properties of this interface are determined by how well the polymer covalently bonds with the inorganic substrate, thereby satisfying dangling bonds and passivating electrically active interface traps present on the surface. We demonstrate here that a variant of the chemical vapor deposition (CVD) polymerization technique, namely initiated chemical vapor deposition (iCVD) can covalently graft a polymer film onto a silicon substrate by initiating a chemical reaction between the surface hydride bonds on silicon and the functional (vinyl or ethynyl) groups of the vapor-delivered monomer. While the CVD process used for depositing inorganic passivating films like silicon nitride requires high temperature (400 - 450 ^oC), the iCVD method offers a solvent-free, low temperature (20-25 ^oC) alternative, which retains delicate organic functionalities in the monomers, enabling the fabrication of hybrid and multifunctional polymer-based devices. Following the iCVD passivation process, the minority carrier lifetimes of a functionalized silicon surface showed over three-fold improvement (upto 94 microseconds at 1x10¹⁵ cm^minus;3 carrier injection levels) compared to bare silicon, suggesting passivation of surface traps. Surface passivation results obtained by iCVD are reproducible and stable during storage in air for over 100 hrs. The roles played by chemical bonding and field effect charges in the observed surface passivation were examined through attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and x-ray photoelectron spectroscopy (XPS) of the functionalized silicon surface. Such a process of chemical passivation when applied to silicon solar cell surfaces can reduce surface recombination of minority carriers, increase solar cell efficiency and lower overall cost per watt. We further show that iCVD polymerization can be used to graft and pattern functional polymer films of hundreds of nanometers thickness on top of this passivated silicon surface. Grafted poly(ethylene glycol diacrylate) (PEGDA) films are dielectric and serve as anti-reflection coating (ARC) layers in solar cells. Grafted poly(para diethynyl benzene) (PPDEB) films show semi-conducting behavior and their aromatic rings can be used to graft poly(ethylenedioxythiophene) (PEDOT) films using Friedel Crafts catalysts like FeCl₃. These grafted PEDOT films can serve as polymer based current collecting electrodes with excellent conductivity approaching 1400 S/cm. Finally, scale-up of the iCVD process has previously been demonstrated in a roll-to-roll system. The novel iCVD passivation can thus provide a simple, commercially viable platform to engineer high quality polymer surfaces and interfaces in the semiconductor, solar and biomedical industries.

Inspired by the long-term effectiveness of living antifouling materials, we have developed a method for the self-replenishment of synthetic biofouling-release surfaces. These surfaces are created by either molding or directly embedding 3D vascular systems into a polymer matrix and infusing them with a compatible lubricant to generate a non-toxic oil-infused material capable of self-lubrication and renewal of the interfacial foul-release layer. Under accelerated lubricant loss conditions, fully-infused vascularized samples retained significantly more lubricant than equivalent non-vascularized controls. Furthermore, non-infused samples could be saturated with lubricant through the vascular system alone. Tests of lubricant-infused samples in static cultures of the infectious bacteria Staphylococcus aureus and Escherichia coli as well as the green microalgae Botryococcus braunii, Chlamydomonas reinhardtii, Dunaliella salina, and Nannochloropsis oculata showed a significant reduction in biofilm adhesion compared to polymer and glass controls containing no lubricant. Further experiments on vascularized versus non-vascularized samples that had been subjected to accelerated lubricant evaporation conditions for up to 48 h showed significantly less biofilm adherence on the vascularized surfaces. These results demonstrate the ability of an embedded lubricant-filled vascular network to improve the longevity of fouling-release surfaces.

Gelatin is a promising starting material for the synthesis of biomaterials, as the resulting materials inherently combine functions like degradability or the ability for interactions with cells by offering motifs for cell adhesion. As gelatin dissolves under physiological conditions, crosslinking has been introduced as a method for tailoring mechanical properties or degradation rate. Besides water, which is an interesting option in view of potential medical applications, the choice of alternative solvents as reaction medium is very limited. Therefore, many reactions, which are suitable for gelatin crosslinking and are available to the synthetic chemist in organic solvents need to be adapted to aqueous conditions. The mechanism of these reactions might be quite different, with many potential side reactions.
We investigated the tailoring of mechanical properties of hydrogels based on gelatin by polyaddition using diisocyanates¹, photopolymerization², and metathesis³ under aqueous conditions. The covalent crosslinking suppresses self-organization of gelatin chains to triple and single helices (< 5% helical content), which enables tailoring the material properties by the amount of crosslinker, and not by the thermal history of the sample. Elastic hydrogel systems with Young&’s moduli of 10-600 kPa, water uptake of 10-1600 wt.%, and degradation times in aqueous solution ranging from few days to several weeks depending on the crosslinking strategy were realized.
Through studying test reactions with mass spectrometry, mechanisms for the crosslinking could be explored, which lays the basis for the knowledge-based design of biopolymer-based networks in the future. In diisocyanate-based crosslinking, we demonstrated that not only direct crosslinking, but also oligomer formation and grafting contribute to the network formation. Low reactivity and solubility of the diisocyanates enhanced the specificity of the reaction. In the photopolymerization of glycidylmethacrylated gelatins, it could be shown that the oligomethacrylate chains formed are short enough to be excreted renally. Cross metathesis ring-opening crosslinking could be realized by reaction of glycidylmethacrylated gelatin and norbornene dicarboxylic acid. Through selection of olefins with different reactivities, selective cross metathesis was achieved allowing for chemoselective crosslinking. The synthestic step can be performed by using either classical Grubbs 1^st or 2^nd generation catalysts in emulsion, or alternatively a water soluble, PEGylated Hoyveda-Grubbs 2^nd generation catalyst.
References
1: G. Tronci, A.T. Neffe, B.F. Pierce, A. Lendlein, J. Mater. Chem.2010, 20, 8875.
2: B.F. Pierce, G. Tronci, M. Röszlig;le, A.T. Neffe, F. Jung, A. Lendlein, Macromol. Biosci.2012, 12, 484-493.
3: A.T. Neffe, K. Chua, K. Luetzow, B.F. Pierce, A. Lendlein, A.D. Abell, PAT J.2014, accepted.

Engineered protein hydrogels hold promise in mimicking the mechanical responses of extracellular matrices (ECMs) due to their similarities in chemistries and structure-property relationship. Therefore, approaches to control hydrogels&’ mechanical properties, relaxation mechanisms, and responsivities to external stimuli are desirable in order to faithfully mimic the mechanical behaviors of natural ECMs. Here, we present a set of versatile methods to orthogonally control the viscoelastic behaviors of engineered proteins hydrogels on small and large length/time scales, respectively, through manipulating the molecular architecture of the artificial proteins.
First, linear multiblock coiled-coil proteins with very high molecular weights up to 500 kDa are produced by coupling the cysteine residues near the N- and C- termini of the protein with different thiol-coupling chemistries: thiol-maleimide, thiol-bromomaleimide, thiol-ene, and disulfide bridging. When the concentration of the chain-extended proteins is above the entanglement threshold, hydrogels exhibit a new plateau modulus at 0.005 rad/s and below, and show a significant delay of entering the terminal relaxation, while the high-frequency modulus of gels is almost unaffected. Due to the subtle differences in stoichiometry and inherent side reactions in the four chain extension chemistries, varying extents of entanglement can be obtained. This demonstrates that the choice of bioconjugation methods clearly has an impact on the mechanics of the final materials.
Second, graft-like protein-polymer hydrogels are prepared through the supramolecular complexation between the chain-extended proteins decorated with β-cyclodextrin moieties and the adamantane end-functionalized poly(N-isopropylacrylamide) (PNIPAM). The resulting hybrid hydrogels exhibit thermoresponsive mechanical properties due to the solvation/desolvation of the PNIPAM grafts at low/high temperatures. The supramolecular association between β-cyclodextrin and adamantane enables facile and easily generalizable methods to incorporating other functionalities into the protein hydrogels.
Finally, branched proteins are synthesized by using di- and tri-functional coupling agents in A₂ + B₂/B₃ mixed thiol-ene reactions. The gel mechanics, especially the long time relaxation, can be significantly changed by over an order of magnitude in the terminal regime, through varying the diene to triene ratio in the reaction. At 20% triene compositions, the most pronounced entanglement effect is achieved, which is hypothesized due to the optimization between the chain length and the number of branched points.
This work demonstrates the concept of manipulating the chain architecture and topology to control mechanical behaviors of engineered protein hydrogels, which provides a new angle to create artificial ECMs to study the cell-matrix interactions.

Natural wood fibers are an earth-abundant, renewable, biodegradable, and non-petroleum based material that offers unique properties. Green electronics are steadily gaining research and commercial interest due to the promise of creating flexible, lightweight, cost efficient, renewable, and biocompatible devices. Nanopaper made from cellulose nanofibers possesses tunable optical properties, mechanical strength, and small surface roughness enabling many types of electronics that were not previously possible using regular paper or plastic substrates. Additionally, the transition from rigid glass to flexible paper substrates enables the creation of flexible and transparent devices that can be produced quickly using established roll-to-roll manufacturing methods. Lowering the cost and improving the performance of devices are essential for making renewable energy feasible for everyday applications. Various nanopaper electronics are demonstrated in our group, including transistors, organic light emitting diodes (OLEDs), touch screens, solar cells, and antennae.
With the cellulose fiber network as a host, we impregnate other functional materials, like boron nitride and Fe₃O₄, to give the paper good thermal conductivity and magnetic properties. Meanwhile, with strong nanocellulose as building blocks, we fabricated multifunctional fibers with high mechanical strength and excellent electrical conductivity for the application in energy storage, smart textiles, and low density materials in space. The manufacturing of 2D paper and 1D fibers based on earth abundant material have the potential to expand green electronics as well as galvanize a new future for renewable multifunctional materials.
Reference:
Zhu, H., Li, Y., Fang, Z., Xu, J., Wan, J., Dai, J., Yang, B., Hu, L. Highly Thermally Conductive Films with Percolative Layered Boron Nitride Nanosheets. ACS Nano. 2014.
Zhu, H., Narakathu, B., Fang, Z., Aijazi, A., Joyce, M., Atashbar, M., Hu. L. Antenna on Shape-Stable Transparent Nanopaper. Nanoscale. accepted.
Zhu, H.,^sect; Fang, Z.,^sect; Preston, C., Li, Y., Hu, L.*. Transparent Paper Fabrications, Properties, and Device Applications. Energy and Environmental Science. 2013, 269 - 287.
Zhu, H., ^sect; Fang, Z., ^sect; Ha, D., Preston, C., Chen, Q., Lacey, S., Li, Y., Han, X., Lee, S., Chen, G., Chai, X., Munday, J., Hu, L.*. Paper with Ultra-High Transparency and Ultra-High Haze for Solar Cells. Nano Letters, accepted, 2013.
Zhu, H., Xiao, Z., Liu, D., Li, Y., Weadock, N.J., Fang, Z., Huang, J., Hu, L. *. Biodegradable Transparent Substrates for Flexible Organic-Light-Emitting Diodes, Energy and Environmental Science 2013, 6, 2105-2111.
Zhu, H., Parvinian, S., Preston, C., Vaaland, O., Ruan, Z., Hu, L.*. Transparent Nanopaper with Tailored Optical Properties, Nanoscale, 2013, 5, 3787-3792.
Zhu, H.^sect;, Huang, J.^sect;, Chen, Y., Preston, C., Rohrbach, K., Cumings, J., Hu, L.*. Highly Transparent and FlexibleNanopaper Transistors, ACS Nano, 2013, 7 (3), 2106-2133.

Polymer gels have attracted a great deal of attention for tuneable soft materials where control over material behaviour is critical. A large fraction of such materials incorporate transient networks, where the use of physical associations as opposed to permanent chemical bonds allows the gels to respond to environmental stimuli. These types of physically associated networks also demonstrate mechanical properties not seen in their chemically crosslinked counterparts, including shear thinning, self-healing, and stress relaxation.^1-3 Transient network theory provides a framework for modelling the rheology of associating polymers using coarse-grained molecular properties such as binding dynamics, association energies, degrees of polymerization, and associating group molecular geometry. Transient network theory has is roots in rubber elasticity theory, which ties a polymer&’s internal stresses to its change in entropy and can be used for both covalent and physical network junctions.^4-8
Here we will discuss a new type of transient network theory that is capable of tracking the rheological properties of associating polymers under time-dependent shear while quantitatively modeling the chain end conformational probability distribution. Specifically, this theory uses a coupled set of Smoluchowski equations for the probability of a chain end being present as a bridged, looped, or dangling chain. Each particular chain end is capable of interconverting via specific reaction terms as a function of the chain end kinetics. This treatment provides for the decreased amount of elastically effective chains present as a result of the presence of looped chains, as well as dangling chain tumbling under high shear. As a result, we are able to provide insight into how chain interconversion and chain tumbling combined result in decreased elastically effective chain extension, often also in lower quantities, corresponding to the stress instabilities frequently seen in steady state and transient shear flow.⁹
Works Cited:
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The ever evolving need for new materials that are biocompatible and able to respond to various external stimuli shapes a great deal of effort of the scientific community as they may serve as the basis for advanced applications in fields ranging from medical sciences to microdevices. Polymer gels that are “wet” materials easy to deform are further privileged by the fact that they can easily be rendered biocompatible and are the natural candidates to be used within this framework. Here, we report on actuation and mechanical properties of macroscopic magnetoresponsive and (biocompatible) electroresponsive gels and investigate their multi-stimuli response at micrometer scales. In this context, we investigate in detail the magneto rheological response (linear and non-linear) of highly swollen physical gels obtained by self-assembling of triblock copolymers containing low remanence ferromagnetic particles in the presence of external homogeneous magnetic fields. In some cases, a very strong relative increase of storage modulus, up to 60 times the off-sate value is obtained. We also show that long time transient rheological responses are correlated to strong rearrangement of the particle network as directly observed under optical microscope with the help of a specially designed magneto-shear cell. Using a responsive polyelectrolyte gel as matrix and microfabritation techniques, we developed a large array of high aspect multi-responsive cilia that can be environmentally (pH), electrically (electrochemical reactions occurring on the electrodes) or magnetically (magnetic field) stimulated. As a resume, we demonstrate how it is possible to integrate various types of stimuli into (potentially) biocompatible gels controlling gel morphology at micrometer scales.

Doubly crosslinked (DX) microgels are macroscopic hydrogels comprised of covalently inter-linked microgels. For this study pH-responsive DX microgels comprised of pH-responsive poly(ethylacrylate-co-methacrylic acid-co-1,4-butanediol diacrylate) (PEA-MAA-BDD) microgels were swollen with an acrylamide (AAm) / N,N&’-methylenebisacrylamide (MBAAm) co-monomer solution which was copolymerised to give double network doubly crosslinked microgels (DN DX microgel). The DN DX microgels contained about 85 vol.% of PAAm-co-MBAAm and 15 vol.% DX microgel in the dry state. The DN DX microgels showed major improvements of their mechanical properties compared to the parent DX microgels and less pronounced pH-triggered swelling changes. The gel mechanical properties were investigated using dynamic rheology and compression stress vs. strain measurements. The new DN DX microgels had much improved shear and compression modulus (435 kPa), yield strains and toughness (105 kJ/m³) compared to the parent DX microgels. By improving both the modulus and ductility of our DX microgels, the double network approach offers improved potential for future application of DX microgels as implantable biomaterials in high load environments as well as membranes.

Smart materials have emerged as a new type of polymeric soft matter in which dynamic bonds are incorporated, thus leading to interesting stimuli-responsive behaviors since the dynamic bonds are able to reversibly undergo tunable changes when exposed to environmental stimuli.^[1] This unique feature provides many opportunities for promising applications in the areas of sensing, biomedicine, environment and energy storage. Among the dynamic bonds, supramolecular complexes based on metal-coordination are particularly attractive because these metal-functionalized species can exhibit added values.^[2-5] We will present a new approach to the synthesis of lanthanide-based hydrogels. In this current study, our design strategy for luminescence tunable metallohydrogels will be discussed with an emphasis on the white light emission and stimuli-responsive properties for potential applications as sensing materials.
[1] (a) R. J. Wojtecki, M. A. Meador, S. J. Rowan, Nat. Mater. 2011, 10, 14; (b) F. D. Jochum, P. Theato, Chem. Soc. Rev. 2013, 42, 7468; (c) Y. H. Jin, C. Yu, R. J. Denman, W. Zhang, Chem. Soc. Rev. 2013, 42, 6634.
[2] G. R. Whittell, M. D. Hager, U. S. Schubert, I. Manners, Nat. Mater. 2011, 10, 176.
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[4] H. Ejima, J. J. Richardson, K. Liang, J. P. Best, M. P. van Koeverden, G. K. Such, J .W. Cui, F. Caruso, Science2013, 341, 154.
[5] N. Holten-Andersen, M. J. Harrington, H. Birkedal, B. P. Lee, P. B. Messersmith, K. Y. C. Lee, J. Herbert Waite, PNAS2011, 108, 2651.

Polymer-based hydrogels are intensively explored for regenerative therapies. A precise control of their physicochemical properties is demanded for their applicability, e.g. for tissue replacement or for the controlled release of bioactive molecules.
This study focused on the effect of crosslinkable endgroups of polymer network precursors on network properties. These hydrogels are based on four-arm oligoethylene glycol (sOEG) bearing terminal desaminotyrosyl tyrosine (DATT) groups [1]. Polymer networks were formed from DATT-sOEG by an enzymatically catalyzed phenol oxidation mediated by tyrosinase, followed by spontaneous covalent crosslinking. In order to study the effect of the amount and type of netpoints on network properties, hydrogels were formed from precursors with different degrees of functionalization with DATT (respectively 65 and 85 mol%) and crosslinked with varying tyrosinase concentrations. The hydrogels were characterized with regard to gelation time, gel content as well as equilibrium swelling and rheological properties at 37 °C. Differences in the hydrogel morphologies were further investigated by diffusion experiments with dextranes of varying molecular weights. The capacity to influence the release of water soluble substances depending on their hydrodynamic radius suggests potential application of enzymatically formed networks for controlled delivery of bioactive macromolecules.
[1] Julich-Gruner K.K., et al. , J Appl Biomater Funct Mater 2012, 10 (3), 170-176.

Self-assembly represents a simple and efficient route to the construction of large, complex structures. Peptide self-assembly in particular offers the possibility to design new functional bio-materials that find application in drug delivery and tissue engineering. The β-sheet motif is of particular interest as short peptides can be designed to form β-sheet rich fibres that entangle and consequently form hydrogels. These hydrogels can be functionalised using specific biological signals and can also be made responsive through conjugation with responsive polymers.
In this work we focussed on the octapeptides: FEFEFKFK (F: phenylalanine; K: lysine; E: glutamic acid), which is known to self-assemble in β-sheet rich fibres and form (C > 10 mg/mL) very stable hydrogels (A. Saiani et al. Soft Matter 2009, 5, 193). We have developed a simple chemistry that allows the conjugation of the octapeptide to the responsive poly(N-isopropylacrylamide) (PNIPAAm) (F. Stoica et al. Chem Comm. 2008, 4433). PNIPAAm is the prototypical responsive polymer which has a lower critical solution temperature around body temperature (LCST ~32^oC) at which the polymer chain collapses from and extended coil into a compact globule.
The main objective was to create hydrogels (peptide based) possessing an internal transition (polymer LCST) in the gel state that could be used as a trigger for, for example, drug delivery.
For this purpose peptide based hydrogels were doped with small amounts of the FEFEFKFK-PNIPAAm conjugate to create new responsive hydrogels. The new hydrogels were then characterised using a variety of techniques including TEM, AFM, mu;DSC and rheology. We showed that the peptide tag allows the conjugate to be incorporated into the peptide β-sheet-rich fibres without affecting neither the peptide network topology nor the polymer LCST temperature. The addition of the conjugate resulted in a 2 to 3 order of magnitude increase in the mechanical properties of the hydrogels at room temperature. Intriguingly when heated above the LCST no changes in mechanical properties were observed. Using small angle neutron scattering (SANS) we have been able to show that this unexpected behaviour was due to the existence at low temperatures of strong h-bonding interactions between the polymer chains and the peptides leading to the polymer chains being already "tightly" wrapped around the peptide fibres. As a result the further collapse of the chain on to the fibre at the LCST does not affect significantly the mechanical properties of the hydrogel (A. Maslovskis et al. submitted 2014).
We have created a new family of simple and flexible responsive hydrogels by exploiting the gelling properties of a family of short peptides and conjugating them to a responsive polymer. These materials are thought to have great potential for applications such as drug delivery and tissue engineering where the polymer LCST can be exploited for the timely release of a drug or a biological active molecule.

Chiral plasmonic nanostructures offer the ability to achieve strong optical circular dichroism activity over a broad spectral range, which has been challenging for chiral molecules. Materials derived from such nanostructures are expected to enrich the field of metamaterials with negative refraction, non-linear optics, and nanolevitation properties. Promising applications of chiral plasmonic nanostructures also include circular polarizers, detectors for circularly polarized light, asymmetric catalysts, and sensors of biomolecules.
We present a new strategy for the preparation of chiral plasmonic films by incorporating gold nanorods and nanoparticles in a macroscopic cholesteric films formed by self-assembled cellulose nanocrystals. Hybrid films revealed strong plasmonic chiroptical activity, dependent on the photonic properties of the cellulose nanocrystal host and plasmonic properties of the nanorods. These tunable chiroptical characteristics are beneficial for fundamental studies of plasmonic chiroptical activity and its potential practical applications. The proposed strategy paves the way for the scalable and cost-efficient preparation of plasmonic chiral materials. The tunability of chiroptical characteristics has potential applications for the development of hybrid materials with advanced optical properties.

Commercialisation of flexible polymer sensors for real-world industry devices has generated immense interest over recent years. This work focuses on the development of conformal, biomedical pressure sensor-electrode assemblies based on flexible Polyether block amide (PEBAX) conductive nanocomposites (nanofibres, nanoplatlets, nanopowders). These free-standing, flexible electrode-sensor assemblies are prepared by various methods including electrospinning. We have a tailored nanocomposite sensor system which detects changes in external pressure, ranging from low (0.1/0.2MPa) to high (12MPa).The non-invasive device will provide more adaptable, integrated connected health system in the future. Numerous advantages include minimal bulk resistance drop and prolonged intimacy of contact between sensor and electrodes, no additional adhesive required, decrease in stress points, uniformity in the coefficients of thermal expansion and dramatic ease of handling.

Membrane bioreactors (MBRs) are very promising for wastewater treatment. MBRs consist of an ultrafiltration membrane for separation of activated sludge form water. Membrane fouling is the main concern in MBR which results in a decrease in permeation of UF membrane during the filtration.
Different methods were investigated to decrease the membrane fouling such as addition of hydrophilic additives to the membrane casting solution. Numerous studies looked into the effect of TiO₂ on membrane surface hydrophilicity because of its photocatalytic under UV light and super hydrophilicity effects. UV light can have a negative effect on the activated sludge. Doping nitrogen into TiO₂ catalyst leads to a shift of its bandgap and allow the catalyst to act efficiently under visible light.
In this paper, the nitrogen N-doped nano TiO₂ particles were synthesized by making the micro emulsion and microwave heat treatment. The micro emulsion phase was prepared by adding aqueous phase (5 mol/L of tetrabutyltitanate in nitric acid) into oil phase (the mixture of Triton X-100, 1-hexanol, cyclohexane) with Urea as nitrogen source. Flat sheet PES UF membranes were fabricated by phase inversion method. Casting solutions were prepared by dissolving 16 wt% PES and 2 wt% PVP as a pore forming additive and five different concentrations (0, 2, 4, 6, 8 wt %) of N-doped nano TiO₂ at room temperature.
Ultrafiltration experiments were carried out in a cross flow flat-frame glass membrane module which is equipped with a 1000 W halogen lamp and glass optical filter with filtration area of 35 cm²at at temperature of 25⁰C and trans-membrane pressure (TMP) of 1.5 bar. The UF set up consists of a 5L activated sludge feed tank equipped with a variable speed rotary vane pump to conduct the feed to the membrane module at room temperature.
The XRD patterns of synthesized N-doped TiO₂ showed that at microwave heating of 60 ⁰C and 75 min, the anatase phase has been appeared with crystallinity of more than 95 %. Nano particle size was calculated about 22 nm using SEM images. The results of N-doped nano TiO₂ particle on pure water flux before activated sludge filtration showed that increasing the nano particles concentration from 0 to 8 wt % causes the water flux to decrease from 38 to 32 L/m².hr. However, different effect was seen on the activated sludge permeation. The result clearly showed that fouling of nano composite membrane was significantly reduced suggesting that these nano particles can increase membrane hydrophilicity and help to mitigate fouling problem of PES UF membrane. Increasing the N-doped nano TiO₂ content in UF PES membrane amplified flux form 6.2 L/m2.hr to 15.4 L/m2.hr until N-doped nano TiO₂ concentration reached 0.6 wt % in the dark condition. The N-doped nano TiO₂ has a photocatalytic activity under visible light which can improve fouling resistance. Under the visible light, the flux of activated sludge filtration increase from 15.4 L/m².hr to 19.1 L/m².hr at 6 wt %.

The dissolved oxygen sensor has played an important role in chemical, biochemical, environmental, industrial and medical fields. Tremendous efforts have been devoted to the development of optical and electrochemical methods for quantitative analysis of dissolved oxygen. Detecting dissolved oxygen in water, however, is more difficult than in air, because the density of oxygen molecules in water is quite lower than that of air under ambient condition. Moreover the gas molecules have a lower diffusion coefficient in liquid than in gas. These factors result in lower quenching efficiency to dissolved oxygen. Herein, we demonstrate a novel approach for creating a highly sensitive dissolved oxygen sensor system. Amphiphibic fluorinated polymer was dissolved in mixed solvent (poor and good solvents). We obtained a superhydrophobic and porous film by dropcasting the solution on solid substrates. An oxygen sensitive dye, platinum porphyrin, was embedded in the amphiphibic fluorinated polymer nano-particles by adding platinum porphyrin-labeled copolymer to the solution. We succeeded in preparing a highly sensitive dissolved oxygen sensor with an enormous sensitivity value.
We synthesized amphiphibic fluorinated polymer, poly(N-(1H,1H-pentadecafluorooctyl)methacryl-amide) (pC7F15MAA) and amphiphibic platinum porphyrin-labeled copolymer (p(DDA/PtTPP)) by free radical polymerization. These amphiphilic polymers allow us to prepare a highly sensitive and superhydrophobic dissolved oxygen sensor by casting method; we used two kinds of solvents, i.e., AK-225 (good solvent) and acetic acid (poor solvent) for dissolving pC7F15MAA and p(DDA/PtTPP). They have different evaporation speeds in the polymer solution at room temperature. This enables two amphiphilic polymers to take nanoparticles formation. The nanoparticles have sphere shape with diameters around 200 nm.
Fluorinated polymer materials have good transparency of oxygen as well as they have been used to prepare a hydrophobic surface. They are desirable for water-repellency. The water contact angle of the film exceeds 150°; the film shows a superhydrophobic surface. Under this situation, the oxygen gas easily enters the superhydrophobic film from water, because the film has a porous structure consisting of amphiphilic polymer nanoparticle assembles. We characterized the oxygen sensitivity of the film in water as a function of dissolved oxygen concentration. The linear type Stern-Volmer plot was gained, and the sensitivity (=I₀/I₄₀) reached 126 in the range 0 mg/L—40 mg/L of the dissolved oxygen concentration in water. The result indicates that the porous fluorinated film with the superhydrophobic surface is promising for dissolved oxygen sensing application.

Abstract: Poly (vinylidene fluoride) hollow fiber membranes were prepared through modified non-solvent induced phase separation process where N, N-dimethylacetamide (DMAC) and tributyl phosphate (TBP) were used as solvent and diluent respectively. Then the structure and performance of prepared membranes were investigated through the methods of scanning electron microscope, fourier transform infrared spectroscopy, differential scanning calorimeter, wide angle X-ray diffraction, mechanical property tests and filtration experiments. The results show that a controlled membrane structure and morphology can be obtained through adjusting the mass ratio of solvent/diluent in casting solution. The resulted membrane presents bi-continuous structure through the whole cross-section when the mass ratio of solvent/diluent is 3:1, which corresponds excellent mechanical property, i.e. tensile strength 5.46MPa and elongation at break 450%, meanwhile, the pure water flux (240Lm^-2h^-1bar^-1) presents a significant increase compared with the present commercial membrane 160Lm^-2h^-1bar^-1. Moreover, it is interesting found that the composition and temperature of coagulation bath play an important role in the structure and performance of the final membranes.
Keywords: poly (vinylidene fluoride); hollow fiber membrane; modified non-solvent induced phase separation; coagulation bath

The use of ionic liquids for CO₂ capture has attracted much attention in recent years due to their unique properties, such as negligible vapor pressure, tunable physicochemical character, thermal stability, and high CO₂ solubility. Poly(ionic liquid)s (PILs), polymers with ionic liquids as the repeating unit, are promising candidate materials for making polymeric membranes for CO₂ separation from power plant flue gases. Here, we prepared polymeric membranes from three types of PIL copolymers with different compositions, morphologies, or architectures. The ionic liquid monomer used in this study were based on 1-(4-vinylbenzyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide. The first type was PIL random copolymer synthesized by conventional free radical polymerization using different acrylates/methacrylates and ionic liquid monomer. The second type was PIL block copolymer synthesized by atom transfer radical polymerization (ATRP). Both AB and ABA type PIL block copolymers with well-defined structures were obtained using various macroinitiators. The third type was PIL grafted polymer synthesized by ATRP grafting from method with PIL side chains grown from the backbone. The physical properties of the resulting membrane are strongly influenced by structures and glass transition temperatures of the copolymers. The structural parameters and membrane preparation procedures were optimized to obtain defect-free free-standing membranes. This study indicates that rational design of PIL copolymer structure is critical for the improvement of properties and performances of the membranes for CO₂/N₂ separation.

Poly(allylamine hydrochloride) (PAH) was layer-by-layer (LbL) assembled with Nickel tetrasulfonated phthalocyanine (NiTsPC), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) thus forming PAH/PPy, PAH/PEDOT:PSS and PAH/NiTsPc ultrathin films. Microfluidics was used to assist the fabrication of 5-bilayers of these LbL nanostructures inside polydimethylsiloxane (PDMS) microchannels sealed onto gold micro interdigitated electrodes (IDEs), assembling individual sensing units to constitute a microfluidic e-tongue system. Fabrication of microchannels and IDEs were made at Microfabrication Laboratory at LNNano/CNPEM (Campinas, Brazil). After oxygen plasma treatment the PDMS microchannel was placed in contact with the IDEs and manually pressed for a few seconds, causing an irreversible sealing. All solutions and polyelectrolytes were prepared with ultrapure water from a Direct-Q5 Millipore system, being inserted and controlled inside microchannels using a micro-syringe housed in a syringe pump. LbL formation was monitored in-situ using impedance spectroscopy measurements, acquired from 1Hz - 1MHz in a Solartron 1260A impedance analyser, with a 20 mV amplitude signal. Impedance was also applied for data acquisition when 200 mL of samples were passed through the microchannels containing the LbL films deposited onto the IDEs. The formed sensor was able to distinguish electrolytes from non-electrolytes, covering all basic tastes relevant to human gustative perception, responding also to suppression effects. Principal Component Analysis displayed a high correlation for all substances tested, conferring high potential for low-cost, easily integrated, multi-functional sensors for food, beverages, clinical and environmental applications.

Treating biomaterial-associated infections is a daunting challenge due to the presence of intra-cellular bacteria. A novel approach to eliminate intra-cellular pathogens and to treat and prevent infections is via cationic antimicrobial peptides (CAMPs). Unlike conventional antibiotics, amphiphilic CAMPs are comprised of hydrophobic and hydrophilic residues aligned on opposite sides of the peptide, facilitating their easy penetration through cell membranes and killing of intra- and extra-cellular pathogens. The objective of this study was to determine the efficacy of CAMPs including LL-37 and lactoferricin B against intra- and extra-cellular Staphylococcus aureus (S. aureus), the main cause of biomaterial-associated infections, and to compare the efficacy of CAMPs with those of conventional antibiotics. A clinical strain of S. aureus was obtained from a patient&’s chronic wound and was studied in its log phase (exponential bacterial growth). Osteoblasts were infected with S. aureus and treated with lysostaphin to eliminate extra-cellular bacteria. S. aureus or infected osteobalsts were then treated with CAMPs or conventional antibiotics, and the survival of S. aureus was examined. We found that LL-37 CAMP was effective in killing extra-cellular S. aureus at nanomolar concentrations, lactoferricin B at micromolar concentrations, and doxycycline and cefazolin at millimolar concentrations. LL-37 was also effective in eliminating intra-cellular bacteria, and was more potent in eliminating intra-cellular S. aureus compared to conventional antibiotics. Kinetic studies further revealed that LL-37 was fast in eliminating both extra- and intra-cellular S. aureus. Therefore, LL-37 was shown to be more effective in killing extra- and intra-cellular S. aureus than commonly used conventional antibiotics. LL-37 could potentially be used to treat chronic and recurrent infections due to its effectiveness in eliminating not only extra-cellular but also intra-cellular pathogens.

Abstract
Paper as one of the most ubiquitous materials has been used for centuries. By virtue of its bargain, the ability of recyclable, biodegradability, high-throughput and many more, paper-based functional electronic devices endow a new era of applications in RFIDs, sensors, transistors, and MEMS. However, most of the electronics rely on external power source, such as Li-battery. The advent of the paper-based electret generator offers the opportunity to close the gap. In this study, we demonstrated a paper-based electret generator (pEG) based on electrostatic effect for converting tiny-scale mechanical energy into electricity. The electrostatic charges on the paper were generated by using a negative corona method. The instantaneous output power density of a single-layer pEG reached ~ 90.6 mu;W/cm² at a voltage of 110 V which could instantaneously light up 70 LEDs in series. Furthermore, under the grace of paper advantages including flexibility and foldability, an innovative design of generator with multiple-fold layers of pEG units was demonstrated. The multiple-fold pEGs could offer the ability to substantially scale up the output power. In addition, by integrated a pEG with paper consumers, such as a page of a book, the power harvested from the action of turning the page can power an LED, presenting its outstanding potential in building paper-based, self-powered systems and as active sensors.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (51322210), a Foundation for the Author of National Excellent Doctoral Dissertation of PR China (201035)
Address correspondence to [email protected]
References
[1] Q. Z. Zhong, J. W. Zhong, B. Hu, Q. Y. Hu, J. Zhou and Z. L. Wang, A paper-based Nanogenerator As Power Source and Active Sensor, Energy Environ. Sci., 2013, 6, 1779-1784

Biomaterial research faces often the challenge that the number of samples or the amount of material required to elucidate structure-property relationships cannot be met by classical synthesis approaches. However, a sufficient number of material samples is required for a knowledge-based approach of material development. This challenge can be addressed by fusing the concepts of combinatorial material research and high#8209;throughput experimentation (CMR/HTE)^[1], which is recently also understood as materiomics.^[2] The main concepts of high throughput experimentation were already introduced in the 70ties by Hannak, when he investigated the development of new superconducting materials by multi-component co-sputtering of metals and ceramics and subsequent characterization by nondestructive methods.^[3] Nowadays, HTE has been substantially speed up by the use of robotic platforms.^[4,5] Nevertheless, in addition to the progress in CMR/HTE approaches for the synthesis of polymer libraries, a vital point is their characterization. As classical methods for the characterization of polymer composition such as ¹H-NMR or elemental analysis are time consuming, high throughput (HT) characterization methods are required as well.^[6] While classic Fourier Transformation Infrared Spectroscopy (transmission and attenuated total reflection) is in general fast a method, it demands a laborious sample preparation (KBr pellets) and/or manual sample handling.
Here the suitability of Diffuse Reflectance Fourier Transformation Infrared Spectroscopy (DRIFT) as a HT characterization method of copolymer libraries was investigated. Four different methyl methacrylate-based polymer libraries containing styrene, N-vinylpyrrolidone, 4-vinylpyridine, or 2-carboxyethyl acrylate as comonomers were synthesized using an automated/robotic synthesizer platform and subsequently analyzed by ¹H-NMR and DRIFT. Both data sets were compared by multivariate data analysis, in which correlations with R₂ between 0.9373 and 0.9971 were determined.^[7] By this means HT screening of comonomer contents of these polymer libraries was enabled and usage of DRIFT as a valuable tool for HT characterization was demonstrated.
References
[1] N. Adams, U. S. Schubert, Comb Sci. 2005, 24, 58-65.
[2] S. W. Cranford, J. de Boer, C. A. van Blitterswijk, M. J. Buehler, Adv. Mater.2013, 25, 802-24.
[3] J. J. Hanak, J Mater Sci.1970, 5, 964-71.
[4] R. Hoogenboom, U. S. Schubert, Rev. Sci. Instrum.2005, 76, 062202.
[5] R. Rojas, N. K. Harris, K. Piotrowska, J. Kohn, J. Polym. Sci., Part A: Polym. Chem.2009, 47, 49.
[6] S. Schmatloch, U. S. Schubert, Macromol. Rapid Commun.2004, 25, 69.
[7] S. Baudis, A. Lendlein, M. Behl, Macromol. Mater. Eng.2014, in print.

The use of TiO₂ as a semiconducting heterogeneous photocatalysts for the photodegradation of organic pollutants has been extensively investigated as the material is non-toxic, inexpensive, and chemically stable over a wide pH range^1-3. The most common method used is to disperse TiO₂ particles into the waste solution². This method gives efficient degradation rates, however the TiO₂ particles are difficult to recover and reuse, which limits the economic feasibility of this approach. In some studies, films with TiO₂ deposited on the surfaces were prepared by dip-coating or spray-coating³. The main drawbacks are that the particles have low adhesion to the surface and so are easily removed, or that the particles become fully embedded in the matrix, thereby lowering their availability for catalysis.
Here, we present a novel lamination fabrication method that enables pre-formed TiO₂ nanoparticles to become partially embedded into the surface of a thermoplastic polymer film. In this way, the particles are strongly adhered to the surface while remaining accessible to the aqueous solution. By modifying the fabrication conditions (e.g. temperature, pressure, polymer melt viscosity, etc.), the morphology of the hierarchical TiO₂-polymer surface can be controlled and thus the rate of photocatalytic reactions can be increased. In addition, the fraction of TiO₂ particles that become fully embedded into the polymer surface, and so inaccessible to photocatalysis reactions, can be reduced through lamination process control.
Nanocomposite films were characterized (XPS, SEM, AFM, TGA) and tested by photo-oxidizing a Rhodamine B solution under either a UV lamp or natural sunlight. The morphology of the surface was correlated with both fabrication conditions and photocatalysis rate. A model for how the fabrication conditions affect surface morphology is presented. The surfaces remain stable after UV exposure due, in part, to shadowing of the polymer substrate by the particles. In addition to Rhodamine B, other dye molecules were tested and the film showed similarly high working efficiencies. Initial results with bacteria (E. coli) indicate that the films are effective at sanitizing drinking water.
This environmentally friendly technique is compatible with any type of TiO₂ catalyst particle and so the wavelength response of the photocatalysis can be improved as particles that retain photocatalytic activity at longer wavelengths become commercially available. The wide variety of thermoplastic polymers that are compatible with the process will facilitate their introduction into a wide range of applications including waste water treatment and water purification.
References
1. Frank, S.N., Bard, A.J. J. Am. Chem. Soc.1977, 99, 303.
2. Kwon,Y.T., Song, K.Y., Lee, W.I., Choi, G.J., Do, Y.R. J. Catal.2000, 191, 192.
3. Priya, D. N., Modak, J. M., Raichur, A. M. ACS Appl. Mater. Interfaces, 2009, 11, 2684.

Organic/inorganic hybrid materials offer numerous advantages in development of new functional materials for design of two/three terminal devices at nanoscale. Devices with integrated hybrid structures offers potential to manifest the properties of both material classes to achieve novel electrical properties to design low cost biosensors. In this work, our major goal was to create an active nanodevice with hierarchical assembly of 1-dimensional (1D, metal nanoparticles) and 3-dimensional (3D, polyaniline nanofibers) that exhibits a switch behavior for detection of biomolecules. The electrical response of crossbar microelectrode pattern with directed assembly of nanostructures for detection was characterized using square wave voltammetry. Polyaniline nanofibers of defined morphology was synthesized using electrospinning. It was observed that by controlling the applied voltage and collector geometry, the nanofibers could be directly electrospun at the crossbar junction. It was also observed that the morphology of nanofibers was strongly dependent on concentration and flow rate. The interaction of biomolecules at electrically active area modulates the charge transport at the junction due to the surface charge associated with biological molecules. The net change in electrical signal can be measured either as change in diode current/source-drain current based on device architecture. Nanotextured surface was characterized using scanning electron microscopy (SEM). It was identified that diameter of prepared nanofibers was between 50-300 nm. Smaller the fiber diameter, larger is the active area and higher is the sensitivity of device. Thus fabricated device was thus tested to biological molecules with sizes ranging between single nanometer to several hundred nanometers. Electrical switch threshold will be determined from binding kinetics and charge transfer associated with it. Experimental results suggest that, the proposed hybrid device is suitable for size based biomolecule detection at ultra-low concentrations.

Recent results on thermally induced fluid instabilities in multi-material fibers have led to the development of a novel approach to efficiently producing size-tunable micro-and nano-particles. The process starts by constructing a macroscopic (centimeter-scale) model called a preform, typically in the form of a cylindrical core embedded in a cylindrical cladding. The preform is thermally drawn into extended lengths of uniform fiber with reduced transverse scale. Thermal treatment of the drawn fiber induces the Plateau-Rayleigh capillary instability (PRI) at the heterogeneous core/cladding interface thereby transforming the initially intact, extended cylindrical core into a necklace of periodically spaced, uniformly sized spheres whose diameters are proportional to the intact core diameter. To date, the materials used to demonstrate this process are characterized with softening temperatures typically above 100 °C. While a wide range of materials are thus amenable to this processing route, most biodegradable polymers are excluded, thereby limiting the utility of particles produced in this manner to drug delivery.
Current efforts in nanoparticle-based drug delivery are utilizing biodegradable polymers such as polyethylene glycol (PEG), polycaprolactone (PCL), polylactic acid (PLA), polyglycolic acid (PGA), and PLGA, the copolymer of PLA and PGA; all of which have a relatively low melting temperature (< 90 °C). Here we extend the in-fiber PRI-based methodology to become a pathway to the scalable fabrication of micro-and nano-particles from low-melting-temperature biodegradable polymers. For the first time, we use the telecommunications-fiber fabrication process of thermal fiber drawing from a preform to draw extended lengths of fiber with a biodegradable polymer (from those listed above) as the core embedded in a thermally matched polymer cladding. After thermal treatment of the drawn fiber, the core breaks up into a sequence of spherical particles shaped under the influence of surface tension, which are then released by selective dissolution of the cladding. As a result, we produce biodegradable particles of controllable diameter independently of the chemistry of the polymer used. Furthermore, inducing the PRI process below 90 °C opens up the possibility of encapsulating or impregnating the particles with biological agents. We demonstrate this possibility by producing PLGA microparticles doped with the antibiotic minocycline. Challenges of thermally extruding and drawing materials at such a low temperature will be discussed. In addition, we will introduce the design and construction of scaled-down versions of extruders and draw towers typically utilized in fiber mass-production to a scale that may be used in a materials or chemistry research laboratory setting.

Hearing loss is a prevalent issue, affecting all ages in innumerable occupations. At the present time, sensorineural deafness can be treated with two types of devices: conventional hearing aids and cochlear implants. Conventional hearing aids are the most common and are used with less severe degrees of loss. Cochlear implants are used in cases of more advanced and profound deafness, where conventional hearing aids are not effective to attain useful hearing. It has been in clinical use for nearly thirty years. There are some aesthetic and functional concerns about the external portion of the device and the sound quality of speech and music is not entirely satisfactory.
This research investigated the feasibility of using a thin polyvinylidene diflouride (PVDF) film in achieving adequate voltage output and frequency selectivity to replace the human cochlea. Piezoelectric films emulate the relationship between the basilar membrane and inner hair cell structures of the human cochlear epithelium. The device mimics the frequency selectivity of the basilar membrane of the cochlea and the electrical output of the hair cells of the organ of Corti through a piezoelectric thin film membrane. In this work, PVDF-TrFE thin films with thicknesses of 20mu;m and 40mu;m were used. The electrode composition was 70Å chromium (Cr) deposited directly to the sheet with 1000Å aluminum (Al) deposited on top of the Cr. The devices were tested in the air with constant 78dB sound pressure level (SPL) in the human speech register of 500Hz to 8000 Hz. The maximum output of the films was found to be 10.4mV, which is two times larger of the required potential change of 5 mV to fire the auditory neurons from the resting potential of the outer hair cells (-70mV). Referencing the basilar membrane structure, larger segments of the PVDF membrane will respond more readily to lower frequencies, as the size endows increased loading to the segment, reducing the resonant frequency. The device demonstrated frequency selective responses at 1700Hz, 4100Hz, and 6400 Hz with device&’s width of 6.0mm, 4mm, and 3.5mm, respectively. In addition, it turns out that the output was decreased as the film thickness increased from 20mu;m to 40mu;m. Excellent agreement has been obtained between the experimental results and the simulations using a MEMs simulator (CoventorWare). These results indicate through proper MEMS fabrication and material selection, an artificial cochlear can be developed utilizing piezoelectrics with a minimal invasive outpatient surgical procedure.

Self-healing polymers have gained considerable attention in recent years due to a myriad of potential applications including protective coatings for electronics, implantable devices, paints, and adhesives. Here, we present a polysulfide with intrinsic healing due to continuous thiol-disulfide exchanges. Thiol-click chemistry is used for its insensitivity to oxygen and its ease in incorporating free thiols into a thermoset by using a stoichiometric excess of thiols. Epoxy-terminated and vinyl-terminated polysulfides are used in conjunction with multifunctional thiols. In addition, photobase generators are synthesized and used to incorporate base into the network. Amineimides or benzyl substituted guanidines have been used as the photobase generators. By using a long wavelength photoinitiator to form the thermoset, the self-healing ability can be separately activated by the photobase generator. This separates the polymerization reaction from the self-healing reaction allowing for better control over the resulting polymer. Once activated, the self-healing occurs continuously. The base reacts with the free thiols in the network, which further reacts with the disulfides in the polymer backbone. The base is incorporated into the thermoset with hydrogen bonding and counterbalancing the thiolate anion. With a strong base, the thiolate/protonated base is stable, allowing for endless thiolate-disulfide exchanges. There are many advantages of this approach. External stimuli, such as heat or ultraviolet light, are not needed to heal the polymer. However, ultraviolet light can expedite the self-healing by breaking the disulfide bonds, allowing for disulfide metathesis. These thiol-disulfide exchanging polymers can also be remolded after setting. With sustained pressure, the thiol-disulfide interchanges will relax stress within the polymer leading to a new permanent shape. This allows for recycling of these thermoset polymers. When used as a substrate for electronics, this remoldability allows for 3-dimensional electronics. In addition, this thiol-click approach is amenable to stereolithographic 3D printing, which has not been demonstrated previously. Finally, the low cost of materials make this system highly scalable and amenable to commercialization.

Recent development of tough hydrogels promises to expand greatly the scope of applications of hydrogels. Most of existing hydrogels dissipate energy by breaking bonds: breaking covalent bonds results in permanent and irreversible damage to the network; physical bonds such as ionic crosslinks and hydrogen bonds are unstable when solute species compete for binding sites. As an alternative, here we report the strain-induced crystallization in hydrogels, and harness this mechanism to toughen hydrogels. The hydrogel, forming with a covalently crosslinked network and crystalline polymers, exhibits transmittance change and stiffening effect under deformation. We demonstrate the presence of strain-induced crystallization in the hydrogel by showing the characteristic dependence of the breaking stress on the crack size. We further study the kinetics of crystallization with stress relaxation and rate-dependence tests, and demonstrate the strain-induced crystallization can improve effectively the toughness of the hydrogel, as the fracture energy reaches 6000 J m^-2.

Conjugated polymers are well established as functional materials in a broad range of applications such as organic photovoltaics, chemical sensors, and organic light emitting diodes. This functionality is mainly derived from their ability to create electron-hole pair excitons through photoexcitation. As these entities travel along and across polymer chains their potential effects on chain conformation, solution behavior, and ultimately macroscopic morphology, are largely unknown. Previous studies have shown significant changes in properties such as viscosity and photoluminescence upon exposure of select conjugated polymer films to white light. In order to expand upon these preliminary findings, we have preformed small angle neutron scattering (SANS) experiments on solutions of several semiconducting, conjugated polymers in both the presence and absence of incident light. Substantial differences are observed between the light vs dark samples, the magnitude of which are dependent on concentration of polymer, solvent choice, and light exposure methodology. Analysis of the neutron curves shows real difference in segmental lengths and radius of gyration values, suggesting possible rearrangement of polymer chain conformation and alteration of chain-solvent interactions.

We have recently developed a new technique for creating hybrid polymer hydrogels wherein two or more gels with distinct chemical formulations are combined into the same material. In our approach, the unique character of each individual gel is preserved in its specific region, and the different regions are covalently linked to each other, thereby ensuring robust interfaces. The utility of this approach is that it can be used to obtain materials with unique properties that were not possible previously. In this talk, we will present some examples to illustrate these unique properties. In the first example, we describe a hybrid gel with a core-shell design that shows a valve-like action in response to temperature or pH. That is, an encapsulated solute placed in the inner core is shown to be ejected into the solution at a particular temperature or pH due to the shrinking of a portion of the outer shell. In a second example, we will demonstrate a hybrid gel in which one zone is significantly stiffer than others. For example, the stiffer zone is structured with nanoscale silica particles, and thereby its elastic modulus is about 10 times the moduli of the other zones. We believe these unique multifunctional materials will be attractive for applications in biology, material science, and chemical separations.

Crosslinked azobenzene liquid crystal polymer films are bent by irradiation of UV light. Utilizing the feature, a plastic motor [1], a robotic arm [2] etc. were developed. The overall mechanism was understood as the surface region of the film was contracted. Although the mechanism has not been fully understood yet on what kinds of interactions between molecules, molecular chains, domains are involved and which time scale they happens. On the other hand, we have developed a new type of the time-resolved technique, called the heterodyne transient grating (HD-TG) method [3,4], which features a highly sensitive detection of the refractive index change and wide temporal response from nanoseconds to seconds. In this study, we studied the molecular dynamics in an azobenzene LC polymer film by using the HD-TG technique, combined with the transient absorption (TA) technique. We could observe 5 components in the range of < 1 mu;s, 1-100 mu;s, 100 mu;s-1 ms, 1-100 ms, 100 ms - 10 s. We have succeeded in attributable those components are volume contraction, rotation, reorientation dynamics and transformation from the cis to trans isomer [5].
1. M. Yamada, M. Kondo, J. I. Mamiya, Y. L. Yu, M. Kinoshita, C. J. Barrett and T. Ikeda, Angew. Chem. Int. Ed., 2008, 47, 4986-4988.
2. M. Yamada, M. Kondo, R. Miyasato, Y. Naka, J.-i. Mamiya, M. Kinoshita, A. Shishido, Y. Yu, C. J. Barrett and T. Ikeda, J. Mater. Chem., 2009, 19, 60-62.
3. K. Katayama, M. Yamaguchi and T. Sawada, Appl. phys .Lett. 2003, 82, 2775-2777.
4. M. Okuda and K. Katayama, Chem. Phys. Lett., 2007, 443, 158-162.
5. T. Fujii, S. Kuwahara, K. Katayama, K. Takado, T. Ube and T. Ikeda, Phys. Chem. Chem. Phys., 2014, 16, 10485-10490.

Currently, there are no existing surgical tissue glues which exhibit strong tissue adhesion under wet environments as well as biocompatibility in the body. Although several advantages of biological tissue adhesives such as biocompatibility and biodegradability, poor mechanical properties and long curing time still remained as unsolved limitations for the clinical use. In the present work, we employed photo-initiated crosslinking strategy to induce simple and stable gelation (curing) for recombinant mussel adhesive proteins (MAPs) in seconds using visible light. This gelation system is expected to be useful for in-situ bio-adhesives in terms of convenient handling, short irradiation time, and non-cytotoxicity of light source. Furthermore, diverse properties such as elastic modulus of the resultant adhesive hydrogel could be easily controlled by changing light intensity and electron acceptor concentration in the system. This photo-responsive adhesive hydrogels strongly bound to the hemorrhaging tissues suturelessly and was rapidly solidified to serve a bleeding-arrest barrier and adhesives at the wounds created on the back of rat. Due to its strong adhesion strength, rapid curing time, and good biocompatibility, this single component protein-derived adhesive biomaterial holds high potential for medical applications in hemostasis and sutureless wound closure of skin and internal organ tissues.

The reversible formation and cleavage of chemical bonds in polymer materials bears the opportunity to introduce functions into polymeric materials. Examples are photoscissable hydrogels [1], photoreversible reactions of polyvinyl esters [2], and light-induced shape-memory polymers [3,4]. In these cases, cinnamylidene acetic acid (CAA) moieties served as photo-sensitive functional groups, which are linked as side group or terminal group e.g. to poly(ethylene glycol)s or polyvinyl alcohol.
Here we investigate the photoreversibility of cinnamylidene acetic acid functionalized four-armed oligo(ε-caprolactone) [M_n = 10 kDa]. Mechanistic model studies were conducted in solution to evaluate the cycloaddition products and back reactions. The precursor solutions in toluene (0.4 wt.%) were treated by irradiation at > 320 nm with subsequent cleavage by exposure to a wavelength < 260 nm. The samples were analyzed by FTIR, UV/Vis and Heteronuclear single quantum coherence NMR-spectroscopy (HSQC-¹H, ¹³C). The results suggested the formation of different regioisomers after the CAA dimerization process, which have different capabilities with regard to photoreversibility: As some of the formed dimers can be expected to be only partially reversible, a part of the crosslinks will remain in the material. In conclusion, possible limitations in reversibility of CAA-derived netpoints in PCL-based polymer network may be assigned to the type of CAA dimers being formed in the polymer network synthesis.
[1] F.M. Andreopoulos, C.R. Deible, M.T. Stauffer, S.G. Weber, W.R. Wagner, E.J. Beckman, A.J. Russel, J. Am. Chem. Soc.1996, 118, 6235-6240.
[2] H. Tanaka, K. Honda, J. Polym. Sci. Polym. Chem. Ed.1977, 15, 2685-2689.
[3] A. Lendlein, H. Jiang, O. Jünger, R. Langer, Nature 2005, 434, 879-882.
[4] H.Y. Jiang, S. Kelch, A. Lendlein, Adv. Mater.2006, 18, 1471-1475.

Oxanorbornadiene dicarboxylate (OND) reagents are potent Michael acceptors that undergo addition with thiols to yield adducts which fragment by a retro-Diels-Alder reactions at rates that vary depending on the identity of the OND linker. We have applied these linkers to prepare degradable hydrogel networks. Conjugate addition between multivalent thiol-terminated macromers and ONDs yields self-supporting hydrogels within one minute at room temperature. The gels exhibit a range of stabilities and erosion rates that vary widely with the identity of the selected OND linker. Varying linker valence and selecting combinations of ONDs with different intrinsic rates of cleavage resulted in tunable gel erosion profiles. These results highlight the utility of OND linkers in the preparation of novel degradable materials with potential applications for sustained drug delivery and tissue engineering.

Injectable protein hydrogels based on coiled-coil building blocks have attracted great interest in biomedical research and applications. Due to the force-sensitive associations between the coiled-coil domains, the reversible physical networks exhibit shear thinning behaviors during injection and show nearly instantaneous recovery after the cessation of shear, which promises their use in minimally invasive surgeries. To better control the self-healing properties of these materials, it is critical to develop a deeper understanding on the dynamics of the proteins in gels. The scientific knowledge on the diffusion behaviors will also provide insight into the erosion mechanisms of gels, which typically have a limited life time under physiological conditions.
Here, shear rheology is first applied to probe the mechanical properties and the relaxation mechanisms of the protein gels. It is found that the static and dynamic properties of gels are greatly influenced by the protein structure. For gels formed by telechelic ABA triblock coiled-coil proteins, the rheological behaviors can be mostly captured by a Maxwell model. However, multiblock B(AB)₄ coiled-coil protein gels show a strong deviation from the Maxwellian behavior. In the high frequency regime, the noticeably broadened relaxation is better described by the Kohlrausch-Williams-Watts (KWW) function. An additional relaxation is observed in the intermediate frequency regime that can be explained by large scale network relaxations known as “sticky Rouse” phenomena. The differences in mechanical properties are due to the interplay between the molecular diffusion and the coiled-coil association. Changes in the number density of the coiled-coils in the proteins lead to differences in the tendency of forming bridge/loop chains within the networks and the entanglement threshold of proteins that can be used to effectively moduluate the long time relaxation. These two effects are not expected from the classic affine/phantom network theories.
To complement the macroscopic rheological studies, forced Rayleigh scattering (FRS) is used to investigate the microscopic diffusion of the coiled-coil proteins. Two distinct regimes of the characteristic time constant of the FRS decay are observed: a “superdiffusion” regime on small length scales (typically < 1 mu;m), and a Fickian diffusion regime where the diffusivity of proteins can be calculated. By considering the kinetics of diffusion and coiled-coil association, a two-state model is developed to capture the observed behaviors.

It has been demonstrated that the use of plasmonic structures increases the performance of photovoltaic devices¹ as well as the fluorescence² of adsorbed molecules. In this study we investigated the interaction of laser radiation (visible region) with a periodic network of copper spherical submicrocavities by Confocal Laser Scanning Microscopy (LSCM) and computer simulation. These structures were produced by electrodeposition and nanosphere lithography. A homogenous polyfluorene (PFO) ultrathin film was deposited on the cavities by spin-coating to be used as an emitting layer to probe surface-enhancement fluorescence phenomena. LSCM measurements in reflection mode show an image patterns for a given confocal plane. Similar behavior was observed in photoluminescence intensity of PFO film deposited on this structure. The PFO emission in the cavity enhances by a factor 7 in comparison with the reference film deposited on flat surfaces. The profile of reflection intensity can be explained by composing reflection process in a spherical metallic cavity and collection of the light by the confocal microscope. Simulations of the image patterns based on geometrical optical approach were carried out by considering the spherical submicrocavities like ideal spherical mirrors. The simulated results reproduce consistently the behavior of the emitted and reflected image patterns along the submicrocavities obtained experimentally. These results demonstrate that copper sub-microcavities.act like spherical sub-micromirrors. In addition, effects of fluorescence quenching via energy transfer processes to copper plasmons states are not observed and that emission enhancement can be associated to interference processes involving the incident and reflected emitted by the mirror.
We acknowledge support from INEO, CNPQ, FAPESP.
¹ M. Heo et al., Adv. Mater 23, 5689 (2011).
² B. Jose et al., PCCP 11, 10923 (2009).

The ability to tune multiple properties of soft tissue may be realized by integrating mechanically robust biomaterials within the host site. Our interest lies in developing methods to address the suboptimal mechanical properties—namely, compression and lubrication—that typically accompany progression of the disease osteoarthritis. As the articular cartilage lining the ends of bones in synovial joints begins to wear away, it often suffers a loss both of load-supporting proteoglycans and of lubricating biopolymers. In a healthy state, these molecules, respectively, allow for load to be borne primarily by the tissue&’s interstitial fluid and maintain low coefficients of friction to minimize wear. As there is an increasing population of individuals experiencing a depletion of these tissue components as they advance from early- to mid-stage osteoarthritis, there is an urgent need to engineer materials that can remedy both the compressive and tribological deficiencies in the cartilage.
To meet this goal, we report the development of a tissue treatment technique involving the formation of a cartilage-interpenetrating poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) hydrogel that improves mechanical properties. The technique involves of the diffusion of polymerizable zwitterionic phosphorylcholine functional groups throughout the cartilage tissue, at which point they are photopolymerized in situ to yield a biomimetic hydrogel that is highly entangled with the native collagen fibrils of the cartilage. Hydrogel-treated samples were characterized by infrared spectroscopy to validate the polymer&’s presence within the tissue, and enzymatic nonspecific degradation of the biological component of the composite structure yielded only the synthetic hydrogel. The functional result of this biomaterial integration process is a polymer-reinforced composite structure that is semi-biological and semi-synthetic, and improves mechanical properties to potentially attenuate the tissue wear that occurs during osteoarthritis. Equilibrium and dynamic compressive moduli were found to increase following hydrogel treatment in a dose-dependent manner, and tissue samples that were artificially depleted of proteoglycan content underwent a greater percent increase in moduli than their non-depleted counterparts. Coefficients of friction of hydrogel-treated samples were measured and found to be maintained at physiologically low levels over long-duration friction testing.

We developed a new pH-sensitive drug delivery carrier based on β-cyclodextrin (β-CD) and 1-methyl-2-(2'-carboxyethyl) maleic anhydrides (MCM). To optimize pH-sensitivity for controlled drug release, we synthesized five maleic acid amide derivatives (maleic, citraconic, cis-aconitic, 2-(2&’-carboxyethyl) maleic, MCM) maleic acid amide), and compared their degradability for the development of pH-sensitive biomaterials with tailored kinetics of the release of drugs. Based on these results, we selected MCM and the primary hydroxyl groups of β-CD were successfully attached to MCM residues to produce a medusa-like β-CD-MCM. The MCM residue was conjugated with cephradine (CP) with high efficiency (>90%). More importantly, β-CD-MCM-CP responded to the small pH drop from 7.4 to 5.5 and released greater than 80% of the drugs within 0.5 h at pH 5.5. In addition, the inclusion complex between β-CD-MCM-CP and the adamantane derivative was formed by simple mixing to show the possibility of introducing multi-functionality. Based on these results, β-CD-MCM can target weakly acidic tissues or organelles, such as tumours, inflammatory tissues, abscesses, or endosomes, and be easily modified with various functional moieties, such as ligands for cell binding or penetration, enabling more efficient and specific drug delivery.

The rapidly diminishing number of effective antibiotics that can be used to treat infectious diseases and associated complications in a physicians&’ arsenal is having a drastic impact on human health today. According to the Center for Disease Control&’s 2013 report on antibiotic resistance in the United States, at least 2 million people acquire serious infections from antibiotic resistant bacteria each year, and over 23,000 die as a direct result. Even when alternative treatments exist, patients with antibiotic resistant infections have significantly higher mortality rates, and survivors often have increased hospital stays and long-term complications. These infections cost an estimated $20 billion in excess direct healthcare expenses. This study explored the development and optimization of a polymersome nanocarrier formed from a biodegradable diblock copolymer to overcome such antibiotic resistance. Here, the polymersomes were designed with silver nanoparticles embedded in the particle&’s hydrophobic membrane bilayer, and an antibiotic solution encapsulated in the particle&’s aqueous core in order to provide a dual-mechanism, concentrated, and localized treatment. These silver nanoparticle-embedded polymersomes (AgPs) were loaded with ampicillin and subsequently tested for bactericidal function against Escherichia coli that had been transformed with a gene for ampicillin resistance (bla). Results showed for the first time that the AgPs killed the antibiotic-resistant bacteria, whereas free antibiotic, encapsulated antibiotic without the addition of the silver nanoparticles, and AgPs without the addition of ampicillin did not kill the bacteria. In this manner, this study introduces a novel nanomaterial that can effectively treat problematic, antibiotic-resistant infections which should be further examined for a wide range of medical applications.

A facile and green starch-gel foaming method that uses gelatinization property of starch was developed to fabricate biomimetic ceramic composite sponge for controlled release of drug. Starch-hydroxyapatite suspension was formed into porous structure by foaming process at temperatures lower than 60 °C and the porous structure was then dehydrated into freestanding sponge with a porosity more than 81 %. The interconnectivity of pores in the scaffold was confirmed by micro-CT and 3-D reconstruction of the porous structure. SEM examination revealed a hierarchical pore structure comprising both large and small pores. Mechanical tests showed that the ceramic composite sponges had viscoelastic behavior and high resilience. The resilience of the sponge remained 98 % after 300 cycles of 10 %-strain compression, indicating its potential for delivering drugs repeatedly. Young&’s moduli of the sponge varied from 29 MPa to 51 kPa when absorbed moisture increased from 1 wt% to 66 wt%. This sponge with variable stiffness could be adjusted to mimic different tissues including cancellous bone, cartilage and muscle. For drug release tests, insoluble bromophenol blue (BPB) and soluble bovine serum albumin (BSA) were used as model drugs under a cyclic compression of 10% strain. The results showed that the release amounts of BPB and BSA from the sponge were proportional to cycle numbers and the average release amounts of BSA and BPB were 0.02 mg/cm³ and 0.08 mg/cm³ per cycle, respectively. More importantly, a new controlled-release system exhibiting “AND” logic was designed, using hydration and stress as logic conditions. Drug release tests showed that the dual-controlled system only released drugs when both logic conditions were met. This new AND logic release system is promising for the delivery of soluble and insoluble drugs under complicated physiological conditions

Multi-axial electrospun fiber mats with controlled release capabilities of antimicrobial agents are being investigated to provide superior approaches for multi-functional protective clothing. The multi-axial fibers consist of multiple layers, each of which can have their own release profile and functionalities. Experiments have been carried out involving: (1) the design of the multi-axial fiber composition and organization; (2) incorporation of bacteriocins (such as nisin) into each layer to establish release kinetics; (3) the testing of short and long-term efficacy of encapsulated bacteriocins.
With the rise of multi-drug resistant bacterial strains against current antimicrobials, there is great interest and need to find alternative agents. Bacteriocins are narrow spectrum antimicrobial peptides that offer a novel alternative to current approaches. Encapsulation of bacteriocins into electrospun membranes provide a unique delivery system for antimicrobial protection. Using multi-axial membranes for this encapsulation should ultimately increase bacteriocin stability while imparting functionality.
The electrospinning technique, including multi-axial electrospinning, is a very versatile tool to produce nanofibrous membranes made of various natural and/or synthetic materials.^1-3 Advantages of the electrospinning process include: (a) control of the fiber diameter from micro- to nano-meter dimensions; (b) control over the fiber compositions; (c) spatial alignment of multiple fibers; (d) formation of highly porous membranes with extremely high surface area.
In this research, several types of fiber membranes incorporating nisin have been successfully produced and characterized for their antimicrobial characteristics. To evaluate the antimicrobial performance, soft agar overlay with Staphylococcus. aureus bacteria has been utilized. In conventional single fibers, higher nisin concentration not only decreases mechanical properties, but also reduces electrospinnability of the solution. While no antimicrobial activity is observed in nisin-incorporated polymer fiber mat produced by single nozzle electrospinning even at 1 wt% nisin concentration, multi-axial fibers with nisin/PVP core are found to provide: (a) excellent antimicrobial properties; (b) good mechanical stability; (c) incorporation of higher nisin concentration > 10wt%; (d) controllability of nisin release profile by changing the sheath thickness (controlled by flow rate ratio during electrospinning); (e) stable electrospinning process and uniform fiber morphologies. The ratio between core diameter and sheath wall thickness are 7.6:1 and 14.5:1 at the flow rate ratio (core to sheath) of 1:1 and 2:1 during electrospinning, respectively.
1. Han, D.; Filocamo, S.; Kirby, R.; Steckl, A. J., ACS Appl. Mater. Interfaces 2011,3, 4633-4639.
2. Han, D.; Steckl, A. J., Langmuir 2009,25, 9454-9462.
3. Han, D.; Steckl, A. J., ACS Appl. Mater. Interfaces 2013,5 (16), 8241-8245.

In medical applications, a precise temporal control of drug release is often of paramount importance. Magnetically¹ and optically² responsive nanoparticles show great potential to allow the external control of drug release by the application of physical stimuli such as magnetic fields or laser light. Here, they act as transducer element within a polymer composite, triggering the release of an embedded active compound. Therefore, tailor-made nanoparticles can allow for a highly selective and controlled administration of active compounds. This feature can be of considerable value when treating complex diseases such as cancer, infections and metabolic diseases.
In this work, a composite multiscale structure consisting of the biopolymer alginate, functional nanoparticles and a model drug is fabricated and analyzed. Multifunctional hybrid plasmonic-superparamagnetic^2,3 nanoparticles are made by scalable flame synthesis and in-situ coated by an amorphous nanothin SiO₂ layer. Such nanoparticles exhibit significant temperature increase in the presence of an external magnetic field³ and/or irradiation with a near-IR laser.² The size and crystallinity of as-prepared particles is analyzed by N₂-adsorption and X-ray diffraction (XRD) while dynamic light scattering (DLS) is used to assess particle dispersibility. Subsequently, microbeads are formed out of an aqueous alginate solution which is loaded with the nanoparticles and a model drug. To analyze the effect of alginate molecular weight and the mannuronate to guluronate monomer (M/G)-ratio, various alginate types are tested. The morphology and magnetic properties of alginate microbeads are investigated by optical microscopy and with a vibrating sample magnetometer, respectively.
Drug release from the fabricated microbeads is measured at a number of different reference (control) conditions and compared to the release observed upon application of the respective physical stimulus (external magnetic field and/or near-IR laser irradiation). The possibility to externally stimulate drug release will open up new possibilities in intelligent, on-demand drug administration.
References
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2. G.A. Sotiriou, F. Starsich, A. Dasargyri, M.C. Wurnig, F. Krumeich, A. Boss, J.-C. Leroux and S.E. Pratsinis: Photothermal killing of cancer cells by the controlled plasmonic coupling of silica-coated Au/Fe₂O₃ nanoaggregates. Adv. Funct. Mater.24, 2818 (2014).
3. G.A. Sotiriou, M.A. Visbal-Onufrak, A. Teleki, E.J. Juan, A.M. Hirt, S.E. Pratsinis and C. Rinaldi: Thermal energy dissipation by SiO₂-coated plasmonic-superparamagnetic nanoparticles in alternating magnetic fields. Chem. Mater.25, 4603 (2013).

The ability to incorporate bioactive molecules in layer-by-layer (LbL) films has generated considerable interest in drug delivery, since the LbL technology based on the sequential adsorption of oppositely charged layers onto a solid substrate may be employed for a variety of nanostructures, including liposomes. This study was aimed at immobilizing dapsone-incorporated liposomes in conjunction with polyamidoamine dendrimer (PAMAM) in LbL films. The process of adhesion and rupture of unilamellar vesicles on solid substrates was investigated using quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Liposomes made with dipalmitoyl phosphatidyl glycerol (DPPG) and dimyristoyl phosphatidic acid (DMPA) phospholipids were prepared by the film hydration method, with dapsone being added at the beginning of the preparation. According to dynamic light scattering measurements, the average diameter of DPPG nanoparticles was 56±1nm, which decreased to 54±3 nm upon incorporation of dapsone. In contrast, the average diameter of DMPA nanoparticles increased from 245±1 nm to 336±18 nm in the presence of dapsone. QCM experiments showed that the mass accumulated for DPPG liposomes is higher than in the presence of dapsone, thus suggesting vesicle rupture during adsorption. On the other hand, DMPA liposomes contaning dapsone remained intact during adsorption, which was confirmed with atomic force microscopy images.

Polyplex micelle gene carrier, prepared by polyion-complexing plasmid DNA (pDNA) with poly(ethylene glycol)-polycation block copolymers (PEG-polycation), is a superior carrier system to pursue systemic non-viral delivery of genes because this structure features a shell of tethered PEG surrounding a core of polyion-condensed pDNA, which provides the structure with stealth property against adverse biological molecules within the bloodstream so that it may finally promote prolonged blood circulation. Pertaining to this aspect, information regarding PEG crowdedness is very important because it is a key physical property of the shell, which determines the extent of protection against serum proteins. Additionally from our recent studies, PEG crowdedness has also been indirectly implicated to have another role in affecting packaging structure of pDNA within polyplex micelles by the observation that decrease in number of tethered PEG on the core affected shape and size of polyplex micelles. Despite these important roles of PEG crowdedness, there has not been, to our best knowledge, the identification of a numerical value for PEG crowdedness in terms of PEG tethering density (σ) and of PEG conformation for the polyplex micelles, mainly because the two components for σ calculation are missing, namely core surface area for tethering of PEG and number of tethered PEG chains. To this point, we are recently equipped to calculate the core surface area of polyplex micelles, and ultimately σ as we have recently revealed detailed packaging structure of pDNA within rod-shaped polyplex micelles based on PEG-poly(L-lysine) (PEG-PLys). Hereby, we report the first successful determination of PEG crowdedness for polyplex micelles from PEG-PLys, and their implication in determining its shape and blood circulation profile. In this study, σ was examined for polyplex micelles prepared based on PEG-PLys (PEG M_w 12,000g/mol (PEG 12K)) of varying PLys segment length (degree of polymerization (DP) 19, 39, and 70), because PLys DP may electrostatically affect number of tethered PEG to pDNA, and thus possibly resulting in different σ. By decreasing PLys DP, we found that polyplex micelles have more number of tethered PEG to pDNA (ultracentrifuge analysis) and that they settled as longer rods having larger core surface area (TEM observation); by the interplay of these two consequences, decrease of PLys DP resulted in overall higher σ with PEG conformation existing as squeezed for PLys DP 19 and 39, as opposed to overlapping mushroom for PLys DP 70 (Cryo-TEM observation). Indeed, our analysis demonstrated that PEG steric repulsion works to counter DNA condensation, which thus supported the anticipated role of PEG crowdedness in determining shape of polyplex micelles. Furthermore, PEG crowdedness also deeply correlated with blood circulation, showing better retention time for polyplex micelles with squeezed conformation, approving its role on shape and systemic circulation.

Surface modification of poly (3-hydroxylbutyrate-co-3-hydroxylvalerate) (PHBV) with 2-hydroxylethylmethacrylate followed by collagen immobilization yields collagen grafted PHBV film. It is believed that loading of bovine serum albumin capped silver nanoparticles (Ag/BSA NPs) on collagen grafted PHBV film can inhibit the growth of bacteria cells. Thus, the primary objective of this study is to evaluate the factors that influence the loading of Ag/BSA NPs on collagen grafted PHBV film. Spectroscopic (FTIR, XPS, EDX), physical (SEM, AFM), and thermal (TGA) techniques were used to characterize the functionalized PHBV films. The amount of collagen covalently attached to PHBV film was quantified by the Bradford method, while the amount of Ag/BSA NPs loaded on collagen grafted PHBV film was measured by atomic absorption spectrometry (AAS) and anodic stripping voltammetry (ASV). Our results showed that the retention of Ag/BSA NPs on grafted PHBV film is influenced by the chemistry of the functionalized PHBV film, the pH of the Ag/BSA NPs suspension, and the concentration of Ag/BSA NPs solution. Maximum retention of Ag/BSA NPs on collagen grafted PHBV film was observed when 16 ppm Ag/BSA NPs solution was used for loading. Also, at physiological pH, more Ag/BSA NPs were retained than at acidic or basic conditions. Higher the molecular weight of collagen grafted on PHBV film, greater is the degree of Ag/BSA NPs retained on PHBV film. The findings of this study can have important impact in the potential design of scaffold to promote the growth of bone cells while inhibiting the bacterial growth.

Hydrogels have gained considerable attention as a controlled-release system for drugs. We have synthesized a transparent hydrogel with three-dimensional fibrous networks by the gelation of sodium deoxycholate in aqueous solution. Doxorubicin (DOX, a cancer drug) is loaded into the hydrogel with the swelling process. We find that the DOX loaded hydrogel can be injected into aqueous solution as hydrogel fibers through a syringe. The release rate of DOX from the injected hydrogel fibers can be tuned by altering the pH of aqueous solution.

Curcumin is a potent small molecule drug that has shown promising results against several types of cancer. It is a hydrophobic drug that has been shown to possess anti-proliferative effects and can induce apoptosis in cancer cells. However the anti-cancer activity of curcumin is hampered by its low bioavailability and sub-optimal pharmacokinetics owing to its hydrophobic nature. Curcumin can also act as a photosensitive agent that can have potential use in photodynamic therapy (PDT), an emerging treatment modality in which light of an appropriate wavelength induces cytotoxic action.
The objective of this research is to increase the solubility and stability of curcumin under physiological conditions by entrapping the drug in a biodegradable copolymer poly(lactic-co-glycolic acid) (PLGA). The focus has been on optimizing the synthesis of a drug delivery system for curcumin using PLGA nanoparticles to enhance the encapsulation efficiency of curcumin. In this study, we have compared the results of passive and active targeting of PLGA nanoparticles to the breast cancer cells.
For passive targeting, PLGA was conjugated with polyethylene glycol (PEG) followed by nanoprecipitation of the polymer that entraps curcumin in its core. The PEG coating on the surface of the nanoparticles has been shown to increase the in vivo half-life of the drug delivery system. On the other hand, for active targeting, PLGA-PEG was conjugated to folic acid followed by encapsulation using nanoprecipitation and sonication. It has been reported that cancer cells over express folate receptors on their cell surface. Thus conjugating the folic acid to the polymer would enhance uptake via folate receptor-mediated endocytosis causing intracellular release of the drug. Curcumin loaded PLGA, PLGA-PEG, and PLGA-PEG-folate were synthesized and characterized for particle size, size distribution, zeta potential, encapsulation and morphology using standard techniques such as dynamic light scattering and electron microscopy. These nanoparticles were tested against breast cancer cell line MDA-MB-231 through a colorimetric viability assay and cell uptake was imaged using confocal microscopy. The curcumin encapsulated polymeric nanoparticles have shown cytotoxic effects and were internalized by the cancer cells. The results of these in vitro studies will be presented.

Chronic dermal wounds represent a major health problem that affects millions of people worldwide [1]. Moist wound scaffolds play a very important role in the wound healing process since a moisture environment can keep tissue from dehydration and subsequent cell death. In addition, accelerated angiogenesis as well as breakdown of dead tissue and fibrin are other benefits of a moist scaffold. The moist scaffolds may facilitate better interaction of growth factors with their target cells as well [2]. Previous research revealed that the swelling ratio of chitosan nanofibers (NFs) is 70% more than chitosan powder [3]. It is believed that the swelling ratio of nanoporous NFs scaffolds is much higher than that of solid NFs [4]. Chitin (the source of chitosan) is the second most abundant polysaccharide after cellulose, and chitosan is a biocompatable and antibacterial polymer. In this research, a nanoporous NFs scaffold was designed by electrospinning of a chitosan/poly (vinyl alcohol) (PVA) blend solution. To fabricate nanoporous NFs, the PVA part of electrospun NFs were extracted by soaking in water. SEM images revealed that chitosan with a high molecular weight can&’t form NFs by electrospinning. Therefore, an alkaline treatment of the chitosan polymer in a 50% NaOH solution was completed to hydrolyize chitosan to decrease its molecular weight. SEM images of chitosan NFs fabricated from alkaline-treated chitosan for 48h revealed an acceptable morphology although a few nanobeads were still observed. After blending a 4 wt% chitosan solution with a 8 wt% PVA solution at different volume ratios (chitosan/PVA: 75: 25, 50: 50; volume %), uniform NFs were formed without nanobeads. In addition, SEM results demonstrated that increasing the PVA ratio resulted in size increments of fibers in the electrospun NFs. Based on SEM images the average diameter of the 75: 25 volume ratio of chitosan/PVA was around 70 nm, while the 50: 50 volume ratio of chitosan/PVA resulted in NFs with an average diameter of 110nm. The impact of this scaffold on wound healing will also be reported. In summary, the alkaline treatment of chitosan for 48h resulted in chitosan and chitosan/PVA blended NFs with a nanoporous structure which can be a very promising scaffold for numerous tissue engineering applications.
References:
[1] Tchemtchoua T, Atanasova G, Aqil A, et al. Development of a Chitosan Nanofibrillar Scaffold for Skin Repair and Regeneration. Biomacromolecules, 2011, 12: 3194-3204.
[2] Field F. K, Kerstein M. D. Overview of wound healing in a moist environment. Am J Surg. 1994, 167 (1A): 2S-6S.
[3] Homa H, Seyed A, Hosseini R, et al. Electrospinning of chitosan nanofibers: Processing optimization. Carbohydrate Polymers, 2009, 77: 656-661.
[4] Ashleigh C, Rachael O, Hongyan M, et al. Chitosan-based nanofibrous membranes for antibacterial filter applications. Carbohydrate Polymers. 2013, 1, 92(1): 254-259.

The recent developments in the field of organic conjugated and conducting polymers show potential growth over conventional silicon based solar cells for low-cost energy source. However, these organic were sensitive towards moisture and oxygen in the ambient; it needs hermitic protection (WVTR of 10^-6 g/m²/d and OTR of 10^-5 g/cm²/d). The use of high barrier polymeric materials can greatly reduce the permeability of gases. In this work, poly(vinyl butyral) containing aromatic carboxy-aldehydes moieties with different mole percent (10-18 %) were copolymerized with poly(vinyl alcohol) followed by acetalization with n-butyraldehyde in acidic medium. These acidic copolymers were neutralized with Zn, Mg and K cation with 20 - 30% neutralization of their acid hydrogen groups. These ionomers are solvent casted in to a film thickness of 70±5 µm. Dielectric spectroscopy was used to access the dynamic relaxation behavior of these cations in the film. Calcium degradation technique was used to access the moisture permeability behavior of these films under various levels of humidity and temperatures. These films were encapsulated with P3HT/PCBM based organic solar cells. The performance evaluations of these solar cells under accelerated and natural aging conditions were carried out for efficiency degradation of these devices after aging. The level and type of ionic content to the thermal stability, glass-transition behavior and dynamic mechanical properties in poly(vinyl butyral) ionomers were also presented in the light existing mechanism of the cluster/multiplet formation in these films. Finally, the PVB Ionomeric films were used as an interlayer with olefinic and surlyn films were carried out to enhance moisture barrier properties for use in organic device encapsulations.

Uncontrolled hemorrhage is the leading cause of pre-hospital death following military and civilian trauma. Early control of hemorrhage can improve immediate care and delay mortality through the prevention of massive blood loss, hypotension, coagulopathy, metabolic derangements, and infection. A number of observational reports support the use of sealants when bleeding cannot be controlled using pressure dressings alone. An ideal sealant does not require manual pressure to properly control external bleeding, is suitable for the management of internal hemorrhage, and can be removed without mechanical debridement. We have developed a reversible dendritic thioester hydrogel (PEG-LysSH) for traumatic hemorrhage control that will safely provide non-clotting cascade dependent hemostasis in abdominal and extremity wounds. This PEG-LysSH sealant has been shown to adhere to and seal injured tissues: when compared to untreated controls, it reduced blood loss by 35% in a rat model of severe hepatic hemorrhage (23.57 ± 8.27 mL/kg v. 35.21 ± 7.47 mL/kg; p = 0.02) and by 20% in a rat model of aortic injury (17.95 ± 3.84 mL/kg v. 23.09 ± 3.80 mL/kg; p = 0.03). A unique feature of our hydrogel sealant is its capability to be gradually dissolved with biocompatible solutions following its initial application - thus the wound area can be re-exposed in a controlled manner to allow for definitive surgical care in an operative setting. Controlled dissolution of the dressing is not a feature available in any other product presently on the market.

Flexible and wearable electronic devices have attracted growing attention worldwide. However, common energy storage devices fail to meet the demand of high volumetric capacitance combined with good flexibility. In this study, we reported the fabrication and properties of a two-dimensional titanium carbide (MXene¹) and polyvinyl alcohol (PVA) composite films, which are both highly flexible and have a large volumetric capacitance. Ti₃C₂, as a typical MXene, was delaminated into single- and few-layered sheets with a lateral size around 2 m and a thickness around 1-2 nm. The nanosheets can be easily assembled into composite by vacuum filtration, forming Ti₃C₂/PVA composite films. The Ti₃C₂/PVA films have sufficient mechanical strength for handling and even folding. The microstructure of films was characterized by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and X-ray diffraction. PVA layers were confined between Ti₃C₂, forming a highly aligned structures. Ti₃C₂ films exhibit excellent volumetric capacitance, yet the PVA addition allows to confine potassium ions in a gel electrolyte between Ti₃C₂ nanosheets by introducing KOH into the Ti₃C₂/PVA during filtration. The composite films, being flexible and mechanically strong, offer volumetric capacitances in excess of 500 F/cm³, which is higher than reported for pure Ti₃C₂ films.²
1. M. Naguib, V.N. Mochalin, M.W. Barsoum, Y. Gogotsi, MXenes: A New Family of Two-Dimensional Materials, Advanced Materials, 26, 992-1005 (2014)
2. M. R. Lukatskaya, O. Mashtalir, C. E. Ren, Y. Dall&’Agnese, P. Rozier, P. Louis Taberna, M. Naguib, P. Simon, M. W. Barsoum, Y. Gogotsi, Cation Intercalation and High Volumetric Capacitance of Two-dimensional Titanium Carbide, Science, 341, 1502-1505 (2013)

Microporous, non-woven nanofiber scaffolds of poly(vinylidene fluoride) (PVDF)-multiwalled carbon nanotubes (MWCNTs) were made by electrostatic fiber spinning. In this process, polymer fibers with diameters down to the nanometer range, or nanofibers, are formed by subjecting a fluid jet to a high electric field. Cell adhesion and proliferation were measured with MTT (Methylthiazolyldiphenyl -tetrazolium bromide) assay. RT4-D6P2T (Schwannoma cell line of rats), U87-MG (glioblastoma cell line of human) and SH-SY5Y (neuroblastoma cell line of human) cells were cultured in Dulbecco&’s Modified Eagle&’s medium (DMEM) supplemented with 10% (v/v) fetal bovine serum (FBS) and 1% (v/v) antibiotic/antimycotic solution at 37#8451; in humidified and 5% CO₂ atmosphere. Scanning electron microscopy (SEM), histological and immunohistochemical examinations were performed. Penetration of cells and abundant extracellular matrix were observed in the cell-polymer constructs for 7days. SEM showed that the surfaces of the cell-polymer constructs were covered with cell multilayers after 1 day. The cell-polymer constructs were cultured with osteogenic supplements under dynamic culture conditions for up to 7 days. Three type&’s cells of nervous system looks like that there is appropriate concentration of MWCNT for each cell. RT4-D6P2T cells were showed the best adhesion on PVDF sheet with 0.5% MWCNT and that significantly higher than 20% compared with pure PVDF. But the adhesion rate were decreased on PVDF sheet with 1% MWCNT than that. U87-MG cells were steadily increased from PVDF with 0.1% MWCNT with increasing concentration than pure PVDF. And SH-SY5Y cells were showed only high attachment on PVDF sheet with 1% MWCNT than pure PVDF.
We also investigated the effects of varying the MWCNT content, as well as the additional use of drawing and poling on the polymorphic behavior and electroactive (piezoelectric) properties of the membranes obtained. Fourier transform infrared spectroscopy and wide angle X-ray diffraction revealed that dramatic changes occurred in the beta-phase crystal formation with the MWCNT loading. This was attributed to the nucleation effects of the MWCNTs as well as the intense stretching of the PVDF jets in the electrospinning process. The remanent polarization and piezoelectric response increased with the amount of MWCNTs and piezoelectric b-phase crystals. In the poled samples, the incorporation of the MWCNTs made it easy to obtain efficient charge accumulation in the PVDF matrix, resulting in the conversion of alpha-phase into beta-phase as well as the enhancement of remanent polarization and the mechanical displacement. The cell growth showed strong correlation with the membranes piezoelectric property changes. Further evidences of the piezoelectric effect on the cell gowth are presented.

Due to their exceptional charge transport properties, single wall carbon nanotubes (SWNTs) are expected to enhance the performance of organic based photovoltaic (PV) solar cells through an ultrafast charge transfer process when placed in contact with a semiconducting organic interface such as poly-3-hexylthiophene (P3HT)¹.
However, in order to produce efficient charge transport through the active layer, a percolated network of interconnected tubes must be formed. Typical methods (e.g. spin-coating, drop-casting) do not form an efficient pathway for charges, and they often result in randomly organized networks and nanotube aggregates which have been shown to lower conductivity^2,3.
Here, we present a new concept where nanoscale nano-engineered SWNT networks are formed in a composite film made of >90% semi-conducting nanotubes in a P3HT matrix.⁴ These nanoscale networks result in several orders of magnitude increase in charge transport through the composite layer made of P3HT, and compared to an identical composite film simply spun or drop-cast. These nano-networks also result in a strong effective decrease of the percolation threshold, thereby offering the possibility to use much lower amounts of nanotubes in devices. We discuss these results and the mechanisms of charge transport enhancement.
1. Stranks, S. D. ; Weisspfennig, C.; Parkinson, P.; Johnston, M. B. ; Herz, L. M. ; Nicholas, R. J. Nano Lett. 2011, 11(1), 66-72.
2. Nirmalraj, P. N. ; Lyons, P. E. ; Coleman, J. N. ; Boland, J. J. Nano Lett. 2009, 9(11), 3890-3895.
3. Kymakis, E.; Amaratunga, G. A. J. J. Appl. Phys. 2006, 99 (8), 084302.
4. Barbero, D. R. ; Boulanger, N.; Ramstedt; M., Yu, J. , Advanced Materials 2014, 21, 3111.

The discovery of carbon nanotubes (CNTs) has stirred a vast research interest in many academic disciplines, from materials to neuroscience, thanks to their extraordinary mechanical, electrical, thermal and optical properties. The ability to fine-tune these properties through functionalization and introduction into various host systems makes CNTs promising candidates as nanofillers in a myriad of foreseen applications. Additionally, certain ‘smart&’ polymer-CNT nanocomposites have shown mechanically-active behaviour, responding mechanically when irradiated by external stimuli.
Near-edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is an invaluable technique to characterise such systems as it is able to probe the interactions at the filler-matrix interface with very high energy resolution, and can identify conformational behaviour. It also allows for in-situ analysis of smart materials. We had examined variations in NEXAFS spectra of thermo-active Ethylene-Vynil Acetate (EVA) |CNT composites, and offered an actuation model based on ‘kinking&’ and twisting CNTs upon excitation. The model confirms the importance of filler alignment, induced here by straining, for coherent actuation response, where dispersant PyChol molecules latched to CNTs by π-π interactions. ¹
We have found however, that molecular durability of EVA|CNT is a strong function of processing.² Indeed, we now report on the effects of π-π aging due to sonication and straining during processing. We report significant spectral variations on in-situ temperature-resolved NEXAFS analysis of aged composites. Supported by AFM phase topography, interactions between filler and dispersant are observed to be compromised, interrupting communication between filler and polymeric host by way of PyChol segregation. By analysing the evolution of conformational relations in fresh and 1 year-aged composites, a quantitative account has been provided, where sonication and straining promote unlatching of 20% and 76% of PyChol molecules; effectively frustrating actuation.
¹ A.D. Winter; E. Larios, F.M. Alamgir; C. Jaye; D. Fischer, M. Omastová; E.M. Campo, Thermo-Mechanical Actuation of EVA-CNT Composites by in-Situ near Edge X-Ray Absorption Fine Structure. The Journal of Physical Chemistry C, 2014, 118 (7), pp 3733-3741
² A. D. Winter, C. Jaye, D. Fischer, M. Omastov' a, and E. M. Campo, Prestrain relaxation in non-covalently modified ethylene-vinyl acetate | PyChol | multiwall carbon nanotube nanocomposites, Applied Physics Letters Materials 2, 000000 (2014)

The sustained delivery of both hydrophobic and hydrophilic drugs from hydrogels remains a challenge that requires the design of complex multifunctional synthetic polymers. In this work we exploit mucin glycoproteins, the gel-forming building blocks of natural mucus to deliver both hydrophobic and hydrophilic drugs. Mucins are a family of high molecular weight proteins which are densely glycosylated. Their central protein backbone contains hydrophobic and charged domains, while the mucin-associated glycans provide hydrogen bonding capabilities, high hydration, and negative charges. The biochemical versatility of mucins represents potential binding sites for certain drugs. If assembled into hydrogels, mucins could prevent drugs from freely diffusing out, leading to their sustained delivery. We generated methacrylated mucins which assembled into a covalently crosslinked mucin hydrogel when exposed to UV light. The rheological properties of the mucin gels were dominated by an elastic component, and the storage and loss moduli were maintained over four weeks when stored in buffer at 370C. We show that paclitaxel, a model hydrophobic anticancer drug and polymyxin B, a positively charged hydrophilic model antibiotic drug, are retained in the gel and release linearly over more than seven days. This was in contrast with the burst release of the negatively charged poly-glutamic acid and neutral dextran molecules. The activity of the released drugs was tested by measuring the decrease in viability of HeLa epithelial cell when exposed to paclitaxel and the killing of E. coli bacteria by polymyxin B. After three weeks of release, sufficient amounts of active paclitaxel were present to reduce HeLa cell viability. In addition, we show that the mucin gels can sequester polymyxin B and release it in sufficient amounts to inhibit bacteria growth over a month. This work shows that naturally occurring mucins have potential as a new building block for drug delivery biomaterials.

Diabetes is not an infectious disease but its increasingly rapid and worldwide prevalence has been recognized as "pandemic". Despite the necessity for continuous and accurate glycemic control in the management of insulin dependent diabetes mellitus (IDDM), the current palliative treatment relies almost solely on the patient-self injection of insulin, which not only impinges on quality of life of the patients but also fails to precisely control dose of insulin where the overdose must be strictly avoided otherwise causing serious hypoglycemia. Development of self-regulated insulin delivery systems is a long-standing challenge of materials science, for which exploitations of glucose oxidase and sugar-binding lectin are two prevalent rationales to install the function of glucose-sensitivity. These protein-based components, however, intolerant of long-term use and storage with their denaturing and cytotoxic natures, are hardly suitable for any implantable applications thus have not yet been in clinical usage to date. Here we describe a thoroughly synthetic and remarkably simple alternative. A polymer gel bearing phenylboronic acid (PBA) derivative was chemically optimized as to elicit abrupt and glucose-dependent transition in the state of hydration under physiological aqueous condition.^1-5 During this transition, development of a thinly surface-dehydrated layer or "skin layer" was identified as a mode that is able to discretely switch the release of gel-loaded insulin, providing an ability to synchronize the dosage with the surrounding glucose-fluctuation in the range between normo- and hyperglycemia.⁶ This synthetic alternative may offer a new material basis for the self-regulated insulin delivery systems to treat diabetes with long-term stability and safety.

Cell encapsulation is a technology with enormous clinical potential for the treatment of a wide range of difficult diseases including type 1 diabetes, neurological and sensory diseases, cancers, and many others. In cell encapsulation, a biomaterial or device with semipermeable membranes protects the transplanted therapeutic cells from immune rejection, without the use of immunosuppression, while simultaneously allowing facile mass transfer to maintain the cell survival and function. Polymer based cell encapsulation devices have been developed for decades with some of them already commercialized, such as TheraCyte ^TM. Although mechanically durable, easy to use and potentially retrievable/replaceable, these current encapsulation devices, mostly made from phase-inverted membranes or expanded Teflon, suffer from fibrosis and insufficient biocompatibility. On the other hand, hydrogels such as alginate and PEG are more biocompatible and have been widely employed for cell encapsulation and delivery. However, hydrogel materials are intrinsically soft due to their large water content and difficult to handle or easy to break. Thus, it remains a challenge to fabricate mechanically robust cell encapsulation devices from hydrogels that permit easy handling, implantation/retrieval/replacement and long-term clinical application.
To address this challenge, here we report a simple, robust and universal approach to fabricate hydrogel microdevices for cell encapsulation, culture and delivery. In this design, we take advantage of the well-known wicking phenomenon where capillary action causes a wetting liquid to impregnate a porous medium. By wicking hydrogel precursor solutions into pre-made nanofibrous microdevices and subsequent crosslinking, we obtained various microdevices with different hydrogel chemistries. The microdevices retained the properties of both the hydrogel (e.g. the biocompatibility) and the nanofibers (e.g. the mechanical robustness). The facile mass transfer was confirmed by encapsulation and culture of different types of cells, loaded in their preferred cellular matrix. Additional compartmentalization of the microdevices enabled paracrine cell co-cultures in single implantable devices. Lastly, we evaluated the biocompatibility, functionality and retrievability of the microdevices by encapsulating and delivering rat islets into chemically-induced diabetic mice. The diabetes was corrected for the duration of the experiment (8 weeks) right before the implants were retrieved. The retrieved devices showed minimal fibrosis according to histology studies and as expected, live and functional islets were observed within the devices, confirming the great potential of these microdevices as a new platform for cell encapsulation therapies.

Microcapsules are of great interest in biomedical applications, the food industry, cosmetics and as catalyst supports. Multifunctional capsules that respond to more than one stimuli are needed in many of these applications to achieve controlled release and enable smart manipulation. With such capsules, targets can be addressed with one stimulus, while a second stimulus triggers release.
Here, we demonstrate a novel method to obtain microcapsules with polymer shells of controlled macroporosity and mechanical properties that can be tuned within a wide range. These capsules contain two liquid compartments: an aqueous core and an oil phase that permeates the macroporous polymer shell. Simultaneously loading of water-soluble chemicals in the core and oil-soluble chemicals in the liquid phase of the biphasic shell can potentially enable the creation of capsules that respond to multiple external stimuli.
Microcapsules are produced by microfluidics, using a co-flow flow-focusing glass capillary device to make water-oil-water (W/O/W) double emulsion templates. A mixture of acrylate monomers (glycidyl methacrylate and ethylene glycol dimethacrylate) and porogens (phthalate-based, alkane or alkanol) is used as oil phase. Heterogeneous polymerization of the acrylate monomers leads to a biphasic structure: a network of polymer particles permeated by the liquid porogen and covered with a thin, tight polymer skin. The diameter of the polymer particles and the pore size can be tuned by varying the amount of porogen or by mixing porogens with different solubility parameters. The permeability of the shell is determined by the polymer skin and the porous structure. Compression tests of single capsules show that the elastic modulus and the force at break depend on the microstructure of the porous network. Highly interconnected networks of many small polymer particles lead to strong and stiff capsules, while larger and fewer particles result in weaker microcapsules. The interstitial liquid porogen can also be loaded with an oil-soluble encapsulant or used as carrier for a chemical trigger. Incorporation of glycidyl methacrylate monomers results in polymer particles with epoxy-functionalized surfaces, which can be further reacted with amine-based functional compounds. In a proof of concept design, we exploited such surface amine groups to create magnetic capsules by covalently binding dopamine-coated iron oxide nano-particles to the outer shell surface.
The proposed multi-compartment structure provides a rich platform for the future design of microcapsule systems capable of responding to multiple external stimuli.

Nanoporous silica nanoparticles have been applied to delivery carriers for various guest molecules based on their large surface area and high pore volume. However, most nanoporous silica nanoparticles have small pore size around 3 nm which is a limitation to load relatively large sized proteins in many bioapplication. Although there have been reports on the preparation of large pore-sized nanoporous silica nanoparticles, it is still challenging to control pore structure of nanoporous silica nanoparticles with large pores and to combine with functional nanoparticles. In this study, we demonstrate the integration of large pore sized nanoporous silica nanoparticles with superparamagnetic nanoparticles, simultaneously. The large pore-sized nanoporous silica nanoparticles encapsulating magnetic nanoparticles were prepared by using water-dispersed magnetic nanoparticles and co-solvent in the synthesis. The pore size, pore shape, and surface area of the resulting nanoporous silica nanoparticles were controlled to change amount of co-solvents. The surface-modified, large pore-sized nanoporous silica nanoparticles resulted in higher loading of model protein and DNA compared to nanoporous silica nanoparticles with small pores. The resulting nanoporous silica nanoparticles were applied as an efficient antigen delivery system to immune cells with a capability of tracking those cells with molecular imaging technique.

In recent years, the use of responsive materials to design intelligent polymer carriers has received great interest, particularly for biomedical applications. Various external and internal stimuli have been incorporated as trigger(s) to induce cargo release and/or carrier degradation. Recently, we reported the design of an inherently smart polymer carrier using layer-by-layer (LbL) assembly. LbL is a versatile technique, as it allows for excellent control over carrier properties based on the materials used for the assembly [1]. Utilizing the common internalization pathway of particulate carriers that involves intracellular pH changes [2] and the presence of specific enzyme (i.e., cathepsin B) [3], a biologically inspired carrier system was designed [4]. In this system, the innate characteristics of an engineered peptide and a synthetic polymer were exploited for the design of bio-responsive carriers [4]. These carriers were tailored to consist of an outer coating that is sheddable at endosomal pH and inner multilayers with an enzyme-specific (lysosomal enzyme) recognition sequence integrated as a cross-linker. The intrinsic cellular variations were shown to induce rapid carrier degradation in vitro inside the cells. In this presentation, we will focus on the use of an engineered peptide and a responsive polymer (as the enzyme- and pH-responsive moieties, respectively) in the design of bio-responsive carriers for enhanced intracellular degradation.
References
[1] F. Caruso, R. A. Caruso, and H. Möhwald Science1998, 282, 1111.
[2] J. Huotari and A. Helenius EMBO J2011, 30, 3481.
[3] C. S. Gondi and J. S. Rao Expert Opin. Ther. Targets, 2013, 17, 281.
[4] S. T. Gunawan, K. Liang, G. K. Such, A. P. R. Johnston, M. K. M. Leung, J. Cui, and F. Caruso Small2014, Submitted.

Utilizing a biomimetic feedback network, we design microcapsules that self-organize and undergo directed, self-sustained motion over a substrate. In our model system, microcapsules act as localized sources of chemicals that diffuse through the surrounding fluid medium. We specifically consider three types of microcapsules, each producing a different chemical species with production rates modulated by a regulatory network known as the repressilator: each species represses the production of the next in a cycle. This network has previously been studied in the context of gene expression regulation where all species are produced in a small, well-mixed volume of space. In this case, the dynamics can be described using ordinary differential equations and it is known that the levels of each species can approach constant values or exhibit large amplitude oscillations, depending on model parameters. In the current work, we present an analysis of the repressilator system with finite spatial separation between sources of each chemical component. Conditions are given for the steady and oscillatory regimes. We then extend the model to allow movement of the microcapsules over a planar substrate. The microcapsules are placed on a surface and the chemicals released into the fluid are adsorbed onto the surface, altering adhesive interactions between the surface and the microcapsules. Gradients in the surface energy resulting from this adsorption generate lateral forces, leading to self-induced motion of the microcapsules. We numerically simulate this system by combining the lattice Boltzmann method to solve the Navier-Stokes equation for hydrodynamics, the immersed boundary method to couple the microcapsule motion to the fluid flow, and finite difference methods for the advection-diffusion of chemical species. This model exhibits a diverse range of behavior, including several distinct modes of sustained motion of the microcapsules. We highlight the role of the repressilator regulation network and demonstrate how combining chemical sensing with motile response can lead to new behavior in the form of spatial organization.

Introduction
Polyplex micelles (PMs), formed through polyion complexation between block copolymer of poly(ethylene glycol) (PEG)-b-polycations and plasmid DNA (pDNA) are attractive delivery system for gene therapy due to their structural characteristics as a core-shell architecture, that a pDNA is packaged into the core surrounded by PEG shell. Through detailed structural investigations, we found that a pDNA is packaged into distinct rod-shape by several times folding to form a bundle within the PM. Taking the principle driving force for the DNA packaging, that is to reduce unfavorable surface energy developed on the charge neutralized DNA, the rod-shape is curious because this shape is not the best favorable structure, as the globule-shape should give the minimal surface area. To this point, we reported that the rod-shape is mainly balanced by following three components; requirement to reduce the surface energy, steric repulsion from the PEG, and rigidity of DNA as the bundled form. Regarding these three components, it is speculated that the globule-shape, as an ideal shape in terms of the surface energy, may be formed even in PMs by reducing commitment of PEG. To examine this possibility, we investigated packaging structure of pDNA within PMs with modulating PEG contribution by changing associating number of PEG on pDNA as well as varying molecular weight of PEG.
Result and Discussion
Packaging structure of pDNA within PMs was initially investigated for fixed PEG molecular weight 12k and various PLys DP. The TEM observation revealed that the rod-shape was dominantly formed in PLys DP 20 minus; 72, whilst the globule-shape was formed in PLys DP 103 minus; 145. Since the pDNA basically forms charge-neutralized complex with PEG-PLys, less number of PEG-PLys associates in PMs formed from higher PLys DP. Therefore, this result suggested that the pDNA packaging structure may be regulated by amount of associating PEG. To confirm this suggestion, packaging structure was further investigated for PMs with various PEG molecular weight in range of 2k minus; 42k. The PMs with higher PEG molecular weight tended to form the rod-shape, whilst the PMs from lower PEG molecular weight tended to form the globule-shape. This observation further supported above-mentioned suggestion about PEG contribution. To investigate this trend quantitatively, PEG density was analyzed for pDNA surface at the onset of transition to the packaged state. Consequently, we found the critical PEG crowdedness that discriminates the packaging structure to be the rod-shape or the globule-shape. In other words, the fate of packaging structure to be the rod-shape or the globule-shape was regulated by the critical PEG crowdedness at the onset of transition to the packaged state.

Tissue reconstruction and closure of incisions/wounds is pertinent to almost all surgical interventions and traumatic injuries. Conventional suturing and tissue stapling have defined limitations, but remain ubiquitous in many procedures and few advances have been made in modern surgery with regards to improving the risks of these techniques. Effective tissue sealants have the potential to reduce risk, reduce cost of complications, enhance surgical competency, and improve patient comfort. These desired attributes have led to our investigation into using solution blow spinning for the direct deposition of biodegradable polymer blend fiber mats as surgical sealants. Solution blow spinning is a polymer fiber mat fabrication technique that requires only a simple apparatus, a concentrated polymer solution in a volatile solvent, and a high-pressure gas source. More importantly, this technique does not have the high voltage/conductivity requirements of electrospinning and does not suffer from a slow deposition rate. These advantages allow for direct deposition on any substrate including use during surgery. Here we report utilizing this technique for generating in situ surgical sealants composed of degradable polymer blend fiber mats using a commercial airbrush and compressed carbon dioxide. Solution and deposition conditions were optimized to rapidly generate polymer fibers at flow rates exceeding 1 ml/min. Fiber morphology was characterized by SEM, mechanical properties by DMA, and thermal properties by DSC. Degradation was monitored by SEM and GPC for morphologic and molecular weight change. In vitro cell viability showed no negative effect of the direct deposition of fibers relative to the live control for both mice fibroblasts (L929) and human coronary artery endothelial cells (HCAEC) using an MTS cell viability assay. A pilot animal study illustrated the utility of this technique, generating conformal sealants for lung resection, liver laceration and femoral vessel injury in chronic studies. Similarly, when used to supplement suturing in an intestinal anastomosis, burst pressure strength was increased by approximately 10 times versus the suture-only control. Ultimately, solution blow spinning offers the ability to generate on-demand conformal polymer mats directly on a wide range of targets, allowing for use during surgery. In vitro biocompatibility and pilot animal studies demonstrate the potential of this technique for medical applications. Future studies will focus on operation and recovery outcomes.

Our research team at UTPA is involved in several research projects that mainly focus on the use Forcespinning TM (FS) technology to produce polymer nanofibers and polymer/ceramic nanofiber composites for use in a wide variety of potential applications such as energy storage devices, filtration, tissue engineering, drug delivery, wound healing dressings, electronics technology and aerospace and defense. Recently, Lozano and her research group [1-2] developed the Forcespinning^TM (FS) method to mass produce nanofibers (NFs) with desired structure and performance. FS is a technology that relies on applying a centrifugal force with an externally imposed rotational constraint to a solution or melt to produce submicron and nanometer fibers.
Here we present results on the use FS method to produce NFs for energy storage devices and biomedical applications, especially for Li-ion batteries, supercapacitors and biomedical sensors. The focus of this work is on the design, synthesis, screening, and in-depth characterization of nanostructured materials with good properties and performance and low cost. The ultimate goal of this project is the development of low-cost, high capacity, long cycle life materials for Li-ion batteries, supercapacitors, biosensors, wound healing dressing and electronic technology. Several systems of composite NFs were prepared by FS method such as polymer Nonwoven mats [3], poly(vinyl) butyral (PVB) NFs and carbon nanotube (CNT)/PVB NF composites [4], silicon carbide (Si/C) NFs and SiC/CNT composite [4], Mixed-valent VOx/polymer nanohybrid fibers [5] and hybrid (BEH-PPV)/PEO nanofibers [2]. The results obtained on the properties and performance of these FS NF-based composite systems are discussed in detail.
References
1.Sarkar, K., Gomez, C., Zambrano, S., Ramirez, M., de Hoyos, E., Vasquez, H., Lozano, K. (2010). Electrospining to Forcespinning. Materials Today, 13(11), 42-44.
2. Padron, S., Patlan, R., Gutierrez, J., Santos, N., Eubanks, T., Lozano, K. (2012). Production and characterization of hybrid BEH-PPV/PEO conjugated polymer nanofiber by Forcespinning^TM” Journal of Applied Polymer Science doi:10.1002/app.36420.
3. F. Xu B. Weng, K. Lozano and M. Alcoutlabi, Forcespun polymer Nanofiber composites as micropourous membranes separators for Lithium-ion Batteries, to be submitted, 2014.
4. B. Weng, G. Garza, M. Alcoutlabi and K. Lozano, The Production of Carbon Nanotubes Reinforced Poly(vinyl) Butyral nanofibers by the Forcespinning Method, Polym. Eng. Sci., 2014, Available online, DOI: 10.1002/pen.23872.
5. A. Altecor, K. Lozano, and Y. Mao, “Mixed-valent VOx/polymer nanohybrid fibers for flexible energy storage materials,” Ceram. Intern. 2014, 40, 5073-5077.

Bone loss and skeletal deficiencies due to disease, traumatic injury, and abnormal development are major problems worldwide. In the U.S. alone, over 3 million orthopaedic procedures are performed every year; approximately 500,000 of these are bone-grafting procedures. Autograft, the gold standard treatment, requires an invasive second surgery and can lead to donor site morbidity. Allografts (bone donated from cadaver) are another popular option, but they can illicit an unfavorable immune response and exhibit a 30-50% failure rate over a period of 10 years. With the drawbacks witnessed from biological grafts, there has been a shift in paradigm towards tissue engineered (TE) bone grafts. The limitless supply and ability to utilize TE scaffolds as carriers for stem cells or growth factors delivery make them advantageous, but the lack of vascularization and nutrients to the graft implant leads to the graft&’s failure in vivo. Current directions to enhance vascularization in bone regeneration are largely aimed at enhancing early vascular support using pre-vascaularization of tissue-engineered constructs. Bone vascularization is housed within mineralized collagenous tubes called osteons that are fused together to form cortical bone. This study focuses on the development of fabricated osteons using nanoscale fabrication techniques and promoting early angiogenesis within the biomimetic osteonic (haversian) canals. We fabricated the biomimetic osteons by electrospinning poly-l-lactic acid (PLLA) with 10% gelatin (from bovine skin) and poly-d-lactic acid (PDLA) nanofibers onto a rotating polyethylene oxide (PEO) and PLLA twist until an approximate scaffold diameter of 500mu;m was reached. PEO is used because it is extremely water-soluble. The electrospun tubes were crosslinked with the FDA approved enzymatic crosslinking agent Transglutaminase (mTG) to increase strength and prevent gelatin leaching. After crosslinking, the inner twist was dissolved out leaving behind a scaffold mimicking the osteonic structure. Human umbilical vein endothelial cells (HUVECs) were seeded inside the hollow scaffolds and evaluated over a 28-day span. SEM images of the fabricated osteon yielded an average inner diameter of 0.495mm±44mu;m. Actin/DAPI stain exhibited circumferential cellular proliferation in confocal microscopy z-stack images. Additionally, preliminary SEM results demonstrated the presence of new ECM indicating the beginning stages of guided neovascularization. Ongoing studies will further characterize the vasculature lumen development within the osteon scaffold over an 8-week time period using a variety of techniques including immunofluorescence staining for CD31 and VE-Cadherin and qPCR assay for expression of endothelial genes such as collagen type 1, elastin, vascular endothelial growth factor type A, and angiopoietin 1. Our ultimate goal is to develop a TE pre-vascularized full-thickness and structurally relevant bone graft for large bone defects.

Harnessing the synergy between materials at the nanoscale can be a valuable tool in understanding and probing cellular phenomena and in driving specific processes that lead to tissue and organ regeneration and repair. In this context, orthopedic implants are designed to restore joint function. The functional success of an implant critically depends on its stable interaction and bonding with the host tissue, yet aseptic loosening accounts for over half of all implant failures. Conversely, autologous bone is used to repair traumatic wounds and congenital defects that result in large defects, but this is a suboptimal clinical therapy that is limited by quantity and pain at the harvest site.
We investigated the use of tunable, modular, nanoscale coatings that can prevent premature implant failure, induce targeted tissue repair. Central to the polymer-based multilayered coating, was a water-based layer-by-layer (LbL) deposition process, by which each component was introduced on the surface in nanoscale layers. On surrogate bone implants, coatings containing osteoconductive hydroxyapatite (HAP) and 5-10 µg of osteoinductive bone morphogenetic protein 2 (BMP-2) contained within the nanostructured coating acted synergistically to induce osteoblastic differentiation of endogenous progenitor cells in a rat. The tuned release of BMP-2 over 3-4 weeks, controlled by a hydrolytically degradable poly(β-amino ester), was essential for tissue regeneration and, in the presence of HAP, the modular coating encouraged the direct deposition of highly cohesive trabecular bone on the implant surface with a high, long-term interfacial tensile strength.
To repair large bone defects scaffolds made of a poly(lactic-co-glycolic acid) (50:50) copolymer were used with multilayer coatings containing tunable amounts of BMP-2 and mitogenic platelet derived growth factor (PDGF)-BB from 0.2-2µg. Complete release of the growth factors occurred over readily adapted time scales, which extended from 8-10 days and 22-25 days for PDGF-BB and BMP-2 respectively. Each component of the system was tested for its effect on tissue formation. The adaptive growth factor release and synergistic effect of BMP-2 and PDGF-BB promoted local bone formation that bridged a critical-size defect in the rat calvaria as early as 2 weeks after implantation. Dual growth factor delivery resulted in mechanically competent bone that restored the properties of the bone and regenerated the native calvaria form.
Collectively, this work provides insight into probing and modifying cellular interactions to control morphogenetic processes at varying length and time scales, and in different disease states with a polymer-based multilayer coating approach. Towards the development of next-generation biomedical therapies this approach allows for driving cell morphogenetic phenomena and controlling local microenvironments to understand and engineer therapies for bone tissue.

Theranostic agents combine both a therapeutic agent and an imaging platform within the same material to simultaneously diagnose and treat diseases, such as cancer. This report describes the development of donor-acceptor polymers into aqueously stable spherical nanoparticles that have the capacity to act as unique theranostic agents. We term these particles, PolyDOTS, for polymer Dynamic Organic Theranostic Spheres. In this application, PolyDOTS were created using the donor-acceptor conjugated polymer, polycyclopentadithiophene benzoselenadiazole (PCPDTBSe), which has tunable optical properties correlating to the molecular weight of the polymer. Various molecular weight fractions were combined at specific ratios to develop a hybrid nanoparticle capable of both fluorescence imaging and heat generation upon exposure to light. PolyDOTS have an approximate hydrodynamic diameter of 90nm and stable fluorescence following multiple heating/ cooling cycles, as well as minimal changes in the optical properties after a 30day exposure to ambient light. Upon exposure to 800nm light, PolyDOTS generated a 42 degrees Celsius temperature increase above ambient temperature. PolyDOTS were evaluated as effective photothermal agents against breast epithelial cells. Minimal cytotoxic response was observed in the absence of infrared light. In the presence of 800nm light, PolyDOTS incubated with MDA MB 231 breast cancer and MCF10A non-tumorigenic cells generate significant heating, resulting in a 90% decrease in cell viability at concentrations of 50ug/ml and higher. Fluorescence microscopy revealed that PolyDOTS localized throughout the cell but were excluded from the nucleus, and no photobleaching occurred during prolonged imaging. These results demonstrate that PolyDOTS represent a new class of theranostic nanoparticles built from the platform of conjugated polymers by selectively combining fluorescent and heat generating polymers into one stable nanoparticle that shows no fluorescence quenching and excellent photothermal capacity.

Human pluripotent stem cells (hPSCs) are invaluable sources for developmental studies, cell transplantation, disease modeling and toxicity screening. However, it is still largely unclear how dynamic cell-biomaterial interactions play a role in regulating hPSC self-renewal, pluripotency and differentiation. In this work, we have leveraged a library of micromolded poly(dimethylsiloxane) (PDMS) micropost arrays (PMAs) developed recently in our laboratory to study mechanosensitive behaviors of hPSCs. These PMAs present the same surface geometry, but different post heights, to modulate substrate rigidity independent of adhesive effects and other material surface properties. Using the PMAs, we have screened a broad range of substrate rigidities, and our results have revealed that substrates with a rigidity less than 5 kPa could promote early neural induction of hPSCs by increasing gene and protein expression levels of Pax6 and Sox1 and decreasing expression of pluripotency genes. Moreover, soft substrates strongly promote caudalization of neural progenitor cells by elevating HOX gene expression. The purity and yield of functional motor neurons (MNs) derived from hPSCs within 30 days of culture using soft PMAs (with a rigidity < 5 kPa) are improved two- and fifteen-fold, respectively, compared to conventional hPSC culture. Motor neurons derived on the PMAs display electrophysiological activities comparable to those from primary neurons in vivo. Mechanistic studies have revealed a multi-targeted mechanotransductive process involving Smad phosphorylation and nucleocytoplasmic shuttling, regulated by rigidity-dependent Hippo/YAP activities and actomyosin cytoskeleton integrity and contractility. Our findings suggest that substrate rigidity is an important biophysical cue influencing neural induction and subtype specification, and that microengineered polymeric substrates can thus serve as a promising platform for large-scale culture of hPSCs.

There has been a recent interest of research to exploit proteins as nanoplatforms for bio-related applications. As natural polymers, proteins often have minimal toxicity and immunogenicity, and can be easily degraded after the therapy has concluded. These advantages may put them ahead of conventional nanomaterials in clinical translation. One candidate protein is ferritin. Ferritin is a major iron storage protein found in most living organisms including humans. Each ferritin nanocage is comprised of 24 subunits, which self-assemble to form a cage-like nanostructure, with external and internal diameters of 12 and 8 nm, respectively. There are a number of features that make ferritins appealing nanoplatforms for imaging or therapy. First, artificially produced ferritins afford a central cavity which, as shown in our recent studies, can encapsulate metals or metal-containing compounds with high efficiency. Second, the surface of ferritins can be modified either chemically or genetically to present functionalities, such as peptides, tumor-targeting molecules, and dye molecules. Third, despite their rigidness under physiological conditions, the nanocages can be broken down into subunits in an acidic environment and reconstituted into intact nanostructures when the pH is tuned back to neutral. This pH-mediated disassembly and reconstitution provides a convenient means to prepare ferritin-based multifunctional nanoplatforms and/or to load species into the interiors of ferritins. Harnessing these properties, we recently constructed ferritin-based MMP activatable imaging probes and PET/fluorescence dual modality imaging probes. We have also reported that RGD modified ferritins can load doxorubicin and photosensitizers for selective and effective tumor therapy. More recently, we found that using RGD modified ferritins as photosensitizer carriers and with light irradiation at relatively fluences, one can site-specifically deliver ¹O₂ to the tumor endothelium to produce mild photochemical stimuli that result in newly formed or enlarged gaps on endothelial walls. The enhanced vessel permeability facilitates the extravasation and accumulation of nanoparticles or macromolecules at tumors, which was observed with albumins, quantum dots, and iron oxide nanoparticles in different tumors. More excitingly, we found that Doxil, a nanoparticle-based doxorubicin formula, can benefit from the ferritin-mediated blood vessel enhancement to achieve improved therapeutic efficacy. All of these findings suggest ferritin and its derivatives as powerful nanoplatforms with great potential in clinical translation.

Conjugated polymers (CPs) show outstanding properties for fluorescence imaging as they exhibit high brightness, large extinction coefficients and greater photostability than conventional fluorescent probes. Although the main focus of their application has been in optoelectronics, recently they have been studied for biomedical applications as imaging agents, drug delivery vectors and biosensors¹. In order to optimize CPs for biomedical applications, these polymers can be encapsulated in nanoparticulate form, thereby protecting the electrically active hydrophobic backbone from its environment, and introducing a protective capping layer on the particle surface².
Capping the nanoparticles with engineered peptides can both protect and stabilize the polymer core and provide functionality to conjugated polymer nanoparticles (CPNs). Peptides provide several advantages over other commonly used capping agents as hydrophobicity/hydrophilicity can be tailored, conjugation to other molecules is easily attained and bioactive sequences can be incorporated. We have developed custom-designed amphiphilic peptides as capping agents for a one-pot synthesis and functionalization of CPNs. The peptides are anchored to the CPN surface by the entrapment of a hydrophobic segment that undergoes hydrophobic interactions with the CP, while a bioactive hydrophilic segment extends from the surface. The CPNs maintain the advantageous optical qualities whilst being effectively protected by the peptide capping agent.
We prove functionalization of CPNs by using an amphiphilic TAT peptide as the capping agent. The TAT peptide is highly positively charged therefore it stabilizes the colloidal CPNs, and at the same time facilitates cell penetration. We demonstrate that this functionalization accelerates and provides more efficient internalization of the CPNs by HeLa cells when compared to non-modified CPNs or CPNs with other capping peptides. Time-dependent cellular uptake is monitored by confocal microscopy and can be easily quantified by flow cytometry due to high fluorescence brightness of the CPNs. We further show that by introducing receptor binding motifs (e.g. folic acid) we can tailor cellular uptake of peptide capped CPNs in cells with high (folate) receptor expression. Importantly, CPNs also show less intrinsic toxicity than alternative fluorescent nanoparticles (e.g. quantum dots), a vital health and environmental issue when developing these technologies for clinical use.
The one-pot synthesis of peptide capped CPNs provides a straight-forward and versatile approach to protect the polymer core and anchor biologically active motifs on the particle surface, extending applications of CPNs in imaging and beyond.
1. L. Feng et al. Chem. Soc. Rev., 2013, 42, 6620-6633.
2. P. Howes et al. J. Am. Chem. Soc., 2010, 132, 3989-3996.

Non-spherical nanoconstructs have been shown to accumulate within the tumor vasculature more efficiently than spherical ones, minimizing the internalization into macrophages. However, bottom-up based synthesis methods using emulsification and nano-precipitation are limited to control these shapes precisely and independently over multiple scales. Therefore, we demonstrate discoidal polymeric nanoconstructs (DPNs) with a diameter of 1,000 nm and a height of 400 nm via our top-down fabrication method. The DPNs are obtained by mixing in one synthesis step of the constituent polymers with poly(lactic acid-co-glycolic acid) (PLGA), polyethylene glycol (PEG) diacrylate, and with the multiple payloads for magneto-optical properties with positron emission by loading 20 nm iron oxide nanocubes (NCs), lipid-DOTA for ⁶⁴Cu chelation, and lipid-Rhodamine B dye (RhB). The DPN geometrical features and in-vitro/-vivo behaviors are characterized by multiple microscopes and imaging modalities including intra vital microscopy (IVM), confocal live imaging microscopy, 3 tesla magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT). Also, the mild toxicity of the DPNs was confirmed by human umbilical vascular endothelial cells (HUVECs) with MTT assay and also blood levels of serum cytokines analysis after 24h post-injection.

Despite wide application of eye drop for ocular drug delivery, it has serious limitations in drug penetration, delivery efficiency, and bioavailability due to corneal barriers. The bioavailability of ocular drugs depends on the residence time of drug carriers in the cornea. Here, we carried out bioimaging of Flt1 peptide - hyaluronic acid (HA) conjugates in the eye after topical administration. In vivo two photon microscopy revealed that Flt1 peptide - HA conjugates more effectively adhered and were absorbed to the corneal epithelia than the dye mixture. Ex vivo two photon microscopy also visualized more effective delivery of labeled Flt1 peptide - HA conjugates with an enhanced residence time into the cornea than the control of dye mixtures. Furthermore, repeated eye drops of Flt1 peptide - HA conjugates resulted in comparable therapeutic effect to the subconjunctival injection for the treatment of corneal neovascularization. Taken together, we could confirm the feasibility of in vivo two photon microscopy as a new bioimaging tool for ocular drug delivery and Flt1 peptide - HA conjugates as a topical drug delivery system for the treatment of corneal neovascularization.
[Keywords] Hyaluronic acid; Flt1 peptide; Two photon microscopy; Corneal neovascularization

Although required for prolonged circulation, PEGylation (PEG; polyethylene glycol) of cationic lipid-nucleic acid (CL-NA) complexes hinders cellular uptake, reducing their efficacy as nucleic acid delivery vectors in vitro. [1] Grafting a targeting peptide at the distal end of PEG improves cellular uptake by allowing sterically-stabilized NPs to undergo internalization through receptor-mediated endocytosis. We have developed PEGylated CL-NA nanoparticles with an RGD or iRGD (internalizing RGD; capable of tumor targeting and penetration [3]) motif present at the distal end of PEG2000 and studied their efficacy and mechanism of entry in vitro. Although RGD-tagging of PEGylated CL-NA NPs improves cellular internalization [2], little is known regarding whether targeting peptides alter the intracellular trafficking of NPs. Using GFP constructs of the Rab family of GTPases, which facilitate various stages of the endocytic and exocytic pathway, we investigated the intracellular fate of our RGD-tagged NPs. We used three Rab-GFP constructs (Rab-5, 7 or 9) to label early and late endosomes and we compare the colocalization of fluorescently labeled RGD- and iRGD-tagged NPs in these endosomes as a function of time in live cells. We also measured the transfection efficiency of RGD and iRGD-tagged lipid-DNA nanoparticles using a luciferase assay. A thorough understanding of the intracellular fate of CL-DNA nanoparticles will allow for optimization of gene delivery vectors. Funded by NIH-GM59288.
[1] Chan, C.L. et al.; Biomaterials, 33, 4928-4935, 2012.
[2] Majzoub, R.N. et al.; Biomaterials, 35. 4996-5005, 2014.
[3] Sugahara, K.N. et al.; Cancer Cell, 16(6), 510-520, 2009.

Light-induced polymerization is an industrially viable process that offers numerous economic and technical advantages over conventional thermal polymerization, particularly toward the fabrication of crosslinked thermoset thin films. These advantages include rapid through cure, low energy requirements, ambient temperature processing, solvent-free resin compositions, and spatial and temporal control over the polymerization process. This presentation will focus on our group&’s recent efforts to use thiol-ene photopolymerizations to fabricate thin, crosslinked polymer networks containing functionality aimed at tailoring the surface chemical functionality and morphology of the films. For example, the spray-deposition of nanoparticle-laden thiol-ene resins provides surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior of such films can be tailored toward superhydrophobicity (anti-wetting with water) or superamphiphobicity (anti-wetting with water and oils) by judicious choice of monomer constituents. Beyond the simplicity offered by thiol-ene photopolymerizations, the cross-linked thiol-ene coatings are solvent resistant, stable at low and high pH, and maintain antiwetting behavior after extended exposure to elevated temperatures. These surfaces exhibit a low propensity toward contamination, and as a result, are of great interest for potential applications in self-cleaning, antifouling, separation processes, and drag reduction coatings.

Prevention of bacterial adhesion and colonization on implant surfaces has been a challenge in orthopaedic surgery. Bacterial infection, extensive inflammation and poor osseointegration have been identified as the major reasons for early orthopaedic implant failures based on titanium (Ti). Creating implants with drug-eluting properties to locally deliver drugs is an appealing way to address some problems like systemic toxicity of the drugs, reaching deliver drugs locally and continuously.
In this study, we focuses on the development of a polymer-coated ceramic composite for antimicrobial drug delivery. Three layers of vertically oriented titanium base, a thin layer of calcium phosphate coating was used a micro-arc oxidation (MAO) to produce a porous structure for improving the biocompatibility of titanium. The coating with controlled and sustained release of antibiotic was highly effective against bacteria. Using a spray coating method, aqueous drug was loaded into the porous surface. Finally, gamma polyglutamic acid (γ-PGA), a well-known natural hydrophilic biodegradable polymer, was coated layer-by-layer through spin coating as a barrier to control drug release. The results demonstrate that using porous structure with γ-PGA is promising as cost-effective drug delivery formulation for delivering drugs locally and continuously.

Reducing protein adsorption onto silicones would improve the performance and safety of a variety of blood-contacting medical devices. Upon incorporation into silicone, the efficacy of poly(ethylene oxide) (PEO) to repel proteins critically relies on its ability to restructure to the water (i.e. biological) interface. PEO is well known to be exceptionally protein-resistant when grafted onto a physically stable surface (e.g. silica). However, when incorporated into a silicone matrix representative of medical devices and coatings, we demonstrate in this study the limited capacity of conventional PEO-silanes to undergo water-driven surface restructuring. This poor surface restructuring resulted in low protein resistance. In order to enhance migration to the water interface, we modified PEO-silanes with a flexible, hydrophobic siloxane tether. These PEO-silane amphiphiles have the basic formula: α-(EtO)₃Si(CH₂)₂-oligoshy;dimethylshy;siloxane₁₃-block-[PEO_m-OCH₃] (m = 3, 8 and 16). Thus, these PEO-silane amphiphiles are multifunctional, with the PEO segment providing protein resistance and the siloxane tether aiding in the rapid restructuring of the PEO to the water interface. The protein resistance of PEO-silane amphiphiles grafted to a silica surface as well as incorporated into a silicone matrix was compared to that of conventional PEO-silanes (i.e. no siloxane tether, m = 3, 8, 16). Water contact angle analysis was utilized to quantify the relative differences in the capacity of the PEO-silanes to undergo surface restructuring. In addition to the enhanced restructuring of the PEO-silane amphiphiles, PEO segment length was also shown to impact migration and protein resistance. These results demonstrate the importance of PEO molecular structure to achieve effective surface modifying behavior of silicones as well as other polymeric materials.

A number of procedures are currently available to encapsulate and solubilize graphene oxide nanosheets for biological applications. Most of these procedures are based on the use of biopolymers. We previously reported the novel hyaluronic acid (HA)-graphene oxide (GO) conjugate system, with size in several tens nanometer scale, for use as nanocarriers combining cancer targeted delivery and switchable photoactivity of photosensitizers for photodynamic therapy. However, it is not fully understood how molecular weight (MW) and graft density of HAs grafted onto GO surfaces affect the colloidal or biochemical stability of GO nanosheets. Here we report a systematic study to examine the effects of surface coating chemistry on the hydrodynamic size, photostability, chemical stability, fluorescence and singlet oxygen quantum yield and biocompatibility of different MW HA-GO nanohybrids. In vivo studies on tumor-bearing animals elucidated the role of MW and graft density of HA coating on the fate of HA-GO nanohybrids after intravenous administration. These results would give insights in the design of long circulating intravenously injectable GO-based drug carriers for tumor active targeting and related imaging and therapy.

Polyvinylidene fluoride (PVDF) is one of the most important membrane materials based on its excellent physical and chemical properties in recent years, nevertheless, membrane fouling is also a technical obstacle that limit the application of PVDF in membrane based separation process due to the hydrophobic material interfaces. In this study, a special four-arm amphiphilic copolymer is synthesized and adsorbed on the surface of PVDF membrane to improve its antifouling properties. Amphiphilic copolymers is prepared by a simple manner of end group reaction with PDMS as hydrophobic backbone segment and PEG as hydrophilic arms. ATR and XPS are employed to prove amphiphilic copolymer is adsorbed on PVDF membrane surface by hydrophobic interaction and the adsorbed amount of amphiphilic copolymer depending on different molecular weight of PEG. In addition, According to the fouling resistance experiment for modified PVDF membrane, the amount of static BSA protein adsorption decrease to 8 ug/cm² and the secondary water flux recovery rate of dynamic fouling test increase to 90%. Due to the double antifouling effect of fouling release and restrain function of PDMS and PEG chain segment, four-arm type of amphiphilic copolymer improve the interfacial properties of PVDF membrane and enhance its antifouling ability.

Semifluorinated thiols are an attractive class of molecules due to their chemical stability, and the control of their surface properties in micro and macro scales is an important scientific and technological issue. In this study a series of semifluorinated thiols of the general formula C_nF_2n+1C_mH_2mSH (abbr. F_nH_mSH) were synthesized and characterized in Langmuir monolayers with surface pressure-area isotherms and measurements of the surface-specific polarization-modulated reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation (SFG) vibrational spectroscopy. A comparative analysis was performed for compounds having the same length of fluorinated segment (F₁₀) and variable length of the hydrogenated part (H₆, H₁₀, H₁₂), and having identical hydrogenated segment (H₁₂) connected to a fluorinated moiety of different lengths (F₆, F₈, F₁₀). For the sake of comparison, an alkanethiol (H₁₈SH) was also examined. SFG was applied to probe the hydrocarbon chain, middle-tail interface (CH₂-CF₂) and the terminal CF₃ group, while PM-IRRAS was used to look at CF₂ groups. The number of gauche defects increased with the increasing length of the molecule, either by elongation of the hydrogenated or perfluorinated part. SFG measurements recorded at three polarization combinations (ppp, ssp, sps) enabled us to estimate the tilt angle of the terminal CF₃ group in semifluorinated thiol molecules as ranging from 450 to 530. Experiments conducted upon increasing the surface pressure indicated that the fluorinated segment is the most affected part of the molecules, with this packing effect extending to the nearest methylene group. The extent of disorder in the hydrogenated segment may be controlled by varying the size of the fluorinated segment or by the insertion of other molecules in the defect region, allowing for the design of functionalized surfaces.

Acanthamoebae are found worldwide and are most commonly present in water reservoirs such as lakes and swimming pools, but even in soil and dust. Some acanthamoeba species are human pathogenic and can cause severe infections, such as acanthamoeba keratitis and granulomatous amoebic encephalitis, which are caused by Acanthamoeba castellanii (A. castellanii). Acanthamoeba keratitis is an infection of the human eye that is mainly caused by insufficient contact lens care and in particular increased for soft contact lenses with higher water content. If A. castellanii trophozoites adhere to a soft contact lens material, they are easily transferred to the eye. This results in a painful infection and permanent visual impairment or even blindness. In order to investigate the influence of substrate stiffness on the adhesion of A. castellanii, we produced Polydimethylsiloxane (PDMS) substrates of different elasticity and quantified the number and spreading area of adherent amoebae as a function of substrate stiffness. Our data show that A. castellanii adhesion is promoted on soft substrates as the spreading area of A. castellanii increases with decreasing Young&’s modulus of the substrate. In conclusion, our results provide for the first time indications for mechanosensory effects in a prevalent human pathogenic amoeba.

We have reported the preparation method for core-shell hybrid microspheres (CSMs) with inorganic nanoparticles (inorganic-NPs) shell layer.¹⁾ This method is characterized by the modified O/W suspension polymerization of polymerizable monomer droplet containing surface modified NPs. NPs are self-assembled to form 2D layer at the O/W interface of the monomer droplets in aqueous media and chemically and/or physically stabilized at the surface of polymer microspheres after polymerization. It is known that ceria-NPs are blended in chemical mechanical polishing (CMP) slurries for planarization of quartz and glass wafers, which are important materials for storage devices, optical devices and energy devices. In this presentation, we demonstrate the applicability of our method to prepare CSMs with ceria-NPs shell layer. It can be expected that the CSMs with a ceria-NPs shell have advantages as polishing materials: a) reduction of ceria-NPs in the polishing process, b) improvement of polishing ability and c) reduction (free) of dispersing agent. To use CSMs with ceria-NPs shell layer for polishing materials, bare ceria-NPs were used to produce core-shell microspheres. Typical preparation procedure of CSMs is as follows: 1) 10 g of ceria-NPs (17.3 wt% to total organic component) were dispersed in polystyrene-dissolved monomer solution (polystyrene: 4 g, styrene: 40 mL, divinylbenzene: 8 mL), and 1 wt% of 2,2'-azobis(2,4-dimethylvaleronitrile) was added as a radical initiator. 2) The mixture was suspended in a polyvinyl alcohol aqueous solution (5 wt%) and stirred at 30 #730;C for 1 h (pre-stirring) and 55 #730;C for 24 h (polymerization). 3) The obtained microspheres were washed with hot water and ethanol, and separated by mesh filters. The microspheres with diameter from 20 to 45 mu;m were collected and dried in vacuo (Yield = 30 g). According to the scanning electron microscopic observations, the spherical core-shell particles were fabricated and the surface of microspheres were fully covered by ceria-NPs. The ceria-NPs were mostly located at the surface of core polymer and formed multi-layered (2-4) shell. The amount of ceria-NPs was determined by thermal gravimetric analysis (TGA) to be 14.4 wt%, which is slightly less than the loaded amount of ceria-NPs. The quartz plate (R_a = ca. 200 nm) was polished using the precision lapping machine with the slurry containing CSMs. The total amount of ceria-NPs for polishing with the slurry containing CSMs could be reduced less than 30% of that with the slurry containing ceria-NPs at the initial stage (200 nm to 50 nm in R_a) of the polishing process. The detailed polishing rate and ability will be discussed in comparison with that in the ceria-NPs slurry.
1) H. Ihara, S. Kubota, A. Uchimura, Y. Sakai, T. Wakiya, M. M. Rahman, S. Nagaoka, M. Takafuji, Materials Chemistry and Physics, 114, 1, 2009.

Surface-enhanced Raman scattering (SERS) enables the analysis of trace amount of chemicals or biological molecules even at single molecule level, detection of explosives, or understanding the reaction dynamics. There are tremendous efforts for understanding precise mechanisms responsible for SERS phenomenon though existing explanations are still insufficient to describe whole underlie processes. However, there are two accepted independent proposals used to explain possible origin of enhancement; (i) electromagnetic enhancement and (ii) chemical enhancement. Since electromagnetic enhancement is proportional to the fourth power of electric field in SERS, it is assumed to take a major role in enhancement factor. In order to obtain high enhancement factors, inter-particle separation between plasmonic nanostructures is kept at minimum values. However, proposed separations are not practical and the obtained signals are not reproducible. As an alternative solution, periodic polymeric structures are fabricated to acquire large-area and reproducible SERS substrates. It is possible to fabricate reproducible and large-area SERS substrates using nanostructure arrays, but they compromise from the high enhancement factors.
In this work, we report fabrication of polymeric anemone-like nanopillars using melt-infiltration technique via AAO template. Formation of the nanostructures depends on the surface tension and capillary forces which were confirmed by the COMSOL simulations. We can control the cap shape and heights of the polymeric pillars by tuning the fabrication conditions. Anemone-like shapes of the pillars are reserved after metal coating with a hole diameter of 40 nm. To predict electric field enhancement and distribution in produced intricate nanostructures, FDTD simulations were performed. We determine that field enhancement significantly increased and reached EF=10⁸ when gap between nanostructures as small as 0-3 nm. We believe, electromagnetic enhancement portion of the SERS can exceed 10⁹.
The SERS performance of nanopillars was demonstrated using Rhodamine 6G (R6G). AAO template provides us hexagonally packed nanopillars at a certain periodicity (120 nm) in large-area. Raman spectra were collected with 50 mu;W excitation power at 532 nm. Time dependent spectra were obtained with an integration time of 10 s and averaged spectra were given for 10^-7, 10^-9, and 10^-12 M R6G on nanostructured film. Main Raman active modes of the dye were observed at 610, 777, 1365, 1578, and 1650 cm^-1 in agreement with previous experimental and theoretical investigations.^[i] It is worthy to note that, Anemone-like nanopillars present an EF value of 5.7 x 10¹¹ with relative standard deviations (RSDs) of 7.2-12.6%, which implies that the reproducible signals were collected from 10,000 individual spots.
[i] Dieringer, J. A.; Wustholz, K. L.; Masiello, D. J.; Camden, J.P.; Kleinman, S. L.; Schatz, G. C.; Duyne, R. P. V., JACS, 2009, 131, 849-854.

Multifunctional superhydrophobic surfaces have been prepared by partially embedding catalytic particles into arrays of polydimethylsiloxane (PDMS) posts. These surfaces exhibit hierarchical roughness similar to those found on plant leaves^{1, 2}. The addition of the particles creates roughness at shorter length scales (~50 µm) which increases the liquid pressure that can be sustained in the Cassie state. Moreover, the particles can catalyze the formation of singlet oxygen (¹O₂) at the solid-liquid-air interface. The ¹O₂ can be trapped and oxidize organic molecules in the droplet.
Aqueous droplets on a catalytic superhydrophobic surface provide a unique environment in which to study reactions at the solid-liquid-gas interface. When the droplet size is small (<100 µL), convection within these droplets is limited. As singlet oxygen has a short lifetime, the diffusion length is approximately 880 nm in D₂O solutions³. As a result, oxidation reactions will occur in the region of the solid-liquid-gas triple contact line and become limited by the diffusion of the trapping agent from the bulk to the interface. However, if convection can be induced, reaction rates are expected to increase due to mixing within the droplet.
Here we describe the effect of convection within droplets on a superhydrophobic surface that incorporates silicon-phthalocyanine (Si-Pc) particles. Singlet oxygen was generated in droplets containing trapping agents (9,10-anthracene dipropionate dianion, or singlet oxygen senser green (SOSG)) on the superhydrophobic surface by illuminating with a 670 nm laser. An environmentally controlled reaction chamber was used to control the evaporation of the small droplets, thus creating environments where there was either no convection, or rapid convection. The efficiency of ¹O₂ trapping was monitored by the decrease in the anthracene dipropionate dianion concentration by UV-vis spectroscopy as a function of trapping agent concentration, evaporation rate as well as gas composition in the chamber. Transport of ¹O₂ trapped by SOSG within the droplet was imaged using confocal microscopy as a function of convection conditions. The results indicate that convection within small droplets can accelerate mixing and thus the reaction rate between singlet oxygen and trapping agents. As singlet oxygen is used for photodynamic therapy (PDT) and water purification,⁴ these results may enhance the effectiveness of such technologically significant applications.
1. Aebisher, D., Bartusik, D., Liu, Y.; Zhao, Y., Barahman, M., Xu, Q., Lyons, A.M., Greer, A. J. Am. Chem. Soc. 2013, 135, 18990minus;18998.
2. Zhao, Y., Liu, Y., Xu, Q. Barahman, M., Bartusik, D., Aebisher, D., Greer, A., Lyons, A. J. Phys. Chem. A. 2014. doi/pdf/10.1021/jp503149x
3. Hatz, S., Poulsen, L., Ogilby, P.R. Photochemistry and Photobiology.2008, 84, 1284-1290
4. Greer, A. Acc. Chem. Res.2006, 39, 797-804

We have performed molecular dynamics (MD) simulations of poly(N-isopropylacrylamide) (PNIPAM), a thermo-sensitive polymer, by utilizing both an all-atom CHARMM force-field (CGENFF) and coarse-grained (CG) MARTINI force-field. The MD trajectories were analyzed in detail to compare the structural and dynamical properties of PNIPAM in aqueous systems for the two simulation approaches. The lower critical solution temperature (LCST) of PNIPAM is at ~305 K, below which PNIPAM is in a coil-state and above which it is in a globule-state. MD simulations of PNIPAM chain consisting of 60 monomer units (60-mer) was conducted at two temperatures, 275 K and 325 K, below and above the LCST of PNIPAM, respectively. The fully-atomistic simulations conducted using CGENFF and modified-TIP3P water model shows a clear coil-to-globule transition in PNIPAM above its LCST at 325 K while remaining in coil-state at 275 K at the end of 35 ns simulation run. For the CG MD simulations, the beads in the CG models of PNIPAM and water were defined based on MARTINI force-field. The PNIPAM CG model undergoes coil-to-globule transition at both studied temperatures of 275 K and 325 K. The underlying differences in the predictions of the coarse-grained and all-atom models originate from the inadequacy of CG models to accurately predict the solvation behavior of the water molecules adjacent to the polymer. Our simulation findings offer some new perspectives on redefining CG parameters to accurately predict the phase transition in this thermo-sensitive class of polymers.

Poly(N-isopropylacrylamide) (PNIPAM) is a temperature sensitive polymer known to undergo a coil-to-globule transition through its lower critical solution temperature (LCST), experimentally measured at ~305 K. Our simulations of systems consisting of single polymer chains in presence of explicit water molecules (~50,000 atoms) predicted the LCST of PNIPAM close to the observed experimental value. This study also suggested that presence of explicit water model and “appropriate” selection of partial charges on hydrophilic atoms is very important in studying the coil-to-globule transition in this class of thermo-sensitive polymers. In the present study, we utilized a range of macromolecular force fields, including PCFF, CHARMM, AMBER, and OPLS, in the presence of explicit water models, including PCFF water model, SPC, TIP3P, and TIP4P, to study the origin coil-to-globule transition in PNIPAM above its LCST. Simulations were carried out at 275 K and 325 K. Our results suggest that the dynamics of the coil-to-globule transition in PNIPAM is very sensitive to and strongly depends upon the choice of the force-fields and water models. While majority of the force-fields predict the thermodynamic end state of globule-like configuration above the LCST of PNIPAM, the dynamical evolution to the equilibrium configurations is significantly different. The vast differences in the dynamical predictions are explained on the basis of the relative energetics of various polymer-polymer, polymer-water and water-water interactions, the hydrogen-bonding characteristics of the solvated proximal water, and the water-induced rigidity of the polymer chains. Our study offers useful insights into tuning of force-field parameters for accurate predictions of conformational dynamics in thermo-sensitive polymers.

An expanding area of green technology is in the wastewater treatment for heavy metal ions. Adsorption of the fluid cations to solids has proven to be successful and recent research has investigated the improvement of this method through novel materials such as grafting dendrimers onto a solid support. We develop a reduced representation of the system via metal cations in an implicit solvent near a surface of grafted dendrimers. The system is modeled after polyamidoamine (PAMAM) dendrimers with carboxylic acid functional groups that promote the adsorption of Pb(II) ions. Martini coarse-grained molecular dynamics simulations using the LAMMPS package are utilized to predict the nanoscale behavior of the system. The goal is to observe the adsorption of the Pb(II) ions to the branched PAMAM dendrimers through the measurement of ion coordination and dendrimer dynamics. Ion coordination analysis is a unique characterization that can be useful in designing chelators. Our project entails investigating the effects of dendrimer generation and surface coverage. These simulations can identify the role of molecular scale properties on the adsorption process, thereby allowing predictions for bulk analysis including the continuum phase. These investigations have the ability to be applied to other chemical processes that make use of polymers grafted onto a support.

Irreversible photodegradation is a problem in many applications of dye doped polymer that require exposure to light. The observation of reversible photodegradation has been continuously reported over the last decade from a wide variety of organic dyes and silicon nano particals doped in polymers using linear and nonlinear optical characterization techniques. We have studied the recovery process of Disperse Orange 11 doped in poly(methyl methacrylate) (DO11/PMMA) after being irradiated by a cw laser using linear absorption spectroscopy. In the earlier work, single-exponential-like recovery of DO11/PMMA was observed and successfully described by the domain model [Ramini S. K. et al., Polym. Chem., 2013, 4, 4948-4954] from experiments using amplified spontaneous emission (ASE) as a probe of pulsed-laser-induced damage and transmittance imaging microscopy (TIM) as a function of time after being irradiated by a cw laser. Domains have not yet been observed experimentally, so the role of the host polymer is not clear. In the present work, a nonexponential recovery process is revealed with linear absorption spectroscopy probing owing to it better signal-to-noise ratio compared with ASE and TIM. The recovery data can be fit to a stretched exponential function, exp[-(t/tau;)^eta;], which implies a distribution of recovery rates, most likely originating in the host polymer. The parameter eta;, which quantifies the spread of the distribution of recovery rates, shows an anomalous temperature dependence that can be attributed to and regarded as experimental evidence of domain formation. A model incorporating both stretched exponential recovery and domain formation will be developed. Understanding the underlying mechanism that governs the reversible photodegradation phenomena can be used to improve device lifetime and enables more applications of soft materials that interact with light.

Levan is a naturally occurring biopolymer with β-D-fructofuranose units with β(2-6) linkages between fructose rings and is produced by various bacteria. Recently, a new bacterial strain was discovered in Turkey. This bacterial strain, Halomonas sp., is an extremophile - an organism that lives in extreme conditions, and is capable of producing levan at high molecular weights. Preliminary experimental studies showed that levan had excellent adhesive properties, and therefore, it could be used in various applications especially in the biomedical field. Understanding of the adhesive properties at the molecular scale could provide further opportunities to improve and tailor the properties of levan and even target applications in other fields. In the current study, Molecular Dynamics (MD) simulations were used to investigate the static, dynamic, and adhesive properties of levan chains on graphene layers with various surface chemistries. Results indicate that the adhesion of levan to graphene is quite strong and among other factors is due to the strong π-π interactions.

Mechanical impact to internal organs via collisions, ballistic loads, and blast waves can result in injury to soft tissues. To understand and prevent this damage, engineered polymers can be optimized as protective materials that minimize organ injury by dissipating mechanical energy, or as synthetic simulants of soft tissue&’s impact response under extreme impact conditions. Here, we synthesized and characterized quantitatively the mechanical response of novel multilayered gels using instrumented nanoindentation customized to simulate ballistic impact loads. These multilayered, hybrid gels consisted of a linear-elastic elastomer layer bonded to a viscoelastic polymer gel layer. Computational models predicted that varying the thickness and stiffness of the elastic layer facilitates the independent tuning of the gel&’s impact penetration depth x_max and energy dissipation capacity K. An increase in the elastomer layer thickness led to a decrease in both x_max and K, whereas an increase in elastomer stiffness led to a significant decrease in x_max but had minimal effects on K. The ability to decouple x_max and K addresses a major limitation of previous designs of polymer-based tissue simulants. As a result, this new multilayer hybrid material can be tuned to reflect the energy dissipation response of soft tissues comprising biological organs ranging from brain to cardiac muscle.

Electrospinning is a cost-effective fabrication technique that creates long, continuous nanofibres through an electrically charged jet of polymer solution. It is primarily based on the uniaxial stretching of a viscoelastic solution using a high strength electric field allowing control over several process parameters such as flow rates, distance between the needle tip and collector and applied voltage. Here, the semi-crystalline polymer, poly(ethylene oxide) PEO, was employed as the template for the controlled linear organization of metallic gold nanoparticles (AuNPs) using the electrospinning technique. Morphologies of the PEO/AuNP nanocomposite fibres and distribution of gold nanoparticles were characterized by Transmission Electron Microscopy (TEM). Such nanocomposite fibres are of interest as self-assembled templates for bottom-up fabrication technologies.
We present devices fabricated with an active layer of these electrospun composite fibres. The device has a simple structure consisting of the electrospun polymer film sandwiched between two electrodes. An external bias is used to program the ON and OFF states of the device that are separated by a six orders of magnitude difference in conductivity. Conductive-Atomic Force Microscopy (C-AFM) was employed to perform scans of morphology on PEO/AuNP films and further on to carry out electrical characterization observing electrical bistability. The performance metrics of the devices presented here have shown promise as nanoscale memory devices.
The present findings also demonstrate that the electrospinning process provides a straightforward technique to fabricate one-dimensional arrays of nanoparticles for future nanodevices. Our results suggest that these composite materials have features and properties befitting a range of applications such as nanoelectronics, functional hybrid materials and high performance digital memory devices.

Abstract
Polymers such as Dupont&’s Surlyn^® can puncture heal following penetration by a 9 mm bullet traveling at speeds around 300 m/sec (1,100 ft/sec), or by a 2 mm projectile traveling at hypervelocity in the micrometeoroid velocity range of 5 km/sec (16,000 ft/sec). Because Surlyn^® has been shown to puncture heal over a temperature range of -30^oC to +70^oC, it may be useful in enhancing impact damage tolerance of pressurized vessels. Such polymers are difficult to process, however; and their low thermal stability, poor chemical resistance, and limited mechanical properties reduce their applicability in aerospace structures. To address these shortcomings while maintaining the puncture healing behavior, several formulations were developed by integrating materials known to puncture heal with mechanically robust, but non-healing, engineering polymers. These melt blended formulations were impacted with a 5.56mm projectile at a nominal velocity of 945 m/sec (3,100 ft/sec), at room temperature (25^oC), 50^oC and 100^oC, depending upon the specific blend being investigated. Self-healing tendencies and residual strengths were assessed after the ballistic tests. Experimental results confirm the formulation of a range of new puncture healing blends that can mitigate damage in the ballistic velocity regime. Results from this study will be used to design reinforced and non-reinforced impact damage resistant structures for space applications.

Electronics keep decreasing in size and weight, while simultaneously increase in flexibility.¹ Electrically conductive polymer nanocomposites are highly prized for such applications,² however, the particle agglomeration tendency within the polymer matrix inhibits them from broad employment because particle agglomerates result in inhomogeneous composite properties.³ Specifically for electrical conductivity, a higher filler fraction is necessary to overcome the percolation threshold.⁴ Metallic nanoparticles, as alternative to carbon-based nano-materials, are beneficial to achieve high conductivities.⁵ Here flame-made silver nanoparticle-PMMA composite films are synthesized based upon flame-aerosol deposition and polymer spin coating.⁶ It does not require any additional sintering process or nanoparticle surface functionalization steps. By carefully tuning the deposition parameters, Ag nanoparticles with high degree of sinter-neck formation can be achieved within seconds. Sinter-necks are beneficial for good electrical properties. Finally after embedding the nanoparticle film within PMMA, sub-micrometer thick nanocomposite films are made with bulk-metal equivalent electrical conductivity. The flexibility of such films was demonstrated after releasing from the substrate by repetitively bending. Throughout the bending the electrical resistance remained unchanged.
1. Dagdeviren C, Hwang S-W, Su Y, et al. Transient, biocompatible electronics and energy harvesters based on ZnO. Small. 9(20), 3398-3404. (2013)
2. Marelli M, Divitini G, Collini C, et al. Flexible and biocompatible microelectrode arrays fabricated by supersonic cluster beam deposition on SU-8. J. Micromech. Microeng. 21(4), (2011)
3. Camenzind A, Schweizer T, Sztucki M, Pratsinis SE. Structure & strength of silica-PDMS nanocomposites. Polymer. 51(8), 1796-1804. (2010)
4. Norkhairunnisa M, Azizan A, Mariatti M, Ismail H, Sim LC. Thermal stability and electrical behavior of polydimethylsiloxane nanocomposites with carbon nanotubes and carbon black fillers. J. Compos. Mater. 46(8), 903-910. (2012)
5. Mutiso RM, Winey KI. 7.17 - Electrical Conductivity of Polymer Nanocomposites. In: Editors-in-Chief: Krzysztof M, Martin M, eds. Polymer Science: A Comprehensive Reference. Amsterdam: Elsevier; 2012:327-344.
6. Sotiriou GA, Blattmann CO, Pratsinis SE. Flexible, multifunctional, magnetically actuated nanocomposite films. Adv. Funct. Mater. 23(1), 34-41. (2013)

While polymers are ubiquitous materials in modern society, low thermal conductivity values associated with bulk polymers (typically 0.1 - 0.4 W m^-1K^-1) have hindered widespread development of these materials in thermal management applications. One promising solution, molecular chain alignment by mechanical drawing, has been demonstrated to greatly improve polymer thermal properties. For example, previous reports on drawn ultra-high molecular weight polyethylene (UHMWPE) nanofibers have demonstrated thermal conductivity values greater than 100 W m^-1K^-1 (higher than that of most metals). High thermal conductivity in drawn fibers is attributed to polymer chain orientation along preferred direction by ultra-drawing, which improves the fiber quality toward an ‘ideal&’ single crystalline fiber. Another direction commonly used to improve thermal conductivity in polymers is through the addition of filler materials - such as metals and ceramics, to create polymer-based composites. While effective, typically high filler loadings are required to achieve substantial increases in composite thermal conductivity values. Such high filler loadings have several unintended consequences, for instance, making polymer processing difficult with conventional equipment.
Therefore, we present a UHMWPE/graphite film with low filler loadings (<15 wt% graphite) that is achieved via mechanical drawing-induced molecular chain alignment. Using a combination of UHMWPE and highly thermally conductive 2D carbon fillers (exfoliated graphite or few-layer graphene), our fabrication method consists of custom extrusion, drying, and drawing platforms. This stretching results in macroscopic UHMWPE deformation and orientation of 2D filler network along the film in-plane direction to achieve higher alignment structure. The draw-induced orientation of the polymer chain matrix combined with high-aspect-ratio structure of the filler material makes for an ideal composite structure, as continuous percolation network and aligned filler particulate interfaces reduces phonon scattering sites. Structural characterization (XRD, SEM, and FTIR) of these films suggests highly aligned polymer chains and crystallinty. We believe that further development of 2D graphite-based polymer composites will extend the promising potential of these versatile materials in a range of thermal management applications.
This work was supported by the U.S. Department of Energy, Advanced Manufacturing Office under Award #DE-EE0005756.

Hybrid organic/inorganic materials that are amorphous, isotropic, flexible have been investigated extensively for application as electrolytes in lithium ion batteries. Desired properties of solid electrolytes are high ionic conductivity and transference number, high shear modulus to prevent dendrite growth, chemical compatibility with the electrodes, and processability into thin films. We use sol-gel synthesis to produce silica-based hybrid organic-inorganic materials that are rubbery, transparent and thermally stable for this application. The organic component is polyethylene glycol, chosen for its ability to dissociate various lithium salts. Ion conduction in the polymer occurs only in the amorphous phase by the segmental reorientations of the neighboring polymer chains. Silica networks provide structural rigidity and chemically stability. Here we investigate the effects of the interactions between the organic and inorganic components on materials performance. To this end we either blend the two components, or covalently bond polyethylene glycol with one or both ends of the polymer chains to the silica network, In addition we vary the polymer chain length. Using concurrent Raman and Brillouin light scattering, IR and dielectric impedance spectroscopy, and differential scanning calorimetry we determine the thermal, chemical characteristics, the ion mobility, and the complex mechanical moduli of these network structures, and elucidate the mechanistic origins of the observed behaviors in view of identifying the design criteria for hybrid materials with desired performance characteristics. Our results reveal that optimal ionic and mechanical properties with longer polymer chains, grafted with one end to the silica backbone, and that further enhancements may be possible by carefully controlling the co-polymerization chemistry.

The discovery of piezoelectricity in bone by Fukada brought to light the idea of using piezoelectrics to enhance bone growth. Some piezoelectrics like Barium Titanate and Polyvinylidene Fluoride (PVDF) have been tested. Among piezoelectric polymers, poly (L-lactic) acid (PLLA), a synthetic semi-crystalline polyester combining adjustable biodegradability and physical properties, stands out and therefore can be used as bone scaffold. In addition, some PLLA products have been approved for implantation in human body by the Food and Drug Administration (FDA). In our previous work we proved the direct evidence of protein adsorption process associated with polar activity of a piezoelectric by showing at the local scale that the process of protein adsorption is highly favoured in the poled areas of PLLA. [Applied Physics Letters 2011; 98:133705] We described the decay kinetics of the electrically-induced polarization of poly (L-lactic) acid (PLLA) via piezoresponse force microscopy (PFM). When poled at room temperature, both PLLA crystalline structures (α and α&’) present a rapid loss of the polarization. But when poled above glass transition temperature PLLA films present a durable polarization, up to 10 days. [Applied Physiscs Letters 2012;101:023701] We also pioneered the demonstration of the positive effect of polarization of PLLA for neuritogenic applications. Our most recent results show that the topography, in itself, of PLLA films and random nanofibers decrease cellular proliferation and, this can be partially reversed by poled platforms. There is a synergistic effect between topography, alignment and polarization of PLLA scaffolds and neuritogenesis [submitted]. However in addition to biological cell growth assays, cell metabolomics is a powerful tool since it can provide detailed information on the specific metabolic pathways responding and adapting to each of the selected material formulations.
In this work we present the first metabolomic study of the cellular metabolic adaptations to contact with piezoelectric PLLA. For that in vitro cell studies of osteoblastic cells were performed using different PLLA thick films differing in crystallinity and polarization. A complete electrical characterization of the different thick PLLA films was performed. Thermal Stimulated Depolarization Currents (TSDC) monitored charges retention of the different films after being polarized. Cell metabolomics was performed by Nuclear Magnetic Resonance (NMR) spectroscopy of whole cells (using high resolution magic angle spinning-HRMAS NMR). Relevant metabolic changes between control and material-exposed cells were identified by unsupervised and supervised multivariate analysis methods (namely, principal component analysis-PCAand partial least squares discriminant analysis-PLS-DA). Metabolite sets, or signatures, of cell response were defined in relation to material type and properties.

Polyaniline (PANI) has attracted more attention for its wide potential applications due to the good properties,e.g. conductivity, and good resistance against acid or alkaline. It has three redox states based on the ratio of the amine group and imine group, e.g. fully reduced leucoemeraldine base (LB), half oxidized emeraldine base (EB) form and fully oxidized pernigraniline base (PB) form. The PANI can act as an electron donor by the oxidation of the LB and EB forms to PB form, which facilitates the reduction of heavy metals with higher valence states. However, there is a recycling and regeneration challenge for PANI application due to its nano size. Recently, the polymer coating is considered as an effective strategy for solving this problem. The magnetic material (Fe₃O₄) and the sustainable materials, e.g. carbon fabric and cellulose, have been investigated as the substrates for the PANI coating. The PANI coated composites are supposed to be good adsorbents for Cr(VI) removal.
This talk will present the preparation of the PANI coated nano Fe₃O₄, carbon fabric, and cellulose, and their performances on Cr(VI) removal from aqueous solutions. After a brief introduction of the emergency situation of the Cr(VI) pollution and the current techniques designed for the Cr(VI) removal, the potential environmental remediation of these composites on Cr(VI) pollution will be reviewed. The composites have shown great potential for Cr(VI) removal with the enhanced removal rate and removal capacity, and easy separation property of the composites after adsorption. Finally, the proposed mechanisms involved in Cr(VI) removal by the PANI coated composites will be discussed as well.

Hybrid hydrogels based on natural polymers are currently receiving a great deal of interest, and are notable for controlled delivery of bioactive molecules. A hybrid hydrogel composed of chitosan/alginate and metallic nanoparticles was prepared associated with a pharmacological active component of an ancient Chinese herb Coptis chinensis and then compared its behavior with the system without the particles. These nano platform were synthetized in aqueous solution and the metallic particles were characterized using DLS (7-20 nm) and hydrogel SEM presented smooth surface morphology. The chitosan/alginate gel was prepared in different ratios and associated with the noble metal nanoparticles which display unique optical properties that differentiate them their bulk counterparts. While the spectra of molecular compound can be understood only in terms of quantum mechanics, the extinction spectra of metal nanoparticles can be treated in terms of classical electromagnetism resulting in localized surface plasmon resonance (LSPR)¹ in the surface of particles both aspects were investigated. In this work we presented the physical properties of this hybrid nano platform, including swelling, hydration, time-course release of a pharmacological fluorescent compound and surface characteristics, UV-Vis, fluorescence spectroscopy, EDS spectrometry and DSC. Moreover, the photochemical properties of the hybrid hydrogel are also being studied in biological model and will be presented. Acknowledgments: CNPq; CAPES; FAPDF; FINATEC; DPP-UnB.

The maltose-pendant polymer (pM) was hybridized with mica by a solution intercalation method in aqueous solution, and the oxygen gas barrier property of the cast film from the hybrid was investigated. Cationic comonomer, N,N-dimethylamino propylacrylamide, methyl chloride quartenary, was introduced to the maltose-pendant copolymer (pMCn, n = % of cationic monomer) by copolymerization for accelerating to exfoliate mica nanosheet. The XRD analyses of polymer/mica hybrids indicate the diffraction peak of original mica at 2theta; = 6.73° (d spacing = 13.1 Å) was broadened by hybridization with pM and distinctly disappeared by hybridization with pMCn. The hybrids of maltose-pendant polymer and mica (pM/mica, pMCn/mica) were applied to a coating material for oxygen gas barrier. The transparent hybrid dispersion was casted on the corona-treated nylon film using wire bar and dried at 100 °C for 30 s, and the film was heat-treated at 210 °C for 15 s. The oxygen transmission rates (O2TR) of the films were evaluated by oxygen permeation analyzer at three relative humidity conditions, 0 %RH, 50 %RH and 90 %RH. The O2TR property of pM-coated nylon film showed better barrier property more than non-coated nylon film under dry condition (0 %RH). However the O2TR was rapidly deteriorated with increasing humidity (90 %RH). The pM/mica hybrid-coated nylon film (pM/mica-X, X = wt% of mica) showed further improvement of O2TR property; O2TR value (cm³middot;m^-2middot;d^-1middot;atm^-1) at 0 %RH was decreased with increasing the amount of mica (pM = 0.93, pM/mica-10 = 0.56, pM/mica-20 = 0.19, pM/mica-30 = 0.13). Under high humid conditions, O2TR values were increased in all cases but distinctly improved by using pM/mica hybrids. For instance the O2TR value of pM-coated film and pM/mica-30-coated film were over 70 and 7.63 cm³middot;m^-2middot;d^-1middot;atm^-1 at 90 %RH, respectively. Similar improvements were observed using pMCn/mica-X hybrid as coating materials. The effects of cationic moiety of the coplymer will be discussed.

Poly (methyl methacrylate) (PMMA) is the acrylic resin most used to develop denture base materials. The thermopolymerization of PMMA could be made either water bath (WB) and or microwave (MW), which influence in the final properties of denture bases. Flexural strength and porosity must be optimized to avoid fracture and adhesion of microorganisms such as Candida Albicans in PMMA dentures. In this work, the physicochemical properties of PMMA composites were evaluated as a function of ultrasonic action. For this, samples (n=36) of about 65x10x2.5mm were prepared with Orthocryl® and EZ-Cryl® acrylic resins in a 3:1 ratio with methyl methacrylate monomer (MMA). Opticryl and EZ-Cryl samples were cured by water bath technique (WB) at 70°C, 90 min (n=12) and by microwave (MW) method during 5 min at 1100W (n=12), respectively. Both resins were also termopolymerized with ultrasonic action (WBUA, MWUA) at 70°C, 2h (n=12). A reference group without ultrasonic action (w/o WBUA, w/o MWUA) was also prepared at the same conditions (70°C, 2h) to complete three groups for each acrylic resin. Porosity, flexural modulus (E_H), and transverse strength (σ_Break) of the composites were evaluated and also they were characterized by SEM, FT-IR and Raman. SEM results showed that the bases thermopolymerized with ultrasound are more homogeneous and slightly less porous than those resins cured by WB and MW. FT-IR results showed the characteristic bands of PMMA, methyl and ester carbonyl groups (CH₃, C=O), at 2950 and 1720cm^-1, respectively, independently of the cured process. The E_H and σ_Break values of PMMA composites were slightly improved with the thermopolymerization under ultrasound (2.45±0.12GPa; 83.87±6.26 MPa) compared with those cured without ultrasonic action (1.15±0.33GPa; 24.27±16.84MPa). Ultrasound does not alter the molecular structure of the PMMA composite and it increases slightly the mechanical properties of the denture bases in comparison to conventional methods. So that ultrasonic action is easy and feasible to improve the physical properties of PMMA for dentures.
ACKNOWLEDGMENTS: SEP-CONACyT CB176450, PAPIIT-TA200414, PAPIME-PE202214 DGAPA/UNAM Projects. The authors thank to Dra. Genoveva Hernández Padroacute;n and Mtro. Gerardo Fonseca and Dra. Marina Vega for their technical support.

There has been considerable interest in the use of hydroxyapatite (HAp) which is a principal inorganic constituent of natural bone for bone substituents and scaffold materials for bone tissue engineering. Recently, composites of biodegradable polymers and HAp have been applied for artificially-grafting materials. These composites are expected to improve poor mechanical properties of HAp and to encourage bone re-mineralization with biodegradation of polymers. In this study, we try to improve the mechanical strength of HAp by fabricating composite materials consisted of HAp and oligo(L-lactic acid) (LLA oligomer) that is the most promising biodegradable oligomer for artificial bone materials. Porous HAp (p-HAp) was synthesized by sintering fibrous HAp (f-HAp). Scanning electron microscopy (SEM) measurements showed that p-HAp has interconnected micro pores. The pore size of obtained p-HAp was about 1 µm, and the porosity was about 40 %. The bending strengths and elastic modulus of p-HAp were about 20 MPa and 10 GPa, respectively. LLA oligomer was synthesized from L-lactide, 1-dodecanol as an initiator, and (N,N-dimethylamino)pyridine (DMAP) and DMAP#12539;HOSO₂CF₃ as catalysts. The oligomerization reactions of L-lactide were carried out for 2 days at room temperature. The obtained LLA oligomers were characterized by using GPC, ¹HNMR, MALDI TOF-MS, and DSC measurements. The weight-average molecular weights (M_w) of obtained LLA oligomers were about 4,000 g mol^-1 with the monomer conversion rate of about 100%. MALDI-TOFMS spectra of the LLA oligomer showed 72 interval peaks which were assigned to the repeating unit of LLA oligomers. The melting temperatures of LLA oligomers measured by DSC measurement was about 140 0C. The LLA oligomer was introduced into pores of p-HAp by repeating vacuum degassing-freeze-thaw operations for 3 times. We found by SEM measurements that the LLA oligomer having a molecular weight up to 4,000 g mol^-1 was introduced into p-HAp, and that the filling rate of the LLA oligomer in the composites was 20 wt.%, which was calculated from the residual weight at 500 0C for TG-DTA measurements. After the LLA oligomer/HAp composites were heated for 5 days at 150 0C, the pores of heated composites were still filled with the LLA oligomer. The M_w and crystallinity of the LLA oligomers introduced in p-HAp were about 5,000 g mol^-1 and 30% determined by DSC measurement. As the reaction time increased, the molecular weights of the LLA oligomers in the composite increased. The mechanical strength of p-HAp was increased by the hybridization with LLA oligomers, and the bending strengths and elastic modulus of the LLA oligomer/HAp composites were 28-35 MPa and 9-14 GPa. Acknowledgements This work was financially supported by FUSION MATERIALS ; Funded by Grant-in Aid for Scientific Research on Innovative Areas(2010-2014), The Ministry of Education, Culture, Sports, Science and Technology(MEXT) Area no. 2206.

Hydroxyapatite (HAp) which is main component of natural bone has the osteoinduction. Composites of HAp and Poly (L-lactic acid) (PLLA) have been expected for applying artificially-grafting materials. It is required that PLLA in the composites decomposes and interchange osteoblast in vivo. Because of the weak interaction between HAp and PLLA, PLLA effluents instantly in vivo and mechanical strength degrades accordingly. In this study, to improve the interfacial adhesive properties of HAp and PLLA in PLLA/HAp composites, initiators which have several hydroxyl groups were used for synthesis of PLLA. PLLA was synthesized for 2 to 10 days by ring-opening polymerization of L-lactide (LLA) using OH-functionalized initiators, myo-inositol, 1,4-cyclohexanediol, 1,2,3-cyclohexanetriol, or meso-erythritol. MALDI-TOF-MS revealed that PLLA was obtained by these initiators and PLLA was bonded with initiators. ¹H NMR and GPC measurements revealed that the conversion ratios of LLA and moleculer weights of PLLA increased as the reaction time increased. Conversions and molecular weights of PLLA obtained by using myo-inositol and 1,4-cyclohexanediol were higher than those of other initiators. PLLA synthesized using myo-inositol was the highest molecular weight (M_w = 14,700). Considering these results, PLLA/HAp composites were fabricated by in-situ polymerization of LLA in porous HAp using myo-inositol. The composites were fabricated by changing the LLA/myo-inositol molar ratios, LLA/myo-inositol = 1.8, 3.1, 6.3. The conversion ratios of LLA in the composites fabricated by either molar ratio were over 98%. TG-DTA revealed that introduction ratios of PLLA into the composites were about 17 wt.%. When the LLA/myo-inositol = 1.8, 3.1, and 6.3, M_w of PLLA were 9,700, 9,900, and 10,800 g mol^-1, respectively. M_w of PLLA in the composites were higher as the molar ratio increased. Mechanical properties of the composites were examined by these bending test. Bending strength and elastic modulus increased as the molar ratio increased, and reached 50 MPa and 12 GPa, respectively. The biodegradability of the composites was evaluated by immersing them in phosphate buffer solution. Acknowledgements This work was financially supported by FUSION MATERIALS ; Funded by Grant-in Aid for Scientific Research on Innovative Areas(2010-2014), The Ministry of Education, Culture, Sports, Science and Technology(MEXT) Area no. 2206.

A novel dielectric nanocomposite comprising high permittivity polymer; cyanoethylated O-(2,3 dihydroxypropyl)-cellulose (CRS) and TiO₂ nanoparticles (50 nm) was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO₂. The intermolecular interactions and morphology within the polymer nanocomposites were analysed using ATR-FTIR, TGA, SEM and AFM. Band gap information of the composite was obtained from UV-Vis spectroscopy. TIO₂/CRS nanofilms on SiO₂/Si wafers were used to form metal-insulator-metal (MIM) type capacitors. Capacitance and loss factor in the frequency range of 1 kHz to 1 MHz were measured. At 1 kHz TiO₂/CRS nanocomposites exhibited ultra high dielectric constants of 140, 210 and 295 for nanocomposites with 10%, 20% and 30% weight of TiO₂ respectively, significantly higher than reported values of pure CRS (30) and TiO₂(41) films. Furthermore, all three TiO₂/CRS nanocomposites show a loss factor < 1 and low leakage current densities. A new class of ultra high dielectric constant hybrids using nanosized inorganic dielectrics dispersed in a high permittivity polymer suitable for energy storage applications is reported.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer is a biodegradable polyester produced by a bacteria and the most widely used member in PHA (polyhydroxyalkanoates) [1]. The presence of nanoparticles in the polymer can control the biodegradation rate and affect their thermal and mechanical properties. Additionally, PHBV/TiO₂ nanocomposites are good candidates for biological application, such as scaffold for tissue engineering, because this polyester is biodegradable, biocompatible, and its mechanical properties are similar to conventional thermoplastics [1]. The TiO₂ nanoparticles were synthesized by the hydrothermal treatment of the peroxo complex of a titanium (PCT) gel solution. PCT gel was prepared from titanium (IV) isopropoxide (Ti(OCH(CH₃)₂)₄ and hydrogen peroxide [2]. Nanocomposites were prepared with 1, 2.5 and 5% of TiO₂ (m/m). Nanoparticles and nanocomposites were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). XRD and TEM analysis of TiO₂ nanoparticles showed a nanorods morphology with predominance of rutile phase and the average crystallite size of 12 nm calculated by the Scherrer equation and confirmed by TEM. All nanocomposites presented similar FTIR spectra with pure PHBV. The thermal properties, such as melting and crystallization behavior of the materials, were characterized by DSC. The glass transition temperature (Tg) of the pure PHBV could be observed around 0°C, but the incorporation of TiO₂ resulted a decrease in Tg because TiO₂ advantages the mobility of the polymeric chains, that is, the material passes from the glass state and get mobility at lower temperatures. The crystallinity is more evident with the higher concentration of nanoparticles, because TiO₂ act as a nucleating agent. There was not a significant variation in T_m and T_c (crystallization temperature) of the nanocomposites compared with the pure polymer. PHBV and nanocomposites samples were also submitted to a degradation tests. In the photodegradation test, the films were exposed to UV radiation in a chamber containing a UV fluorescent lamp. The total exposure time was 300 hours. There was not a significant change in mass, but it was observed that the films became very brittle and fragile. The biodegradation test was in aqueous medium consisting of a mineral solution with soil microbes, as described by Hong et al. [3]. The biodegradability was determined by loss mass over the time. The results showed a higher activity of polymer degradation. There was a tendency in a mass reduction; the decrease in PHBV mass was 51.7% after 8 days of incubation and nanocomposite with 1% of TiO₂ had a decrease of 54.6% in mass after the same time of incubation.
References: [1] W. Yu, et al. Polymer, 51, 2403, 2010.
[2] C. Ribeiro, et al. J. Phys. Chem. C 111, 5871, 2007.
[3] L. Hong, et al. J. Apll. Polym. Sci.; 87, 205, 2003.

Inorganic nanoparticles have a widespread use in polymer composites as functional component, improving its properties or scribing new ones. However, the development of inorganic nanoparticles with high chemical compatibility with polymer matrices, and high reproducibility is still a barrier to fully reach the potential of these composites. In this way, this work focuses on the development of polymer composites with high compatibility between the inorganic nanoparticles and polymer matrix. For this purpose Fe₃O₄ nanoparticles were synthesized and functionalized with hydroxyl groups in one-step reaction using iron (III) acetylacetonate as precursor and poly(1,4-butanediol) as solvent and functionalizing molecule [1]. Comercial isocyanate terminated polyester urethane (PU) and bisphenol A diglycidyl (BADGE) were used as polymeric matrices. After synthesis the nanoparticles were characterized by transmission electron microscopy and it was possible to observe 8 to 10 nm spherical nanoparticles with single crystalline domains. Thermogravimetric analysis (TGA) has shown that the surface organic functionalization was responsible by 30% of the system mass. After removal of excess non-reacted solvent, nanoparticles were dispersed in tetrahydrofuran to facilitate incorporation into the polymer matrix. Samples with concentrations ranging from 1 to 50 % for PU and from 1 to 15% for BADGE in weight of Fe3O4 nanoparticles (disregarding the organic mass and certified by TGA) were produced by mixing the colloidal dispersion of nanoparticles and the polymers. Small-angle x-ray scattering (SAXS) measurements shown good nanoparticles dispersion in bulk samples and scanning electron microscopy realized on thin film samples deposited on aluminum foil has corroborated the result. Also, no agglomerates were observed even in high magnification images and high concentrated samples. SQUID (superconducting quantum interference device) measurements have shown a superparamagnetic behavior of the composites, even in high concentration. These results also indicate absence of agglomerates and high dispersivity of nanoparticles, mainly because the chemical compatibility of the organic molecules on the nanoparticles surface and the polymer molecules of matrices.
1. Goncalves, R.H., C.A. Cardoso,E.R. Leite, Synthesis of colloidal magnetite nanocrystals using high
molecular weight solvent. Journal of Materials Chemistry, 20(6): p. 1167-1172, 2010.

Electrospinning is employed to prepare conductive polypyrrole (PPy) nanofibers with uniform morphology and good mechanical strength. Electrodeposition is a useful method for producing a thin, crystalline, homogeneous, and adherent film, and this method is rapid, reproducible, efficient, and low cost for recovered conductive materials with nanohydroxyapatite (nHAp) crystals. In the present work, we have developed a way to electrodeposited nHAp crystals on electrospun poly(butylene adipate-co-terephthalate)/Polypirrol (PBAT/PPy) blends ultrafine fibers. Soluble PPy (1%, 3% e 5%) was synthesized dopant and then applied to electrospinning with PBAT as carrier. The electrodeposition process was carried out using a Potentiostat/Galvanostat (AUTOLAB®, PGSTAT 128N, NETHERLANDS) working in potentiostat mode. PBAT/PPy attached to an electrode holder (Teflon) and used as the anode for the nHAp electrodeposition. Ag/AgCl electrode used as reference (3M); and platinum as counter electrode (99.99% pure). We used scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and differential scanning calorimetry (DSC) analyses to characterize the morphological and structural of nHAp crystals. We electrodeposited stoichiometric nHAp crystals homogeneously on PBAT/PPy blends. This new composite nanobiomaterial is very attractive to bone regenerative medicine.

The search for materials with biocompatibility properties with the human body constitutes a major challenge for researchers in the field of biomaterials. Among them, multifunctional polymeric materials have attracted attention due to their versatility properties and molding processing, since they respond to small external stimuli (temperature, pH, ionic force, and magnetic fields), changing their form and volume. A potential candidate for this application is the poly (N- vinylcaprolactam) (PNVCL), which is a biocompatible and temperature sensitive polymer. Allied to the polymers, compatible ceramics, as hydroxyapatite nanoparticles (HA), can result in innovative hybrid materials and used as a biomaterial alternative, since they improve the interaction with the human tissue and the properties found in pure polymers. Thus, in this study, nanocomposites of PNVCL with hydroxyapatite (HA) nanoparticles were prepared seeking to obtain biocompatible materials for use as scaffolds in medical/dental applications. The best conditions for the synthesis of nanocomposites, as well as the synergism of the incorporation of nanoparticles were studied. The HA nanoparticles were synthesized by hydrothermal processing and presented crystalline hydroxyapatite colloidal nanoparticles with hexagonal phase, as seen by X-ray diffraction (XRD) and Raman spectroscopy. In addition, transmission electron microscopy images showed HA nanoparticles with well-defined nanorod shapes and narrow size distributions with dimensions around 5 nm (width) and 10 nm (length). The nanocomposites were prepared by in situ polymerization of NVPCL monomer in the presence of HA nanoparticles (1% w/w) using azobisisobutyronitrile as a radical initiator at 70 °C in dimethyl sulfoxide as solvent with reaction time of 4 h. The complete polymerization of the monomer was showed by typical spectra of ¹³C, ¹H nuclear magnetic resonance, infrared and Raman spectroscopies. The differential scanning calorimeter analysis showed the same glass transition temperature (Tg) in 147 °C for the PNVCL and nanocomposite, which is the typical value for the dry polymer. The PNVCL and the nanocomposites presented lower critical solution temperature (LCST) with similar values around 34°C, though the PNVCL/Ha nanocomposites exhibited a wide range of decline 30-34°C, measured by ultraviolet-visible transmission spectrophotometer of samples with 1% in mass. The dynamic light scattering (DLS) resulted in a decrease of the hydrodynamic diameters of 350 nm for pure PNVCL polymer to 32 nm for the PNVCL/HA nanocomposite, indicating that the HA nanoparticles influenced in polymeric chains conformational in aqueous solution. Thereby, the nanocomposites maintained the thermo-response properties of the polymer as well as its Tg, characteristics of significant importance for their use as multifunctional polymeric materials with osseointegration capability in scaffolds applications.

Resistance to insertion of a sharp object into a soft solid is known to depend upon the macroscopic geometry of the tool and the consequent fracture mechanisms involved. In this article, we have examined it by carrying out displacement controlled puncturing into soft, brittle polyacrylamide gels using hypodermic needles of different diameters. These experiments show that in contrast to a rigid, flat bottom punch and a punch with sharp tip, for these needles, puncturing of the gel does not occur continuously but intermittently with the fracture progressing alternately in the wedge opening and the shear fracture modes. Correspondingly, the force versus displacement plot too shows sharp increase in load and catastrophic falls, occurring at regular intervals. We have shown that these data can be used to estimate the toughness of the material in both these fracture modes. In addition, we have examined the effect of asymmetry in the needle geometry and importantly the co-operative effect of several closely spaced needles by designing multi-tip needles consisting of several tips of different diameters and relative orientations. Experiments with these needles show that compared to a conventional single tip needle of equivalent diameter, the multi-tip needles penetrate the solid at smaller load with a smaller energy cost for fracture. Importantly, fracture occurs near simultaneously in the two fracture modes, so that the oscillations in the puncturing load is arrested. The lateral fracture of the gel and the consequent excess damage too is minimized.
We have examined the co-operative effect by embedding a planar tracer grid within a brittle gel and by driving hypodermic syringe needles of different inter-tip spacing through this plane. These experiments show propagation of the primary crack ahead of the needle-tip, but also of a periodically appearing secondary radial crack from its side. The strain field around the side crack remains oscillatory with a characteristic wavelength which varies with both modulus of solid and needle diameter. For closely spaced indenters their overlapping strain profiles cause compressive stress at the vicinity of the needles, which arrest the side cracks. Diminishing effect of side crack leads to stress concentration for the primary crack and resultant decrease in required load for driving it through the solid.

Genetic manipulation of the biopolymers that compose plant cell walls is emerging as a powerful tool for modification of the properties of biomass. Recently we have shown that altering the lignin monomer composition can yield plants that are more susceptible to deconstruction for biofuels applications, or plants that are hyper-resilient to deconstruction for materials applications. In this presentation I will describe several genetic variants of Arabidopsis: the wild type, which makes a lignin polymer of primarily guaiacyl (G) and syringyl (S) monomeric units, the fah1 mutant, which makes lignin from almost exclusively G subunits, and a ferulate 5-hydroxylase (F5H) overexpressing line (C4H:F5H) that makes lignin from S subunits. Multiscale, multimodal electron and laser imaging techniques reveal that biomass of with a high content of S subunits is more susceptible to deconstruction by maleic acid treatment than the other variants. Enzymatic digestion assays of the treated materials show that the high-S transgenic tissue is also significantly more digestible than the wild type, while the high-G material is clearly the least digestible of these variants. We also show by contact resonance force microscopy, an atomic force microscopy technique, that the high-S cell walls are significantly less stiff in the region of the compound middle lamella relative to wild type and high-G material. Finally, I will describe a newly discovered mutation that causes Arabidopsis plants to produce lignin from almost purely p-hyrdroxyphenol (H) lignin. The resultant tissue is highly susceptible to enzymatic digestion without thermochemical treatment, which holds great promise for reducing the cost of biofuels production.

Superior mechanical and thermal properties in bulk polymers can be achieved by aligning the molecular chains through drawing-induced plastic deformation. Although highly aligned polymer films (HAPFs) are in demand, current fabrication methods are limited to manual, lab-scale batch processes. Here we report a continuous fabrication platform for HAPFs consisting of a three-step sol-gel extrusion, structure freezing and drying, and mechanical drawing process. First, a polymer-solvent solution is subjected to a high shear, high temperature, Couette flow extrusion into a thin film, resulting in initial chain disentanglement. Next, the extruded disentangled structure is frozen using a liquid N₂-cooled substrate, and then solvent is removed from polymer gel through ambient evaporation. Finally, dried films are mechanically drawn within a heated enclosure using a constant-force adaptive-thickness drawing system. The performance of this platform has been confirmed by fabricating polyethylene HAPFs with >99% crystallinity and draw ratios up to 100× (creating continuous films >15 m in length). This work was supported by the U.S. Department of Energy, Advanced Manufacturing Office under Award #DE-EE0005756.

Biomaterial-based therapeutic strategies require biomaterials with properties and functions tailored to the demands of specific applications. Hereby, a reasonable biocompatibility including cyto-, tissue-, and immunocompatibility is generally essential. Recently, it could be demonstrated that starshaped amino oligo(ethylene glycol) (sOEG) functionalized with the aromatic compounds desaminotyrosine (DAT) or desaminotyrosyl tyrosine (DATT) with defined number average molecular weight behave in aqueous solution like surfactants without inducing a substantial cytotoxicity.^[1] Due to the amphiphilic structure of the DAT(T)-sOEGs and based on the degree of functionalization (57-89 %), micelle formation can occur, which was checked by determination of the critical micelle concentration (CMC). Interestingly, only for DAT-functionalized sOEGs, the CMC could be estimated using a fluorescence spectroscopic analysis with pyrene as hydrophobic dye. According to these data the different DAT(T)-sOEGs could be used as solubilizer for hydrophobic drugs in aqueous solution or to mediate particle formation. However, for biomedical applications the polymer solutions need to be free of immunogenic contaminations and should not induce uncontrolled or undesired immunological effects arising form material intrinsic properties.^[2] Using a macrophage-based assay it is shown here that all DAT(T)-sOEGs solution are free of endotoxins but also other microbial contaminations such as fungal products. Such microbial contamination cannot only induce undesired immune cell activation in vitro and in vivo, but also bias the readout of experiments with immune and non-immune cells.
Since all DAT(T)-sOEG solutions can be considered as free of microbial contamination, their intrinsic immunological properties could be investigated. Using whole human blood the capacity of the different DAT(T)#8209;functionalized sOEG solutions to induce cytokine secretion and generation of reactive oxygen species (ROS) by leukocytes such as monocytes and neutrophils was investigated. It was observed that low levels of the pro-inflammatory cytokines such as IL-1β and IL-6 were detected for all sOEG solutions but only when used at concentrations above 250 mu;gmiddot;mL^-1. High ROS levels induced by the DAT(T)#8209;sOEGs solutions may facilitate tissue damage, OEG degradation, or the formation of new crosslinks by oxidizing the phenols and a subsequent reaction with amino groups of sOEGs. Here, only sOEG-DAT 20 kDa induced low amounts of ROS-producing monocytes, which might induce proliferation, and migration, particular cell types such as endothelial cells.
Conclusively, our data indicate that the materials were not contaminated with microbial products and do not induce substantial immunological adverse effects in vitro, which is a perquisite for future biological applications.
[1] K. K. Julich-Gruner, et al. J Appl Biomater Funct Mater2012, 10, 170.
[2] A. Lendlein, et al. Int. J. Artif. Organs2011, 34, 71.

Polymers typically have low thermal conductivity values that are unfavorable for thermal management of microelectronics. However, precise control of the molecular weight, molecular structures and crystallinity can increase thermal transport. The goal of this study is to investigate thermal conductivity and thermal conductance of various model polymer systems with different molecular structures, molecular weights, and crystallinity. Well characterized polymer standards of polystyrene (PS), poly(vinyl acetate) (PVAc), polyvinyledene fluoride (PVDF) were analyzed by Frequency Domain Thermoreflectance (FDTR) to determine their thermal conductivity and thermal conductance. A two-layer model corresponding to the experimental Si-polymer configuration is used to analyze the laser flash results. For FDTR, Si/Au-polymer-Au configuration was used, where the polymer layer was deposited using Langmuir-Blodgett (LB) film technique. Experimental results obtained provide insights on factors determining heat conduction in polymeric materials and directions for developing high performance thermal interface materials.

The dynamics and structure of diblock copolymers have been thoroughly studied, yet similar properties of random copolymers are poorly understood. We have studied the effect of a variation in monomer friction factor of the two monomer components and repulsive interactions between the monomers on the diffusion and structure of copolymers in copolymer/homopolymer blends via Monte Carlo simulations utilizing a modified bond-fluctuation model. This modified model uses a thermodynamic overlap penalty to simulate the effect of dimensionless compressibility in the blends and also incorporates a monomeric friction factor for slow and fast components on a move-by-move basis resulting in an effective copolymer chain friction factor (zeta;_eff). The composition of the copolymer is varied while maintaining a 10% copolymer loading in a copolymer/homopolymer blend and a monomeric friction ratio of 1/30. Initial results indicate an exponential dependence of the copolymer effective zeta;_eff on the copolymer composition. This starkly contrasts with a linear dependence, which is observed in homopolymer and diblock copolymer blends reported in the literature. Structural analysis of the final simulation configuration also reveals a structural transition of the copolymer chains in the blend around a 50/50 copolymer composition.

Our objective is to investigate the design of sterically stabilized hybrid biomaterials through the self-assembly of the end-functionalized amphiphilic molecular species. Individual molecular species are represented by a hydrophilic head group and two hydrophobic tails. The species can differ in terms of specific chemical properties of the polar head groups and the hydrocarbon tail groups. The stable hybrid vesicles can be formed through the self-assembly of amphiphilic molecules in the presence of hydrophilic solvent such as water. We use a Molecular Dynamics-based mesoscopic simulation technique called Dissipative Particle Dynamics to simultaneously resolve the aggregation dynamics, structure and morphology of the hybrid aggregate. In addition, we investigate the factors that control the self-organization of the molecular species within the hybrid soft biomaterials. We characterize the effects of functional groups grafted to hydrophilic segment of the lipid species on the stability, the aggregation kinetics, the equilibrium structure and morphology of the hybrid soft materials. The results of our investigations can be used for the design and prediction of novel hybrid soft materials such as sterically stabilized vehicles for drug delivery.

Research in stretchable conductors has expanded significantly due to interest in materials for mechanically deformable circuitry with application in flexible electronics including flexible displays, antennas, transistors, solar cells, smart textiles, and actuators. Current state of the art stretchable conductors consist of a variety of polymer nanoparticle composite formulations. Electrical conductivity is retained at high levels of applied tensile strain by the rearrangement of conductive nanoparticles in elastomer matrices. This rearrangement leads to the dynamic formation or loss of conductive pathways in the composite. Here we report a novel fabrication method for highly conductive stretchable composites by utilizing two nanoparticle networks assembled in and around polymer microfibers. First, an elastic conductive network is formed via solution blow spinning dispersions of iron-silver core-shell magnetic nanoparticles in poly (styrene-block-isoprene-block-styrene)-tetrahydrofuran solutions. The solution blowspinning technique allows for fiber mat deposition conformally onto 3D substrates. The microfiber mats containing the initial conductive pathway of magnetic nanoparticles are then swollen in a silver precursor solution, to nucleate a second silver nanoparticle conductive network around the preformed microfibers with the aforementioned magnetic nanoparticles within the fiber diameter. The resulting composite exhibits a uniform conductivity of 7620 S/cm at zero applied strain, which is retained to a level of 2200 S/cm at 100% strain. We believe this dual conductive nanoparticle network method can be beneficial for the fabrication of stretchable conductors with high electrical conductivity. Additionally, it is possible to utilize the strain-mediated change in electrical and magnetic properties to fabricate motion and tactility sensors deposited conformally on non-uniform 3D substrates including textile materials.

The co-occurrence of the percolation threshold of adsorbed water network and the transition of moisture and mechanical properties behavior is reported for an adsorption process. Because of their porous structure and the presence of the exposed hydroxyl sites of the glucopyranose rings, amorphous cellulose (AC) and galactoglucomannan (GGM) are hydrophilic and water adsorber. The adsorbed water is known to rearrange the structure of these polymers and to drive changes in their mechanical properties and geometry, as seen in composite natural materials like wood.
By Molecular Dynamics simulation, we investigate the influence of adsorbed water on the AC and GGM structure and properties, within the full range of moisture content from dry state to saturation. Increasing water content results in overall swelling, substantial decrease in stiffness and higher diffusivity of the water molecules. The obtained sorption curve as well as the range of swelling and weakening are confirmed by experiments. The measured properties undergo a noticeable change at about 10% of moisture content, which suggests that a transition occurs in the porous system, indicating that the sorption process is stage-wise. We carry out an analysis of the water network and find out that water molecules form clusters that percolate at the same range of moisture content where the transition occurs. It is remarkable that the percolation co-occurs with the observed changes. A direct physical causal effect between the percolation and the change of mechanical properties has yet to be made, as the mechanical changes are expected to be more related to the breaking of hydrogen bonds and other structural changes.

Varying the amount of specific interface area in the CeO₂-Na₂CO₃ nano-composite fuel cell electrolyte helped reveal the role of interfaces in ionic conductivity. We mixed ceria particles with micrometer or nanometer size distributions to obtain a specific surface area (SSA) in the composite from 47 m²/g^minus;1 to 203 m² /g^minus;1.
Micro-structural investigations of the nano-composite showed that the Na₂CO₃ phase serves as the glue in the microstructure, while thermal analysis revealed a glass transition-like behavior at 350 °C. High SSA enhanced the ionic conductivity significantly at temperatures below 400 °C. Moreover, the activation energy for the Arrhenius conductivity (σT) of the composites was lower than that of the Na₂CO₃ phase. This difference in the activation energies is consistent with the calculated dissociation energy of the carbonate phase.
The strong dependence of conductivity on the SSA, along with differences in the activation energies, suggests that the oxide surface acted as a dissociation agent for the carbonate phase. The spectral elemental mapping by TEM-EELS mode showed that carbonate phase constituted the majority of the matrix. A rim around the SDC oxide particles with a high concentration of carbon was imaged. A model for the solid composite electrolyte is proposed: in the nano-composite electrolyte, the oxide surface helps Na₂CO₃ dissociate, so that the “liberated” ions can move more easily in the interaction region around the oxide particles, thus giving rise to high ionic conductivities.

Currently, approximately 50-70% of the denture wearers present pathogenic state known as denture stomatitis, i.e., an inflammatory process caused by the Candida Albicans. The silver nanoparticles have been effectively employed as antimicrobial agent because their large surface area allows the exposition of micro-organisms. Moreover, silver nanoparticles have been incorporated in different polymers to medical applications, specially the Poly(methyl methacrylate) (PMMA). The PMMA is an acrylic resin biocompatible used in the anchorage of prosthetic joint components due to its long-term permanence and it is not able to cause adverse reactions to the human health. Thus, the PMMA/Ag nanocomposites can be used as potential candidates for dental prosthesis. Therefore, the aim of our study was estimate the effect of the insertion of different concentrations of silver nanoparticles in a commercial acrylic resin for dental application. The silver nanoparticles were synthesized by the Turkevich method, and PMMA was obtained by the thermal polymerization of Lucitone 550 acrylic resin, according to manufacturer&’s instructions. The PMMA/Ag nanocomposites were synthesized by adding 0.05, 0.5 and 5% volume/weight of silver nanoparticles to the polymer during the thermal polymerization stage. The phase structure was analyzed by means of Raman and nuclear magnetic ressonance spectroscopies employing ¹³C-CPTOSS (cross polarization with total sideband suppression). The Raman spectra showed typical absorption bands of PMMA and NMR revealed that the PMMA and PMMA/Ag nanocomposites are atatic. The scanning electron microscopy micrographs evidenced the presence of a heterogeneous distribution of silver particles with spherical shapes and sizes of about 20 nm. The thermogravimetric analysis demonstrated that higher silver concentrations improves the thermal stability of PMMA/Ag nanocomposites because the barrier effect. The decrease in the glass transition temperature in PMMA/Ag nanocomposites, when compared the pure PMMA, indicated an increase in the polymeric chains mobility. The molecular dynamics of PMMA and nanocomposites was studied by dynamic mechanical thermogravimetric analysis. These results indicated a β relaxation, which involves the ester side group occurring around the room temperature, and the glass transition, predominantly involving the main chain dynamics at around 110°C for PMMA, and decreasing for nanocomposites. It was possible with this methodology to insert the silver nanoparticles in a polymeric matrix and increase the thermal stability of the nanocomposites formed.

In the present investigation, the dynamic mechanical behavior, the thermal properties, the decomposition process and the thermal stability of an epoxy resin-fly ash system are studied as a function of sonication time during the sample preparation and the filler content. The variation of T_g, tanδ and bending moduli (E#900;and Epsi;#900;#900;), was measured as a function of sonication time and fly ash content. An increase in E#900; and a decrease in the T_g values with sonication time were observed. These variations could be explained on the basis of the deaggregation and better dispersion of the filler and to free volume increase due to sonication. The respective variation for the storage modulus was no significant in the rubbery state.
Concerning the sample preparation, a combination of mechanical stirring and ultrasonication effectively disperses fly ash into the matrix.
Acknowledgement:
This research has been co#8208;financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) #8208; Research Funding Program: THALES. Investing in knowledge society through the European Social Fund. Grund number MIS 379346.

Oxidation-responsive nanomaterials (nanoparticles, micelles) allow to sense and respond to biologically occurring, inflammation-related oxidants (Reactive Oxygen Species); by doing so, they can produce therapeutically relevant actions, such as the release of a drug, in a fashion proportional to the ROS concentration, which is most often proportional to the severity of an inflammatory reaction.
The presentation will review recent advances in the design of oxidation-responsive amphiphilic organic polymers, specifically focusing on the influence of macromoleculararchitectural details on their self-assembly and oxidation responsiveness. In particular, we will discuss the influence of branching (star or comb polymers) on these properties, highlighting the cross influence between macromolecular crowding, composition of the macromolecular chains, possibility of self-assembly and kinetics of response and finally linking this to in vitro cellular responses.

Selenium (Se), an essential element for animals and humans, possesses unique chemical and biological properties.¹ The lower bond energy of C-Se and Se-Se than those of C-S and S-S (C-S 272 kJ mol^-1; S-S 240 kJ mol^-1; C-Se 244 kJ mol^-1; Se-Se 172 kJ mol^-1) makes it easier for low valence state selenium compounds to be oxidized than low valence state sulfur compounds. As reactive oxygen species (ROS) are natural by-products of oxygen metabolism that may cause chronic diseases such as cancer and heart disease to human beings, great effort has been put to synthesize numerous antioxidant compounds based on selenium-containing small molecules. However, literatures on selenium-containing polymers are rather scarce. This report is going to highlight the most recent advances on selenium-containing polymers and their potential bio-applications as ROS-responsive drug delivery vehicles in physiological conditions. We introduced selenium into polymer of different topology through various approaches. Take the linear polymer for example, diselenide-containing amphiphilic block copolymer PEG-PUSeSe-PEG was synthesized and could form micelles in water. The micelles exhibited unique dual redox triggered disassembly behavior in response to a very dilute concentration of ROS (H₂O₂, 0.01%, v/v) or reductant (glutathione, 0.01 mg/mL).² The diselenide bonds could also be cleaved by ROS generated by photosensitizer under light radiation. The micelles in solution state could achieve red light responsive disassembly.³ As gamma rays is one of the most widely used radiation in clinical application and that gamma radiation on water could also produce ROS, selenium-containing polymers were used for the combination of chemotherapy and radiotherapy. A gamma-ray responsive hydrogel was fabricated by combining a diselenide-containing polymer and a peptide amphiphile. The diselenide gel degraded into sol under 500 Gy gamma-radiation, which is much more sensitive than its disulfide analogue.⁴ The radiation dosage can be decreased to 5Gy in solution, with a release of 45% of the loaded doxorubicin.⁵ It is hoped that the novel selenium-containing polymers can provide a new platform for the next generation of biomaterials, enriching the field of ROS-responsive materials and opening new avenues for programmable responsive systems of controlled release. References: (1) Xu, H.; Cao, W.; Zhang, X. Acc. Chem. Res.2013, 46, 1647-1658. (2) Ma, N.; Li, Y.; Xu, H.; Wang, Z.; Zhang, X. J. Am. Chem. Soc.2010, 132, 442-443. (3) Han, P.; Li, S.; Cao, W.; Li, Y.; Sun, Z.; Wang, Z.; Xu, H. J. Mater. Chem. B2013, 1, 740-743. (4) Cao, W.; Zhang, X.; Miao, X.; Yang, Z.; Xu, H. Angew. Chem., Int. Ed.2013, 52, 6233-6237. (5) Ma, N.; Xu, H.; An, L.; Li, J.; Sun, Z.; Zhang, X. Langmuir2011, 27, 5874-5878.

Restoration of heterogeneous and avascular articular hyaline cartilage has been a primary target in the field of tissue engineering due to the lack of functional regeneration of even small defects in a joint. In recent years, researchers have sought to enable rapid regeneration of bone and cartilage defects through a combination of scaffolds, cells, and biomolecular signals.
In particular, the structure of the scaffold plays a critical role in guiding tissue development. Scaffolds for osteochondral injuries must not only be biocompatible, bioresorbable, and able to withstand the mechanical forces typically experienced at the joint surface, but also guide the complex and heterogeneous repair of a multi-tissue defect. The major focus thus far has been in constructing implantable scaffolds, which can be readily designed to offer appropriate mechanical properties and enable 3D spatiotemporal control over the defect repair process. However, the use of implantable scaffolds can become very challenging as it requires open surgery and osteochondral defects of irregular shapes can prove quite problematic to repair. Moreover, previous research using implantable scaffolds has shown inability to effectively promote good integration of the new cells with the host tissue.
Thus, it has become of high interest to discover minimally invasive methods using injectable polymeric biomaterials capable of gelling in situ as scaffolds to stimulate osteochondral tissue regeneration. Degradable hydrogelshy;based materials are versatile polymeric materials that are well suited for this task as they are capable of delivering and maintaining encapsulated cells in a nonshy;toxic manner. Thermogelling polymers, which pass through a lower critical solution temperature (LCST) upon injection into the body to spontaneously gel in situ, have shown much promise in this regard due to a nearly instantaneous physical gelation mechanism. The next grand challenge in the development of injectable scaffolds is to endow them with spatiotemporally-controlled signaling to guide the regeneration of heterogeneous and multi-tissue defects.
This paper reports on the synthesis and characterization of a novel class of injectable, thermally and chemically dual-gelling bionanocomposite hydrogels from thermogelling macromers based on poly(N-isopropylacrylamide), degradable polyamidoamine-based crosslinking macromers, and functional hybrid inorganic/organic nanoparticles capable of responding to external stimuli to stimulate cell activity and the regenerative process in situ. The efficacy of in situ hydrogel formation, dimensional stability, mechanical properties, reaction kinetics, and cytocompatibility were evaluated; and the effects of polymer and nanoparticle chemistry and loading were investigated.

Skin is one of the most important organs of the human body. It is responsible for sensing the external environment and for autonomously repairing damaged tissue. The translation of these properties to synthetic materials to create strong films able to self-repair and sense changes in the environment could open new technological opportunities. Examples can be found in the fields of robotics and bioengineered organs, where these functions cannot be performed by living tissues. Here we present an innovative method for the production of skin-like films, able to flex and completely and autonomously repair via hydrogen and dative bonds. These materials, obtained by the careful infiltration of graphene ultra-light cellular networks (1) with a self-healing polymer, show repair times of the order of a few minutes, where the “skin” recovers its flexibility just by putting the two fractured surfaces back into contact. The material is able to repair scratches and superficial damage as well as deep tissue tear. Furthermore, it presents the properties of an electrical sensor by varying its conductivity under applied pressure or flexion. The chemistry of the graphene aerogels has been tailored to achieve excellent adhesion with the organic phase. The continuous graphene network provides structural integrity, strength and electrical conductivity while keeping the graphene contents below 0.5 wt.%. We have characterized the mechanical strength, viscoelastic response and electrical properties of the material. Tensile strengths of the order of 0.2 MPa are combined with conductivities that can be as high as hundreds of S/m. Both can be recovered after damage in a few minutes. We therefore show here how it is possible to mimic key properties of skin via a synthetic route to create a strong and flexible electronic sensor able to autonomously self-heal without the use of pressure or heat.
(1) Barg, S. et al. Mesoscale assembly of chemically modified graphene into complex cellular networks. Nat. Commun. 5:4328 doi: 10.1038/ncomms5328 (2014).

This presentation will describe a novel reaction cascade for detecting the effects of small mechanical stresses in hydrogels. Due to their highly hydrated nature and mechanical tunability, hydrogels are common scaffolds for cell growth and tissue engineering. To grow viable tissue for applications such as cardiovascular repair and cartilage replacement, the mechanical properties of the gels must be controlled to mimic the native tissue. Additionally, the hydrogel scaffold must retain its mechanical integrity for the duration of cellular development. It is therefore important to be able to detect scaffold degradation as early as possible in order to monitor and improve upon implant performance. Since hydrogel failure begins with breakage of the crosslinks, a sensor for these bond breakages would provide a means for early detection. We hypothesized that the radicals formed upon bond breakage would react with the ambient water in the hydrogel to form hydroxyl radicals, which in turn could activate certain masked fluorophores to produce a fluorescent signal. We synthesized a series of hydrogels from 4-arm poly(ethylene glycol) derivatives with crosslinks of varying strength and a range of moduli for each crosslink type. These were loaded with the masked fluorophore 3&’-(p-aminophenyl) fluorescein. The gels were then subjected to compressive stress at strains up to 30 %. We observed fluorescence activation at compressive stresses as low as 5 kPa, with the effect of compression primarily dependent on the crosslink strength; as crosslink strength decreased, fluorescence activation increased. We also saw a dependence of fluorescence activation on the modulus of the gel, with the activation decreasing as modulus increased. In future studies we will adapt this system to study mechanical variability and defects within cell-laden hydrogels.

Pressure sensing, is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. We present here an ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film was prepared from a polypyrrole hydrogel using a multi-phase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1 Pa and exhibits a short response time, good reproducibility, excellent cycling stability, and temperature-stable sensing.
Reference
1. Pan, L.; Chortos, A.; Yu, G.; Wang, Y.; Isaacson, S.; Allen, R.; Shi, Y.; Dauskardt, R.; Bao, Z. Nature Communications 2014, 5, 3002.

Loosely crosslinked pseudo-interpenetrating polymer network (pseudo-IPN) hydrogels with double, triple and quadruple-network structures were synthesized from acrylamide (AAm) and their mechanical properties were studied. The building blocks of a pseudo-IPN hydrogel are IPNs covalently attached to each other at some points. The single-network (SN), double-network (DN) and triple-network (TN) hydrogels were used as precursors for the DN, TN and quadruple-network (QN) hydrogels, respectively. Increasing the number of polymeric networks significantly changed the mechanical properties, even though the chemical composition and polymerization procedure of each individual network was the same. The SN and DN hydrogels showed rubber-like tensile behavior, but the TN and QN hydrogels exhibited strain localization during tensile deformation.
For the QN hydrogel the strain localization occurred at two different stretch ratios during tensile loading. The strain localization was attributed to the brittle regions within the material due to locally increasing the effective crosslinking density when the number of loosely crosslinked networks increased. The strain localization at two stretch ratios in QN hydrogel indicated a more heterogeneous distribution of effective crosslinking density in the system for a high number of networks. Uniaxial tensile tests for QN hydrogels that were previously damaged with a compression load demonstrated that the strain localization that occurred at the lower of the two stretch ratios disappeared and the second one remained. That observation supports the hypothesis for the origin of strain localization. In fact, by applying of the compression preload, the brittle regions in the sample responsible for strain localization at low stretch ratios break and, therefore, they cannot be effective to cause strain localization. Loading-unloading tensile experiments indicate that in SN and DN hydrogels the amount of energy dissipation due to damage was very low. In samples where strain localization occurred, unloading before strain localization resulted in very low energy dissipation, but unloading after strain localization showed a large energy dissipation due to damage to the internal structure of the sample in form of a hysteresis.
For uniaxial compression, the data for two successive compression tests on the same sample coincided for SN, DN and TN hydrogels, indicating that no damage occurred in those hydrogels. However, for the QN hydrogel the mechanical properties changed after application of the first compression test. The mechanical results indicate that the highest toughness occurs for an optimum number of loosely crosslinked IPNs. Increasing the number of loosely crosslinked networks, even when the crosslink density in each network is very low, leads to heterogeneities in the distribution of crosslink density, which creates brittle regions of high local crosslink density where catastrophic failure of the sample may occur.

Ionogels are emerging materials that combine the solid-like behavior of a gel, with the ion conductivity and non-volatility of an ionic liquid. Ionogels are ionic conductors and, as such, they are being considered for use in stretchable electronics and artificial muscles or nerves. Previous work on ionogels has focused mainly on their thermal and ion transport properties. But use of ionogels in these applications is limited in part by their mechanical behavior and requires models to describe and predict the mechanical behavior of these materials.
Here we present an ionogel prepared by swelling covalently cross-linked poly(methyl methacrylate) in 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide. The resulting ionogel is compliant, stretchable, and relatively tough. We demonstrate that the swelling ratio, elastic modulus, stretchability, and fracture energy of the ionogel depend sensitively on the cross-link density of the polymer network. The inverse dependence of the fracture energy on the cross-link density agrees with the Lake-Thomas model and suggests that energy dissipation during fracture arises mainly from the fracture of carbon-carbon bonds. We further demonstrate that the chemo-mechanical behavior of the ionogels is well captured by the model of the ideal elastomeric gel combined with the Flory-Huggins model for the free energy of mixing. Only two material parameters are required for the equations of state for these ionogels: the elastic modulus of the gel and a single Flory interaction parameter.

Thermal approaches for rigidity tunable composite design have been limited due to the relatively long activiation time. In this work, rapid and reversible changes in the mechanical rigidity of an elastic composite are accomplished with a conductive propylene-based elastomer (cPBE) embedded in an electrically and thermally insulating sheet of poly(dimethylsiloxane) (PDMS). These rigidity-tuning composites are activated by passing electrical current through the cPBE, which increases in temperature through resistive (i.e. ohmic or “Joule”) heating. Because of its relatively low Vicat softening point, only moderate current is required to rapidly heat and soften the rubber. At room temperature, the cPBE has an elastic (Young&’s) modulus of 175.5 MPa and is observed to soften into a viscoplastic fluid when heated above 75 ^oC. Depending on the area fraction of cPBE, a composite can exhibit reversible changes in effective tensile modulus between ~0.1 and 100 MPa. Moreover, the cPBE&’s unique combination of conductive, elastomeric, and thermoplastic properties eliminates the need for external Joule heating and allows for rapid activation in seconds. Lastly, we demonstrate the potential for soft robotics integration with an inflatable bending actuator that contains several cPBE-PDMS “tendon” elements. Selectively activating the tendons controls the neutral axis and direction of bending during inflation.

Photo-actuating structures inspired by the chemical sensing and signal transmission observed in sun-tracking leaves have recently been proposed by Dicker et al.¹ These structures are complex multicomponent material systems, designed to actuate in order that a desired orientation be maintained between the structure and a light source. Within the structure sensing occurs from the light exposure of a reversible photoacid² or base³, whilst actuation results from the swelling of a pH responsive hydrogel. The two components are separated, with a control signal being sent from one location to the other by the diffusion of ions, and the resulting pH change. By carefully designing the system geometry such that light exposure is a function of the device&’s orientation (through angled shades), and by linking through solution appropriate sensing and actuating elements, it is anticipated that precise and stable control can be imparted to the structure.
However, the realisation of such a structure requires the development of new modelling tools and an improved understanding of the repeatability of hydrogel actuation. This work first presents new modelling concepts for predicting hydrogel swelling in systems where the pH change is a variable resulting from the equilibrium interaction of all free and fixed (hydrogel) species in the system. The model developed incorporates a homogenised solution method to predict the final composition of the combined system. Donnan equilibrium⁴, considering conservation of mass and electro-neutrality within the hydrogel is then calculated to arrive at the final ion composition in both the hydrogel and surrounding solution. This in turn allows for the osmotic pressure and resulting degree of swelling for the actuated hydrogel to be determined. Preliminary findings of interest include a clear optimum for fixed charge concentration for a given hydrogel/solution ratio, and applied change in proton concentration.
This work also examines experimentally the repeatability of reversible hydrogel swelling. In particular, swelling resulting from limited shifts in pH around the hydrogel&’s transition pK_a is examined. The investigations involve simultaneously performing a titration of the hydrogel (measuring degree of protonation), whilst visually determining the hydrogel&’s state of swelling in order to separate the chemical and mechanical contributions to actuation performance. The polyether-based polyurethane and poly(acrylic acid) hydrogel developed by Naficy et al.⁵ and shown to have rapid and repeatable load recovery is used in this work. Experimental results are used to provide both model validation and guidance for model improvements and material/system design.
¹Dicker et al.Bioinspir. Biomim.2014, Accepted. ²Shi et al. J. Am. Chem. Soc.2011, 133, 14699-14703. ³Irie, M. J. Am. Chem. Soc.1983, 105, 2078-2079. ⁴Ricka and Tanaka. Macromolecules1984, 17, 2916-2921. ⁵Naficy et al.ACS Appl. Mater. Interfaces2014, 6, 4109-4114.

The formation of polymer composites by incorporation of e.g. inorganic fillers into a polymer matrix is an efficient method for creation of multifunctional materials. One example are magneto-sensitive shape-memory nanocomposites (SMPNC), containing magnetic nanoparticles (MNP), that are capable of a thermally-induced shape-memory effect (SME), whereby the SME can be activated either by direct heating or inductive heating in an alternating magnetic field (AMF) [1, 2].
While thermal activation can be achieved through the transfer of thermal energy from the environment directly into the polymer matrix via conduction, thermal radiation, during inductive heating in an AMF the MNPs heat the polymer matrix via hysteresis loss and/or superparamagnetism related processes [2, 3]. Besides the generation of heat inside the nanocomposite sample, caused by inductive heating of the magnetic fillers, the heat dissipation (heat loss) at the surface, which is in contact to the surrounding environment, has to be considered. In this context the surface area to volume (S/V) ratio of the test specimen is an important parameter for the achievable temperature (T_max) [4].
Two SMPNCs were prepared by incorporation of silica coated magnetite nanoparticles in two different SMP polymer matrices, while the MNP content was varied. As polymer matrices a thermoplastic polyetherurethane (PEU) containing amorphous switching domains with an mixed glass transition temperature of T_g,mix = 74-76 °C [2], as well as a covalently crosslinked polymer network (cPCL) prepared from crystallizable poly(ε-caprolactone)diisocyantoethyl dimethacrylate with a melting temperature of T_m = 51-52 °C were used [4].
First the behavior of the PEU- and cPCL- composite samples comprising different MNP contents but with constant S/V-ratio in an AMF at different magnetic field strengths H was investigated. T_max was observed, while H was varied at fixed frequency of 258 kHz from 7 kA#8729;m^-1 to 27 kA#8729;m^-1. In a next set of magnetic heating experiments the S/V-ratio of the samples was varied by uniaxial deformation.
A heat transfer model description was derived with a relation for the decrease in T_max as function of elongation. The experimentally achieved temperatures could be accurately predicted by the presented model. The developed model approach was also able to describe the recovery process of a magneto-sensitive SMPC, i.e. the stepwise uncoiling of a rolled stripe, by stepwise increase of the field strength H.
References:
[1] Heuchel M, Sauter T, Kratz K, and Lendlein A. Journal of Polymer Science Part B: Polymer Physics 2013;51(8):621-637.
[2] Mohr R, Kratz K, Weigel T, Lucka-Gabor M, Moneke M, and Lendlein A. Proceedings of the National Academy of Sciences of the United States of America 2006;103(10):3540-3545.
[3] Razzaq MY, Behl M, and Lendlein A. Nanoscale 2012;4:6181-6195.
[4] Razzaq MY, Behl M, Kratz K, and Lendlein A. Advanced Materials 2013;25(38):5514-5518.

Polymer nanofibers with high thermal conductivities and outstanding thermal stabilities are highly desirable in heat transfer-critical applications such as thermal management, heat exchangers and energy storage. In this work, we unlock the fundamental relations between the thermal conductivity and thermal stability of polymer nanofibers and their molecular characteristics by studying the temperature-induced phase transitions and thermal transport of a series of polymer nanofibers. Ten different polymer nanofibers with systematically chosen molecular structures are studied using large scale molecular dynamics simulations. We found that high thermal conductivity and good thermal stability can be achieved in polymers with rigid backbones, exemplified by π-conjugated polymers, due to suppressed segmental rotations and large phonon group velocities. The low probability of segmental rotation does not only prevent temperature-induced phase transition but also enables long phonon mean free paths due to reduced disorder scattering. Although stronger inter-chain interactions can also improve the thermal stability, polymers with such a feature usually have heavier atoms, weaker backbone bonds, and segments vulnerable to random rotations, which lead to low thermal conductivities. This work elucidates the underlying linkage between the molecular nature and macroscopic thermal properties of polymer nanofibers, which is instrumental to the design of thermally conductive polymer nanofibers with high temperature stabilities.

The prediction of material properties is crucial to minimize the costs of experimental exploration of new materials. This will allow the design of the microstructure to create a material with the desired properties and the design of the optimal processing conditions. Therefore, we develop a computational tool for a priori prediction of the properties of nanostructured polymers dependent on processing conditions and surface energies of the components. Our hypothesis is that the relative nonpolar and polar surface energies of the components as well as the processing conditions, such as flow type and stress, control the nanoparticle dispersion of nanocomposites. Therefore, process-structure-process relationships have to be known. Up to now, nanocomposites have not been analyzed sufficiently regarding their process-structure-property relationships.
In a first step, melt mixing under varying process conditions, such as rotation speed, is performed to provide a systematic set of data on processing parameters and outcomes for systems in which interface parameters, such as surface energies, have been controlled. Generally, the polymer extrusion processing can be divided in the following functions: solid conveying, plastification, melt conveying, devolatilization, dispersion and distribution and pressurization. Analytical models are applied to correlate the specific energy input in the material and the surface energy with the nanocomposite microstructure. The processing conditions regarding laminar and elongational flow have to be well known. Polymers are used, that have various surface tensions, like PP and PMMA. The silica filler is modified in order to gain different surface energies of the filler. The shear stress and residence time are the key parameters in creating good dispersion and are utilized as processing descriptors parameters in the model. Therefore, the rotation speed of the extrusion processing is varied. Second, the microstructures are quantified via TEM and the image-based microstructure characterization is conducted to statistically quantify the microstructure using a two-point correlation function and microstructure descriptors. In a third step, the surface energies for each polymer and functionalized nanoparticle is calculated using heuristic Materials Quantitative Structure Property Relationships (MQSPR) models based on the chemical properties of the constituents.
The used descriptors are for example based on electron density distribution, Electrostatic Potential and Active Lone Pair potential. The physical properties are then related to the 3D microstructure and through statistical learning we have developed the analytical relationship between the selected structural parameters (descriptors) and the infinite dimensional 2-point correlation function.
With this method, we are able to predict material properties from the structure of nanocomposites and we can design the processing conditions to achieve the desired material structure.

Nature designs hierarchical structures with feature sizes that range over multiple length scales to achieve extraordinary functions. Hierarchical structures formed by physical-field-driven self-assembly are mostly static, as the hierarchical structures are fixed at their final states. However, hierarchical structures capable of dynamic control and tunability are highly desirable for various applications such as on-demand super-hydrophobicity, tunable adhesion, dynamic antifouling, and cell culture. Here, we report a simple yet effective method that can dynamically generate hierarchical patterns with feature sizes ranging from one to hundreds of micrometers on large-area elastomer surfaces under the control of applied electrical fields. The method is achieved by harnessing the electro-creasing instability in multilayer elastomer films. The critical electric field for inducing electro-creasing instability in a layer of an elastomer scales with square root of the elastomer&’s modulus, while the wavelength of the instability pattern scales with the layer&’s thickness. By rationally designing elastomer films with varied modulus and thickness throughout different layers, we control the formation of surface instability patterns with feature sizes of different scales under prescribed voltages. The method is very versatile, giving various types of hierarchical patterns such as randomly oriented, aligned, and gradient ones. A theoretical model is developed and validated to guide the design of hierarchical patterns.

Variations in the microtopography can alter surface functions such as wetting behavior or adhesion property.¹ One example for switchable microstructures based on stimuli-responsive polymer materials are micropatterned shape-memory polymers, where the topographical changes occur when a predefined response temperature is exceeded.²
In this work, we explored whether a temperature-memory effect (TME) can be achieved in microstructured surfaces prepared from polymers exhibiting a broad glass transition or melting temperature range and in this way enable the implementation of different response temperatures in one and the same material. As polymers we selected a copolyether urethane (PEU) comprising a broad glass transition associated to a mixed phase in the range from 20 to 90 °C ³ and a crosslinked poly[ethylene-ran-(vinyl acetate)] (cPEVA) blend with a melting transition range of almost 100 °C.⁴
The micropatterned polymer surfaces were prepared by a hot-embossing technique using polydimethylsiloxane soft molds, resulting in arrays of uniformly spaced micropillars with a height and width of 10 µm. For quantification of the temperature-memory capability the prepared samples were programmed at different deformation temperatures (T_deform = 40, 55, 60, 70 or 80 °C) using a smooth Si-wafer substrate. The recovery was followed via light microscopy either in an off-line or online manner, which enabled the determination of changes in micropillar height during heating the programmed surfaces to T_high = 80 °C (PEU) or 130 °C for cPEVA.
Both microstructured surfaces presented an evident TME, where the response temperatures could be systematically tailored in the range from 40 to 70 0C by selection of T_deform. Intelligent TMP microstructured surfaces could serve as microfluidic valves, programmable adhesives, or switchable cell culture substrates.
¹ C. M. Kolodziej, H. D. Maynard, J. Am. Chem. Soc. 2012, 134, 12386.
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