Symposium Organizers
Andreas Lendlein Institute of Polymer Research
Yakai Feng Tianjin University
Tao Xie General Motors Research and Development Center
Zhibin Guan University of California-Irvine
V1: Multifunctional Surfaces and Interfaces I
Session Chairs
Monday PM, November 28, 2011
Room 312 (Hynes)
9:45 AM - V1.2
Adaptive and Dynamic Optical Materials for Improving Energy Efficiency of Buildings.
Philseok Kim 1 2 , Mathias Kolle 2 , Mughees Khan 1 , Lauren Zarzar 3 , Joanna Aizenberg 1 2 3
1 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States, 2 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Show AbstractOur recent developments for hybrid actuation systems combining patterned micro/nanostructures and artificial muscle system (HAIRS: Hydrogel-Actuated Integrated Response System) have shown promises for producing responsive and dynamic surfaces in emerging technologies. In particular, when these micro/nanostructures are combined with thermoresponsive materials, the hybrid system can be used as roofs, windows, or shades in buildings that self-regulate the light transmission/reflection and the thermal gain in response to temperature change. We have recently developed such adaptive and dynamic shading systems based on deformable micromirror arrays integrated with a temperature-responsive hydrogel that exhibit LCST behavior. The deformable mirrors can be reversibly actuated by temperature change, which in turn dynamically tunes the optical properties of the surfaces. We will present the detailed analysis of optical and thermal characteristics of these dynamic hybrid systems and show how these adaptive screens and windows can effectively control the shading and thermal gain.
10:00 AM - V1.3
Bio-Inspired Self-Cleaning Living-Materials.
Lukas Gerber 1 , Fabian Koehler 1 , Wendelin Stark 1
1 Institute for Chemical and Bioengineering, ETH Zurich, Zurich Switzerland
Show AbstractThe furry white surface of a Camembert cheese is an impressive example of a functional living-material. The inoculation of the raw cheese’s surface with the edible mold Penicillium camemberti does not only lead to the exquisite taste of the Camembert, but also prevents the contamination with other microorganisms that may spoil the cheese and trigger diseases. [1]Inspired by this concept, we designed surfaces combining dead (classical polymer science) and living (a biological organism) materials. Depending on the organism, its nutrition, secondary metabolites, or growth conditions, various forms of such living-materials are imaginable: Penicillin producing molds (e.g. Penicillium jensenii [2]) may lead to antibacterial surfaces, where the mold competes against external organisms. Other systems may be used for biochemical production, or, with a dry/wet interface, for air quality improvement, or improved haptic and visual properties of a consumer exposed surface. In this work we focus on the concept of enforcing microorganisms into a defined planar habitat to prove the conceptual design of a living-material. We further demonstrate the cyclic behavior of a living-surface (dormant/active phase), and investigate its self-cleaning properties.In a dormant state the fungus has no interaction with the surroundings (some fungal spores can outlive millions of years). When a nutrient (food spill, bacterial contamination) is brought onto the surfaces, the living part becomes active. The fungus proliferates within its domain, consumes the provided nutrients, and defends its food against other microorganisms such as other fungi or bacteria e.g. by the production of mykotoxins. After all nutrients are consumed, the fungus goes back to a dormant state.More specifically, we encapsulated Penicillium roqueforti into a thin two-dimensional polymer-based microenvironment, while maintaining the possibility for exchanging nutrients and metabolites. Such encapsulation avoids possible negative effects of the fungi, such as infection. The nourishment of the living layer with different growth media (i. e. food) shows different metabolism rates, different glucose consumption rates, and different fungal growth in the living layer. Living layers with a porous top layer sustain harsh treatments. We proved the conceptual design (repetitive operation) by running two full nutrition cycles while tracking food consumption and the fungal growth. [3] [1] M.S. Nielson, et al., Int J Food Microbiol 42, 91-99 (1998).[2] P. Farber, et al., Appl Environ Microbiol 60, 3401-3404 (1994).[3] L.C. Gerber, F.M. Koehler, W.J. Stark, in preparation.
10:15 AM - V1.4
Surface Modification of Polycarbonateurethane by Grafting Phosphorylcholine Glyceraldehydes for Improving Hemocompatibility.
Wei Gao 1 , Yakai Feng 1 , Jian Lu 1 , Jintang Guo 1
1 , Tianjin University, Tianjin China
Show AbstractHigh hemocompatibility is one of the important properties required for vascular grafts and other biomedical devices contacting with blood in vivo for a long period of time.[1] An effective way to improve the hemocompatibility of relative biomaterials is to modify the surface structure and optimize the surface properties of the materials correspondingly, since the interactions between blood components and biomaterials occurred mainly on material surface [2]. In this study, phosphorylcholine glyceraldehyde (PCGA), a phosphorylcholine (PC) groups containing compound, was grafted onto the surface of polycarbonateurethane (PCU) films in order to introduce biomimetic structure onto the polymer surfaces. Specifically, PCGA was grafted onto PCU surface via three-steps. Firstly, hexamethylene diisocyanate (HDI) was covalently coupled onto PCU surface. Secondly, 1,6-hexanediamine (HDA) or diamino-poly(ethylene glycol) (APEG, Mn=200) was linked to PCU surface through the coupling of the amino group of HDA or APEG with the rest isocyanate group of HDI. This reaction introduced primary amine groups onto the polymer surface. Finally, PCGA were grafted onto PCU surface via the reductive amination reaction between the aldehyde group in PCGA and the primary amine groups on PCU surface. X-ray photoelectron spectroscopy (XPS) analysis and water contact angle test showed that PCGA had already been covalently linked to the PCU surfaces. Scanning electron microscope (SEM) observation of the PCU films after treated with plasma-rich plasma demonstrated that platelets rarely adhered to the surface of the PCGA grafted PCU films but large numbers of platelets adhered to the surface of ungrafted PCU film. The result indicated that the hemocompatibility of the PCU films was improved obviously after grafted with PCGA. [1] Ratner, B. D., Biomaterials, 2007, 28, 5144-5147.[2] Zhao, H. Y., et al., Journal of Applied Polymer Science, 2011, 119, 3717–3727.
10:30 AM - V1.5
Mechanics of Geometrically-Tuned pH-Responsive Polymers.
Lifeng Wang 1 , Lin Han 2 , Christine Ortiz 2 , Mary Boyce 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractStimuli-responsive polymer materials have been extensively explored over the past two decades because of their promising applications. We consider the mechanics of mechanomutable polyelectrolyte multilayers (PEMs), which undergo reversible pH-responsive transition from a condensed, ionically crosslinked state (small pH) to a hydrated, ionized state (large pH). Instrumented indentation and micro-structurally-based finite element analysis are conducted on the PEM thin films and PEM tube forests to determine the effective elastic properties and further the mechanomutability as a result of the coupling between inherent responsive material properties and geometry. We demonstrate that geometry can be used to introduce and tailor different deformation mechanisms as a means to tune mechanomutabilibility of stiffness and dissipation in addition to the constitutive material properties. The rate-dependent stimulus-responsive mechanomutability can be finely controlled within a wide range from ~ 2 – 100 times by tailoring the tube geometrical factors at different indentation rates. We also explore the swelling effect on the mechanical property of polyelectrolyte multilayer thin film. The thickness and stiffness of the thin film are observed to be strongly pH-dependent. A theory of active polymeric materials, accounting for changes in material volume and properties due to actuation, is used to explain the observed phenomena. We show that the indentation stiffness of the thin film is affected by not only the change of ionic crosslink density at different environmental pH but also the compressive stress induced during swelling in the polyelectrolyte film. These studies provide fundamental understanding and mechanics of indentation of PEM thin films and tube forests and show the tremendous potential for dynamically tuning surface and bulk properties of novel complex structured materials.
10:45 AM - V1:MfSaI1
BREAK
V2: Stimuli-Sensitive and Shape-Memory Polymers I
Session Chairs
Monday PM, November 28, 2011
Room 312 (Hynes)
11:15 AM - V2.1
Water-Triggered Shape Memory Study of Electrospun Nanofibrous Mats.
Xinzhu Gu 1 , Sandra Moreau 2 , Patrick Mather 1
1 Department of Biomedical and Chemical Engineering and Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York, United States, 2 Department of Material Sciences, University of Nantes, Nantes France
Show AbstractShape memory polymers (SMPs) are a class of smart materials that can be deformed and fixed into a temporary shape, and recover their original, permanent shape by an external stimulus, such as heat, light, electromagnetic induction, and solvents. Compared with the most popular heat-induced SMPs, water responsive SMP can regain its original shapes simply by immersing samples in water. In this way, unfavorable effects resulting from external heating, such as damage of surrounding tissue when activating a smart implant, can be avoided. Based on the fact that the rate of diffusion can be greatly accelerated though a decrease in the diffusion distance, we propose to achieve fast water triggering through the processing of selected SMPs in the form of nanofibers. Specifically, multi-block thermoplastic polyurethanes (TPUs) consisting of poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) blocks was synthesized. The resulting TPUs were subsequently electrospun to yield fibrous webs featuring diameters of 180±30 nm. Due to high molecular weight (Mn >200 kDa), high degrees of entanglement were expected, which serve as physical crosslinking points within the network, in turn affording the novel hydrogels in the water-swollen state. The resulting nanofibrous scaffolds not only feature excellent mechanical properties, but also display a desirable water-triggered shape memory property. We observed that our electrospun nano-fibrous mats showed more than 55% recovery within 2 sec upon immersing in water at ambient temperature; In contrast, the hot-pressed films made from the same material recovered 43% in 45 sec. To date, the fastest water-induced recovery reported in literature is 150 sec in water at 37 °C. The fast actuation, the good shape memory properties, and the convenience of room-temperature water as a stimulus make these materials potential candidate for applications encompassing water responsive sensors, actuators, and medical devices.
11:30 AM - **V2.2
Multiswitchable Polythiophenes Bearing a Spiropyran Functionality.
Klaudia Wagner 1 , Robert Byrne 2 , Michele Zanoni 2 , Sanjeev Gambhir 1 , Pawel Wagner 1 , Dermot Diamond 2 , Gordon Wallace 1 , David Officer 1
1 , ARC Centre of Excellence for Electromaterials Science and Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia, 2 , National Centre for Sensor Research, Dublin City University, Dublin Ireland
Show AbstractThe immobilization of light–responsive molecules on electroactive surfaces provides an exciting opportunity for the development of smart materials and devices. Spiropyrans are one of the most widely studied classes of photoswitchable compounds. Irradiation of spiropyrans with near-UV light or electro-oxidation induces heterolytic cleavage of the spiro carbon-oxygen bond to produce ring-opened merocyanine structures. The intense absorption in the visible region of this open form has led to the advance study of spiropyrans in photochromic, molecular optoelectronic, optobioelectronic fields, and chemical sensing.The introduction of switchable molecules into polymers has proved valuable for sensing and actuation. In these cases, light is the most common trigger for transforming the molecules. The use of conducting polymers opens up a new avenue for electrochemical control of the multifunctional material. The switchable moiety can be appended to the polymer backbone or incorporated into it with quite different effects.In this regard, polythiophene derivatives are of particular interest due to their stability and relative ease of synthesis and functionalization, and they have been applied in a broad range of devices, from simple solar cells to complex electroluminescent devices.We have synthesized spiropyran-functionalized poly(terthiophene)s and investigated their electrochemical and photochemical properties. The spiropyran unit is covalently linked to the thiophene monomer, which is electropolymerized. The resulting film is electroactive and shows multiswitchable behavior. The spiropyran incorporated into the polymer backbone leads to multiple colored states as a result of both photochemical and electrochemical isomerization of the spiropyran to merocyanine, as well as electrochemical oxidation of the poly(terthiophene) backbone and the merocyanine substituents [1]. This unique multichromophoric and multiswitchable polymer system provides an exciting platform for the development of future materials that can exploit the other physical and chemical properties of spiropyrans and merocyanines such as variation in hydrophobicity, ion and molecular complexation, and conformational effects leading to polymer actuation. [1]. K. Wagner, R. Byrne, M. Zanoni, S. Gambhir, L. Dennany, R. Breukers, M. Higgins, P. Wagner, D. Diamond, G.G. Wallace, D.L. Officer. J. Am. Chem. Soc. 2011, 133, 5453-5462
12:00 PM - V2.3
Property Control of Polyimides Film for Substrates.
Sangmo Kim 1 , Youngsuk Jung 1 , Jungha Chae 1
1 , samsungelectronics, Yongin-si, gyeonggi-do, Korea (the Republic of)
Show AbstractWe have controlled the optical and thermal properties of polyimide films prepared from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) diamine and two dianhydrides, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), and 3,3',4,4‘-biphenyltetracarboxylic dianhydride (BPDA) by copolymerization methods. However, to obtain polyimide blends, the mixing of BPDA/TFDB and 6FDA/TFDB polyamic acid solution fails to become a homogeneous solution. The thermal properties of the copolyimide films are enhanced with increasing BPDA/TFDB content. Especially, the coefficient of thermal expansion (CTE) can be controlled between 18.4 x 10^-6 and 51.1 x 10^-6 C by copolymerization methods. On the other hand, the optical properties, transmittance, yellow index, etc. are improved with increasing 6FDA/TFDB content in the copolyimides. The transmittance was improved from 87% to 90% and Yellow Index (YI) values could be reduced from 5.5 to 2.0. The refractive index decreases with increasing 6FDA/TFDB content in the copolyimides and the in-plane refractive index values are higher than the out-of-plane refractive index value. The in-plane and out-of-plane refractive index can be controlled by copolymerization techniques from 1.66 to 1.56 and from1.59 to 1.54 at 633nm, respectively.
12:15 PM - V2.4
Triple-Shape Effect of Copolymer Networks.
Marc Behl 1 2 , Jörg Zotzmann 1 2 , Yakai Feng 2 3 , Andreas Lendlein 1 2
1 Center for Biomaterial Development and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 , Tianjin University - Helmholtz-Zentrum Geesthacht Joint Laboratory for Biomaterials and Regenerative Medicine , Teltow Germany, 3 School of Chemical Engineering and Technology, Tianjin University, Tianjin China
Show AbstractShape-Memory polymers are an emerging class of functionalized materials, which are able to change their change in a predefined way upon appropriate stimulation.[1] Recently, multi-phase shape-memory polymers with an additional switching phase were introduced.[2] Such triple-shape polymers can perform two consecutive shape changes in response to heat. These shape changes correspond to the recovery of two different deformations in reversed order, which were programmed before at elevated temperature levels (Tmid and Thigh) by application of external stress.[3] The triple-shape functionality requires a phase-segregated morphology with pronounced physical crosslinking from both switching domains, which both contribute to the fixation of the applied deformations. Various polymer network architectures providing the triple-shape capability were investigated. A first system, called MACL, consisted of cyclohexylmethacrylate (CHMA) copolymerized with poly(ε-caprolactone)dimethacrylate (PCLDMA) as macro-crosslinker. The polymer network structure is formed by PCL and the PCHMA segments, which both are contributing to the overall elasticity of the polymer network. A second polymer network system, named CLEG, was prepared by copolymerization of PCLDMA and poly(ethyleneglycol)mono-methylethermethacrylate (PEGMA) (Mn = 1,000 g.mol-1, Tm = 38 °C).[4] In the resulting polymer network structure, the elasticity is mainly determined by the PCL segments, which are crosslinking polymethacrylate segments with dangling poly(ethyleneglycolmonomethylether) (PEG) chains. A third system consisted of a copolymer network based on star-shaped precursors of polypentadecalactone- and poly(ε-caprolactone)-segments crosslinked with a low molecular weight diisocyanate.[5] In this copolymer network both semicrystalline segments contribute to the overall elasticity. Here, we discuss the dual- and triple-shape behavior of the different polymer network architectures, which were investigated for various programming conditions. Surprisingly, certain polymer networks displayed an one-way triple-shape effect after an one-step deformation, some even after a deformation at ambient temperature (cold drawing).[5,6] References [1] M. Behl, M. Y. Razzaq, A. Lendlein, Adv. Mater. 2010, 22, 3388.[2] I. Bellin, S. Kelch, R. Langer, A. Lendlein, Proc. Natl. Acad. Sci. USA 2006, 103, 18043. [3] M. Behl, A. Lendlein, J. Mater. Chem. 2010, 20, 3335.[4] I. Bellin, S. Kelch, A. Lendlein, J. Mater. Chem. 2007, 17, 2885.[5] J. Zotzmann, M. Behl, Y. Feng, A. Lendlein, Adv. Funct. Mater. 2010, 20, 3583.[6] M. Behl, I. Bellin, S. Kelch, A. Lendlein, Adv. Funct. Mater. 2009, 19, 102.
12:30 PM - V2.5
Multi-Shape Memory, Temperature Memory, and Selective Actuations.
Tao Xie 1
1 Global R&D, General Motors, Warren, Michigan, United States
Show AbstractA shape memory polymer (SMP) traditionally refers to a polymer that can fix one temporary shape and recover to its permanent shape upon exposure to an external stimulus. Recent progress has led to SMPs capable of fixing multiple temporary shapes as well as temperatures. In this talk, I will first describe the multi-shape memory and temperature memory behaviors of Nafion, a material that is more commonly known for its proton conductivity instead of memory functions. The ever increasing polymer memory potential demands precise control on how the external triggers are applied. On this front, I will describe a multi-composite capable of sophisticated shape shifting beyond multi-shapes, via remote and selective RF actuations.
12:45 PM - V2.6
Shape-Memory Properties of Multiphase Grafted Polymer Networks with Crystallizable Poly(ε-caprolactone) Switching Segments in Aqueous Environments.
Karl Kratz 1 , Uttamchand Narendra Kumar 1 , Ulrich Noechel 1 , Andreas Lendlein 1
1 Centre for Biomaterial Development and Berlin-Brandenburg Center for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractThermo-sensitive multiphase polymer networks which are capable to exhibit a triple-shape effect have been introduced recently as a promising class of active polymers [1, 2]. Such polymers or magneto-sensitive nanocomposites thereof are able to change from a first temporary shape (A) to a second temporary shape (B) and from there to the original shape (C), when stimulated either by increasing the environmental temperature or the applied magnetic field [2, 3].In this study we explored whether dual-shape properties can be achieved for grafted multiphase polymer networks named CLEG containing water swellable poly(ethylene glycol) (PEG) side chains and crystallisable poly(ε-caprolactone) (PCL) segments acting as crosslinks, which were explored in a aqueous environment. CLEG with variable PCL contents ranging from 30 wt-% and 70 wt-% were synthesized by thermally-induced radical polymerization according to a previously reported method [4].The different polymer networks were investigated by swelling experiments using chloroform and water as solvents. The thermal and mechanical properties of pure and water swollen CLEG samples were investigated by means of DSC, DMTA and tensile tests. Furthermore, DSC and wide angle X-ray scattering was applied for exploring the crystallinity of the polymer networks. For quantification of the shape-memory properties bending experiments in aqueous environment and uniaxial tensile tests were conducted.The swelling capability of the CLEG polymer networks increased with increasing weight content of PEG, when exposed to an aqueous environment. The melting temperatures of the PCL crystalline domains were found at temperatures around 40 °C, whereby the overall crystallinity was strongly related to the PCL content in the CLEG polymer networks. Excellent dual-shape properties could be obtained in both bending and tensile-test experiments for CLEG materials with a PCL weight content >40 wt%, while all samples exhibited an almost identical characteristic switching temperature of Tsw = 46±1°C. References[1]M. Behl, A. Lendlein, Journal of Materials Chemistry 2010, 20, 3335.[2]I. Bellin, S. Kelch, R. Langer, A. Lendlein, Proceedings of the National Academy of Sciences of the United States of America 2006, 103, 18043.[3]U. Narendra Kumar, K. Kratz, W. Wagermaier, M. Behl, A. Lendlein, Journal of Materials Chemistry 2010, 20, 3404.[4]U. Narendra Kumar, K. Kratz, M. Behl, A. Lendlein, Mater. Res. Soc. Symp. Proc. 2009, 1190, 55.
V3/KK2: Joint Session: Cell-Biomaterials Interactions
Session Chairs
Andreas Lendlein
Kaiming Ye
Monday PM, November 28, 2011
Room 312 (Hynes)
2:30 PM - **V3.1/KK2.1
Micro- and Nanoscale Technologies for Stem Cell Bioengineering and Tissue Regeneration.
Ali Khademhosseini 1
1 Harvard-MIT HST, Harvard Medical School, Cambridge, Massachusetts, United States
Show AbstractMicro- and nanoscale technologies are emerging as powerful tools for mimicking cell microenevironment by controlling the interaction between cells and their surroundings and have been applied to biological studies, tissue engineering, and cell-based screening. In addition, hydrogel biomaterials have been increasingly used in various tissue engineering applications since they provide cells with a hydrated 3D microenvironment that mimics the native extracellular matrix. In this talk, I will discuss this emerging research area with a focus on our laboratory’s work on the application of microfabrication techniques to the manipulation of hydrogel biomaterials for directing stem cell differentiation and engineering 3D tissue with controlled microarchitecture. In addition, I will describe the fabrication and the use of microscale hydrogels for tissue engineering by using a ‘bottom-up’ and a ‘top-down’ approach. Top-down approaches for fabricating complex engineered tissues involve the use of miniaturization techniques to control cell-cell interactions or to recreate biomimetic microvascular networks within mesoscale hydrogels. Our group has also pioneered bottom-up approaches to generate tissues by the assembly of shape-controlled cell-laden microgels (i.e. tissue building blocks), that resemble functional tissue units. Using this approach, we have demonstrated the use of the directed assembly of cell-laden microgels to create complex tissue structures consisting of multiple cellular components.
3:00 PM - V3.2/KK2.2
Tissue and Disease-Specific Adhesive Materials.
Natalie Artzi 1 2 , Maria Carcole 1 3 , Nuria Oliva 1 , Sagi Shitreet 1 , Elazer Edelman 1 4
1 Health Sciences and Technology, MIT, Cambridge, Massachusetts, United States, 2 Anesthesiology , Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States, 3 Chemistry, Institut Quiimic de Sarria`, Universitat Ramon Llull, Barcelona Spain, 4 Cardiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States
Show AbstractTo avoid stress concentrations and tissue damage, nature often employs physical property gradients at interfaces between tissues with different functionality through subtle chemical variations. We hypothesized that within the three regions of the small intestine, variation in chemical composition serves as a mean to support the diverse functionality of these regions. Disease type and state would further alter tissue properties and alter the interaction of such tissue surfaces with implanted materials. Existence of chemical gradients takes increasing importance when designing adhesive materials that chemically interact with tissue surfaces to prevent leakage after surgeries by sealing and by providing mechanical support to the wounded tissue. Leakage of gut content is a frequent surgical complication that results in high morbidity and mortality. We designed tissue responsive adhesive materials by matching material and tissue properties. We used aldehyde-amine chemistry to determine if alterations in tissue surfaces (amine density in duodenum, jejunum and ileum) could affect interactions with materials of varied (aldehyde content and density) composition. A two component material based on dextran aldehyde and dendrimer amine provides cohesive gel through aldehyde-amine crosslinking, and adhesive interface by dextran aldehyde selective reaction with tissue amines. At the same time, material amines absorb excess non-reactive aldehydes and thus prevent toxicity. Adhesive strength varied dramatically with material chemistry and is tissue-specific. Tissue:material interfacial region changed when the same material composition was applied to the three small intestinal regions. These data support the notion that both tissue and material functional groups influence aldehyde-mediated adhesive interactions, providing a functional basis for tissue-specific sealant design. As disease state often alters tissue properties, we have analyzed the effect of colon inflammation and colon cancer on the interaction with our adhesive materials. The severity of the disease as well as type of disease have differently affected tissue properties, and in our case amine density, modifying both adhesion and cohesion strength of the materials employed. Amine groups are ubiquitous on tissue surfaces and their density varies from tissue to tissue and in diseased tissues to a different extent. By providing chemical key in the form of tethered aldehydes for specific tissue locks (tissue amines), we modulated adhesion while maintaining biocompatibility.
3:15 PM - V3.3/KK2.3
Self-Assembled Peptide-Based Hydrogels as Scaffolds for In Vitro Cell Culture.
Ayeesha Mujeeb 1 3 , Jie Gao 1 3 , Kate Meade 1 , Julie Gough 1 , Catherine Merry 1 , Aline Miller 2 3 , Alberto Saiani 1
1 School of Materials, University of Manchester, Manchester United Kingdom, 3 Manchester Interdisciplinary Biocentre, University of Manchester, Manchester United Kingdom, 2 School of Chemical Egineering and Analytical Sciences, University of Manchester, Manchester United Kingdom
Show AbstractNature has evolved a variety of creative approaches to many aspects of materials synthesis and microstructural control. One such approach is self-assembly, which represents a simple and efficient route to the construction of large, complex structures. De novo designed peptides are in particular attracting considerable interest due to their structural simplicity, diverse functionality and their ability to self-assemble into a variety of structures and form hydrogels.We have recently investigated the self-assembling and gelation properties of a series of ion-complementary peptides based on the alternation of non-polar hydrophobic and polar hydrophilic residues. In this work we focus on one specific octapeptides: FEFEFKFK (F: phenylalanine, E: glutamic acid, K: lysine) which has been shown to self-assemble in solution and form β-sheet rich nanofibres which, above a critical gelation concentration (CGC), entangle to form self-supporting hydrogels. (A. Saiani et al. Soft Matter, 5, 193, 2009). Here we show that this system can be used for the in-vitro culture of a variety of cells with different requirement: chondrocytes, fibroblast and stem cells showing the flexibility and versatility of the materials developed.Chondrocytes were cultures over 21 days in 3D conditions. Light microscopy and ESEM images revealed that the cells adopted a rounded morphology. Live-dead staining and collagen antibody-staining results show the presence of living chondrocytes and the production of mainly collagen II. The cell proliferation results demonstrated the scaffolds to be cytocompatible with the cells showing varying metabolic activity.Pluripotent embryonic stem (ES) cells have the unique capacity to form any adult cell phenotype. However, effective differentiation into organised tissue constructs is limited by current two dimensional (2D) culture techniques. In this work mouse ES cells containing an Oct4-GFP reporter construct were seeded within the octapeptide gels in 3D conditions. The cell grew into rounded aggregates and could be retrieved and directly passaged into fresh octapeptide gels and after a fifteen day culture period, consisting of three passages. Levels of Oct4-positive cells remained elevated through the passaging showing that the cells remained pluripotent.Fibroblast were culture on non-functionalised and “RGD”-functionalised hydrogel. Live/dead stained and cell counting showed an extensive proliferation of the cells in the functionalised hydrogel. Collagen and F-actin stained show the extensive production of matrix by the cells.By exploiting the simple self-assembly of short peptides we have developed a platform that allows to design “simple” 3D hydrogels for the culture of a variety of cell. The physical, in particular mechanical, properties and functionality of the hydrogels can be tailored by design to suit the cell cultured.
3:30 PM - V3.4/KK2.4
Biological Applications of Nanoparticle Modified Polyelctrolye Capsules.
Susana Carregal-Romero 1 , Markus Ochs 1 , Pilar Rivera Gil 1 , Wolfgang Parak 1
1 FB Physics, Biophotonics, University of Marburg, Marburg Germany
Show AbstractThe fabrication and engineering of three-dimensional delivery vehicles is one of the issues of the bio-nanotechnology field attracting increasing interest for a variety of different applications, ranging from drug delivery systems and targeted gene therapy to biosensor devices. Engineered polyelectrolyte multilayer (PEM) microcapsules offer a unique opportunity to combine surface multifunctionality with design flexibility for the delivery of encapsulated macromolecules into designated compartments and cells. Though several methods exist for delivering molecules inside cells, still the number of carrier systems which allow for controlled release of the molecules is limited. One major requirement is that the molecules which are going to be delivered are released only inside the target cells but not in the extracellular space. For this purpose these molecules can be for example encapsulated in a shell of a material which is enzimatically degraded inside the cell. Alternatively, the molecules to be delivered can also be encapsulated in a shell of a material which is responsive to external triggers. In this context, plasmon assisted photothermal processes provide a powerful tool for controlled release. Gold nanoparticles can be easily incorporated in PEM microcapsules. Due to their plasmonic resonance, metallic nanoparticles are able to absorb light and dissipate this energy into heat. The hereby created heat locally melts or ruptures the wall of the PEM microcapsules and the encapsulated molecules can be ralease. Release of different macromolecules conjugated with organic fluorophores from so-modified capsules has been studied via fluorescent microscopy and electron microscopy imaging.
3:45 PM - V3/KK2:CElMat
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4:15 PM - V3.5/KK2.5
Development of a Multifunctional Synthetic PEG-Based Hydrogel with Independent Control of Mechanical and Bioadhesive Properties to Probe Stem Cell Behavior.
Anirudha Singh 1 , Jianan Zhan 1 , Jennifer Elisseeff 1 2 3
1 Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Jules Stein Chair in Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States, 3 Department of Orthopedic surgery, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractMesenchymal stem cells (MSCs) hold great promise in tissue engineering because of their proliferative capacity and ability to differentiate into several phenotypes, and ultimately built new tissues. However, to enable translation of stem cell therapies, there is a significant need to generate materials that can be used to study fundamentals in biology and modulate or enhance differentiation. Poly(ethylene glycol) (PEG)-based hydrogels are frequently utilized to encapsulate cells in a 3D environment. Unfortunately, PEG based biomaterials lack functionality to incorporate multiple chemical and biological moieties as signals for stem cells to probe behavior and guide development. Conventional methods to modify PEG hydrogels include copolymerization and chain extension, which leads to changes in mechanical properties of the material. We therefore developed an advanced multifunctional hydrogel by combining PEG- and α-Cyclodextrin (α-CD). α-CD is a six membered oligosaccharide ring, which threads onto the PEG chains.[1] The hydroxyl groups of α-CD provide necessary functional sites to introduce various moieties, such as integrin-binding peptide RGD by chemical modifications. This simple strategy provides a unique ability to independently control mechanical and bioadhesive properties of the hydrogels to probe stem cell behavior. MSCs were seeded onto PEG-CD hydrogels with varying stiffness and adhesive peptide concentrations. We found that cell spreading and morphology are dependent on both stiffness[2] and concentrations of adhesive peptide. On the stiffer substrate, MSCs adopted elongated morphology at all the concentrations of RGD. Interestingly, on the softer substrate MSCs adopted elongated morphology at higher concentrations of RGD. In summary, we developed an interesting and simple biomaterial platform for probing stem cell behavior, such as proliferation and lineage specific differentiation by independently controlling the mechanical and bioadhesive properties of the material.References:1.A. Harada, J. Li, M. Kamachi, Nature, 1992, 356, 325-327.2.A.J. Engler, S. Sen, H.L. Sweeny, D.E. Discher, Cell, 2006, 126(4), 677-689.Acknowledgements:Maryland Stem Cell (TEDCO) fellowship, Dr. Mooney O. Uy, Cindy Berlinicke, JHE lab members.
4:30 PM - V3.6/KK2.6
Organic Conducting Polymers: A Multifunctional Stimulus Platform for Mammalian Cells.
Gordon Wallace 1
1 Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
Show AbstractOrganic conductors have emerged as being excellent candidates as platforms for mammalian cell culturing (1-4). Our recent studies demonstrate that this compatibility is dependent on the inherent nanostructure of ICP surfaces (5). Furthermore, the introduction of nanostructure via templates has been shown to enhance the ability of ICPs to provide electrically stimulated release of bioactive molecules at the interface (6).Organic conducting polymers provide a platform capable of delivering direct electrical stimulation to excitable cells such as nerve or muscle. In addition, they are capable of responding to electrical stimulation to provide triggered drug or growth factor release. They can also be configured to provide electromechanical effects, enabling the modulus to be tuned in response to electrical stimulation, and/or movement/force to be generated in response to electrochemical stimulation.This multifunctional behaviour is complex, being determined by the initial polymer composition, the nature of the electrochemical structures used and the operational environment (7-10). Understanding and controlling the different dimensions of this multifunctional behaviour is critical to the development of efficient platforms for mammalian cell culturing and then to the use of these materials in implantable medical bionic devices such as in electrodes for the bionic ear implant or as conduits for nerve or muscle regeneration.References1.Wallace, G.G., Moulton, S.E., Clark, G.M. Science 2009, 324 (5924), 185-186.2.Wallace, G.G., Moulton, S.E. Chemistry in Australia 2009, 76 (5), 3-8.3.Quigley, A.F., Razal, J.M., Thompson, B.C., Moulton, S.E., Kita, M., Kennedy, E.L., Clark, G.M., Wallace, G.G., Kapsa R.M.I. Advanced Materials 2009, 21 (43), 4393-4397.4.Razal, J.M., Kita, M., Quigley, A.F., Kennedy, E., Moulton, S.E., Kapsa, R.M.I., Clark, G.M., Wallace, G.G. Advanced Functional Materials 2009, 19 (21), 3381-3388.5.Gelmi, A., Higgins, M.J., Wallace, G.G. Biomaterials 2010, 31 (8), 1974-1983.6.Thompson, B.C., Chen, J., Moulton, S.E., Wallace, G.G. Nanoscale 2010, 2 (4), 499-501.7.Thompson, B.C., Moulton, S.E., Richardson, R.T., Wallace, G.G. Biomaterials 2011, 32, 3822-3831.8.Foroughi, J., Spinks, G.M., Wallace, G.G. Sensors and Actuators B: Chemical 2011, 155, 278-284.9.Halldorsson, J.A., Wu, Y., Brown, H.R., Spinks, G.M., Wallace, G.G. Thin Solid Films (In Press).10.Wagner, K., Byrne, R., Zanoni, M., Gambhir, S., Dennany, L., Breukers, R., Higgins, M., Wagner, P., Diamond, D., Wallace, G.G., Officer, D.L. Journal of the American Chemical Society 2011, 133 (14), 5453-5462.
4:45 PM - V3.7/KK2.7
Photocrosslinked Co-Networks with Multifunctional Properties Based on Glycidylmethacrylated Gelatin and Poly(Ethylene Glycol) Methacrylates.
Benjamin Pierce 1 , Axel Neffe 1 , Friedrich Jung 1 , Andreas Lendlein 1
1 Center for Biomaterial Development and Berlin-Brandenburg Center for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractBiopolymer-based systems with adjustable macroscopic properties, which can be varied in a wide range by only small changes in their chemical composition are promising candidate materials for biomaterial-induced autoregeneration. Such systems may be formed by functionalizing biopolymers with synthetic components to enable hybrid materials that can perform a variety of functions, such as cell attachment, which is enabled by the biopolymer component, segmented hydrolytic degradation kinetics, which is due to the presence of degradable biopolymers and non-hydrolyzable components, and dynamic load support, which is due to the synergistic properties of both components. To achieve such an array of functions, glycidylmethacrylated gelatin was photopolymerized with the addition of poly(ethylene glycol) (PEG) mono- or dimethacrylate to form co-networks in pH 7.4 PBS buffer solution. The crosslinking step was performed by employing an Excimer laser so that an addition of a potentially toxic photoiniator was not necessary. The tailorability and potential as a class of biomaterials were investigated by rheology, WAXS, tensile tests, DMTA, as well as water uptake and swelling properties. The networks exhibited Young’s moduli E = 1 – 192 MPa and helical contents <3% in the dry state at room temperature, Q = 243 – 1077 vol% and G’ = 0.7 – 145 kPa in 37 °C pH 7.4 PBS buffer solution. The mechanical properties of these materials in the swollen state at 37 °C were tailorable and in the low kPa range, which are applicable for biomaterials in regenerative therapeutic applications. An initial screening of their degradability was performed for the homonetwork and representative co-networks, which showed that the homonetwork degraded completely within 24 h, while the co-networks only partially degraded to materials that still contained gelatin fragments. While the eluates from the co-networks based on PEGMA (<25wt%) induced some morphological changes in L929 mouse fibroblasts, the eluates of the homonetwork and PEGDMA-based co-networks were well-tolerated by the cells, which indicated that this class of materials may be further studied as biomaterials.
5:00 PM - V3.8/KK2.8
Gelation Characteristics and Encapsulation of Stromal Cells in Star Acrylate-Functionalized Poly (Ethylene Glycol-co-lactide) Macromonomers.
Seyedsina Moeinzadeh 1 , Danial Barati 1 , Esmaiel Jabbari 1
1 Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractIntroduction: In situ crosslinkable hydrogels coupled with minimally invasive arthroscopic techniques are an attractive alternative for treating irregularly shaped or inaccessible defects. Polyethylene glycol (PEG) hydrogels have been used extensively to study the effect of bioactive factors in the microenvironment on cell function because PEG gels do not illicit an immune response and biomolecules retain their activity in PEG gels. However, PEG gels are not degradable, thus limiting their use for minimally invasive applications. In an attempt to develop degradable PEG-based hydrogels for cell encapsulation, multi-arm PEG was used as the polymerization initiator in ring-opening polymerization of L-lactide to produce degradable polyethylene glycol-co-lactide (SPEL) macromonomers. Next, the chain ends of the macromonomer are functionalized with reactive acrylate groups for is situ crosslinking. The objective of this work was to investigate gelation characteristics of star and linear acrylate-functionalized polyethylene glycol-co-lactide (SPELA and LPELA) macromonomers and viability of marrow stromal cells encapsulated in those macromonomers.Experimental: SPEL and LPEL were synthesized by ring-opening polymerization of L-lactide with 4-arm and 2-arm PEG, respectively, with 5 kDa molecular weight. Next, the chain ends were acrylated by the reaction of acryloyl chloride with the hydroxyl end-groups of the macromonomer. The macromonomers were crosslinked in aqueous solution by UV polymerization. The hydrogels were characterized with respect to gelation by rheometry, sol fraction, water content, degradation, and viability and osteogenic differentiation of bone marrow stromal (BMS) cells. BMS cells were isolated from the bone marrow of young adult male Wistar rats. The sol fraction of the 4-arm SPELA was significantly less than that of the linear LPELA for all concentration. Results: The numbers of lactides on each arm of the linear and star macromonomers was 3 and 3.7, respectively. The shear modulus of the hydrogels increased with the concentration of linear and star macromonomers. Both macromonomers had gelation times of < 60 s but the gelation time of SPELA was lower than that of LPELA. The shear modulus of the SPELA increased by 2.2 fold from 28 to 60 kPa as the macromonomer concentration was increased from 10 to 25%. For example, as concentration was increased from 10 to 25%, sol fraction of the star SPELA decreased from 13 to 5% while that of Linear LPELA decreased from 32 to 19%. Encapsulation experiments demonstrated that the SPELA hydrogel supports viability and osteogenic differentiation of BMS cells. Conclusions: Star SPELA macromonomer, due to the higher functionality and lower viscosity, produced hydrogels with higher modulus and lower sol fraction compared to the linear LPELA. SPELA macromonomer is potentially useful as a degradable carrier in cell-based minimally-invasive therapies.
5:15 PM - V3.9/KK2.9
Live Detection of Neural and Glioma-Derived Stem Cells by an Oligothiophene Derivative.
Shirin Ilkhanizadeh 1 , Rozalyn Simon 2 , Andreas Aslund 2 , Markus Back 2 , Ana Teixeira 3 , Peter Konradsson 2 , Johan Holmberg 3 , Per Uhlen 4 , Bertrand Joseph 5 , Peter Nilsson 2 , Ola Hermanson 1
1 Dept Neuroscience, Karolinska Institutet, Stockholm Sweden, 2 IFM, Dept Chemistry, Linkoping University, Linkoping Sweden, 3 CMB, Karolinska Institutet, Stockholm Sweden, 4 MBB, Karolinska Institutet, Stockholm Sweden, 5 CCK, Karolinska Institutet, Stockholm Sweden
Show AbstractThe development of molecular probes for non-invasive live detection of specific cell types is a critical issue in cancer and stem cell biology. Here we report the synthesis of a luminescent conjugated oligothiophene (LCO), named p-HTMI, which could be used in conventional microscopy for near instant real-time detection of live embryonic neural stem cells, but not other types of stem cells, differentiated cells, or cancer cells investigated. Interestingly, whereas p-HTMI stained only a fraction of glioma cells in culture, 100% of glioma-derived stem cells were stained. The completely opposite result was obtained with a LCO having an alternative side chain functionalization. Cell sorting experiments proved that neural and glioma-derived stem cells could be specifically detected in samples of mixed cell types. p-HTMI is functionalized with a methylated imidazole moiety resulting in a structure similar to methylated histidine/histamine and importantly non-methylated analogues did not show the same characteristics. We propose that LCOs with distinct and defined side chain functionalities represents a novel generation of molecular probes for immediate and specific detection of specific stem and cancer cell types.
5:30 PM - V3.10/KK2.10
Injectable Solid Peptide Hydrogel as Cell Carrier: Effects of Shear Flow on Hydrogel and Cell Payload.
Congqi Yan 1 , Michael Mackay 1 , Joel Schneider 2 , Darrin Pochan 1
1 Materials Science and Engineering, Delaware Biotechnology Institute, University of Delaware, Newark, Delaware, United States, 2 Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States
Show AbstractPeptides were designed to fold into β-hairpins once they are exposed to physiological conditions and then subsequently self-assemble into a rigid hydrogel with a network structure of branched and entangled, 3nm-wide fibrils. These physical hydrogels can be injected as preformed solids, because they can shear-thin and consequently flow under an appropriate shear stress but immediately recover back into solids on removal of the stress with gel stiffness restoring over time. These properties suggest that it is possible to deliver the hydrogel construct with a desired encapsulated therapeutic payload toward an in vivo site by syringe injection. In this work, mechanisms of gel shear-thinning and immediate recovery were elucidated by investigating gel behavior during and after flow via mechanical and structural characterizations. Importantly, hydrogel flow behavior was studied in a capillary geometry that mimicked the actual situation of syringe injection. Hydrogel flow profiles were obtained via fluorescent particle tracking and the profile shape was found dependent on flow rate and gel stiffness. Also living cells were 3D encapsulated in hydrogel and then injected via the same capillary geometry. Flow profile for cellular delivery was investigated and live-dead assay was performed to evaluate effects of flow rate on encapsulated cells. The results demonstrate that these hydrogels can be excellent candidates for tissue regeneration substrates and injectable therapeutic delivery vehicles.
Symposium Organizers
Andreas Lendlein Institute of Polymer Research
Yakai Feng Tianjin University
Tao Xie General Motors Research and Development Center
Zhibin Guan University of California-Irvine
V4: Multifunctional Surfaces and Interfaces II
Session Chairs
Tuesday AM, November 29, 2011
Room 312 (Hynes)
9:15 AM - **V4.1
Direct Write 3-Dimensional Nanopatterning Using Thermodynamically Unstable Polymers.
Urs Duerig 1 , Felix Holzner 1 , Philip Paul 1 , Michel Despont 1 , Armin Knoll 1 , Jim Hedrick 2
1 , IBM Reserach - Zurich, Rueschlikon Switzerland, 2 , IBM Research - Almaden, Almaden, California, United States
Show AbstractA novel probe patterning method based on the local evaporation of organic resist materials been developed [1-3]. A three dimensional relief pattern is written directly into the resist without the need for a development step. The technology has a number of unique attributes: High resolution patterning capability compatible with the requirements of future transistor technology; high patterning speed comparable to electron beam lithography high resolution EBL, and direct writing of three dimensional relief structures with nm precision, which is not possible with any other technology. Virtually without exception, glassy organic materials, and in particular polymeric materials, can be readily mechanically deformed on the nanometer scale by applying a suitable force and temperature stimuli. The deformation is volume preserving and reversible which severely constrains the shapes that can be written. Ideally, one would like to locally remove the material which would allow one to sculpture arbitrary relief shapes using the probe tip as a chisel. In order to achieve this, the organic resist needs to be decomposed in low molecular weight fragments which can easily evaporate at the hot tip. Because of the high activation energies involved in the breaking of chemical bonds, the overall process is inefficient, however. The problem can be overcome by resorting to thermodynamically unstable polymers, such as for example poly-phthalaldehyde. Here, an entire polymer chain spontaneously unzips into the monomer units if just one bond in the back-bone is opened. Phthalaldehyde polymers, which we use in our studies, have a long but almost forgotten history for lithographic applications. The generic chemistry is amenable to modifications yielding a wide range of physical properties such as etch resistance or thermal stability. From the point of view of nano-patterning it is essential to understand the kinetics of the unzip mechanism. We discovered that the decomposition is governed by two processes. Approximately 50% depolimerization occurs simultaneously with the glass to liquid transition of the polymer. Complete depolymerization is achieved in a second process which is triggered over a wide temperature range above the glass temperature. For our probe patterning we target low temperatures for the overall decomposition process by fine tuning the glass transition temperature with additives and by facilitating the second decomposition process using thermally activated protonic accelerators. [1] David Pires, James L. Hedrick, Anuja De Silva, Jane Frommer, Bernd Gotsmann, Heiko Wolf, Michel Despont, Urs Duerig, and Armin W. Knoll, Science 328, 732-735 (7 May 2010).[2] Armin W. Knoll, David Pires, Olivier Coulembier, Philippe Dubois, James L. Hedrick, Jane Frommer, Urs Duerig, Adv. Materials 22, 3361-3365 (2010).[3] Philip C. Paul, ArminW. Knoll, Felix Holzner, Michel Despont and Urs Duerig, Nanotechnology 22, 275306 (2011).
9:45 AM - V4.2
New Composite Microstructured Surfaces with Different Response Modalities: Towards Efficient Self-Regulating Chemo-Mechano-Chemical Transduction.
Ximin He 1 2 , Ankita Shastri 3 , Philseok Kim 1 , Lauren Zarzar 3 , Ronn Friedlander 2 , Michael Aizenberg 1 , Joanna Aizenberg 1 2 3
1 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States, 2 School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, United States, 3 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Show AbstractWe are working towards creating dynamically reconfigurable surfaces that interconvert chemical and mechanical energy and thereby, exhibit adaptive and self-regulating behavior. The inspiration for these studies comes from the stunning sensitivity and efficiency of such biological structures as the cilia on single cells, the pedicellaria and spines on the skin of echinoderms and sensors on the legs of spiders. These high-aspect-ratio, hair-like structures act as mechanochemical receptors that can extract meaningful information from a noisy environment, and allow the organisms to respond, adapt and move essentially instantaneously. We will present our latest achievements in designing biomimetic analogs of such systems. In particular, we investigate composite microstructured surfaces in which mechanical input from chemical reactions in hydrogels that respond to various physical and chemical stimuli (temperature, light, pH, chemical reactions) is coupled with concerted movement of arrays of synthetic high-aspect-ratio structures. We are exploring a range of chemical transformations that are compatible with such mechanochemical transduction and we will report on the progress made towards developing responsive systems with positive feedback, based on inorganic, organic and biochemical reactions. By designing systems that translate a small-scale input into a large-scale motion and programmable self-organization, we aim at creating new, energy-efficient, environmentally-responsive materials for a variety of applications - from tunable smart surfaces and chemical sensing devices to micropumps and switches for microfluidics systems.
10:00 AM - V4.3
Superhydrophobic Hierarchical Polymer Surfaces via Single-Step Solvent-Induced Crystallization.
Yuehua Cui 1 , Adam Paxson 1 , Katherine Smyth 1 , Kripa Varanasi 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractSuperhydrophobic surfaces are widely present in nature and have inspired a significant body of research due to their wide range of applications including self-cleaning, drag reduction, and droplet impact resistance. Although synthetic superhydrophobic surfaces are now prevalent, their means of manufacture often are expensive and time-consuming, or require exotic materials and tools. Here we report on a rapid, single-step method using simple materials to produce large-area superhydrophobic surfaces via acetone-induced phase transformation of polycarbonate. Crystallization of the polymer leads to the formation of a hierarchical structure composed of microporous spherulites covered with nano-fibrils, and results in superhydrophobic wetting behavior. We systematically investigate the influence of the solvent treatment time on the surface morphology and wettability of the polycarbonate and outline the mechanism of structure formation. The resulting surfaces exhibit high contact angles, low contact angle hysteresis, and complete dewetting during droplet impact. Theoretical analysis of the wetting and anti-wetting pressures show that the nano-scale morphology is critical for achieving droplet impact resistance. This simple phase transformation approach could be more broadly applied to other solvent-polymer systems for fabricating large-area hierarchical surface textures.
10:15 AM - V4.4
Study on Fluorine-Containing Block Copolymers Designed for Top-down and Bottom-up Lithography: Synthesis, Morphology and Fabrication of Integrated Nanopatterns.
Rina Maeda 1 , Teruaki Hayakawa 1 , Christopher Ober 2
1 Organic and Polymeric Materials, Tokyo Institute of Technology, Tokyo Japan, 2 Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show Abstract Advances in nanoscience and nanotechnology increasingly rely on the availability of wide variety of objectives in nanometer-scale resolution. One proposed pathway to achieving desired objectives with high resolution involves combining “bottom-up” self-assembly approaches and conventional traditional “top-down” lithographic processes. Because self-assembly alone is sufficient for fabrication of simple periodic structures in nanometer-scale high resolution but insufficient for making complex structures easily attainable by “top-down” lithographic processes. We are focusing on designing polymeric resist materials which are patternable through both conventional lithography and self-assembly techniques. In this study, a new series of fluorine-containing block copolymers of poly(styrene-block-2,2,2-trifluoroethyl methacrylate) (PS-b-PTFEMA) and poly[styrene-block-(methyl methacrylate-co-2,2,2-trifluoroethyl methacrylate)] (PS-b-(PMMA-co-PTFEMA)) which can be applied for both top-down and bottom-up lithography was developed. PTFEMA is known as one of the most sensitive positive-tone resist polymers degradable under deep-UV, e-beam and X-ray while PS is crosslinked. Thus, it is envisaged integrated patterns can be obtained by combination of top-down methods as well as bottom-up methods. The block copolymers were synthesized by anionic polymerization. Morphological studies in bulk and thin films were carried out by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and revealed the formation of highly ordered self-assembled structures. Highly lateral ordering of arrays of dots was observed in the thin films of PS-b-PTFEMS in which PS was minor block and the thin film of PS-b-(PMMA-co-PTFEMA) in which PS was major block. The thin film of PS-b-PTFEMS was applied to conventional lithography of e-beam and deep-UV to generate integrated patterns. Integrated patterns like “dots within lines” (~20 nm diameter of crosslinked PS hexagonally ordered dots within several hundreds of nanometers width of lines arbitrary drawn by e-beam) were successfully obtained from combination of highly lateral ordering by self-assembly of the fluorine-containing block copolymers and selective degradation followed by washing of fluorine-containing block domains under e-beam. We promise these polymeric resist materials designed based on novel concept open a much wider window for advanced lithographic patterning by efficiently implementing both top-down and bottom-up approaches.
10:30 AM - V4: MfSaI2
BREAK
V5: Multifunctional Biomaterials
Session Chairs
Tuesday PM, November 29, 2011
Room 312 (Hynes)
11:00 AM - V5.1
A New Way to Nanostructure Hydrogels: Electrospun Thermoresponsive Islands-in-Sea Nanofibers.
Jing Wang 1 , Alessandra Sutti 1 , Xungai Wang 1 , Tong Lin 1
1 Institute for Technology Research and Innovation, Deakin University, Waurn Ponds, Victoria, Australia
Show AbstractIslands-in-the-sea nanofibres are a very interesting system: one polymer (islands) is distributed in fibrillar domains within a second polymer (sea). This fibre geometry is often used in microfiber technologies to obtain very fine fibers, by removing the “sea” polymer. This geometry also allows to combine two polymers with very different properties. In this work this geometry is introduced applied to electrospun hydrogel nanofibers, in a novel fashion, and as a way to improve and stabilize the hydrogel nanofibers. Thermo-responsive islands-in-the-sea nanofibers are here produced by electrospinning solutions of a hydrogel-forming thermo-responsive polymer (crosslinked poly(N-isopropylacrylamide), PNIPAM) and a reinforcing polymer (polyetherketone cardo, PEK-c). The two polymers are thermodynamically incompatible in solution and phase separation takes place, which allows the instant formation of islands-in-the-sea nanofibers upon electrospinning. PNIPAM was then crosslinked post-spinning using an oligomeric silsesquioxane.The formed nanocomposite nanofibers showed intrinsic nanostructure, where the fibril-like PNIPAM domains are intimately adjacent to the strong PEK-c domains.Upon contacting with water, the hydrogel domains became instantly highly swollen, while the PEK-c domains did not. As a result, very wrinkly, swollen fibers were obtained, with increased capillary action, as demonstrated through confocal microscopy. The composite nanofibers in water showed excellent swelling ratios and very fast responses to temperature variations (of the order of 1 second) with morphological and optical effects: variations in fiber-diameter were accompanied by optical transitions: transparent-opaque. The produced hydrogel nanofibers also presented improved mechanical properties (even with small amounts of PEK-c), when compared to their crosslinked-PNIPAM-only nanofibers. It will be also shown how these materials can be used as optical actuators and smart hydrogel platforms with tuneable contact angle and morphology. In brief, this work aims to demonstrate a new platform technology which can be applied to several hydrogel systems, to achieve hydrogel-based composites with new and improved properties, while retaining (and improving) the main properties of the hydrogel. Here this was demonstrated by showing that the composite materials showed thermo-responsiveness, and enhanced transition kinetics.
11:15 AM - **V5.2
Apatite/Collagen Scaffolds for Bone Tissue Regeneration.
Xiaohua Yu 1 , Zengmin Xia 1 , Liping Wang 2 , Xi Jiang 2 , Fei Peng 1 , Jianping Huang 2 , David Rowe 2 , Mei Wei 1
1 Department of Chemical, Materials, and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States, 2 2Department of Reconstructive Sciences,, University of Connecticut Health Center, Farmington, Connecticut, United States
Show AbstractRecently, tissue engineering approaches combing cells with appropriate scaffolds with/without osteogenic agents to regenerate bone has demonstrated to be a promising method to address this clinical problem. The regeneration of functional tissue-engineered bone requires an adequate source of healthy expandable cells, optimum scaffolds, tissue-stimulating compounds, and an efficient method to deliver these molecules to targeted tissues. In this process, the architecture and geometry of scaffolds and progenitor cell sources play critical roles in bone tissue engineering. In the present study, scaffolds with different architectures: lamellar (LS) and cellular (CS) collagen/apatite scaffolds were prepared by a one-step co-precipitation and freeze-drying technique. In addition, four different cells were chosen as the cell source, including mouse calvarial cells (mCalv), bone marrow cells (BMC), mCalv+ BMC, bone marrow stromal cells (BMSC). The effect of scaffold structure on new bone formation was evaluated by a two-hole mouse calvarial model loaded with osteogenic cells. The progenitor cells were loaded into both types of scaffolds and transplanted into calvarial defects for two and four weeks to assess new bone formation in different cell/scaffold combinations. Transgenic mice harboring GFP reporters for early-stage osteoblasts (pOBCol3.6GFPcyan and topaz) were used to differentiate the contribution of host/donor cells to new bone formation. Our results showed that the calvarial defects were fully filled by woven bone after 4 weeks of implantation when osteoprogenitor cells present in the scaffold. For both donor mCalv and BMSC loaded onto the two types of scaffold, earlier bone formation was observed in defect loaded with LS compared to CS. Cortical-like bone was formed in the defect filled with LS while trabecular-like bone was observed in the defect filled with CS. BMSC has enhanced bone marrow and vascular reconstruction capacity in the defects compared to mCalv. With the participation of GFP reporter on osteoblasts, we also found BMSC was capable to induce better host integration due to the hematopoietic cell population in BMSC. Ingrowth of host derived bone into the lamellar structure of the scaffold was also observed when only bone marrow cell was loaded onto the scaffold. This study successfully demonstrated the appropriate scaffold architecture can better guide new bone formation, and the structure of the newly formed bone can adapt to the structure of the scaffold. Also, it has successfully demonstrated the importance of cell source in bone tissue engineering. The application of transgenic mice provided us with a powerful tool to appreciate the mechanism of new bone regeneration.
11:45 AM - **V5.3
Engineering Functional Surfaces.
V. Prasad Shastri 1 2
1 Institute for Macromolecular Chemistry, University of Freiburg, Freiburg Germany, 2 BIOSS-Center for Biological Signalling Studies, University of Freiburg, Freiburg Germany
Show AbstractThe role of polymeric materials in life sciences has evolved over the decades from that off a cheap raw material to make disposable lab ware to being the cornerstone of a new generation of materials that borrow from nature in both design and function. One of the design criteria of this new generation of biomaterials is their ability to interact, interrogate and influence the biological environment at the cellular level. In this context the physicochemical characteristics of the biomaterial surface become extremely important. Surface properties such as topography, elasticity, and in the case of polymer based systems-molecular mobility; can manifest itself as changes in the biology of the interface. This in turn can result in biomaterial-induced changes to the immediate microenvironment such as denaturation and activation of proteins, initiation of signaling cascades and unexpected cell fate choices. In this context, the engineering of a biomaterial surface at length-scales that are relevant to cellular processes are highly relevant. Over the past decade we have developed novel strategies for nano-scale engineering surfaces to bear both chemical and physical information that can impact device performance and cell function. The impact of these systems on directing cell fate, targeted and localized delivery of therapeutics and imaging will be discussed.
12:15 PM - V5.4
Knowledge-Based Design and Tailoring of Gelatin-Based Hydrogels by Functionalization with Tyrosine-Derived Groups.
Axel Neffe 1 2 , Alessandro Zaupa 1 2 , Benjamin Pierce 1 , Andreas Lendlein 1 2
1 Center for Biomaterial Development and Berlin-Brandenburg Center for Regenerative Therapies (BCRT), Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 Institute of Chemistry, University of Potsdam, Potsdam-Golm Germany
Show AbstractGelatin-based materials have raised interest as biomaterials substituting the extracellular matrix in regenerative medicine applications, combining degradability with cell adhesion sites. However, for such demanding applications, control over mechanical properties of the materials is necessary. The sol-gel transition of native gelatin-based hydrogels is observed because of the formation of triple helical protein chain superstructures which function as netpoints. This process is slow at room temperature but thermodynamically favoured and therefore results in changing material properties. Controlling the material properties of gelatine-based material is only possible when the helix formation is controlled and, beneficially, defined netpoints are formed. For the knowledge-based design of physically crosslinked gelatine-based gels with defined netpoints, we have developed molecular models of gelatin as amorphous material with different water contents, comparing pure gelatin with gelatin functionalized with tyrosine-derived groups, which can potentially interact via π-π interactions and hydrogen bonds. The models were validated by comparison of the calculated structural properties with experimental data and were then used as predictive tools to study chain organization, cross-link formation, and estimation of mechanical properties. The models showed an increasing number of physical crosslinks by increasing the number of aromatic rings, leading to about six times lower swelling. Experimental proof of the predicted behaviour was gained by studying mechanical behaviour at different water contents and after different processing with tensile tests and rheological measurements, and materials with e.g. Young’s moduli of 4-700 kPa were synthesized. Furthermore, changes of thermal transition temperatures (TM-DSC), as well as swelling behaviour could be related to material composition and triple helical content. Initial biological evaluation of the materials (e.g. in a HETCAM test) was positive. The introduced tyrosine-derived moieties were furthermore used to increase the stability of composites with hydroxyapatite through supramolecular interactions, whereby materials were received which displayed Young’s moduli of up to 2 MPa, tensile strengths of up to 1.1 MPa, and a gel-sol-transition temperature of > 85 °C. The knowledge-based design enabled the development of physical-crosslinked gelatins with defined netpoints and high potential for biomedical applications.
12:30 PM - V5.5
Biomimetic Modular Design of Polymers for Dynamic Properties.
Aaron Kushner 1 , Zhibin Guan 1
1 , University of California, Irvine, California, United States
Show AbstractUnder eons of evolutionary and environmental pressure, biological systems have developed strong and lightweight peptide-based polymeric materials, using the twenty naturally occurring amino acids as principal monomeric units. These materials outperform their man-made counterparts in the following ways: 1) multi-functionality/tunability, 2) adaptability/stimuli-responsiveness, 3) ambient and aqueous synthesis and processing, and 4) recyclability and biodegradability. The universal design strategy enabling these advanced properties involves modular and hierarchical organization both within and across multiple length scales. Given the current environmental pressures facing our society, it is imperative that we incorporate into our synthetic materials the advantages found in natural systems. One research thrust in our group is the design of advanced soft materials by mimicking biological systems. In this presentation, we will discuss what has been discovered about the structure and molecular mechanisms of natural modular polymers, as well as the progress towards synthetic “mimics” of these remarkable modular systems. A major contrast between natural and synthetic macromolecules is that the latter usually lack well-defined high order structures. Following Nature's strategy, we are introducing weak molecular forces into synthetic macromolecules to guide the formation of high order structures. In one example, using spider silk and β-amyloid fibers as models, we have created synthetic polymers that fold into extensive beta-sheets and self assemble into nanofibrils. In another example, by mimicking skeletal muscle protein titin, we have designed multidomain polymers having tandem arrays of modules folded by well-defined hydrogen bonds. Drawing various inspirations from Nature, we are programming covalent and subtle non-covalent molecular forces to create a plethora of biomimetic materials showing dynamic, responsive, shape-memory, and self-healing properties.
V6: Liquid Crystalline Polymers I
Session Chairs
Tuesday PM, November 29, 2011
Room 312 (Hynes)
2:30 PM - V6.1
Self-Assembly of Stimuli Responsive Pentablock Copolymers Containing Liquid Crystalline Moiety in Solution.
Rubinder Kaur Lakhman 1 , Yuxiang Zhou 2 , Rajeswari Kasi 1 2
1 Institute of Materials Science, Polymer Program, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractStimuli responsive polymers that respond to multiple stimuli like temperature, magnetic field, electric field, light and pH have been a subject of interest since many years. These materials find applications in fields of actuators, shape memory devices, artificial muscles and vehicles for delivery of drugs and other encapsulated agents. In our contribution, we aim to investigate the unique self assembly of liquid crystalline (LC) motif and block copolymer that have stimuli responsive groups and bioactive cues incorporated in them. In aqueous solution these systems will self assemble at different hierarchical length scales due to microphase separation, LC behavior and solvent interactions to give exotic structures. In our work, we have also prepared a series of complex pentablock copolymers by using RAFT polymerization, which contains PEO, polymethacrylate bearing side-chain cholesteryl mesogens (PC5MA) and poly(acrylic acid) (PAA) in the sequence of PAA-PC5MA-PEO-PC5MA-PAA. These amphiphilic LC block copolymers, when dispersed in an aqueous solution of magnetic nanoparticles (MNPs), self-assemble to form multilayered hierarchically-structured spherical micelles encapsulating MNPs. Freeze-drying the resulting micellar solutions results in polymer/MNP nanocomposites, which can swell in water to give free-standing magnetic hydrogels with thermotropic LC domains and MNPs functioning as dual physical crosslinkers. In the future, by replacing MNPs with other type of nanoparticles like TiO2 these materials could also be targeted for solar cell applications. Work in progress includes synthesis of a biocompatible and biodegradable pentablock copolymer PAA-b-PLA(Ch)-b-PEO-b-PLA(Ch)-b-PAA, where PLA(Ch) is a polyacrylate block grafted with side-chain polylactide (PLA) containing a cholesteryl pendant. This carefully designed pentablock copolymer contains PLA-b-PEO-b-PLA segments which is known to show a LCST behavior around body temperature, cholesterol which can function as a bioactive cue to increase cell affinity, and PAA which is used for anchoring magnetic nanoparticles. Free standing hydrogels containing MNPs can be prepared with this polymer, which can display multi-responsive behavior as well as biocompatibility and biodegradability. Along with inorganic nanoparticle, this scaffold can be used to template proteins and DNA based particles as well. In summary this study offers a promising and general approach on including various nanoparticles into a multi-functional amphiphilic block copolymer, which can lead to hierarchically-structured hybrid hydrogel systems with tailorable stimuli response.
2:45 PM - V6.2
Reflective/Diffractive Fibres for Smart Textiles Applications.
Olivier Picot 1 , Mian Dai 2 , Ton Peijs 1 , Kees Bastiaansen 2
1 , Queen Mary University of London, London United Kingdom, 2 , Technische Universiteit Eindhoven, Eindhoven Netherlands
Show AbstractSmart textiles represent the next generation of fibres, fabrics and the articles produced from them. Recent research has been focused on the creation and intoduction of new functionalities into textile fibres, wovens and non-wovens to generate specific properties for a broad range of potential applications. Within this context, this work aims at changing the perception of the textiles. Traditionally, inorganic or organic dyes are used to produce colours in textiles which are based on absorption of light. Here, novel techniques to obtain visual effects based on diffraction and/or reflection of visual light are developed. The concept is based on a bi-component fibre system where a fibre (natural or synthetic) is coated with a functional layer which gives the new properties to the fibre. Here reflective fibres are successfully produced using chiral nematic liquid crystal coatings on PET monofilament and multi-filament. Chiral nematic thin films have unique properties such as selective wavelength reflection as well as selective polarization and angular dependence which give new optical properties to the fibre. Diffractive fibres are also produced but in a two-step method. First a PET fibre is coated with a photopolymer. Then periodic relief structures on the surface of the fibre are generated by photo-embossing. Both the production of reflective and diffractive fibres will be presented, and there specific properties evaluated.
3:00 PM - **V6.3
Self-Assembly Mediated by Arene-Perfluoroarene Interaction: Solid State Reaction, Gel and Liquid Crystalline Phase Formation.
Yuguo Ma 1
1 Chemistry, Peking University, Beijing China
Show AbstractThe noncovalent interactions between arenes and perfluorinated arenes are mainly attributed to dispersion and quadrupolar interactions. The alternative face-to-face stacking feature of the arene-perfluoroarene system has attracted much recent attention due to the exhibited unique properties. By introducing arene and perfluoroarene moieties and harnessing such specific face-to-face stacking motif in designed molecules, a 1,3-dipolar cycloaddition between azide and alkyne proceeded in the crystals at room temperature in the absence of copper(I) catalyst, and the reaction was confirmed to be a highly regioselective process giving 1,4-triazole product.[1] In addition, facilitated by arene-perfluoroarene interaction in such designed molecules, acid-responsive gel formation from low molecular weight gelator can be achieved. Taking advantage of the facile cleavage of the imine bond in the gelator, gel-sol transition was realized in the presence of catalytic amount of acid. Study on structurally different arene-perfluoroarene based gelators and their non-perfluoroarene containing analogue suggested that the arene-perfluoroarene interaction played a critical role in aggregation of such gelators. In the bulk state, due to similar interaction, formation of the columnar liquid crystalline phase has also been achieved.[2] References [1] B.-B. Ni, C. Wang, H. Wu, J. Pei, Y. Ma, “Copper-Free Cycloaddition of Azide and Alkyne in Crystalline State Facilitated by Arene-Perfluoroarene Interaction”, Chem. Commun. 2010, 46, 782.[2] H. Wu, B.-B. Ni, C. Wang, F. Zhai, Y. Ma, “Self-Assembly Mediated by Arene-Perfluoroarene and Hydrogen Bonding Interactions: Oblique Columnar Liquid Crystal and Acid-Responsive Organogel”, Submitted.
3:30 PM - V6.4
Optically Directing out-of-Plane Shape Adaptations in Azobenzene Functionalized Liquid Crystalline Polymer Networks.
Timothy White 1 , Kyung Min Lee 1 2 , Matthew Smith 1 3 , Richard Vaia 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States, 2 , Azimuth Corporation, Dayton, Ohio, United States, 3 , NRC, Dayton, Ohio, United States
Show AbstractWireless reconfiguration of photoresponsive polymeric materials can offer a number of distinct advantages in aerospace and medical applications. Our group has synthesized and examined a variety of azobenzene-functionalized liquid crystal polymer network materials and examined their resulting photomechanical output. Typical outputs have been observed as in-plane bending of a cantilever or uniaxial contraction of a thin film. Only recently have out-of-plane deformations been reported. This presentation will describe our recent work in optically directing and optically fixing complex shapes, such as left-handed or right-handed coils, in glassy azobenzene-functionalized polymer networks both in static and oscillatory cases.
3:45 PM - V6: LCP 1
BREAK
V7: Micro-/Nanostructured Systems I
Session Chairs
Tuesday PM, November 29, 2011
Room 312 (Hynes)
4:15 PM - V7.1
Controllable Assembly of Magnetic Janus Particles.
Bin Ren 1 , Jung Hun Song 1 , Ilona Kretzschmar 1
1 Chemical Engineering, City College of New York, New York, New York, United States
Show AbstractMagnetic nanoparticles have potential applications in position sensing, ultrahigh density magnetic storage media, clinical diagnosis and treatment, biological labeling, and separation applications. However, their use is hampered by non-specific aggregation due to the interaction of their magnetic moments. Janus particles with magnetic caps have a distinct advantage over symmetric particles. They exhibit an asymmetric magnetization that makes them suitable building blocks for directed three-dimensional assembly under the exposure of external magnetic fields. Here, we present a study of the preparation and assembly behavior of iron oxide capped Janus particles in a magnetic field. Iron oxide capped Janus particles are prepared via deposition of iron onto a polystyrene particle monolayer using physical vapor deposition in an oxygen/argon atmosphere. Subsequently, the modified particles are exposed to a magnetic field and the iron oxide Janus particle assembly is followed over a 30 min period. Three assembly behaviors are observed: (i) staggered chains, (ii) double chains, or (iii) no assembly. We will report on the changes observed in the assembly behavior as a function of deposition rate, iron oxide cap thickness, particle volume fraction, and assembly time. A diagram will be presented relating deposition rate and assembly behavior. In addition, we will show scanning electron microscopy data giving insight in the detail of the chain structure and convective chain assembly during drying.
4:30 PM - V7.2
Unique Phase Transition Behavior of ``Janus” Particles Covered by a Thermoresponsive Polymer.
Young Kuk Jhon 1 2 , Douglas Kiserow 1 , Jan Genzer 2
1 Chemical Sciences Division, Army Research Office, Research Triangle Park, North Carolina, United States, 2 Chemical and Biomolecular Engineering, NC State University, Raleigh, North Carolina, United States
Show AbstractControlled fabrication of hybrid organic/inorganic materials has had a great impact on many novel structures and devices. Various approaches have been developed to prepare particles covered with a tethered polymer brush on one side to provide bridge between organic compounds (i.e. polymers) and non-organic materials (e.g. silicon oxide, gold, silver, aluminum oxide, and ferro oxide). One of the promising routes to forming these hybrid materials involves fabrication of asymmetrically functionalized particles, i.e., Janus particles. We will present a novel synthetic route for forming organic/inorganic hybrid particles by growing polymer brushes using surface-initiated atom transfer radical polymerization (SI-ATRP). First, a monolayer of spherical silica particles was cast on flat silicon wafers or glass slides using “convective assembly”. Subsequently, the upper surface of the particles at the free surface was exposed to vapors of organosilanes with three types of functional groups, i.e., amine (-NH2), methyl (-CH3), and trifluoromethyl (-CF3), forming organized monolayers. After removing from the substrates, the unmodified hemispheres of the particles were coated with organosilane-based initiators, which served as active centers for SI-ATRP of thermoresponsive (poly(N-isopropylacrylamide) (pNIPAM) brushes. We will discuss the cloud point and the size changes of these three Janus particles for various concentrations and changes in phase transition as a function of solution pH.
4:45 PM - V7.3
Breaking Symmetry towards Polyhedral Oligomeric Silsesquioxanes-Based Non-Spherical Molecular Janus Particles for Hierarchical Structure Formation.
Yiwen Li 1 , Wenbin Zhang 1 , Stephen Cheng 1
1 , Department of Polymer Science, The Univeristy of Akron, Akron, Ohio, United States
Show AbstractThe synthesis, assembly and applications of Janus particles have significantly intensified over the past two decades since de Gennes introduced of the “Janus grains” concept in his Nobel lecture. It was found that a three-dimensional well-defined, dissymmetrical distribution of certain physical and chemical quantities, such as size, shape, bulk composition, and surface chemistry, shall lead to the formation of specific hierarchical structures with novel functional properties. Therefore, a simple, modular, and efficient synthetic approach to precisely defined molecular Janus particles with both amphiphilic and geometrical symmetry breakings is very desirable. In particular, it could be very interesting if these molecular Janus particles are conformationally rigid and thus, the molecular symmetry of the self-assembled can be directly associated with their supramolecular structural symmetry.In this work, a series of precisely defined, non-spherical, molecular Janus particles possessing two polyhedral oligomeric silsesquioxane (POSS) cages connected by a short covalent linkage are reported. The synthesis fulfills the “click” philosophy by using thiol-ene chemistry to efficiently install versatile functionalities on one of the POSS cages. In this way, both the geometry (overall molecular shape) and chemical (selective amphiphilic interactions) symmetry were broken and the Janus feature was created. These particles could self-organize into hierarchically ordered supramolecular structures in the bulk. For example, the Janus particle with isobutyl groups on one POSS (BPOSS) and carboxylic groups on the other (APOSS) self-assembled into a bi-layered structure, and there still exist ordered structures within each layer. The driving force of the hierarchical structure formation was attributed to the free energy minimization via the pathway guided by the symmetry breaking of molecular POSS Janus particles. Our study provides a model system of well-defined, molecular Janus particles and has more implications in the understanding of the self-assembly and hierarchical structure formation of other types of Janus particles in general.
5:00 PM - V7.4
Synthesis and Application of Hyperbranched Poly-Amidoamine Conjugated Multi-Functional Hybrid Silica Particles for Metal Ion Sensors.
Sang Man Koo 1 2 , Jung Min Ha 2 , Eun Gu Jung 1 , Jung Soo Kim 1
1 Chem. Eng., Hanyang University, Seoul Korea (the Republic of), 2 Fuel Cells and Hydrogen Technology, Hanyang University, Seoul Korea (the Republic of)
Show AbstractThe combination of organic sensor molecules with inorganic particles has led to the development of new types of hybrid materials with improved physical and chemical properties, and offers a promising approach for simple and efficient detection of metal ions for biological and environmental applications. Due to the fact that the environmental pollution with heavy metals, such as Cd and Pb, has been increased throughout the world, the detection of their minute existence with high sensitivity and selectivity is of great importance. TMPyP (α,β,γ,δ–tetrakis (1-methylpyridinium-4-yl) porphine p–toluenesulfonate) has been known as an excellent sensor material for heavy metal ions due to the stability and metal-binding capability. Despite of several merits of TMPyP molecules, the poor recyclability limits its independent and wide uses in practical application. In order to solve this recyclability problem, several methods have been developed including grafting TMPyP molecule in metal oxide such as silica. However, these methods have usually suffered from time consuming, long and multi-step process. In this study, we prepared multi-functional hybrid silica (MHS) particles containing vinyl, amine, and thiol functional groups by the modified sol-gel process and oxidized SH groups in MHS particles to SO3H for the introduction of TMPyP molecules. TMPyP sensor molecules were successfully anchored on the surface of MHS particles by using strong ion-pair interactions between the positively charged ammonium groups in TMPyP molecules and the negatively charged SO3- groups on modified MHS particles. The color of sensor loaded MHS particles changed from brown to green as the concentration of Cd2+ metal ion increased. Qualitative as well as quantitative measurements could be possible through either on site colorimetric or more precise spectroscopic analysis. Hyperbranched poly-amidoamine conjugated multi-functional hybrid silica particles for higher loading of TMPyP molecules were synthesized by the repetitive reaction of Michael addition with methylacrylate (MA) and the amidation of ethylenediamine (EDA), alternately. These hyperbranched poly-amidoamine conjugated MHS particles are able to amplify the visible and spectroscopic signals for Cd ion sensing due to huge increase in TMPyP concentration. The 3rd, and 5th generation of hyperbranched poly-amidoamine conjugated MHS particles were prepared and used for investigation of their cadmium ion sensing capability. IR spectroscopy and Electron Microscopy were use to characterize MHS and hyperbranched poly-amidoamine conjugated MHS particles. Colorimetric method and UV/vis spectroscopy was used to investigate the detection capability of these sensor molecule loaded MHS particles. This type of organic-inorganic hybrid chemo-sensor particles is promising for potential applications in drug extraction and biological industries.
5:15 PM - **V7.5
Stimuli Responsive - Shape Specific Colloids.
Kevin Herlihy 1 , Janine Nunes 2 , John Savage 1 , Jie-Yu Wang 1 , Yapei Wang 1 , Edward Samulski 3 , Joseph DeSimone 1 3 4
1 Lineberger Comprehensive Cancer Center, UNC Chapel Hill, Chapel Hill, North Carolina, United States, 2 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 3 Chemistry, UNC Chapel Hill, Chapel Hill, North Carolina, United States, 4 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractWe are developing methods for directing the self-assembly processes by using particles with pre-determined shape, size, surface chemistry, and composition. In particular, we have designed nanometer and micrometer size anisotropic particles to study interfacial and bulk self-assembly behavior and their response to external stimuli. Anisotropic diblock Janus-like particles possessing a hydrophobic and a hydrophilic component were used to determine the role of shape on self-assembly at an oil/water interface, micelle formation, and emulsification. Anisotropic particles in the presence of an attractive depletion interaction were used to study the role of shape in directing self-assembly to form novel crystalline phases and micrometer scale supramolecular assembly. Particles with specified shapes composed of electronically/magnetically responsive materials were used to control hydrodynamics and assembly in the presence of an external dielectrophoretic or magnetic field. The design of such particles provides the opportunity for use as particulate surfactants, non-FCC crystalline structures for applications in photonics, and new methods to control rheological properties of colloidal suspensions.
Symposium Organizers
Andreas Lendlein Institute of Polymer Research
Yakai Feng Tianjin University
Tao Xie General Motors Research and Development Center
Zhibin Guan University of California-Irvine
V8: Liquid Crystalline Polymers II
Session Chairs
Wednesday AM, November 30, 2011
Room 312 (Hynes)
9:15 AM - V8.1
Responsive Polymer/Liquid Crystal Nanocomposites Enabling Large Scale Coloration Changes.
Michael McConney 1 , Madeline Duning 1 , Lalgudi Natarajan 1 , Vincent Tondiglia 1 , Timothy White 1 , Timothy Bunning 1
1 , Air Force Research Laboratory, Wpafb, Ohio, United States
Show AbstractAdding polymer into responsive liquid crystalline fluids can be utilized to overcome a number of drawbacks of the bulk fluid itself. Here we discuss the incorporation of helicoidal liquid crystalline polymer gels formed by anisotropically polymerizing a template LC monomer in a cholesteric fluid. With proper design of the thickness, concentration, and molecular architecture of the polymer component, films which exhibit large scale changes in their optical properties can be formed. These changes are due to complex swelling/deswelling transitions enabled by anisotropic cell design. Both light and heat have been utilized to dynamically tune the color of these naturally reflective films over 100’s of nanometer’s. Discussion will center on making the templated liquid crystal polymer constituent stimuli-responsive.
9:30 AM - **V8.2
Liquid Crystal Elastomer Photo-Actuators for Haptic Display Applications.
Jean Marshall 1 , Yan Ji 1 , Eugene Terentjev 1
1 , University of Cambridge, Cambridge United Kingdom
Show AbstractFor two decades liquid crystalline elastomers (primarily nematic) have been known to possess unique actuation properties, with very large stroke (the record extension of 500%) and full reversibility (two-way actuation). However, stimulating the mechanical response by heating is impractical, and by electric field is ineffective, hence the increasing attention to photo-induced actuation. Previous research into light-responsive liquid crystal elastomers focused on materials containing such chemical groups as azobenzene or stilbene, which isomerize when irradiated with a suitable light frequency, thus triggering a phase change and an overall change in the bulk dimensions. However, the wavelength of light that is usually used to ‘switch’ these materials is usually in the UV range and the speed of response very long. This, and the complicated chemistry involved, impose practical limitations on these materials as useful actuators. We have developed a new approach, of sensitizing the matrix to the broad-spectrum light (visible to IR) by dispersing short segments of carbon nanotubes within an elastomer. Such composites retain the structure of liquid crystal matrix and acquire the fast mechanical response to illumination by light. The mechanism of this actuation is the fast local release of heat once a nanotube absorbs a photon, i.e. this is essentially a new way of delivering local heat to a classical thermal actuator. In this talk the application of these composites in haptic displays (such as the Braille matrix) will be illustrated.
10:00 AM - V8.3
Thermally-Induced Shape-Memory Effect of a Liquid Crystalline Elastomer.
Christian Melchert 1 , Danish Iqbal 1 , Marc Behl 1 , Andreas Lendlein 1
1 Active Polymers, Center for Biomaterial Development and Institute of Polymer Research, Helmholtz-Zentrum Geesthacht , Teltow Germany
Show AbstractABSTRACTLiquid crystalline elastomers (LCE) are a class of actively moving polymers, which have the ability to change their shape as long as they are exposed to a suitable stimulus [1; 2]. Azobenzene based LCE’s are one of the most important class of light-induced LCE’s due to their ability of macroscopic movement when irradiated with light of a suitable wavelength [3]. In contrast, shape-memory polymers (SMP) display a unidirectional change of shape. SMP can be deformed and fixed to a temporary shape by application of an external mechanical stress, while stimulation with a suitable stimulus initiates recovery of the original shape [4]. Here we report the shape-memory properties of a LCE system. The monodomain LCE was obtained, by thermally-induced free radical polymerization between two rubbed polyimide coated glass plates. Mono- and diacrylates containing azobenzene chromophores were used as monomers and crosslinkers respectively. The aliphatic chain of the monoacrylates was varied to study the influence of the different spacer length on the mechanical properties.We explored whether the Tg of this system can be used to enable a thermally-induced shape-memory effect. Programming of the LCE was performed in bending experiments by cooling the polymer films quickly to temperatures below their Tg about 50 °C. The original, permanent shape was recovered by heating films to 90 °C. In addition, the influence of different crosslinking densities and the spacer length of the polymer network on shape-memory properties are discussed and the morphology of the LCE-network in the different states of deformation is described. Such stimuli-sensitive materials might be an important material class for applications such as artificial muscles, actuators and sensors.[1]Behl, M., J. Zotzmann, and A. Lendlein (2010) Shape-Memory Polymers and Shape-Changing Polymers. Shape-Memory Polymers. 226: 1-40.[2]Ohm, C., M. Brehmer, and R. Zentel (2010) Liquid Crystalline Elastomers as Actuators and Sensors. Advanced Materials. 22: 3366-3387.[3]Ikeda, T., J. Mamiya, and Y. L. Yu (2007) Photomechanics of liquid-crystalline elastomers and other polymers. Angewandte Chemie-International Edition. 46: 506-528.[4]Behl, M., M. Y. Razzaq, and A. Lendlein (2010) Multifunctional Shape-memory Polymers. Advanced Materials. 22: 3388-3410.
10:15 AM - V8.4
Photomechanical Response of Highly Glassy Azobenzene Polyimide Networks.
Kyungmin Lee 1 2 , David Wang 1 3 , Hilmar Koerner 1 3 , Richard Vaia 1 , Loon-Seng Tan 1 , Timothy White 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wrigh-Patterson AFB, Ohio, United States, 2 , Azimuth Corporation, Dayton, Ohio, United States, 3 , UES, Dayton, Ohio, United States
Show AbstractWe report the synthesis and photodirected bending of high Tg (240-362°C) azobenzene-functionalized polyimide polymers and copolymers (azo-PIs). Comparatively distinctive photomechanical response are observed upon exposure to to linearly polarized, 442 nm and 365 nm lights. The focus of this work is on polarization controlled forward/backward bending which is shown to be strongly dependent on azobenzene concentration and aspect ratio of the cantilevers. Notably, we find strong correlation between the free volume/crystallinity of the given azo-PI and the ability to induce bending. Photo-generated stress measurements via dynamic mechanical analysis for the azo-PI materials are compared against azobenzene functionalized liquid crystalline polymer networks (azo-LCNs).
10:30 AM - V8.5
Multi-Responsive Multi-Functional Smart Materials from Hierarchically-Structured Polymeric Systems.
Rajeswari Kasi 1
1 Polymer Program, IMS & Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractCholesterol can be used as a building block to prepare side-chain liquid crystalline polymers (LCPs) in which the cholesteryl moieties self-assembles into layered smectic A liquid crystalline (LC) mesophases. We exploit the stimuli-responsive properties of these LCPs bearing side-chain cholesteryl moieties towards the creation of multi-functional smart materials. We have synthesized cholesterol bearing liquid crystalline random and block polymers with additional functional (or polar) groups, composition, and architecture. Our synthetic protocol has been used as a handle to tailor the thermal and morphological properties of these LCPs. We have investigated strategies to direct ordering and packing of hierarchical meso- and nanostructures originating from these LCPs both in solid state and in solutions. These nanostructured polymers with and without inorganic nanoparticle additives will be used to create shape memory devices, actuators, and multi-stimuli responsive materials.
V9: Micro-/Nanostructured Systems II
Session Chairs
Wednesday PM, November 30, 2011
Room 312 (Hynes)
11:15 AM - **V9.1
Multifunctional Dendritic Architectures.
Rainer Haag 1
1 Chemistry, Freie Universitaet Berlin, Berlin Germany
Show AbstractApplication of nanotechnology in medicine and pharmaceuticals is a rapidly moving field that is gaining fast acceptance and recognition as an independent area of research and scientific endeavor.1,2 The combination of a high density of endgroups and a compact well defined molecule structure makes dendritic architectures attractive for biomedical applications. The synergy between their multivalency and size in nanoscale provides a range of options for chemical “smartness” along their molecular scaffold to achieve environment sensitive modalities.3Due to their low degree of molecular weight dispersity, flexible design, and biocompatible nature, dendritic polyglycerols (PGs) have a broad range of potential applications in medicine and pharmacology.4 The versatility of the polyglycerol scaffold for application in the biomedical field has been recently reviewed.5 Dendritic polyglycerol architectures have already been demonstrated to be useful in therapeutic approaches related to multivalency because of the synergy between the nano-sized dimensions combined with the high density of functional groups.6,7 A challenging approach to the application of multivalent interactions is the mimicry of functional biomacromolecules with therapeutic relevance. Several attempts have been made to mimic specific proteins, e.g. histones or polysaccharides like heparin. In these cases, mimicry is mostly based on the surface charge of the polymer molecules. In the particular case of dPGs, (i) the neutral species with hydroxyl end groups represents a good analogue of polysaccharides, (ii) polyanionic derivates present similar activities to negatively charged polysaccharides, e.g., heparin, polysialic acid, and (iii) the amine terminated PGs can act in a similar fashion as histones binding and compacting DNA, as well as a scaffold for drug conjugation. Applications range from protein resistant coatings (neutral species) to DNA-transfection agents (polycationic systems), anticoagulating and anti-inflammatory drugs (polyanionic systems).(4) References:(1) Duncan, R. (2006) Nat. Rev. Cancer 2006, 6, 688-701. (2) Haag, R., Kratz, F. Angew. Chem. Int. Ed. 2006, 45, 1198-215. (3) Gillies, E. R., Frechét, J. M. Drug Discov. Today 2005, 10, 35-43. (4) Calderón, M., Quadir, M., Sharma, S., Haag, R. Adv. Mater. 2010, 22, 190-218. (5) Khandare, J., Mohr, A., Calderón, M., Welker, P., Licha, P., Haag, R. Biomaterials 2010, 31, 4268-77. (6). Calderón, M., Welker, P., Licha, K., Fichtner, I., Graeser, R., Haag, R., Kratz, F. J Control Release 2011, 151, 295–301. (7) Dernedde, J., Rausch, A., Weinhart, M., Enders, S., Tauber, R., Licha, K., Schirner, M., Zügel, U., von Bonin, A., Haag, R. Proc Natl Acad Sci 2010, 107, 19679-84.
11:45 AM - V9.2
Thermoresponsive Supramolecular Dendrimers Synthesized by Programmed Self-Assembly.
Partha Ghosh 1 , Andrew Hamilton 1 2
1 Chemistry, Yale University, New Haven, Connecticut, United States, 2 Chemistry, Oxford University, Oxford, OX13TA, United Kingdom
Show AbstractThermosensitive dendrimers were prepared by noncovalent synthesis. Short oligonucleotides containing guanine repeats were linked to the focal point of a dendron using “click chemistry”, and quadruplex formation was used to drive the self-assembly process in presence of metal ions. The dynamic nature of these non-covalent assemblies can be exploited to create combinatorial libraries of dendrimers as demonstrated by co-assembly of two components. These supramolecular dendrimers showed thermoresponsive behavior that can be tuned by varying the templating cations or the number of guanines in the oligonucleotide strand.
12:00 PM - V9.3
Surfactant Free Preparation of pH Labile Polyglycerol Nanogels by Nanoprecipitation.
Dirk Steinhilber 1 , Michael Staegemann 1 , Rainer Haag 1
1 Institute of Chemistry and Biochemistry, Free University Berlin, Berlin Germany
Show AbstractNanogels, which are hydrogel particles on the nanometer scale, are highly water swollen scaffolds that exhibit similar mechanical properties as many biological objects, thus making them excellent candidates for biomedical applications.[1] Our group recently reported the preparation of polyglycerol nanogels by miniemulsion polymerization. These highly functional and biocompatible materials showed an efficient uptake by cancer cells.[2] The introduction of disulfide bonds enabled intracellular degradation.[3] However, ultrasonication conditions and toxic surfactants are required for nanogel preparation by miniemulsion polymerization. Additionally, the slow degradation kinetics of disulfide crosslinked polyglycerol nanogels in intracellular environments may hinder a controlled release of bioactive agents. Here we report the surfactant free synthesis of pH labile polyglycerol nanogels by a modified nanoprecipitation method. We injected aqueous solutions of hyperbranched polyglycerol, equipped with crosslinkable groups, into nonsolvent. Nanoprecipitation causes high polymer concentrations and fast gellation of polyglycerol precursors to well defined spherical nanoparticles. Sizes of the nanogels were controlled between 100 and 500 nm by variation of the polymer precursor concentration. Stimuli-responsive nanogels were obtained by the introduction of benzacetal bridges into nanogel net points. Interestingly, the nanogels quickly degraded into low molecular weight fragments at intracellular low pH values and they remained stable at physiological pH values a long time. After the encapsulation of a model peptide into the polyglycerol nanogel matrix, a controlled release of the peptide at intracellular pH was obtained. Additionally, we functionalized low molecular weight polyglycerol precursors with Fluorescence Resonance Energy Transfer (FRET) dye pairs prior to nanoprecipitation. Nanogel degradation triggered the disappearance of the FRET signal due to spatial separation of the FRET dye pair. This effect will be used for the direct visualization of nanogel degradation in intracellular compartments. In conclusion we report for the first time the surfactant free preparation of pH responsive polyglycerol nanogels by nanoprecipitation. This powerful approach to polymeric nanomaterials may find broad application in the area of functional biomaterials. References[1] Hendrickson, G. R.; Smith, M. H.; South, A. B.; Lyon, L. A. Adv. Funct. Mater 2010, 20, 1697-1712.[2] Sisson, A.L.; Steinhilber, S.; Rossow, T; Welker, P.; Licha, K.; Haag, R. Angew. Chem. Int. Ed. 2009, 48, 7540-7545; Sisson, A.L.; Haag, R. Soft Mater. 2010, 6, 4968-4975.[3] Steinhilber, D.; Sisson, A.L.; Mangoldt, D.; Welker, P.; Licha K.; Haag, R. Adv. Funct. Mater. 2010, 20, 4133-4138.
12:15 PM - V9.4
Synthesis of Sugar-Based Polyamides: Hydrogen-Bonding Mediated Self-Assembled Nanoparticles for Biomedical Applications.
Keunsoo Jeong 1 2 , Yong-Deok Lee 2 , Chang-Keun Lim 2 , Sehoon Kim 2 , Chong Rae Park 1
1 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Center for Theragnosis, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractThe advent of new polymeric materials has been demanded over the past decade to overcome the instability of therapeutic agents including imaging probes in physiological condition. Polyethylene glycol (PEG) has been recognized as a promising material to improve the bioavailability of imaging probes by acceptable biocompatibility, less toxicity, and characteristic anti-fouling effect. However the utility of PEG for widening the application areas has been limited, since it does not have reactive functional groups on its main chain, thus the chemical modification is allowed only at the chain ends. Here we report novel synthetic sugar-based polyamides (SPA) as an alternative to PEG. Galactaric acid (GA), a natural monosaccharide diacid containing four hydroxyl groups, was polymerized with oligo-ethylene oxide (EO) diamines, to produce hydroxyl-rich polyamides with combined functionalities (the intermolecular hydrogen bonding induced by GA units, the anti-fouling effect induced by oligo-EO units, additional backbone modification at GA units). Self-assembled SPA nanoparticles were formed in aqueous SPA solution due to the intermolecular hydrogen bonding of hydroxyl groups and amide groups in the backbone of SPA, and Near-infrared fluorescent (NIRF) SPA nanoparticles were formed through self-assembly of SPA conjugated with NIRF dye. The anti-fouling effect was confirmed by examining the cell attachment behavior to the plate surface treated with SPA and in vivo biodistribution after intravenous injection of NIRF SPA nanoparticles to the mouse model. Further, the cell-SPA interaction could be controlled by direct conjugation of folic acid (a targeting moiety) to GA units in the backbone, suggesting potential uses of pendant hydroxyl groups as a chemical attaching point.
12:30 PM - V9.5
Controlled Alignment and Positioning of Nanoscale Objects in Electrospun Polymer Nano/Microfibers.
Kristen Roskov 1 , Joseph Tracy 2 , Amy Oldenburg 3 , Lyudmila Bronstein 4 , Richard Spontak 1 2
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 3 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina, United States, 4 Department of Chemistry, Indiana University-Bloomington, Bloomington, Indiana, United States
Show AbstractFormation of polymer nanocomposites is becoming an increasingly attractive and facile means by which to combine the desirable properties of metals and metal oxides (e.g., electrical, magnetic, optical, and thermal) with those of polymers (e.g., flexible, lightweight and tough). Incorporation of nanoscale objects such as spheroidal nanoparticles or elongated nanorods into electrospun polymer nano/microfibers measuring from 50 nm to 1 μm in diameter yields functional nanomaterials that can be used in various applications ranging from data storage and conductive nanowires to nonwoven sensors, magnetic filters and drug delivery patches. By aligning nanoscale objects in one-dimensional constructs, we expect that desirable attributes arising from highly anisotropic electronic, optical, thermal, magnetic, and catalytic properties can be realized. The objective of this study is to gain a better fundamental understanding of how to controllably align and position nanoparticles and nanorods within polymer nano/microfibers to generate unique properties. To achieve this objective, we focus on three specific process strategies. In the first, superparamagnetic iron oxide nanoparticles (SPIONs) are aligned into one-dimensional nanoarrays through the use of magnetic field-assisted electrospinning. In this case, an electromagnet is positioned near the Taylor cone of the suspension to be electrospun so that the magnetic field is oriented perpendicular to the electric field. Transmission electron microscopy (TEM) is utilized to ascertain the morphology of the resultant nanocomposite fibers and reveals that the SPION nanoarrays persist intact beyond 1 μm. Since the magnetic field can be pulsed, the length of the nanoarrays can be judiciously controlled. Magnetization hysteresis curves measured on a superconducting quantum interference device yield saturation magnetization and mean magnetic moment values. Secondly, gold nanorods (GNRs) varying in aspect ratio have been flow-aligned in electrospun fibers, and the fibers have likewise been aligned to permit long-range orientation order at both the nanoscale and macroscale. This is an important consideration in the fabrication of devices spanning multiple size scales. The GNRs within nano/microfibers exhibit excellent alignment with their longitudinal axis parallel to the fiber axis. Optical absorbance spectroscopy measurements reveal that the longitudinal surface plasmon resonance bands of the aligned GNRs are highly anisotropic, depending on polarization angle, and that maximum absorption occurs when polarization is parallel to the fiber axis. Lastly, blends of hydrophobic and hydrophilic polymers have been prepared to control the spatial position of SPIONs within electrospun fibers on the basis of thermodynamic compatibility. In this case, TEM confirms that a core-sheath nanostructure naturally forms due to polymer-polymer phase separation and that the hydrophobic nanoparticles are sequestered in one preferred phase.
V10: Stimuli-Sensitive and Shape-Memory Polymers II
Session Chairs
Wednesday PM, November 30, 2011
Room 312 (Hynes)
2:30 PM - V10.1
High Temperature Shape Memory Polymer.
Ying Shi 1 , Mitra Yoonessi 2 , Robert Weiss 1
1 Polymer Engineering, The University of Akron, Akron, Ohio, United States, 2 , OAI/NASA Glenn Research Center, Cleveland, Ohio, United States
Show AbstractThermally-actuated shape memory polymers (SMP) change shape in a predefined manner when exposed to heat. These materials have either a covalently cross-linked or physical cross-linked structure as a permanent network and a low temperature reversible physical transition, e.g., vitrification, melting or microphase separation, as a temporary network. The thermodynamic origin of shape memory is the shape change that accompanies a conformational entropy change at the transition temperature. Elastic strain energy is stored by the temporary crossed structure during shape fixing, while the shape recovery to original shape formed by the permanent network is due to the release of the stored energy. Most SMPs are elastomers with relatively low actuation temperatures, e.g., < 100°C. In this talk, we will describe the development of a high switching temperature shape memory polymer system that may be suitable for aerospace applications. Polyether ether ketone (PEEK) is a semi-crystalline thermoplastic polymer with excellent mechanical properties. It is highly resistant to thermal degradation and has a maximum service temperature of 260°C. Neat PEEK has some shape memory behavior with a crystalline phase providing a permanent network and the glass transition temperature providing the reversible thermally actuated temporary network. However, the deformation of PEEK is small due to its relatively high crystallinity (~40%), and it exhibits rather poor shape fixing and low shape recovery ratio, ~35%. The poor shape memory behavior is probably a consequence of creep of the “permanent” crystalline network. Sulfonated PEEK (S-PEEK) exhibited better shape memory behavior. Sulfonation increased Tg, decreased Tm and reduced the crystallinity, and at sufficiently high sulfonation levels, >18 mol%, S-PEEK was amorphous. That increased the extensibility of the polymer above Tg. Neutralization of S-PEEK to a metal salt, such as Zn2+ provided a physical crosslink due to dipolar associations and microphase separation of an ion-rich nanophase, which provided a more robust “permanent” network than the PEEK crystallites. An 18 mol% sulfonated ZnS-PEEK exhibited a Tg of ~200°C and it showed shape memory behavior above Tg with a shape recovery of 70%. The shape memory characteristics of S-PEEK and mixtures of S-PEEK with crystalline low molar mass compounds are studied. For the latter materials, the strong dipolar interactions of the low molar mass crystals with the ionomer provide a temporary network1, so that two-way shape memory behavior can be obtained. 1 Weiss, R. A.; Izzo, E.; Mandelbaum, S.. Macromolecules. 41, 2978-2980 (2008).
2:45 PM - V10.2
On the Fabrication and Processing of Novel Shape Memory Polymer Multi-Electrode Arrays.
Dustin Simon 1 , Taylor Ware 1 , Ed Keefer 3 4 , Walter Voit 1 2
1 Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas, United States, 3 , University of Texas Southwestern Medical Center, Dallas, Texas, United States, 4 , Plexon, Inc., Dallas, Texas, United States, 2 Mechanical Engineering, The University of Texas at Dallas, Richardson, Texas, United States
Show AbstractA thermoresponsive polymer substrate for flexible electronics has been developed and characterized for use as a central nervous system recording interface. We develop a new method using photolithography to pattern specific electrode geometries on shape memory polymers (SMPs) to allow for the fabrication of smart multi-electrode arrays (MEAs) with increased biocompatibility, tailorable mechanical properties, and the ability to respond controllably to a wide variety of stimuli. We adapt standard semiconductor wafer processing techniques to decrease the maximum processing temperature to 40 degrees C and enable incorporation onto SMP substrates with glass transition temperatures above 60 degrees C. The crosslinked polymer network is formed directly on the fabricated devices by copolymerization of methyl acrylate, isobornyl acrylate and acrylic acid with poly(ethylene glycol) diacrylate—such that the interfacial adhesion is enhanced over traditional flexible electronic processing techniques. By varying the amount of acrylic acid (10-20%wt), while keeping Tg constant, we demonstrate a substrate with a tunable swelling profile in order to minimize glial scarring. The prototype devices are stiff enough (1 GPa) to assist with device implantation and then swell in vivo to approach the modulus of brain tissue (~10 kPa) within 24 hrs. Samples were immersed in vitro in PBS solution to mimic physiological conditions over 1 day, 1 week, and 1 month. Shear modulus was measured by dynamic mechanical analysis (DMA) of the swollen samples at each time point. Acute in vivo studies demonstrate the signal recording capability and successful softening of these SMP MEAs in animal models. These smart material interfaces allow for greater strain-resistance capacity, better neural attachment to electrode sites, low impedance measurement and compatibility with a metal-organic or fully organic implantable device. Softening MEAs have the potential to enable chronic explorations that monitor and manipulate brain function in neurobiology and electrophysiology research.
3:00 PM - **V10.3
Mechanochemical Functionality for Adaptive Polymers.
Stephen Craig 1
1 Department of Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractMechanical stress fields are generally destructive actors in polymeric materials and composites. This talk will describe how those stress fields can be used to trigger constructive covalent chemistry in regions of high stress within polymers, resulting in improved mechanical properties. The behavior of single polymer molecules under tension will be related to the mechanical response of sheared polymers in solution and in the solid state, including a new mechanism for stress-strengthening and/or self-healing. Lastly, the combination of mechanical stimulus-response behavior with thermal and/or photochemical stimulus-response will be shown to result in multi-responsive and reverisbly switchable polymers.
3:30 PM - V10.4
Biodegradable Amorphous Networks with Shape Memory Properties for Use in Medical Applications and Tissue Engineering.
Shariar Sharifi 1 , Dirk Grijpma 1 2
1 , University Medical Center Groningen, Groningen Netherlands, 2 , University of Twente, Enschede Netherlands
Show AbstractIn tissue engineering, flexible, form-stable and resorbable elastomeric networks can be used to prepare scaffolding structures with most advantageous properties. Here we describe the synthesis and characterization of a series of amorphous photo-crosslinked networks with tunable thermal- and mechanical properties based on trimethylene carbonate and D,L-lactide. The (co)oligomers were synthesized by ring opening polymerization of the corresponding monomers in the presence of varying amounts of hexanediol, and then functionalized by methacrylation. Networks were obtained by UV crosslinking in the presence of a photoinitiator. Of the obtained crosslinked structures, the network properties and the thermal- and mechanical properties were assessed. The shape recovery behavior of the different networks was evaluated quantitatively. Amorphous networks were prepared from macromers with different molecular weights in which the monomer molar ratios were varied between 0:1 and 1:0. This allowed tuning of the glass transition temperature and mechanical properties. The values of the toughness, ultimate tensile strength and elongation at break of flexible networks with glass transition temperatures above room temperature increased with increasing macromer molecular weights. Networks prepared from macromers with a TMC content of 0.4 to 0.6 had Tg values close to or below body temperature. These networks are especially interesting as they are relatively rigid at room temperature, and flexible with mechanical properties in the range of soft tissues at body temperature. From these materials, porous and non-porous devices were fabricated. At room temperature these devices are relatively rigid and can be implanted non-invasively in their temporary shape, while at body temperature they return to their original permanent shape to perform a desired function. These properties, and their biodegradability and elasticity, make these networks materials very well-suited for the preparation of self-deploying implants in medical applications like tissue engineering, drug delivery, stenting and the support of soft tissues.
V11: Multimaterial Systems
Session Chairs
Wednesday PM, November 30, 2011
Room 312 (Hynes)
4:15 PM - V11.1
Shape Memory Polymers Based on Blends of Ethylene Ionomers and Fatty Acids and Their Salts.
Rostyslav Dolog 1 , Robert Weiss 1
1 Polymer Engineering, University of Akron, Akron, Ohio, United States
Show AbstractShape memory polymers (SMP) are materials that can change shape when exposed to an external stimulus, such as temperature. Thermally-actuated shape memory polymers can be deformed when heated above a critical temperature (Tc) of a reversible network, and then fixed into a temporary shape when cooled down under stress below Tc. When the material is reheated above Tc, the reversible network disappears and material recovers its original, permanent shape. The permanent shape of an SMP can be provided by chemical crosslinks or physical crosslinks that persist above Tc. The reversible, temporary network is created by physical crosslinks or hard domains that vanish above Tc. The unique properties of SMPs can be used in various applications, such as intelligent packaging, reconfigurable tooling, aerospace systems, biomedical devices, artificial muscles and self-deployable devices.We recently reported [1] a new type of SMP based on compounds of low molecular weight fatty acids or fatty acid salts (FAS) with an elastomeric ionomer, the zinc salt of sulfonated poly{ethylene-r-propylene-r-(5-ethylidene-2-norbornene)}, Zn-SEPDM. In our current work, we have prepared SMPs from compounds of partially neutralized (Zn-salt) poly(ethylene-co-r-methacrylic acid) ionomer (Zn-E/MAA) and fatty acid (salts), such as Zn-stearate and myristic acid. The ionomer, itself, exhibited shape memory behavior. Physical crosslinks in the ionomer result from dipole-dipole associations of the zinc carboxylate groups, which produced microphase separated ionic domains that were responsible for the permanent shape. The temporary shape for the ionomer was provided by polyethylene crystallites, and the critical temperature was the melting transition of the crystallites. Shape memory cycles measured by dynamic mechanical experiments indicated that the ionomers had shape fixation values as high as 90% and good shape recovery. Blends of the ionomer and a fatty acid (salt) also exhibited shape memory behavior. The addition of a fatty acid (salt) also provided a second crystalline domain that can support a temporary shape [1] and allow triple shape memory behavior. Strong dipolar interactions between the ionic groups of fatty acids (salts) and the zinc methacrylate groups of the ionomer facilitated compounding and provided another temporary network. This talk will describe the thermal and mechanical properties, morphology and the shape memory behavior (shape fixation and shape recovery) of these compounds. [1] Weiss, R. A.; Izzo, E.; Mandelbaum, S. Macromolecules. 41, 2978-2980 (2008).
4:30 PM - V11.2
Nanocomposite Sintering as a Novel Adhesive Switching Mechanism.
Robert Gurney 1 , Robert Adams 1 , Damien Dupin 2 , Keltoum Ouzineb 3 , Steven Armes 2 , Joseph Keddie 1
1 Physics, University of Surrey, Guildford, Surrey, United Kingdom, 2 Chemistry, University of Sheffield, Sheffield United Kingdom, 3 , Cytec Surface Specialties, Drogenbos Belgium
Show AbstractPressure-sensitive adhesives (PSAs) adhere instantly and firmly to a substrate upon the application of a light pressure. With increased emphasis on recycling and re-use of materials, there is a strong interest in adhesives that de-bond or “switch off” on demand, when triggered by an external stimulus. There are also continuing demands for environmentally-friendly PSAs, leading to greater reliance on PSAs made from colloidal dispersions of soft polymers in water, known as latex, to avoid the emission of organic solvents during processing. This presentation will describe the development of a new type of waterborne PSA that has thermally-switchable adhesion.The blending of colloidal particles (e.g. rubbery (soft) and glassy (hard) particles) is an ideal way to adjust the structure to achieve the right balance between elastic and viscous properties, which is required for PSAs [1]. Small, hard particles can be packed around larger soft particles as a means of tailoring the structure. Above the percolation threshold, there is connectivity of the small hard particles, leading to some mechanical reinforcement [2].In our approach, a soft poly(butyl acrylate) copolymer latex was blended with glassy poly(methyl methacrylate) nanoparticles (NP) (52 nm diameter). AFM analysis of PSA film cross-sections reveals that - at optimal concentrations - the NPs created a continuous percolating network while adhesive performance is not adversely affected. To “turn off” the adhesion, the nanocomposite adhesive is heated above the NP’s Tg, so that the percolating particles sinter to create a continuous skeleton throughout the material. Adhesion measurements show that the tack adhesion energy falls significantly after sintering, and bulk mechanical analysis reveals a simultaneous rise in the elastic modulus. The adhesion is lost because of the stiffening of the composite to modulus values above the acceptable limit. We have found that if the concentration of hard NP is too low, a percolating network is not created upon sintering. If the concentration is too high, then the initial composite is too stiff to be an effective PSA. We have optimised the volume ratio of the hard and soft phases to ensure a successful loss of adhesion after sintering without compromising the initial adhesive properties.[1] F. Deplace et. al. J. Adhesion 85, 18 (2009).[2]E. Degrandi-Contraires et al., Macromolecules, 44, 2643 (2011).
4:45 PM - **V11.3
Multifunctional Composites from Three-Dimensional Microvascular Structures.
Jeffrey Moore 1 2 3 , Aaron Esser-Kahn 1 2 , Hefei Dong 1 3 , Piyush Thakre 1 4 , Jason Patrick 1 4 , Nancy Sottos 1 2 4 , Scott White 1 4 5
1 Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, Illinois, United States, 2 Chemistry, University of Illinois, Urbana, Illinois, United States, 3 Materials Science & Engineering, University of Illinois, Urbana, Illinois, United States, 4 Mechanical Science and Engineering, University of Illinois, Urbana, Illinois, United States, 5 Aerospace Engineering, University of Illinois, Urbana, Illinois, United States
Show AbstractSelf-healing microvascular material systems have attracted attention for their ability to achieve multiple healing cycles in response to mechanical damage. Current microvascular fabrication methods are limited in their ability to integrate microvascular networks into commercial composite materials. This presentation will describe the use of sacrificial fibers to enable the seamless fabrication of 3D microvascular composites that are both strong and multifunctional. Underpinning the method is the efficient thermal depolymerization of catalyst-impregnated polylactide (PLA) fibers with simultaneous evaporative removal of the resulting lactide monomer. The hollow channels produced are high-fidelity inverse replicas of the original fiber's diameter and trajectory. The method has yielded microvascular materials with channels over one meter in length that can be subsequently filled with a variety of liquids including aqueous solutions, organic solvents for applications such as self-healing and thermal management. Adding a thermally stable coating to sacrificial fibers is being developed as a means to manipulate the spacing and transport properties between the microchannels.
5:15 PM - V11.4
Shape-Memory Properties of Nanocomposites Based on Poly(ω-pentadecalactone) and Covalently Integrated Magnetite Nanoparticles.
Muhammad Razzaq 1 , Marc Behl 1 , Andreas Lendlein 1
1 , Center for Biomaterial Development, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Kantstr. 55, D-14513 Teltow Germany
Show AbstractBy incorporating magnetic particles in thermally-induced shape-memory polymers, a remote triggering of the shape-memory effect has been realized by inductive heating of these composites in an alternating magnetic field [1-3]. In order to avoid the aggregation and sedimentation of the magnetic particles during network synthesis, the particles should be covalently integrated into the polymer matrix. Here, we report on the shape-memory properties of nanocomposites based on poly(ω-pentadecalactone) (PPDL) and covalently integrated magnetite nanoparticles (mgNP). Thermosets of shape-memory nanocomposites with PPDL coated mgNP (mgNP-PPDL), which acted as additional crosslinking agents, were synthesized by cocondensation of hydroxy terminated mgNP-PPDL and PPDL-macrotriol (3PPDL, Mn = 3400 g/mol with an aliphatic diisocyanate. The selected mgNP-PPDL has a core of magnetite with particle diameter of 10 nm and surface grafted PPDL oligomers with Mn of 3300 g/mol. Thermal and mechanical properties of the nanocomposites were explored as a function of crosslinking density by varying the ratio of mgNP-PPDL and 3PPDL. The morphology of the nanocomposites was determined by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) revealed an increase of the melting point (Tm) and the crystallization temperature (Tc) of the nanocomposites with increasing content of mgNP-PPDL. The shape-memory properties of the nanocompsoites were quantified in cyclic thermomechanical experiments, which consisted of a one step programming procedure followed by recovery under stress-free or strain-controlled conditions. All the nanocomposites exhibited excellent shape-memory properties with shape fixity rates above 90% and shape recovery rates between 85% and 98%. The maximum stress (σmax) obtained under strain-control recovery conditions was decreased by increasing the content of mgNP-PPDL, while the corresponding temperature (Tσ,max) as well as switching temperature (Tsw) determined during stress-free recovery conditions were slightly increased. Potential applications for such shape-memory nanocomposites include smart implants, medical instruments, which could be controlled on demand, as well as sensors and actuators [4].References[1] M.Y. Razzaq, M. Behl, K. Kratz, A. Lendlein, Mater. Res. Soc. Symp. Proc. 2009, 1140. 185-190[2] M.Y. Razzaq, M. Y., Anhalt, M., Frormann, L. & Weidenfeller, B. Mater. Sci. Eng. A 444 (2007) 227-235.[3] R.Mohr, K. Kratz, T. Weigel, M. Lucka-Gabor, M. Moneke & A. Lendlein Proc. Natl. Acad. Sci. USA 103(2006), 3540-3545.[4] M. Behl, M. Y. Razzaq, A. Lendlein, Adv. Mater. 2010, 22, 3388-3410
5:30 PM - V11.5
Three-Dimensional Manipulation of Bi-Functional Magnetic-Luminescent Polymer Nanorods.
Chris Bardeen 1 , Taehyung Kim 1
1 Chemistry, U. California Riverside, Riverside, California, United States
Show AbstractNanoscale objects that combine high luminescence output with a magnetic control may be useful for probing local environments or manipulating objects on small scales. Ideally, these two properties would not interfere with each other. In this report, we show that a fluorescent polymer host material can be doped with high concentrations of 20-30 nm diameter superparamagnetic γ-Fe2O3 particles. The doped polymers can then be formed into 200 nm diameter nanorods using porous anodic alumina oxide templates. The length of these nanorods can be varied between 5 and 15 microns by controlling the processing time. By using two different polymer systems (the conjugated polymer polydioctylfluorene and also polystyrene doped with the fluorescent dye Lumogen Red) the wavelength of the luminescent output can be varied. Fluorescence lifetime measurements show that 14% by weight loading of the γ-Fe2O3 nanoparticles quenches the fluorescence of the polydioctylfluorene by approximately 33%, but the polystyrene/Lumogen Red fluorescence is almost unaffected. The high loading fraction permits the three-dimensional orientation of both types of nanorods to be precisely controlled by the application of moderate strength (~0.1 Tesla) external magnetic fields. The nanorod response time is less than 1 second, consistent with calculated response time for a magnetic rod composed of γ-Fe2O3 that is “diluted” by the polymer host. Transmission electron microscope images reveal that the inorganic nanoparticles cluster in the polymer matrix, and these clusters may serve both to prevent fluorescence quenching and to generate the magnetic moment that rotates in response to the applied magnetic field. These bifunctional nanostructures may prove useful for probing local viscosity, for example inside living biological cells, and for manipulating microscale objects.
5:45 PM - V11.6
Evaluation of Oscillating Magnetic Field Induced Losses of Thermoresponsive, Multifunctional, Magnetic Nano-Carriers for Hyperthermia and Controlled Drug Release.
Jason Lumpkin 1 , Christopher Yuen 1 , Nathan Burford 1 , Elwood Gidney 2 , Thomas McCallister 2 , Jian Peng 1 , Santaneel Ghosh 1
1 Physics and Engineering Physics, Southeast Missouri State University, Cape Girardeau, Missouri, United States, 2 Department of Biology, Southeast Missouri State University, Cape Girardeau, Missouri, United States
Show AbstractRecently, huge interest has been generated in investigating the possible therapeutic use of tunable magnetic nanostructures to overcome the existing challenges to treat cancer or neurodegenerative disorders. However, several issues, e.g., poor biocompatibility and intracellular uptake of the nanomagnets or uncontrolled temperature modulation of the intracellular domain arising from various loss mechanisms in the alternating magnetic field limit the use of conventional magnetic nanoparticles for biomedical applications. To address these concerns, we have designed the polyethylene glycol (PEG) analogue biopolymer based magnetic nanostructures that are non-toxic at relatively higher concentrations, and anti-immunogenic by Food and Drug Administration standards. The polymeric shell acts as the reservoir of the drug molecules, while the superparamagnetic nanoparticles act as nano source of heat, and thus, initiates release of imbibed drug from the tunable excipient by causing volumetric shrinkage of the polymer network when exposed to oscillating magnetic field. Ac magnetic field modulated drug release and remote controlled heating are extremely promising characteristics for combinatorial therapeutics to facilitate cancer therapy or axon growth. However, to effectively modulate the release behavior of the therapeutic agents, temperature regulation needs to be extremely precise. Thus, understanding the different loss mechanisms inside the alternating magnetic is very important, particularly considering the fact that the system retains temperature induced volumetric transition behavior close to the normal physiological temperature, which can severely impact the Brownian loss. The highlight of this work is to portray potential opportunities for the combination of hyperthermia-based therapy and controlled drug release paradigms -towards successful application in combinatorial therapeutics.In this work, we have quantified the relaxation losses of the thermoresponsive core-shell nanostructures. Field and frequency dependent temperature modulation demonstrates the loss mechanism primarily related to the Brown relaxation. The predicted Neel maximum, however, is above the frequency range of practical interest. Moreover, the transmission electron micrographs revealed that the nanomagnets were located near each other inside the polymer shell, but were separated and did not agglomerate. This further supports the consistent Brownian loss and absence of ferromagnetic behavior and subsequent agglomeration of nanomagnets even after volumetric shrinkage, which is very typical for thermo-responsive magnetic colloids. We are currently observing the frequency spectra of the ac susceptibility to precisely quantify the optimum range for using these nano-carriers in hyperthermia and drug release. The possibility to induce controlled localized heating while allowing sustained release of therapeutic agents makes these nanoparticles attractive for biomedical applications.
V12: Poster Session: Multifunctional Polymer-Based Materials I
Session Chairs
Yakai Feng
Zhibin Guan
Andreas Lendlein
Thursday AM, December 01, 2011
Exhibition Hall C (Hynes)
9:00 PM - V12.10
PDA-Based Immunosensor for the Colorimetric Detection of Genetically Modified Organisms.
Min-Cheol Lim 1 , Yeo-Jae Shin 1 , Tae-Joon Jeon 2 , Hae-Yeong Kim 1 , Young-Rok Kim 1
1 Institute of Life Sciences and Resources & Department of Food Science and Biotechnology, Kyung Hee University, Yongin Korea (the Republic of), 2 Department of Biological Engineering, Inha University, Incheon Korea (the Republic of)
Show AbstractPolydiacetylene (PDA) has attracted much attention in recent years as a material for sensors because of its special features that allow optical transduction of sensory signals and its inherent simplicity and ease of use in supramolecular chemistry. PDA sensors are generally classified into liquid-phase sensors and solid-phase sensors. Liquid-phase sensors are simply PDA matrices dispered in a buffer solution, while solide-phase PDA sensors employ some form of immobilization of PDA supramolecules onto a substrate. In this study, a simple and sensitive approach for the detection of marker protein, phosphinothricin acetyltransferase (PAT), from genetically modified crops was developed based on the colorimetric transition of PDA vesicles in combination with silica microbeads. PDA has attracted a great deal of interests as a transducing material due to their special features that allow colorimetric response to sensory signals. But most PDA-based biosensors require additional equipments such as fluorescence microscope or UV-vis spectroscopy. In this study, we report a new approach to increase the degree of color transition by coupling antibody-conjugated PDA vesicles with silica microbeads in an effort to monitor the results with the naked eye or RGB analysis. By immobilizing PDA vesicles on silica microbeads, we were able to overcome the disadvantages of colloidal PDA-based sensors and increase the degree of blue-red color transition in response to target molecules to the concentration as low as 20 nM. All the result showed that PDA vesicles in conjunction with silica microbead will be promising transducing material for the target protein detection in diagnostic and biosensing applications.
9:00 PM - V12.11
Mechanical and Thermal Properties of HTPB-Based PU/POSS Nanocomposites.
Ho-Joong Kim 1 , Chang Kee Kim 2 , Younghwan Kwon 1
1 Chemical Engineering, Daegu University, Gyeongsan, Gyeongbuk, Korea (the Republic of), 2 , ADD, Daejeon Korea (the Republic of)
Show AbstractResearch into organic–inorganic hybrid nanocomposites has recently become popular, particularly the development of new polymer nanocomposites. Compared to pristine polymers or conventional composites, these hybrid nanocomposites exhibit improved properties. Therefore, this method delivers new materials with significantly improved thermal and mechanical properties, while still permitting the use of existing commercial processes. Currently, a new class of materials has been used to investigate the behavior of nanoparticles, called polyhedral oligomeric silsesquioxanes (POSS). These are a class of three dimensional organic–inorganic hybrid silicon–oxygen particles with the generic formula of (RSiO1.5)n. These molecules contain an inner inorganic framework covered by inert and/or reactive organic substituents. POSS molecules with well defined shapes and sizes ranging from 1 to 3 nm have been described as the smallest version of colloidal silica. When there is covalent bonding between the POSS and polymeric matrix, reinforcement is favored. In this study, effect of incorporation of functionalized POSS molecular particles covalently into thermoplastic PUs on their thermal and mechanical properties was investigated by means of DSC, TGA, and tensile test. The results showed that thermal/mechanical properties of the nanocomposites were linearly related with the POSS content. The thermal degradation behavior of the POSS hybrid nanocomposites was evaluated by taking into considering the rate of weight loss and characterization of the char formed during high temperature oven test. The thermal stability of POSS hybrid nanocomposites were improved significantly under the experimental conditions employed.
9:00 PM - V12.13
Multifunctional Polymer Nanocomposite.
Georgi Georgiev 1 2 , Gajinder Hoonjan 1 , Ananta Adhikari 1 , Germano Iannacchione 3 , Peggy Cebe 2
1 Natural Sciences, Assumption College, Worcester, Massachusetts, United States, 2 Physics and Astronomy, Tufts University, Medford, Massachusetts, United States, 3 Physics, Worcester Polytechnic Institute, Worcester, Massachusetts, United States
Show AbstractThe need for polymer-based materials that can respond to the environment stimuli, classified as intelligent materials is increasing by the day. The history of human technology has been substitution of machines with materials that can do their function much more efficiently and without much maintenance. The most obvious example is the watch mechanism being replaced by quartz crystals. We present a hybrid structure of Isotactic Polypropylene (iPP) nanocomposite with multiwall carbon nanotubes (CNTs). The polymer component contributes to the optical properties, flexibility and integrity of the polymer film and the carbon nanotubes to the increased thermal and mechanical stability, electrical and thermal conductivity and sensitivity. The multifunctional characteristics of this nanocomposite material are enhanced by anisotropic organization of the nanotubes and polymer through melt shearing, providing organization of the structural constituents at molecular, nano, and micro length scales. This provides for anisotropic split of the macroscopic active polymer film properties in direction of its orientation and perpendicular to it. On molecular scale the CNTs control the arrangement of the polymer atoms in a crystal lattice. On nanoscale, the CNTs couple to the smectic director of the liquid crystal form of iPP and align. On microscale the secondary polymer crystal structure is rearranged on the CNTs surface to form fibrillar, instead of spheruclitic structures. All those scale rearrangements affect the optical, thermal, electrical, mechanical and chemical properties of the nanocomposite. We use iPP with different concentration of carbon nanotubes (CNTs): 0.01%, 0.1%, 1%, 2% and 5% and oriented the thin film samples using melt-shear at 200°C and 1Hz in a Linkam microscope sharing hot stage. To confirm anisotropy, the sheared samples were analyzed using polarized optical microscopy (POM) and Two Dimensional Microscopic Transmission Ellipsometry (2D-MTE). Light scattering patterns are also altered by aligning the nanocomposite films uniaxially. 2D-WAXS technique was used to measure the anisotropy indicating strong ordering of the crystals as a function of the CNTs concentration.
9:00 PM - V12.14
Development of Multifunctional Structural Composite Supercapacitors.
Edwin Gienger 1 , James Snyder 1 , Eric Wetzel 1 , Kang Xu 2
1 Materials and Manufacturing Science Division, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States, 2 Direct Energy and Power Generation Division, U.S. Army Research Laboratory, Adelphi, Maryland, United States
Show AbstractThe weight and volume of conventional energy storage technologies greatly limits their performance in a range of mobile platforms. Significant research efforts are currently underway to reduce device size and mass through improvements in energy density and power density. Enabling a device to perform additional functions, such as bearing mechanical load, is an alternative approach to weight reduction if it operates at a high enough efficiency relative to the individual materials it replaces. Our research focuses on structural batteries and structural supercapacitors, which could be used to replace conventional structural components, such as vehicle frame elements, with power-generating components to provide significant system-level weight reductions and extend mission times. In this study, structural properties are being designed directly into the electrolyte and electrode materials. Novel solid polymer electrolyte materials are being developed to transfer load to the fibers while providing ions necessary to achieve an electrochemical double layer for energy storage between electrodes. These structural electrolytes are integrated into systems constructed of high surface area carbon fiber electrodes to optimize both energy storage and load-bearing capabilities. The style, architecture, conductivity, and surface area of different fabric electrodes are being systematically investigated with a range of structural electrolyte formulations provide optimal structural and electrochemical performance. Metrics have been developed to correlate material properties with multifunctional performance. The components are being integrated using scalable, cost-effective composite processing techniques. This processing route is scalable and amenable to complex part shapes, and the resulting fully processed supercapacitor composites have demonstrated reasonable structural properties as well as charge storage performance.
9:00 PM - V12.15
Characterization and Evaluation of Mechanical and Thermal Properties of Natural Rubber Composites.
Anderson Manoel 1 , Mariselma Ferreira 1
1 CCNH, UFABC, SAO PAULO, SP, Brazil
Show AbstractRecently, polymer-nanocomposites have attracted the attention especially for developing of nanocomposites using layered silicates, which provides an alternative to composites fabricated with conventional fillers [1]. This study proposes one new material using montmorillonite, chitosan and natural rubber latex. The process for intercalation the chitosan molecules between clay lamellae used in this study was described in the literature for Darder et al [2]. Chitosan solutions were prepared by the addition of 1% (v/v) acetic acid, and after the resulting solutions were slowly added to 2% clay suspension and kept under magnetic stirring for 24 hours. The dispersion was added progressively to the latex while stirring.The product obtained was cast onto a Teflon mold and dried for 48 h in room temperature. Due to natural latex instability was used a nonionic detergent to prevent coagulation of the latex. Nanocomposites were prepared from natural rubber at concentrations of 1, 3, 5 and 10% montmorillonite and chitosan. To check the intercalation of polymer molecules between the lamellae of clay X-ray diffraction (XRD) analysis was performed. Results showed that the polymeric nanocomposites prepared had an effective intercalation of polymers between the lamellae of montmorillonite. The intercalation was confirmed by the decrease of the 2θ value. The clay interlayer space showed an increase in basal spacing between lamellae as filler concentrations increases. Subsequently, was performed thermal and mechanical analysis for to evaluate of properties of material. The glass-transition behaviors of the natural latex and natural rubber composites systems were measured by the DSC analysis. The curves showed a peak transition temperature in the range between -64.0°C and -63.0°C for all composites prepared. The same value was found to pure natural rubber. The thermal stability of rubber and composites prepared also was evaluated. It was observed that the initial decomposition temperature is around 300°C for all composites but until this temperature was observed a mild weight loss in relation to initial mass and in all cases at 380°C the initial mass was reduced to about 50%. In mechanical analyze the stress versus strain curves showed that the all nanocomposites prepared present greater strain than natural rubber. The intercalation of the cationic biopolymer chitosan into Na + montmorillonite through a cationic exchange process provides nanocomposites with thermal properties according to the international standard for natural rubber. From the results it can be assumed that the organic treatment with chitosan increases the interlayer spacing of silicate which allows the dispersion of silicate layers into the matrix at a nanoscale level.[1] S. Varghese and J. Karger-Kocsis, Polymer, 44 (2003) 4921-4927.[2] M. Darder, M. Colilla and E. Ruiz-Hitzky, Chem. Mater., 15 (2003) 3776-3777.Acknowledgements: Capes, Fapesp, CNPq, UFABC
9:00 PM - V12.16
Studies and Characterization of Spraying LbL Natural Rubber Latex Films.
Christiane Davi 1 , Luiz Fernando Dias Galdino 1 , Mariselma Ferreira 1
1 CCNH, UFABC, SAO PAULO, SP, Brazil
Show AbstractNR latex can be described as a polydispersive system that has negatively charged particles. We were able to mount polyelectrolyte multilayers films of NR particles using polyethylenimine (PEI) or polyallylamine hydrochloride (PAH) as positive counterpart. (PEI/NR)n and (PAH/NR)n films were made employing simple hand-operated devices to spray the solutions. We tested to trigger the spraying device 2, 5 and 7 times with and without rinsing steps. Sample films were evaluated by UV-vis up to 10 bilayers and AFM with 5 and 15 bilayers. AFM was used to obtain statistical data, which allowed us to compare the different films fabricated. Data of surface coverage, size distribution and presence of flatten shaped particles were obtained by Gwyddion software. Particles were considered flattened when its height was 20 times lower than length. Contact angle measurements were also performed.The results showed that all sample films had linear growth besides the fabrication methodology. (PEI/NR) 10 non-rinsed films presented significant higher absorbance than the rinsed samples. However, no difference on this matter was observed when comparing (PAH/NR)10 films. AFM images showed mostly round shaped particles, as expected, but samples had significant differences of surface coverage. Rinsed films of (PAH/NR)n presented higher surface coverage than (PEI/NR)n . Furthermore opposite results were obtained for non-rinsed films. It implies that the non-rinsing method is better suit for PEI films, while apparently it does not matter for PAH films. Analyzing data separately for samples built up with 2, 5 and 7 spray times we identified better surface coverage at: a) 7 spray times for (PEI/NR)n rinsed and non-rinsed films; b) 5 spray times for (PAH/NR)n rinsed film; and c) 2 spray times for (PAH/NR)n non-rinsed films. Films with 15 bilayers had a tendency to show higher surface coverage than 5 bilayers. In addition, particles size on the 15 bilayers films were in greater number and bigger than those on the 5 bilayers surface. Regarding to the particles shape, only 7 sprays rinsed(PEI/NR)5 film had 8% of flattened particles. On the other hand,7 sprays non-rinsed films of (PAH/NR)5 and (PAH/NR)15 presented 77% and 7% of flattened particles respectively. Shape might indicate higher adsorption forces between particle-surface, however no correlation with contact angle was found. Higher angles were detected on PAH films (74° rinsed, 78° non-rinsed) rather than PEI (57° rinsed, 70° non-rinsed) and spraying times did not influenced it. This work showed the importance of using different analyses before point out the best parameters for spraying LbL latex films. Therefore, we identified for (PEI/NR)n and for (PAH/NR)n non-rinsed 7 sprays that as long as we keep sprays number lower than 5 times, we can choose to rinse it or not.Acknowledgements: Capes, Fapesp, CNPq, UFABC
9:00 PM - V12.17
Actuation of Photonic Crystals Embedded in PDMS Membrane for Reflective Displays.
Jae-Hoon Choi 1 , Tae Soup Shim 1 , Jae Young Sim 1 , Seung-Man Yang 1
1 , KAIST, DaeJeon Korea (the Republic of)
Show AbstractRecently, researches of photonic crystals for reflective displays have been carried out extensively. The use of photonic crystals for the display has advantages such as low cost and simple fabrication procedures. However, reflective color change of photonic crystals by swell/deswell has slow response time. Also, stability of photonic crystals during actuation is a problem. To overcome these problems, we fabricated a photonic membrane which is a photonic crystal embedded in thin PDMS film. The photonic membrane attached to PDMS mold which has microchannels could be expanded to outside of the channels by pressurized gas. Color of the expanded photonic membrane was red-shifted compared with original color of the photonic membrane because of incidence angle of the light. With designed microchannels, we demonstrated single digit numbers for display application by using programmed actuation. Response time of the photonic membrane is less than 100 ms. Moreover, actuation of the membrane was stable for a long time.
9:00 PM - V12.18
Multi-Functional Polymer Base Nano-Composite with Super-Hydrophobic Properties.
Sunghoon Park 1 , Eunhyoung Cho 2 , Hajin Kim 1 , Yoonchul Son 1 , MinJong Bae 1 , Sangeui Lee 1 , Dongouk Kim 1 , Dongearn Kim 1 , Kunmo Chu 1 , Intaek Han 1 , Jinseung Sohn 2 , Paul Theilmann 3
1 Organic & Composite Material Group , Samsung Advanced Institute of Technology (SAIT), Gyeonggi-do Korea (the Republic of), 2 Nano Fabrication Group, Samsung Advanced Institute of Technology (SAIT), Gyeonggi-do Korea (the Republic of), 3 Electrical enineering, University of California, San Diego, San Diego, California, United States
Show AbstractWe report on a new type carbon nanotube (CNT)-polymer nanocomposites with superior surface properties. Such composites were synthesized through a new methodology for multifunctional nanotube composites, where Nanoimprint Lithography (NIL) techniques were used to form super-hydrophobic and scratch durable surface. Different with spray methods or chemical etching methods to form conducting and super-hydrophobic coating layer, our strategy directly imprint super-hydrophobic pattern on the surface of nanocomposites through stamping hard (or soft) mold into a soft material. Therefore, it contains bulk properties such as mechanical, electrical and microwave properties and enhanced surface properties also in one material. Such composite, e.g., CNT-PDMS (Polydimethylsiloxane), incorporate good dispersion of nanotubes and Nil techniques, yielding outstanding electrical properties (over 500 S/m for DC conductivity) with super-hydrophobic properties (contact angle ~ 167 degree) and microwave shielding efficiency, SE (over 30 dB) for electromagnetic interference (EMI) applications. In addition, dual hole pattern on the nanocomposite surface enable long-term endurance against environment exposure while existing super-hydrophobic pattern are easily fragile. The above achievements are expected to lay a strong foundation for the widespread use of CNT composites for a whole of applications including electromagnetic interference shielding, microwave absorbing material, reinforce materials for vehicle, ship and structure unit, sensor device,heat unit and solar cell electrodes.
9:00 PM - V12.19
Rubber/Laponite Nanocomposites with Prepare by Collodial Route.
Tatiane Arantes 1 , Renata Sala 1 , Emerson Camargo 1
1 Chemistry, Federal University of São Carlos, São Carlos, São Paulo, Brazil
Show AbstractAiming to overcome the limited performance of polymeric materials, a new class of hybrid materials called nanocomposites has been emerged through the controlled insertion of nanoparticles into a polymer matrix, [1-4]. In our group we are interested in preparing nanocomposites based in commercial polymer matrix, like styrene butadiene rubber (SBR) or nitrile rubber (NBR), by the insertion of pure and silanized synthetic clays by means of simple mix of components using the colloidal route. All the nanocomposites were characterized by X-ray diffraction, small angle X-ray scattering (SAXS), differential calorimety scanning, thermal gravimetric analysis coupled with infrared spectroscopy (TGA-FTIR), 13C nuclear magnetic resonance in solid state (NRM) and dynamic mechanical thermal analysis (DMTA). The nanocomposites showed exfoliated structure, which was confirmed by XRD, SAXS and solid state 13C NMR. TGA-FTIR analysis showed that the incorporation of clay into NBR and SBR polymers improved the thermal stability of all nanocomposites and the addition of nanometric particles increased the elastic modulus of NBR and SBR nanocomposites, as observed by DMTA. The properties of nanocomposites were explained in terms of classical mechanical reinforcements. The molecular mobility of the polymer chains was lowered after the insertion of exfoliated clay, restricting the movement of polymer chains, which was confirmed for solid state 13C NMR through the broadening of the peaks in the nanocomposites spectra and by the increase of the proton spin-lattice relaxation time (T1H). The experimental results could associate the confinement effect of polymer chains in the interface clay/polymer with the restriction caused in the polymer mobility by the presence of clay layers.
9:00 PM - V12.2
Self-Assembled Hierarchical Structure from Side-Chain Liquid Crystalline Block Copolymer Brushes.
Prashant Deshmukh 1 , Suk-kyun Ahn 2 , Rajeswari Kasi 1 2
1 Chemistry, University of Connecticut, Storrs, Connecticut, United States, 2 Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States
Show AbstractWe investigate a series of side-chain liquid-crystalline (SCLC) block copolymer brushes which form self-assembled hierarchical architectures in different length scale. These block copolymers are prepared by sequential ring-opening metathesis polymerization (ROMP) of two different functionalized norbornenes comprising cholesteryl ester and poly(ethylene glycol) (PEG) as side-chain, respectively. Cholesteryl side-chain provides LC ordering, while semi-crystalline PEG (Mn= 2000 g/mol) forms molecular brushes. Molecular composition of block copolymers is determined by 1H NMR, while narrow distribution of molecular weight (polydispersity < 1.2) is observed by gel permeation chromatography (GPC). Thermal transitions including glass transition (Tg), liquid-crystalline clearing transition (Tcl) and melting temperature (Tm) are determined by differential scanning calorimetry (DSC). Self-assembled hierarchical structures in the melt state are explored by small-angle and wide-angle X-ray scattering (SAXS and WAXS). Cholesteryl side-chains provide smectic A (SmA) mesophases in the LC block in which the layer spacing range from 6 to 8 nm. Due to the incompatibility with LC block, molecular brushes segregate into nanostructures such as lamellar or cylinder on the length scale of 40 -80 nm depending on composition. Design of polynorbornene based brush block copolymers has made it possible to design complex macromolecule. Brush architecture having steric repulsion of densely grafted side chains, to mimic features of biomolecule is interesting to study. Combining this brush copolymer with liquid crystalline polymer will introduce hierarchical self-assembly at two lengths of nanoscale. We believe that self-assembly of these synthetic macromolecules mimicking organization of biomolecule in nature can find potential applications in nanomedicine, nano-template and design of functional soft actuators.
9:00 PM - V12.22
Multifunctional Microvascular Composites Fabricated from Coated Sacrificial Fibers (CSFs).
Hefei Dong 1 6 , Sarut Chayanupatkul 1 6 , Aaron Esser-Kahn 5 , Nancy Sottos 1 3 6 , Scott White 3 4 6 , Jeffrey Moore 1 2 6
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 6 Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 5 Chemistry, University of California, Irvine, Irvine, California, United States, 3 Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractThis talk will present the development of a new type of microvascular composites having independent, intermingled channel networks. Inspired by natural composite structures found in living organisms, these synthetic analogs have desirable dynamic functionalities of energy and mass transport that come from controllable vascular spacing and interchannel transport. In our recent work[1], we constructed vascular networks within a fiber-reinforced composite using a method called Vaporization of Sacrificial Components (VaSC) and we demonstrated the ability to move various liquids through the composite. However, composites fabricated using this method are limited to a single vascular network because of the need to control the channel spacing. Here we provide a general solution to this limitation by adding a coating on sacrificial components (fibers) which can be used to deliberately manipulate the spacing and transport properties between the microchannels. The variable properties of the coating will add new functionalities by allowing transport properties between channels to be controlled. Coated sacrificial fibers (CSFs) are thus envisioned as a building block for fabricating the next-generation of advanced composites. The availability of these CSF building blocks might enable manufacturable routes to synthetic composites that emulate countercurrent circulatory and respiratory functions. This talk will cover two polymer coating techniques we developed. The first is an UV curable PDMS protective coating. Microvascular composite fabricated from PDMS coated sacrificial polylactide (PLA) fibers are aimed at countercurrent energy/mass exchange. The second coating technique involves a proton conductive material, Nafion, which allows ions to be conducted between two microchannels. Endowed with tunable interchannel transport, microvascular composites fabricated from Nafion coated PLA fibers may find applications in fuel cells and flow batteries. [1] Esser-Kahn, A. P.; Thakre, P. R.; Dong, H.; Patrick, J. F.; Vlasko-Vlasov, V. K.; Sottos, N. R.; Moore, J. S. and White, S. R. Adv. Mater. 2011 (in press).
9:00 PM - V12.23
A Sequentially Synthesized Semi-Interpenetrating Network from Oligo(ethylene glycol) and Poly(ethyl-2-cyanoacrylate).
Giuseppe Tripodo 1 2 , Christian Wischke 1 2 , Andreas Lendlein 1 2
1 Center for Biomaterial Development, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 , Berlin-Brandenburg Center for Regenerative Therapies, Teltow Germany
Show AbstractPolyalkylcyanoacrylates (PACA) are a class of hydrophobic polymeric biomaterials, which have been employed for a long time as surgical glues and were proposed as drug delivery systems. However, they suffer from great brittleness, which limits their applicability [1-3]. Oligo(ethylene glycole) [OEG] is a widely studied biomaterial, which is highly hydrophilic and, if crosslinked to networks, shows high degrees of swelling, which may limit its use as implant material. Stiffness and brittleness of PACA on the one hand as well as extensive swelling of OEG-based networks on the other hand may be overcome by properly combining both materials.Due to the presence of two strong electron-withdrawing groups at α-carbon resulting in low electron density at the double bond, the reaction of cyanoacrylate monomers to a linear polymer is extremely fast, which makes it highly sensitive to any kind of nucleophiles such as water. Another class of functional groups sensitive to nucleophiles are epoxids, which can be employed for crosslinking of, e.g., OEG with epoxy-functionalized end groups. However, epoxy groups are much less reactive in the presence of nucleophiles than cyanoacrylates due to higher activation energies for the epoxy ring [4]. Therefore, curing agents are required to initiate the crosslinking of di-epoxides. This allowed the anionic homopolymerization of poly(ethyl-2-cyanoacrylate) [PECA] in the presence of OEG diglycidyl ether (OEGDG), which then could be crosslinked in a second step of a one-pot synthesis to give semi-interpenetrating polymer networks (sIPN).In order to obtain networks with degradable ester bonds [5], crosslinking of OEGDG was performed with anhydrides in the presence of catalytic amounts of acids or bases. By systematically changing the types of base catalyst and anhydride, triethylenetetramine (TETA) and succinic anhydride or maleic anhydride were finally selected as the most promising system. FT-IR studies showed consumption of epoxy groups by the disappearance of the peak at 912 cm-1 as a proof of crosslinking. In its handling, the material exhibited no brittleness and appeared as an elastic material. The obtained sIPN networks were insoluble in the most common organic solvents and had, in contrast to pure PEGDG networks, only a minor water uptake of 8 wt.% in 24 h. Furthermore, after drying of the sample as obtained from the water uptake studies, the sIPN did not show any macroscopic crystallization and retained a high flexibility. The gel content was shown to be 90 wt.% in water and 85 wt.% in acetone, indicating reasonable PEGDG crosslinking and good entanglement of PECA in the sIPN.References:[1] D. P. Melody, British Polymer J. 1989, 21, 175.[2] C. Vauthier, et al., Adv. Drug Del. Rev. 2003, 55, 519.[3] C. Wischke, et al., Int J Artif Organs 2011, 34, 243.[4] K. Sun et al., Chem. Phys. Lett. 2009, 470, 259.[5] I. Nishimura, et al., Macromol. 1996, 29, 3818.
9:00 PM - V12.24
Broadband near-Infrared Luminescence from Bi-Doped Zeolite-Polymer Composites.
Zhenhua Bai 1 , Minoru Fujii 1 , Shuohei Kitano 1 , Kenji Imakita 1 , Shinji Hayashi 1
1 Department of Electrical and Electronic Engineering, Kobe University, Kobe Japan
Show Abstract Bi-doped materials have attracted great interest for the potential applications in fiber amplifiers, owing to their ultra-broad near-infrared (NIR) luminescence in the wavelength region from 1000 nm to 1600 nm with FWHM over 200 nm, covering the whole telecommunications window. Such broad emission band is also favorable for ultra-short pulse lasers. Up to now, broadband NIR emission from Bi ions has been reported in various glasses and crystals. On the other hand, efficient NIR luminescence has not been achieved in Bi-doped organic materials. Polymer-based organic materials have been extensively investigated for applications in optical devices, because of their easy fabrication, rapid processibility, cost effectiveness, low optical loss, and small birefringence. A large array of rare-earth functionalized organic complexes has been developed to be used as dopants in polymer. However, these complexes suffer from instability and low optical efficiency. More recently, zeolite-polymer composites have attracted considerable attentions owing to their enhanced thermal and mechanical properties and higher optical efficiency. Visible luminescence with high efficiencies from optically functionalized zeolite-polymer composites has been reported. In contrast, it is difficult to realize highly efficient NIR emission in these composites, because of the quenching effect of O-H and C-H vibrations. In this work, we prepare transparent Bi doped zeolite-polymer composites and study the optical properties. We show that long-lived broadband NIR emission can be realized from the Bi doped zeolite-polymer composites. The emission covers the range of 980~1630 nm, with a lifetime of as long as 0.37 ms. In the zeolite matrix, Bi ions exist as Bi-related NIR active centers and Bi compound agglomerates. The Bi compound agglomerates act as a blockage to seal the pores of zeolites, which isolate the NIR active centers from the quenchers (C-H and O-H bonds). Our results may pave the way for the applications of these hybrid composites in NIR photonics.
9:00 PM - V12.25
Use of Organically Modified Montmorillonite in Simutaneous Impact Modification and Strengthening of Polystyrene.
Canan Yeniova 1 , Ulku Yilmazer 1
1 Chemical Engineering, Middle East Technical University, Ankara Turkey
Show AbstractThe impact strength of brittle polymers can be increased by melt compounding with elastomeric materials. However, this procedure results in low tensile strength and modulus. To overcome this deficiency, in this study, organoclays were added during compounding. High impact polystyrene was produced by melt blending polystyrene, poly(styrene-b-(ethylene-co-butylene)-b-styrene) grafted by maleic anhydride (SEBS-g-MA) and organoclay (Cloisite® 25A). The compounding was done in a corotating twin screw extruder. The content of Cloisite® 25A in the nanocomposites was kept at 1 and 2 wt %, while the elastomeric phase content varied from 5 to 40 wt %. When the ternary systems were analyzed with XRD, it was seen that all of the compositions exhibit exfoliated structures. The TEM results indicated that the degree of organoclay dispersion is the highest for the compounds containing 15 wt % SEBS-g-MA. In accordance with this result, the highest improvement in the mechanical properties was found in nanocomposites prepared with 15 wt % SEBS-g-MA. With increasing elastomer content, the toughness and the elongation at break values increased. However, further addition of elastomer to 30 – 40 wt %, affected the tensile strength and stiffness in an adverse way. Thus, it can be said that 15 wt % SEBS-g-MA usage is optimum to prepare this type of nanocomposites. TEM results also showed that, clay particles are localized in the elastomer phase and at the interface of SEBS-g-MA and polystyrene. Thus, the clay particles lead to enlarged elastomeric domains that improve not only the tensile but also the impact strength. In conclusion, the impact strength of the PS was enhanced by 400 % in the presence of 15 wt% SEBS-g-MA and 2 wt % Cloisite® 25A. Besides improving the impact strength of the material, tensile properties were not deteriorated.
9:00 PM - V12.26
Preparation of Highly Elastic and Conductive Films Derived from Poly(3,4-ethylenedioxythiophene)-Polystyrenesulfonic Acid (PEDOT:PSS) on Nonwoven Fabrics.
Chieh-Han Wu 1 , Hsiu-Ping Shen 2 , Trong-Ming Don 3 , Wen-Yen Chiu 1 2 4
1 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan, 2 Department of Chemical Engineering, National Taiwan University, Taipei Taiwan, 3 Department of Chemical and Materials Engineering, Tamkang University, Taipei county Taiwan, 4 Department of Materials Science and Engineering, National Taiwan University, Taipei Taiwan
Show AbstractIn this research, a highly conducting poly(3,4-ethylenedioxythiophene)- polystyrenesulfonic acid (PEDOT:PSS) aqueous dispersion was synthesized at first via chemical oxidative polymerization and followed by mixing it with poly(styrene-r-butyl acrylate) P(St-BA) aqueous latex, creating a novel conductive material with outstanding elasticity and conductivity. The elastic conductive composite films were then formed on the glass and nonwoven fabric substrate by spin coating and dip coating, respectively. Various contents of PEDOT:PSS polymer (10, 25, 50, 75, and 100 wt.%) in the dried PEDOT:PSS/P(St-BA) composite films were prepared. The surface resistance of PEDOT:PSS/P(St-BA) composite film was measured by a ohmmeter and the conductivity was calculated. From the conductivity measurements, the conductivity as high as 331 S/cm for pure PEDOT:PSS thin films was obtained. The conductivity was still kept at 88 S/cm even the PEDOT:PSS content was lowered to 10 wt.%. Furthermore, the elasticity of conductive films on the nonwoven fabric substrate was evaluated by the 180° bending test repeating 100 times. The changes of surface resistance for different PEDOT:PSS contents and different concentrations of PEDOT:PSS/P(St-BA) dispersions on the nonwoven fabric substrate were recorded with bending times. With introducing soft P(St-BA) material in the PEDOT:PSS phase, the surface resistance increased 3 - 6 times after bending 100 times, while the surface resistance for pure PEDOT:PSS films could reach 18 - 20 times. The elasticity of PEDOT:PSS/P(St-BA) composite films was demonstrated.
9:00 PM - V12.27
Thermoelectric Properties of PPV-Based Block Copolymers and Their Composites.
Patrick Taylor 1 , Paul Lahti 2 , Frank Karasz 1 , Eugene Wilusz 3
1 Department of Polymer Science and Engineering, UMASS-Amherst, Amherst, Massachusetts, United States, 2 Department of Chemistry, UMASS-Amherst, Amherst, Massachusetts, United States, 3 , Natick Soldier RDE Center, Natick, Massachusetts, United States
Show AbstractA range of alternating block co-polymers have been synthesized consisting of p-phenylene vinylene (PPV) based oligomers interspersed with flexible aliphatic blocks using a modified Wittig polymerization. The resulting polymers were characterized by NMR, UV-Vis, GPC, and DSC. Films of the polymers blended with single-walled carbon nano-tubes (SWCNT) were prepared, p-doped using I2 and their electrical conductivities determined using a four-point probe measurement. Seebeck coefficients were determined by measuring the resultant potential as a temperature gradient was applied across the macroscopic sample. The dimensionless thermoelectric figure of merit ZT was estimated from the expression ZT = S2σ/κ, where S is the Seebeck coefficient, σ the electrical conductivity and κ the total thermal conductivity. The ZT’s of the composite films were found to be of the order of 10-3.
9:00 PM - V12.28
The Electromechanical Behavior of a High-Modulus Electroactive Polymer Acting as a Robust Ionomer for Micro-Ionic Actuators.
Hatipoglu Gokhan 1 , Yang Liu 1 , Ran Zhao 1 , Yoonessi Mitra 2 , Dean M. Tigelaar 2 , Srinivas Tadigadapa 1 , Qiming Zhang 1
1 , Pennsylvania State University , State College, Pennsylvania, United States, 2 , NASA Glenn Research Center, Cleveland, Ohio, United States
Show AbstractA high modulus, sulfonated polymer synthesized from a one-to-one ratio 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5 triazin-2-amine and 4,4′-biphenol with bis(4-fluorophenyl) sulfone (DPA-PS:BP)is exploited as an ionomer for micro-ionic actuators. A unique and attractive feature of the ionomer is that it can be swelled by high amounts of ionic liquid (IL) as an electrolyte (up to 150 wt%) while maintain a high elastic modulus of 600 MPa, which is more than an order of magnitude higher than the state-of-the-art of ionomers with working electrolytes. Such a high modulus makes it possible for the ionomer to be fabricated into micro-actuators in various free standing forms, with high uptake of ILs and low operation voltage (<4 V), which are attractive for MEMs applications. As an initial demonstration of a DPA-PS:BP based micro-ionic actuator, a cantilever (200 µm x 33 µm x 5 µm) is manufactured by Focused Ion Beam (FIB) and characterized. Under the voltage of 1.6 V, the bending actuator exhibits a 0.54% bending strain. The corresponding estimated blocking force is 5 µN.
9:00 PM - V12.29
Electrochemically Generated Strains of Polypyrrole Film in Ionic Liquids.
Keiichi Kaneto 1 , Kazuo Tominaga 1
1 LSSE, Kyushu Institute of Technology, Kitakyushu Japan
Show AbstractConducting polymers are prospective materials for soft actuators to build human friendly robots. The strain and stress of electrochemomechanical deformation (ECMD) have been recorded to be 39% and 22MPa[1,2], respectively, which are better than those of skeletal muscles. The ECMD is generated mainly by insertion of ions or solvated ions into polymer matrix. The cycle stability and creeping under loads are major issues for the practical use. Ionic liquids (ILs) are interested in electrochemical reactions[3,4], because of the stability, non volatile and non flammable features. In this paper, study on the ECMD of porous polypyrrole (PPy) using IL under tensile loads is reported. It is found that the ECMD of the PPy film doped with bis(trifluorometylsulfonyl)imide (TFSI) was initiated by reduction showing swelling 20% by soaking of IL of 1-butyl-1-methylpyrrolidionium (BMP)TFSI[5]. Usually, PPy does not swell by immersion in IL. The cyclic strain due to doping and dedoping of cation was 3-5 % in the manner of cation doping with the blocking stress of 2 MPa. The strain is smaller than those of using conventional organic electrolytes, even large cation of IL is inserted. The fact indicates that the bare cation is inserted, being supported by the numeral calculation of electrical charges and the volume of cation. The blocking stress of the film was 2MPa and electrochemical creeping occurred at the tensile load of 0.7 MPa. The smaller values are due to porous PPy films.By mixing IL with organic solvent like propylene carbonate (PC), the strain of ECMD successfully increased to more than 20% superimposed to 40% swelling due to soaking of PC. However, the strain of ECMD diminished to few % by several electrochemical cycles, which is conjectured to decrease in electrochemical activities partially by loss of electrical conductivity.[1] S. Hare, et.al, Smart Mater. Struct. 14 (2005) 1501-1510.[2] S. Hara, et.al, Polym. J. 38 (2006) 669-677. [3] W. Lu, et.al, Science, 297 (2002) 983-987 .[4] K. Yamato,et. Al, Synth. Metals. 159 (2009) 839-842. [5] K. Kaneto, et.al, Jpn. J. Appl. Phys.(2011) in press.
9:00 PM - V12.3
Formation of Liquid Crystalline Order in Mesogenic Epoxy Resin/AlN Composite and Its Effect on Thermal Conductivity.
Shingo Tanaka 1 , Fusao Hojo 1 , Hiroyuki Kagawa 1 , Yoshitaka Takezawa 2
1 Hitachi Reserch Laboratory, Hitachi. Ltd., Hitachi-shi, Ibaraki-ken, Japan, 2 Tsukuba Reserch Laboratory, Hitachi Chemical Co., Ltd, Tsukuba-shi, Ibaraki-ken, Japan
Show AbstractCeramic fillers are widely used to increase thermal conductivity of epoxy resin composites [1]. In particular, aluminum nitride (AlN) has been extensively studied as the material for high-thermal conductive fillers [2]. Meanwhile, an epoxy resin containing mesogenic moieties has been reported to enhance thermal conductivity by forming liquid crystalline order spontaneously [3]. In this paper, we report the effect of ceramic surfaces on liquid crystalline ordering of the mesogenic epoxy resins and its effect on thermal conductivity of the composite.Firstly, thin mesogenic epoxy resin layers were cured on AlN and alumina (Al2O3) plates. Structures of the resins cured on each of the plates were analyzed by x-ray diffraction. Consequently, diffraction peaks corresponding to a periodicity of 2.2 nm were only detected from the resin cured on the Al2O3 plate, which indicates that the mesogenic epoxy resin is more likely to form a liquid crystalline order on the Al2O3 surface but not on the AlN surface. Secondly, we studied the effect of AlN filler treatment on the structure of the mesogenic epoxy resin composites by employing untreated and thermally treated fillers. The composites were both cured between glass plates to observe the liquid crystallinity by polarized optical microscopy. The orientational structure of the mesogenic epoxy resin composite with the untreated filler was found to be similar to that cured without the fillers. In contrast, the structure of the composite with the thermally treated AlN filler was found to be different from that of the original structure. Thermal treatment of AlN filler forms α- Al2O3 layer on its surface. Therefore, the present results may imply that α- Al2O3 have a significant effect on the molecular orientation of the mesogenic epoxy resin. Finally, we measured the thermal conductivity of these composites. The thermal conductivity of the composite with thermally treated filler was confirmed to be approximately 20% larger than that with the untreated filler.In conclusion, we revealed that thermal conductivity of the mesogenic epoxy resin composite with AlN filler can be improved by thermal treatment of the fillers. This improvement can be attributed the formation of liquid crystalline order with 2.2 nm periodic length enhanced by the Al2O3 surface. References [1] Y. Agari et al., J. Appl. Polym. Sci., 49, 1625-1634 (1993) [2] S. Tanaka et al., ISAOP-10 & ISSM-1, P081 (2010) [3] M.Akatsuka and Y. Takezawa, J. Appl. Polym. Sci., 89, 2464-2467 (2003)
9:00 PM - V12.30
Donor-Acceptor Polymeric Systems for Resistive-Type Memeory Device Applications.
Cheng-Liang Liu 1 , Yi-Kai Fang 2 , Wen-Chang Chen 2 3
1 Department of Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, Japan, 2 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan, 3 Department of Chemical Engineering, National Taiwan University, Taipei Taiwan
Show AbstractDonor-Acceptor (D-A) polymers-based including pendent polymers, functional polyimides and composites are demonstrated to have a promising applications in memory device since due to the advantages of simplicity of structure, low-cost and 3D-stacking capability. The resistive-type memory cell containing active polymer materials sandwiched between two metal electrodes that efficiently store the data based on the current response to an applied voltage. Various memory effects such as non-volatile (flash or write-once read-many times (WORM)) and volatile (dynamic random-access memory (DRAM) or static random-access memory (SRAM)) memory are realized. Different switching mechanism such as trapping/detrapping or charge transfer has been provided. D-A polymers for memory device is based on conjugated donors that allow the charge transport via hopping process with appropriate acceptors for preparing charge-trapping condition or charge transfer conducting complex as the external voltage is applied. The tunable switching behavior are explored through the different ratio of D/A moieties, D/A strength, film thickness and self-assembled morphology. The analysis of structure-memory performance relationship would establish the direction of future development of polymer memory materials.
9:00 PM - V12.31
Manufacturing Issues around World First Commercial EAP (Electro-Active Polymer) Based Haptic Actuator and Its Scale-up.
Duk Su Kim 1 , Jae Ik Yang 1 , Dong Hyuk Shin 1
1 , ELK Corporation, Daejeon Korea (the Republic of)
Show AbstractSince the finding of EAP (electro-active polymer) by Stanford Research Institute, many researches and commercialization efforts have been conducted. ELK Corporation, which collaborates with Artificial Muscle / Bayer MaterialScience, developed and manufactured the world first commercial product for haptic actuator out of EAP technologies. This study deals with difficulties and issues to produce haptic actuators, and ways to overcome the low yield / performances. Current production is based on proprietary silicone film as substrate material, which is extremely tacky and fragile. ELK chose screen printing for deposition method for facilitated scaling up efforts. Printing on silicone film caused lots of troubles, such as film sticking into mask screen, tearing during print or holding, curing issues, etc. After series of attempts to alleviate the defects and failures during the manufacturing process, the completely different way of thinking showed the unexpected and exceptionally high performance and yield. This study will talk about how to manage the issues in production, and become successful. Also, retrospective view on the previous mistakes and way to realize fool-proven process setup will be highlighted.
9:00 PM - V12.32
Bistable Electroactive Polymers Combining Large Strain Actuation and Shape Memory.
Xiaofan Niu 1 , Qibing Pei 1
1 Materials Science and Engineering, University of California, Los Angeles (UCLA), Los Angeles, California, United States
Show AbstractBistable Electroactive Polymer (BSEP) is a new category of smart materials that is rigid at ambient conditions and turn into a dielectric elastomer at above the polymer’s glass transition temperature. The BSEP combines shape memory property with dielectrically induced actuation. Strains larger than 500% have been observed. The glass transition temperature of the material can be tuned in a broad range with the addition of a plasticizer. As such, a series of new BSEP polymers are now available to meet the temperature requirements of different applications. The actuation strain, shape fixity, and shape recovery of the new BSEP have been extensively characterized. Application for refreshable Braille displays will also be discussed using a BSEP polymer with a glass transition temperature suitable for direct touch.
9:00 PM - V12.33
Polar-Fluoropolymer Blends with Tailored Nanostructures for High Energy Density Low Loss Capacitor Applications.
Shan Wu 1 2 , Minren Lin 1 , David S-G Lu 1 , Lei Zhu 3 , Qiming Zhang 1 2
1 Materials Research Institute, The Pennsylvania State Univeristy, University Park, Pennsylvania, United States, 2 Electrical Engineering, The Pennsylvania State Univeristy, University Park, Pennsylvania, United States, 3 Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractDielectric polymers with high energy density with low loss at high electric fields are highly desired for many energy storage and regulation applications. A polar-fluoropolymer blend consisting of a high energy density polar-fluoropolymer of poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) with a low dielectric loss polymer of poly(ethylene-chlorotrifluoroethylene) (ECTFE) was developed and investigated. We show that the two polymers are partially miscible which leads to blends with high energy density and low loss. Moreover, by introducing crosslinking to further tailor the nano-structures of the blends a markedly reduction of losses in the blend films at high field can be achieved. The crosslinked blend films show a dielectric constant of 7 with a dielectric loss of 1% at low field. Furthermore, the blends maintain a high energy density and low loss (~3%) at high electric fields (> 250 MV/m).
9:00 PM - V12.34
Adjustment of Piezoelectric Properties of Cellular Ferroelectrets by Foam-Structure and Geometry Variations.
Martynas Sborikas 1 , Michael Wegener 1 2
1 Functional Materials and Devices, Fraunhofer IAP, Potsdam Germany, 2 Institute of Physics and Astronomy, University of Potsdam, Potsdam Germany
Show AbstractPiezoelectric materials are of broad interest for sensor and actuator applications as well as for research of dipolar orientation processes, space-charge trapping mechanism and electrical mechanical interactions. Ferroelectrets are presenting one of the recent developments in the field of piezoelectric transducer materials [1-3]. In between their processing and working mechanism are well investigated. In summary, the concept is like this: huge electrical dipoles based on trapped charges are embedded in a soft cellular polymer matrix. Thus, all requirements for piezoelectricity, a symmetry breaking of the polarization and a deformable matrix which allows dipole size changes are given in those ferroelectrets.Within the last years, ferroelectrets with a cellular-foam structure were developed from different kinds of polymers such as polypropylene (PP), polyethylene terephthalate, polyethylene naphthalate as well as cyclo-olefine polymers (c.f. Ref. [3]). Recently, first investigations are published in order to broaden the ferroelectret concept to fluorinated space-charge electrets [4] and other polymers such as polycarbonate and polyetherimide [5]. However, in terms of applications, PP ferroelectrets still play the major role. Here, the ferroelectret concept will be discussed briefly. In detail, we evaluate optimisation attempts such as coating layers and geometrical variations in order to provide transducer materials with high operating voltages and low resonance frequencies. The processing of such systems, their electrical charging and the resulting mechanical and piezoelectric properties are discussed. The suitability of the developed materials for air-borne ultrasonic purposes is proved with demonstrated high piezoelectric activities and low resonance frequencies of down to about 120 kHz determined on freely vibrating samples.[1] S. Bauer, R. Gerhard-Multhaupt, and G.M. Sessler, Today 57 (2), 37-43 (2004).[2] M. Wegener and S. Bauer, ChemPhysChem 6, 1014-1025 (2005).[3] M. Wegener, in: New Materials for Micro-scale Sensors and Actuators – An Engineering Review, ed. S. Wilson and C. Bowen, Mat. Sci. Eng.: R: Rep. 56, 78-83 (2007).[4] O. Voronina, M. Wegener, W. Wirges, R. Gerhard, L. Zirkel, and H.Münstedt, Appl. Phys. A 90, 615-618 (2008).[5] N. Behrendt, IEEE Trans. Dielectr. Electr. Insul. 17 (4), 1113-1122 (2010).
9:00 PM - V12.35
Textile Transistor Building Blocks - Development of Functional Thin Film Layers.
Lina Rambausek 1 , Bram Van Genabet 1 , Anne Schwarz 1 , Els Bruneel 2 , Isabel Van Driessche 2 , Lieva Van Langenhove 1
1 Department of Textiles, Ghent University, Zwijnaarde/Ghent Belgium, 2 Department of Inorganic and Physical Chemistry, Ghent University, Ghent Belgium
Show AbstractTo advance in the development of fully integrated electronic textiles, a study was made to develop a flexible organic field effect transistor. On a polyester fibre, which served as substrate, different subsequent layers were deposited through low temperature solution processes allowing economically viable up-scaling. The transistor gate layer is deposited in two steps. During the electroless plating process, first a polypyrrole layer is deposited then a DC conductive copper layer. For the copper deposition, ideal pH was found at 13. Ideal reaction time was 6 minutes. A correlation between reaction time, layer thickness and conductivity was found. Resistivity of the copper layer was 6,5.10-7Ω.m. The fibre diameter had a huge impact on reproducibility and conductivity of the copper layer. The best results were found for a diameter of 888 µm. The layer had a very good stability over time in ambient conditions. The dielectric layer is applied by a dipcoating process. A polyimide layer from DMF or NMP solution is added onto the gate layer. High humidity was shown to cause a deterioration of the surface morphology, due to vapour induced phase separation. Phase separation sensitivity to moisture was found to depend on the used solvent mixing potential. Evaporation of solvent in dry conditions at 60 °C was shown to improve the morphology significantly and resulted in a dense transparent film.To finally deposit the gold electrodes, a deposition using vacuum evaporation was chosen. Both bottom- and top-contact architecture have been tried. Fibre masking leads to good results when an channel layer with a length of 73,1 µm is isolated and a masking fibre of 150 µm is used.TIPS-pentacene was chosen as a self-organizing soluble organic semiconductor. It has a bad solubility in dodecane and good solubility in aromatic solvents such as toluene and tetralin. Wettability of the dielectric layer coated at low humidity was good on flat PES substrates, but rather poor on round fibre shapes. Besides dip-coating, also drop-casting was applied but results were dissatisfying. To obtain a measurable transistor effect will be further investigated in terms of optimisation in deposition method and conditions of the active layer.
9:00 PM - V12.36
High Transparent Conductive Polymer PEDOT:PSS/PVP Served as Anode Materials in Electroluminescent Devices.
Hui-En Yin 1 , Chieh-Han Wu 3 , Kai-Shiang Kuo 1 , Wen-Yen Chiu 1 2 3 , Chia-Fen Lee 4 , Nien-ting Li 5 , Pei-Jing Chen 5
1 Department of Chemical Engineering, National Taiwan University, Taipei Taiwan, 3 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan, 2 Department of Materials Science and Engineering, National Taiwan University, Taipei Taiwan, 4 Department of Cosmetic Science, Chia Nan University of Pharmacy and Science, Tainan Taiwan, 5 , Taiwan Textile Research Institute, New Taipei City Taiwan
Show AbstractIn this research, Electroluminescent (EL) device was fabricated by using the conductive polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) (PEDOT:PSS) dispersions as the anode material. Via introducing Poly(vinyl pyrrolidone) (PVP) ethanol solution into the PEDOT:PSS dispersion, viscosity and wetting ability of the mixed PEDOT:PSS/PVP dispersion were enhanced simultaneously. The PEDOT:PSS/PVP conductive thin films presented good conductivity and high transmittance (transmittance > 76%). The different PEDOT:PSS/PVP dispersions were further used as the anode material in the EL flat plate by dip coating process. Uniform and smooth conductive films with high transmittance were formed on the low dielectric resin layer. The luminance of these EL devices was observed and photographed after connecting to 110V AC power.
9:00 PM - V12.37
A Novel Protein-Polymer Based Surface Plasmon Resonance Sensor for the Detection of Disease Biomarkers.
Victoria Briand 1 , Vindya Thilakarathne 1 , Challa Kumar 1 , Rajeswari Kasi 1 2
1 Chemistry , University of Connecticut , Storrs , Connecticut, United States, 2 Institute of Material Science , University of Connecticut , Storrs , Connecticut, United States
Show AbstractWe have developed a new protein-polymer hybrid nanomaterial that is used with surface plasmon resonance for the detection of small molecules. The sensor is currently able to detect heme, a biomarker for malaria. The hybrid material is synthesized by attaching a hemoglobin (Hb) polyacrylic acid conjugate onto the SPR sensing surface. The use of polyacrylic acid allows for high loading of Hb onto the sensor surface and as we have previously shown has negligible effects to the native structure of Hb due to polymer attachment. We have shown that the apo form of Hb (prosthetic group removed) is able to successfully bind rebind heme while producing a measurable SPR signal. Various amplification strategies have been employed to allow for lower detection limits. This approach exploits the natural recognition of protein-prosthetic group complexes for small molecule detection with high selectivity and sensitivity as well as potential for point-of-care detection.
9:00 PM - V12.38
Multifunctional Polymer Coatings for the Prevention of Marine Biofouling.
Peter Coneski 1 , Nickolaus Weise 1 , James Wynne 1
1 , Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractIncreased operational and maintenance costs are significant problems associated with the fouling of marine vessels. Traditionally, fouling of such vessels was mitigated via paints that released metallic or organometallic compounds that were toxic to fouling species. However, increased regulation of these paints has stimulated research into the development of environmentally benign alternatives. Low surface energy materials, such as silicone elastomers and fluoropolymers have shown great promise due to their ability to resist initial microbial colonization as well as possessing excellent “fouling release” characterisitics. However, the implementation of these materials as marine coatings remains problematic and the development of a suitable antifouling coating has remained elusive. In order to maximize the efficiency of suitable marine coatings, the development of materials with multiple antifouling mechanisms may be required. As such, a series of polymeric materials that exhibit a threefold barrier to fouling is described. Urethane materials with low surface energy domains, tethered broad spectrum antimicrobials, and non-toxic scissile linkages have been prepared. Low surface energy materials have shown great promise at reducing the adhesion and colonization of microbes at surfaces and remain a suitable first line of defense. Additionally, low surface energy domains may provide fouling release characteristics, or the ability for materials to release accumulated fouling via hydrodynamic forces as a ship moves through water. Despite reduced adhesion and fouling release properties that are well known for low surface energy materials, a portion of microbes may still be able to colonize at the material interface, which may lead to the formation of biofilms. To minimize the formation of biofilms from adhered microbes, quaternary ammonium salts (QAS) have been incorporated into the urethane structure to provide an active antimicrobial defense mechanism. The broad spectrum nature of QAS are well known and has been utilized for many different applications including a wide range of antimicrobials and disinfectants. Finally, the incorporation of non-toxic scissile linkages should provide the material with “renewable” characteristics that are activated by the gradual sloughing of the coatings providing “new” active antimicrobial interfaces over time. Additionally, the gradual sloughing of the coatings should also provide a second fouling release mechanism capable of removing any fouled portions of the coating. Synthesis, structure-property relationships, and antifouling behavior of these materials will be discussed.
9:00 PM - V12.39
Sequential Complex of π-Conjugates and Helical Peptides: A Novel Strategy for Designing Opto-Electronic Materials.
Hidenori Nakayama 1 , Shunsaku Kimura 1
1 Engineering, Kyoto University, Kyoto, Kyoto, Japan
Show AbstractWe focus our attention on three distinct properties of helical peptides (HPs), which are macrodipole, chirality, and self-assembling, to find out their specific electronic properties, etc. Here, we have challenged to develop a strategy to utilize HPs for designing organic opto-electronic materials. We found that complex of HPs and π-conjugates in a sequential manner is one promising candidate as opto-electronic materials as follows.2nOP2m ((n,m) = (4,0), (4,4), (8,0), (8.4), (8,8)) is a series of complexes of HPs and an oligo(phenyleneethynylene) (OPE), described as (Ala-Aib)n-OPE-(Ala-Aib)m (Ala = L-alanine, and Aib = α-aminoisobutyric acid, respectively). 2nOPE2m has lipoic acid moiety at the N terminal of the HP for linkage to gold surface to form self-assembled monolayer (SAM). When n = 8, 2nOPE2m formed a well-packed and vertically oriented SAM as revealed by infrared-reflection absorption spectroscopy, cyclic voltammetry, and ellipsometry. Absorption spectra of the OPE moiety in the SAMs showed a bathochromic shift of ca. 25 nm from a reference compound composed of 11-mercaptoundecanoic acid and OPE (C11OPE). Electric field generated by the peptide dipoles is responsible for this shift, as supported by density functional theory calculations.Scanning tunneling spectroscopy revealed electronic properties of this complex. 8OPE was inserted in a SAM of 1-decanethiol on gold. The OPE moiety was completely exposed over the SAM since the molecular length of the HP moiety is longer than 1-decanethiol. The I–V curves obtained from the 8OPE were nearly symmetric when the molecule–tip gap is wide (1 V, 5.5–6 pA), while asymmetric when the gap is narrow (1 V, 19 pA). This is interpreted as distance-dependent interaction of the π-cloud of the OPE moiety with the STM tip. When the tip is close to the OPE moiety, the interaction makes the potential drop at the tip–OPE contact smaller than that at gold–HP contact via lipoic acid.Chiral second harmonic generation active SAMs were also designed. L17 and D17 are consisted of (Ala-Aib)8-Ala (L-alanine for L17, and D-alanine for D17, respectively) and a D-π-A moiety (diphenylacetylene with N,N-diethylamino group and nitro group at the both ends). The D-π-A group is bonded to the C terminal of the HP moiety via an amide bond. L17 showed a negative Cotton effect in methanol solution in the absorption range of D-π-A group, while D17 showed a positive Cotton effect. The chirality in the D–π-A group is a result of connecting the group with the right-handed HP. The SAM of the compounds on fused silica surface showed SHG due to large hyperpolarizability of D-π-A. We are now trying to detect circular polarization in the SHG signal.
9:00 PM - V12.4
Molecular Orientation and Temperature Effects on Photodriven, Bending/Twisting and Mulitidimensional Oscillation of Azobenzene Liquid Crystalline Polymer Networks.
Kyungmin Lee 1 2 , Matthew Smith 1 , Hilmar Koerner 1 3 , Richard Vaia 1 , Timothy Bunning 1 , Timothy White 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wrigh-Patterson AFB, Ohio, United States, 2 , Azimuth Corporation, Dayton, Ohio, United States, 3 , UES, Dayton, Ohio, United States
Show AbstractPhotodirected mechanical response of uniaxially aligned monodomain azo-LCNs were investigated as a function of molecular orientation and temperature (above and below the glass transition temperature (Tg)). Out of plane deformations are observed in these materials when the nematic director of the material is offset from the principal axes of the cantilever geometry. The resulting flexural-torsional responses are observed in both the context of static and oscillatory bending. Comparatively larger magnitude twisting is shown to be observed in twisted nematic geometries, observed as photoinduced coiling of a cantilever.
9:00 PM - V12.40
Surface Energy Control Using Perfluorinated Compounds and Their Practical Applications.
Hiroshi Samukawa 1 , Makiya Ito 1 , Kyungsung Yun 1 , Hirofumi Kondo 1
1 Material development Dept., Sony Chemical & Information Device Co., Kanuma, Tochigi, Japan
Show Abstract The industry is strongly interested in highly engineered surfaces for many applications. The general state of bio-inspired and self-cleaning surfaces or super hydrophobic nano-structured surfaces [1, 2]; they have great potential, but many practical challenges still remains. Such surfaces must be self-cleaning in practice, durable, and easy to manufacture. Any practical surface also must withstand touching or rubbing, as well as exposure to environmental contamination. Several novel approaches have been developed in our company to synthesize and realize the surface engineering materials and processes [3].Especially, it is well known fluorine based materials have been used for many kinds of surface treatment from their low surface free energies. Among the fluorine based materials, perfluoropolyethers (PFPE) is one of the promising candidates due to the low surface free energy and low frictional properties [4]. We have reported the surface characteristics strongly depend on the molecular structures of PFPE [5, 6]. As the results of previous study, the linear molecular structure (-CF2CF2CF2O-) provides lower friction than the branched (-CF2CF(CF3)O-) structure and the surface free energy is smaller than that of the (-CF2CF2OCF2O-) structure. An alkoxy silane modified PFPE thin layer has shown environmental durability and high contact angles with water and hexadecane. Also the coating layer shows low coefficient of friction and good abrasion resistance. The average surface free energy was as low as ~0.013J/m2.The anti-reflection (AR) film surface was examined with the ion liquids with ammonium perfluorooctanate (APFO). It is found the coefficient of friction is especially low against a steel ball test. We expect these salts may provide good abrasion resistance for metal scratch. In this study, we report the surface chemical characteristics of the various molecular structures of PFPE and their derivatives for practical applications. We will discuss about the possibility of PFPE and APFO mixture and the selective paths for applied research into practical surfaces are also presented.References1. J. P. Youngblood, N. R. Sottos, MRS Bull. 33, 732 (2008)2. A. Tuteja, W. Choi, M. L. Ma, J. M. Mabry, S. A. Mazzella, G. C. Rutledge, G. H. Mckinley, R.E. Cohen, Science 318 (5856), 1618 (2007)3. Japan Pat., S61-1309024. M. Stone, T. G. Nevell, J. Tsibouklis, Materials letters, 37 (1-2), 102 (1998)5. H. Kondo, S. Lee, H. Hanaoka, Tribology Transaction, 52, 29 (2009)6. 18th Int. Sym. on Surfactants in Solution, Melbourne, Nov. p22 (2010)
9:00 PM - V12.41
Gold Nanoparticle Grown on Star-Shaped Block Copolymer Monolayers.
Rattanon Suntivich 1 , Ikjun Choi 1 , Maneesh Gupta 1 , Constantinos Tsitsilianis 2 , Vladimir Tsukruk 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Chemical Engineering, University of Patras, Patras Greece
Show AbstractWe report on the growth of gold nanoparticles in polystyrene/poly(2-vinyl pyridine) (PS/P2VP) star-shaped block copolymer monolayers. These amphiphilic PSnP2VPn heteroarm star copolymers differ in molecular weight (149 000 and 529 000 Da) and number of arms (9 and 28 arms). Langmuir-Blodgett (LB) deposition was utilized to control the spatial arrangement of P2VP arms and their ability to reduce gold nanoparticles. The PSnP2VPn monolayer acted as a template for the gold nanoparticle growth due to their high micellar stability at the air-solid interface, well-organized domain morphology, and ability to adsorb Au ions from the water subphase. UV-vis spectra, AFM, and TEM images confirmed the formation of the individual gold nanoparticles with an average size of 6 ± 1 nm in P2VP-rich outer phase. This facile strategy is critical for the formation of ultrathin polymers-gold nanocomposite layers at large surface areas with confined, one-sided positioning of gold nanoparticles in an outer P2VP phase at polymer-silicon interfaces.
9:00 PM - V12.42
Patterned and Controllable pH-Responsive Actuation of Polymer Microstructures.
Lauren Zarzar 1 , Ximin He 2 , Yuhang Hu 2 , Philseok Kim 2 3 , Joanna Aizenberg 1 2 3
1 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States, 2 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts, United States
Show AbstractResponsive actuation on the microscale is of interest for applications ranging from MEMS to biofilm prevention to microfluidics and propulsion. We design pH-responsive actuating surfaces consisting of high-aspect-ratio polymer structures embedded in and driven by the volume-phase transition of a poly(acrylic acid - co - acrylamide) hydrogel. These polymeric actuators can be patterned within microfluidic channels by non-conventional methods and we demonstrate how laminar flow of acid and base can be used to control not only where actuation occurs but also in which directions the structures bend. We also investigate how the hydrogel thickness influences the localized actuation of structures.
9:00 PM - V12.43
Interfacial Behavior of PSn(P2VP-b-PtBA)n Star-Shaped Heteroarm Terpolymers.
Ikjun Choi 1 , Ray Gunawidjaja 1 , Rattanon Suntivich 1 , Constantinos Tsitsilianis 2 , Vladimir Tsukruk 1
1 School of Materials Science and Engineering, Georgia Inst. of Technology, Atlanta, Georgia, United States, 2 Department of Chemical Engineering, University of Patras, 26504 Patras Greece
Show AbstractWe demonstrate the surface behavior and morphologies of two series of pH-responsive amphiphilic heteroarm star block copolymers: polystyrene/poly(2-vinylpyridine)/poly(tert-butylacrylate), PSn(P2VP-PtBA)n, heteroarm star block terpolymers and their precursors, PSnP2VPn, star copolymers. pH responsive surface assembly of star block polymers is explored as a function of architecture (copolymer vs terpolymer), block topology and arm length (molecular weight of PtBA segments varies from 8 900 up to 15 250), and number of arms (n = 9, 22, and 28) using Langmuir-Blodgett method. The pressure-area (π-A) isotherms at different subphase pH (pH = 5.8 and 2.0) revealed strong pH dependence leading to different limiting molecular area and surface micelle stability. The pH-induced ionization of the P2VP block results in distinct surface morphology for two heteroarm stars. Star copolymers bearing the free P2VP arms was found strongly dependent on the pH of the subphase enabling the transformation of spherical at pH 5.8 to labyrinth micellar structure at pH 2.0. In contrast, the star terpolymers containing the protonated hydrophilic P2VP block as midblocks maintained the same circular morphology at low pH and high pressures. Surface morphology analysis suggests that the heteroarm star polymers with higher number of arms allow for the formation of unimolecular micelles at the air-water interface.
9:00 PM - V12.44
pH-Controlled Growing Behavior of Star-Shaped Polyelectrolyte Layer-by-Layer Multilayer Film.
Ikjun Choi 1 , Rattanon Suntivich 1 , Felix Plamper 3 , Christopher Synatschke 2 , Axel Mueller 2 , Vladimir Tsukruk 1
1 School of Materials Science and Engineering, Georgia Inst. of Technology, Atlanta, Georgia, United States, 3 Institute of Physical Chemistry, RWTH Aachen University, Landoltweg,2, 52056 Aachen Germany, 2 Makromolekulare Chemie II and Bayreuther Zentrum fur Kolloide und Grenzflächen, Universität Bayreuth, D-95440 Bayreuth Germany
Show AbstractThe pH-controlled layer-by-layer (LbL) growth behavior of star-shaped polyelectrolytes has been explored based on cationic poly[2-(dimethylamino)ethyl methacrylate] and anionic poly(acrylic acid) stars synthesized via “core-first” atom transfer radical polymerization (ATRP) based on multifunctional initiators, in addition to their linear analogues. We studied the linear and exponential growth modes controlled by pH-sensitive star architecture along with variable assembly conditions including deposition pH (ranging from 5 to 7), number of layers (up to 30 bilayers), and the method of assembly (dip- vs spin-assisted LbL). The spin-assisted LbL assembly was found to enable the formation of smoother and thinner LbL films with parameters controlled by the shear rate and pH conditions, whereas for dip-assisted LbL assembly, the pH-dependent exponential growth was observed for both linear and star polyelectrolytes. The exponential buildup of linear/linear pair showed a notable surface segregation which led to dramatic surface non-uniformity, “worm-like” heterogeneous morphology, and surface roughening. In contrast, star/linear and star/star LbL films displayed very uniform and smooth surface morphology (roughness below 2.0 nm on the scale 10 μm x 10 μm) with much larger thickness reaching up to 1.0 μm for 30 bilayers with rich optical interference effects. This unique growth behavior of star polyelectrolytes could be attributed to partially screened charges and high mobility caused by compact branched architecture which, as a result, facilitates fast diffusion and exponential buildup of LbL films. We suggest such fast buildup prevents long-range lateral diffusion of polyelectrolyte star components, hinders large-scale microphase separation, leading to unique thick, smooth, uniform, transparent, and colorful LbL films from star polyelectrolytes.
9:00 PM - V12.45
Enrichment Polymer Layer System as a Functional Coating for Micro-Disk Resonator Sensors.
James Giammarco 1 , Bogdan Zdyrko 1 , Igor Luzinov 1 , J. David Musgraves 1 , Jackie Wilkinson 1 , Kathleen Richardson 1 , Anu Agarwal 2 , Lionel Kimerling 2 , Juejun Hu 3
1 Materials Science & Engineering, Clemson University, Clemson, South Carolina, United States, 2 Materials Science & Engineering, Massachusetts Institute of Technology, Boston, Massachusetts, United States, 3 Materials Science & Engineering, University of Delaware, Newark, Delaware, United States
Show AbstractThe work being reported focuses on the design of a nanothick multilayered enrichment polymer layer system (EPLS) as a functional coating for a chalcogenide glass (ChG) micro-disk resonator sensor. The polymer layers were designed to promote the attraction of analytes from the vapor phase to the sensor. The criteria for selection of the macromolecules used for EPLS were: (a) immiscibility, to ensure individuality of the each layer, (b) chemical structure, to ensure that each layer is capable of attracting substances of different nature, and (c) complementary chemical reactivity, to ensure that each consecutive top layer is chemically anchored to the bottom layer. The polymers selected for the EPLS were poly(glycidyl methacrylate) [PGMA], polyacrylic acid [PAA], 60% epoxidized polybutadiene [EPB60], and carboxy terminated poly 2-vinylpyridine [P2VP]. With the EPLS coated on a ChG resonator, a unique shift in the output 1512nm resonant peak is observed for various analytes. To study further the characteristics and performance of the EPLS aided detection, we also used mid-IR ATR Si crystals as a model for the resonators.
9:00 PM - V12.46
Biomimetic Blood-Compatible Surfaces of Polyurethane by Grafting Copolymer Brushes of PEG and MPC.
Dazhi Yang 1 , Yakai Feng 1 3 , Marc Behl 2 3 , Andreas Lendlein 2 3 , Haiyang Zhao 1 , Jintang Guo 1 3
1 , School of Chemical Engineering and Technology, Tianjin University, Tianjin China, 3 , Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, Teltow Germany, 2 , Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractPolyurethanes (PU) have been widely used as medical materials in recent years, while thrombus formation can still occur when contacting with blood for extended periods of time [1,2]. Non-biofouling surfaces have an important medical application as blood-compatible materials for antithrombogenic implants. Poly(ethylene glycol) (PEG) and phosphorylcholine (PC)-based polymers were most commonly employed for surface grafting to create nonbiofouling surfaces. In this study, we aimed to modify PU with PEG and 2-methacryloyloxyethyl phosphorylcholine (MPC). Through molecular design, the copolymer brush of PEG-b-poly(MPC) was synthesized via ATRP on the initiator surfaces. The flexible PEG chains were varied from 200 g/mol to 1000 g/mol, while the poly(MPC) chain lengths was controlled by the ratio of monomer to sacrificial initiator in solution. The topology of the modified surfaces was characterized by the phase image of AFM. The unmodified and modified surfaces were characterized by FTIR, XRD, water contact angle and platelet adhesion. The results demonstrated that super-low fouling surfaces with copolymer brush of PEG-b-poly(MPC) were achieved. The PU surfaces modified with PEG and phosphorylcholine zwitterionic brushes showed effective resistance to platelet adhesion and high blood compatibility in vitro. These PEG and PC-grafted PU materials might be potentially applied in blood-contacting materials or devices due to their good mechanical and hemocompatible properties.[1]Zhao, H. Y.; Feng, Y. K.; Guo, J. T. Journal of Applied Polymer Science 2011, 119, 3717-3727.[2]Feng, Y. K.; Xue, Y.; Guo, J. T.; Cheng, L.; Jiao, L. C.; Zhang, Y.; Yue, J. L. Journal of Applied Polymer Science 2009, 112, 473-478.
9:00 PM - V12.47
Utilizing the Shape Memory Effect to Enable New 3D Geometries for Flexible Electronics.
David Gehlhausen 1 , Walter Voit 2 1 , Taylor Ware 2 , Dustin Simon 2
1 Mechanical Engineering, University of Texas at Dallas, Richardson, Texas, United States, 2 Materials Science Engineering, University of Texas at Dallas, Richardson, Texas, United States
Show AbstractShape memory polymers (SMPs) possess the ability to recover imparted strain with tuned recoverable force at specific, tailorable temperatures. In this study, SMPs are utilized as substrates for a new generation of flexible electronics in which devices can be manufactured on a flat metastable SMP surface. Upon heating the devices above the glass transition temperature (Tg) of the SMP substrate, the devices will recover into a predefined three-dimensional shape. To accommodate this shape change, local deformation cannot exceed the strain capacity of the embedded electrodes of devices that are made from among other materials, gold and chrome, carbon nanotubes (CNTs), and aluminum. For instance, the strain capacity of 300 nm gold electrodes with a 50 nm chrome adhesion layer on acrylic SMPs already show permanent structural damage below strains of 15% while the underlying substrate can be tuned to show recoverable strains of 800%. We use a combination of acrylic monomers to design the custom copolymers and adjust their Tgs between 40°C and 100°C. Furthermore, we adjust the crosslinker concentration to control the recovery force of the devices by varying the concentration of multifunctional monomers such as trimethylol propane triacrylate (TMPTA). We use atom transfer radical polymerization (ATRP) with activators regenerated by electron transfer (ARGET) to control polymerization kinetics and subsequent network architecture and enable the incorporation of specialty monomers into the polymer backbone. This allows control of the hydrophobicity of the resulting substrate and further functionalization for performance in biological applications. This technique is used to design devices such as 3D RFID antennas, cortical probes or other flexible electrodes that must conform to non-flat surfaces but require a precise flat surface for photolithographic processing. Future studies seek to build active semiconductor devices such as components for organic solar cells and 3D thin film transistors.
9:00 PM - V12.48
Shape Memory Polymer Coated Local Sonic Resonators to Enable Dynamic Acoustic Metamaterial Fabrication.
Connie Manz 1 , Brayden Ware 1 , Jessie Gonzales 2 , Walter Voit 1 3
1 Materials Science & Engineering, The University of Texas at Dallas, Dallas, Texas, United States, 2 Electrical Engineering, The University of Texas at Dallas, Dallas, Texas, United States, 3 Mechanical Engineering, The University of Texas at Dallas, Dallas, Texas, United States
Show AbstractShape memory polymers (SMPs) are self-adjusting, smart materials in which stiffness can be tuned at specific, tailored temperatures. Acoustic metamaterials are composite materials capable of damping specific frequencies of incident sound waves. They consist of local sonic resonators, which are dense, coated spheres that resonate at a specific frequency depending on their size, density, and the modulus of their coatings. In this study, SMPs serve as a critical component of a dynamic acoustic metamaterial as the coating for the local sonic resonators. The tuned SMP coatings controllably soften as a function of temperature to block out different acoustic frequencies. Thus, small changes in temperature have a dramatic effect on the attenuation of the specific frequency of sound across the audible spectrum from 16 Hz to 20 kHz. Within these specialty coatings, we have demonstrated the ability to control the glass transition temperature (Tg) of the acrylic shape memory polymers between approximately -40°C and 80°C with a tunable modulus between 0.1 MPa (in the rubbery region) and 1500 MPa (in the glassy region). More specifically, this study characterizes the Tg and rubbery modulus (Er) of a crosslinked poly(alkyl (meth)acrylate-co-crotyl acrylate) polymer system with varying concentrations of crotyl acrylate and trimethylolpropane triacrylate (TMPTA) to control coating stiffness. Selected compositions are used to coat 5-15mm metallic spheres before the local sonic resonators are positioned and cured into an epoxy matrix. It is necessary to eliminate unwanted shrinkage effects during free radical polymerization in order to improve the interface between the metallic spheres and the surrounding polymer. To accomplish this, we use atom transfer radical polymerization (ATRP) that enables synthesis of a thermoplastic precursor oligomer, which can be post-crosslinked with UV light to improve adhesion onto the spheres. The temperature-dependent sound attenuation capabilities of the acoustic metamaterials are confirmed through testing with a dynamic mechanical analyzer (DMA) up to 300Hz and impedance tube testing up to 10 kHz. The results of this study are also incorporated into a multi-scale modeling effort for predicting wave behavior through these acoustic metamaterials.
9:00 PM - V12.49
Influence of Two-Step Programming Procedures on the Triple-Shape Effect of Copolymer Networks Based on Poly(ω-pentadecalactone) and Poly(ε-caprolactone) segments.
Joerg Zotzmann 1 , Marc Behl 1 , Andreas Lendlein 1
1 Center for Biomaterial Development and Berlin Brandenburg Center for Regenerative Therapies (BCRT), Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractTriple-shape polymers are able to switch from a first temporary shape (A) to a second temporary shape (B) and from there to the permanent shape (C) when triggered by subsequent increases of temperature, whereas the programming of the two temporary shapes (A) and (B) is required before.[1,2] Several triple-shape creation procedures (TSCP) were established, enabling multiphase polymers to perform a triple-shape effect (TSE).[3,4] A triple-shape material based on two crystallizable segments poly(ω-pentadecalactone) (PPD) and poly(ε-caprolactone) (PCL) was synthesized showing triple-shape capability after gentle programming procedures applying only one deformation at high temperature or even at ambient temperature. Copolymer networks with a certain segment ratio showed a reversible triple-shape behavior under constant stress, which was based on crystallization induced elongation (CIE) and melting induced contraction.[5]This versatile triple-shape material was investigated further in order to examine the influence of the programming procedure on TSE, as for instance the CIE might interfere with shape fixation. Copolymer networks incorporating a PPD precursor with Mn = 3400 g/mol were expected to show only a weak TSE after standard TSCP (TSCP1) due to incomplete crystallization of the PPD segment. A new programming procedure TSCP2 was applied to these copolymer networks, at which an additional cooling step to a temperature being lower than the crystallization temperatures of both segments was inserted between both deformation steps. Excellent triple-shape properties could be obtained for copolymer networks with different composition (Mn and mass fraction of the PCL precursor in the starting reaction mixture) when TSCP2 was applied. Enabling TSE in these materials was attributed to two separated crystallization processes of both segments during TSCP2.References[1] I. Bellin, S. Kelch, R. Langer, A. Lendlein, Proc. Natl. Acad. Sci. USA 2006, 103, 18043.[2] M. Behl, A. Lendlein, J. Mater. Chem. 2010, 20, 3335.[3] J. Zotzmann, M. Behl, Y. Feng, A. Lendlein, Adv. Funct. Mater. 2010, 20, 3583.[4] M. Behl, I. Bellin, S. Kelch, W. Wagermaier, A. Lendlein, Mater. Res. Soc. Symp. Proc. 2009, 1140, 3.[5] J. Zotzmann, M. Behl, D. Hofmann, A. Lendlein, Adv. Mater. 2010, 22, 3424.
9:00 PM - V12.5
A Melt Processing Study Liquid Crystal Polymers for High Barrier Food Applications.
Jo Ann Ratto 1 , Greg Pigeon 1 , Sarah Schirmer 1 , Christopher Thellen 1
1 , U.S. Army Natick RD&E Center, Natick, Massachusetts, United States
Show AbstractLiquid Crystal Polymers (LCPs) have attractive barrier performance properties, yet melt processing of LCPs by extrusion remains a challenge. Blown films were obtained from a high temperature extruder with a counter rotating die that allows orientation within the melt. The die rotation varied from 0 to 30 rpms with the oxygen and water barrier properties being examined for all films. The LCP showed a dependence on oxygen barrier properties as function of the rotation. The oxygen barrier values of .057 cc/m2day was obtained and meets the military specification for oxygen barrier. Films were alsomade by the cast film process with oxygen barrier films for comparison. These films were also subjected to the retort process and the oxygen barrier values were maintained or improved after retort. Films were also evaluated for morphology, rheology, thermal and mechanical properties.
9:00 PM - V12.50
Shape Memory Behavior of Ultra-High Molecular Weight Polyethylene.
Sergey Kaloshkin 1 , Alexey Maksimkin 1 , Mihail Zadorozhnyy 1 , Maria Kaloshkina 1
1 CAMN, NUST "MISIS", Moscow Russian Federation
Show AbstractShape memory effect (SME) has been observed in polymers and extensively studied for many copolymers, including copolymers of low-density polyethylene. However shape memory behavior of pure ultra-high molecular weight polyethylene (UHMWPE) has not been extensively studied. UHMWPE is interesting for research as, due to its high density, it is expected to have relatively higher recovery stress. In our work we studied the properties of UHMWPE that define the functional characteristics of shape memory polymers: strain, thermal transition temperature, recovery stress and recovery strain. UHMWPE powder was compressed into monolithic samples using thermopressing method. The samples were deformed by 200% (εm) in room temperature. Shape memory properties have been studied using dynamic mechanical analyzer (DMA). It was found that loosely fixed deformed samples of UHMWPE start to contract intensively upon heating from room temperature to 423 K, trying to return to original shape. It was registered that recovery contraction brings the sample size down to 115% of initial sample length. The process of shape recovery was triggered even by a small increase of temperature. The increase of the degree of shape recovery is proportional to the increase of temperature. Tests with rigidly fixed edges of samples of deformed UHMWPE heated from room temperature to 423 K showed that the material develops recovery force as the temperature increases. Recovery force for UHMWPE has a distinct maximum (up to 7 MPa) at 406 K. Further temperature increase leads to a decrease of recovery force. After the rigidly fixed sample of deformed UHMWPE is heated above melting temperature and cooled down in the same position, the original shape cannot be restored due to re-crystallization of the polymer and memorizing of the new shape. The work suggests an explanation of the shape memory effect in UHMWPE.
9:00 PM - V12.52
Synthesize and Self Assembly of Novel Polymer-Nanoparticle Hybrids.
Xuehui Dong 1
1 Dept. of Polymer Science, The University of Akron, Akron, Ohio, United States
Show AbstractNovel polymer-nanoparticle hybrids with different architectures were synthesized with a combination of anionic polymerization, control/living polymerization and click chemistry. The nanoparticles, e.g. Fullerene and Polyhedral Oligosilsesquioxanes (POSS), were designed to be located at chain end, at junction point of two blocks, or randomly distributed on one block. Their structure was fully characterized by NMR, GPC, MALDI-TOF, and IR. The self assembly of those molecules both in bulk and in solution was studied by TEM, SAXS, DSC, and Light Scattering. Well defined structure of polymer was obtained and their behavior as a template for arranging of nanoparticles was studied
9:00 PM - V12.6
Study on Mechanism of High Thermal Conductivity in Mesogen-Containing Epoxy Resins.
Shi-hui Song 1 , Yuka Yoshida 1 , Yukihiko Yamashita 1 , Yoshitaka Takezawa 1
1 , Hitachi Chemical Co.,Ltd., Tsukuba-shi, Ibaraki Japan
Show AbstractThe demand for high thermal conductive insulating resin sheets has greatly increased with specific application in car inverter, motor, LED lighting and various electric devices. We have developed high thermal conductive epoxy resins containing mesogen groups that form high-order structures by self-ordering during the curing process. Recent work has been focused on developing applications of these mesogen-containing epoxy resins in high thermal conductive composite sheets. For instance, many kinds of elastomers were added to the resin sheets to improve flexibility and adhesion properties. Our results showed that the thermal conductivity often decrease greatly when elastomers are added to the mesogen-containing epoxy resins. However, the effect of the elastomers on the higher-order structure of the mesogen-containing epoxy resins has not been investigated. In the present study, we report the mechanism underlying the high thermal conductivity of epoxy resins with mesogen groups by using polarized optical microscope (POM), scanning electron microscope (SEM), and X-ray diffraction (XRD). Results revealed that epoxy resins that exhibit higher thermal conductivity tend to form bigger spherulite-like structures. Also, specific elastomers that can be used in the mesogen-containing epoxy resins with high thermal conductivities had been identified. Current effort of our group is geared towards the discovery of the practical applications of these resin sheets.
9:00 PM - V12.7
Director Configuration Transitions of Polyelectrolyte Coated Liquid-Crystal Droplets.
Tanmay Bera 2 1 , Jiyu Fang 2 1
2 Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, Florida, United States, 1 Dept of Mechanical, Materials and Aerospace Engg., University of Central Florida, Orlando, Florida, United States
Show AbstractLiquid-crystal droplets are of great interest because of their large surface areas, rich phases, and tunable optical properties. The director configuration of liquid-crystal droplets provides a unique optical sign to detect the events occurring at the droplet surface. We find the alternating bipolar/radial configuration transitions of 4-n-pentyl-4’-cyanobiphenyl (5CB) droplets triggered by the layer-by-layer coating of negatively charged poly(styrenesulfonate sodium (PSS) and positively charged poly(diallyldimethylammonium chloride) (PDADMAC) on the droplet surface. The alternating configuration transitions are due to the interactions of the 5CB with polar vs. non-polar PDADMAC/PSS multilayer coatings. Furthermore, we find that the coating of PDADMAC/PSS multilayers makes the director configuration of the 5CB in the droplets sensitive to local environments such as salt concentrations, pH and the presence of charged species.
9:00 PM - V12.8
Mathematical and Numerical Modeling of Liquid Crystal Elastomer Phase Transition and Deformation.
Mariarita de Luca 1 , Antonio DeSimone 1
1 Sector of Functional Analysis and Application, International School for Advanced Studies (SISSA), Trieste, Trieste, Italy
Show AbstractLiquid crystal (in particular, nematic) elastomers consist of cross-linked flexible polymer chains withembedded stiff rods molecules that allow them to behave as a rubber and a liquid crystal. Nematicelastomers are characterized by a phase transition from isotropic to nematic past a temperaturethreshold. They behave as rubber at high temperature and show nematic behavior below thetemperature threshold. Such transition is reversible. While in the nematic phase, the rod molecules arealigned along the direction of the "nematic director". This molecular rearrangement induces a stretch inthe polymer chains and hence macroscopic spontaneous deformations. The coupling between nematicorder parameter and deformation gives rise to many interesting phenomena.Research on these materials is also stimulated by many interesting applications. In biological field, theability to considerably change their length, make them very promising for artificial muscles actuators.Besides, their optic properties make them suitable, for example, as lenses for new imaging systems.We present a mathematical model able to describe the behavior of nematic elastomers and numericalsimulations reproducing such peculiar behavior. We use a geometrically linear version of the "Warnerand Terentjew" model and consider cooling experiment and stretching experiment in the directionperpendicular to the one of the director at cross-linking.
9:00 PM - V12.9
Characterization of Fe2O3 and Fe3O4 Prepared Ferrogels under Uniform Magnetic Field.
Kamlesh Suthar 1 2 , Muralidhar Ghantasala 2 , Derrick Mancini 1 , Jan Ilavsky 1
1 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 2 Mechanical Engineering, Western Michigan University, Kalamazoo, Michigan, United States
Show AbstractThis paper presents characterization of ferrogel under uniform magnetic field. We have compared the characteristics of the ferrogels prepared using Fe2O3 and Fe3O4 nanoparticles. The magnetic nanoparticles (sizes ~20 nm) were distributed in N-isopropylacrylamide (NIPAm) based gels. Particle distribution and agglomeration characteristics of the prepared gels were investigated using ultra small angle x-ray scattering (USAXS) under uniform magnetic field and with transmission electron microscopy (TEM) techniques. The magnetic property was investigated using direct current superconducting quantum interference device (DC-SQUID) under hydrated conditions. These results showed that the ferrogel samples prepared using Fe3O4 and Fe2O3 particles have similar particle size distribution. The gel samples prepared with Fe2O3 nanoparticles, however, demonstrate significantly different agglomeration characteristics compared to the gel samples prepared using Fe3O4. In both systems, the agglomerates of particles appear to be roughly spherical, with few forming chain-like structures. The USAXS analysis shows a progressive increase in magnetic field strength during the measurements increases the ordering in to two-particles aggregates. The ferrogel has not shown any sedimentation or particles detachment from the gel. These particles are immobilized inside the porous gel network. Details of our results and analysis will be presented in this paper.
Symposium Organizers
Andreas Lendlein Institute of Polymer Research
Yakai Feng Tianjin University
Tao Xie General Motors Research and Development Center
Zhibin Guan University of California-Irvine
V17: Poster Session: Multifunctional Polymer-Based Materials II
Session Chairs
Marc Behl
Rainer Haag
Tao Xie
Thursday PM, December 01, 2011
Exhibition Hall C (Hynes)
V13: Stimuli-Sensitive and Shape-Memory Polymers III
Session Chairs
Thursday PM, December 01, 2011
Room 312 (Hynes)
9:15 AM - V13.1
Soft Microorigami: Stimuli-Responsive Self-Folding Polymer Films.
Leonid Ionov 1 , Svetlana Zakharchenko 1 , Georgi Stoychev 1 , Nikolay Puretskiy 1 , Evgeni Sperling 1
1 , Leibniz Institute of Polymer Research, Dresden Germany
Show AbstractAsymmetry is intrinsic to natural systems and is widely used by living organisms for efficient adaptation, mimicry and movement. Polymer bilayers are the example of synthetic asymmetric systems, which are able to generate macroscopic motion and fold by forming different 3D objects such as tubes and capsules. Similar to bimetal films, the polymer bilayer consist of two substances with different swelling properties. One polymer is non-swellable and hydrophobic. Another polymer is water-swellable hydrogel. The folding, which might occur in response to temperature or pH, is caused by swelling of the hydrogel layer. The formed tubes and capsules can be manipulated using magnetic field. Reversible folding and unfolding of the polymer films is applied for reversible capture and release of cells in response to change of temperature and other signals. This novel biomimetic approach can be used for controlled encapsulation and release of microparticles, cells and drugs as well as fabrication of 3D scaffolds for tissue engineering.
9:30 AM - V13.2
Tuning Activation Parameters for Mechanochemical Reactions in Bulk Linear Polymers.
Brett Beiermann 1 4 , Jeffrey Moore 2 4 , Scott White 3 4 , Nancy Sottos 1 4
1 Materials Science And Engineering, University of Illinois (Urbana-Champaign), Urbana, Illinois, United States, 4 , Beckman Institute for Advanced Science, Urbana, Illinois, United States, 2 Chemistry, University of Illinois (Urbana-Champaign), Urbana, Illinois, United States, 3 Aerospace Engineering, University of Illinois (Urbana-Champaign), Urbana, Illinois, United States
Show AbstractMechanoresponsive polymeric materials are created by incorporating a force-activated molecule, i.e. mechanophore, into the polymer backbone. Several force-sensitive polymers have been synthesized, but most require large strains to trigger the desired chemical reaction. Understanding the reaction conditions in bulk polymers is critical for use in potential applications such damage sensing, self-healing, and catalysis. In this work, we investigate the physical mechanisms for mechanochemical activation in two linear polymers and identify the range of conditions for which activation occurs. We select spiropyran (SP) as the mechanophore. Under mechanical force, SP reacts via electrocyclic ring-opening, indicated by a color change and generation of a fluorescence signal. SP is incorporated into linear poly(methyl acrylate) (PMA) and poly(methyl methacrylate) (PMMA) backbones. The SP-linked PMA has a relatively low glass transition temperature (Tg = 15°C) and is elastomeric at room temperature (RT). Activation under tensile load at RT occurs at strains greater than 600%. In contrast, SP-linked PMMA has a much higher Tg (130°C) and exhibits glassy response at RT. Brittle failure precedes any detectable activation in SP-linked PMMA. We are able to control Tg and thus mechanical behavior of SP-linked PMMA through the addition of plasticizer. SP activation in PMMA at RT is achieved within a range of plasticizer content which allows polymer yielding and drawing, while maintaining enough stiffness to reach a threshold stress of ca. 10 MPa. By varying the Tg of the polymer, onset strains ranging from 8% to 150% for SP activation in linear PMMA are achieved. The role of mechanophore orientation is also investigated by in situ monitoring of the polarized fluorescence of the reacted SP. We find that mechanophores aligned in the direction of tensile force activate preferentially. Work is in progress to further regulate the mechanophore activation by controlling polymer alignment prior to mechanical testing.
9:45 AM - V13.3
Self-Folding of Polymer Sheets Using Local Light Absorption.
Ying Liu 1 , Julie K. Boyles 1 , Jan Genzer 1 , Michael D. Dickey 1
1 Dept of Chemical & Biomolecular Engineering, North Carolina State Univ, Raleigh, North Carolina, United States
Show AbstractWe describe a simple approach to self-folding that uses localized light absorption on a pre-stressed polymer film. Self-folding is a deterministic assembly process that causes a predefined 2D template to fold into a desired 3D structure with high fidelity. Self-folding takes advantage of the multitude of available 2D patterning techniques (e.g., lithography, inkjet printing, screen printing). Self-folding is attractive as a cost-effective 3D fabrication strategy for applications such as packaging, robotic actuators and sensors, biological devices, solar cells and reconfigurable devices. Most approaches to self-folding use hinges (i.e., regions of a substrate that fold) that have a unique chemical composition from the bulk, which requires complicated photolithography or other multiple fabrication steps.Our approach to self-folding relies on printing patterns of ink on a pre-stressed polymer film. The substrates are commercially available pre-stressed polymer sheets (Shrinky-Dinks). The black ink forms 'hinges' that are patterned using a desktop printer on either side of the optically transparent sheets. Hinges absorb selectively the light to heat the underlying polymer and causes the polymer sheets to fold into complex 3D structures (e.g., cubes, tetrahedrons) within seconds. The approach is appealing because it uses inexpensive materials and simple patterning techniques to form complex structures.We study experimentally the impact of the hinge geometry, line width and the support temperature of 2D pattern on folding. Wide hinges fold faster than narrow ones, while patterns at high support temperatures fold faster than at low support temperature. Modeling of the temperature profile inside the polymer films captures effectively the folding trends measured experimentally based on the predicted time when the folding starts. This simple folding strategy is appealing as a means to convert 2D patterns into 3D shapes and may be applied as a low-cost packaging technique. The folded shapes can revert back to a flat, shrunken version of the initial 2D sheet by uniformly heating the shapes above glass transition.
10:00 AM - V13.4
Dynamic Acoustic Metamaterials with Temperature-Sensitive Damping.
Brayden Ware 1 , Taylor Ware 1 , Connie Manz 1 , Walter Voit 1 2
1 Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas, United States, 2 Mechanical Engineering, The University of Texas at Dallas, Richardson, Texas, United States
Show AbstractShape-memory polymer (SMP) acoustic metamaterials are dynamic composites containing local sonic resonators with variable stiffness coatings that soften controllably as a function of temperature to block out different acoustic frequencies. The resonators absorb incident sound waves in specific frequency ranges depending on the temperature of the metamaterial to annihilate further acoustic propagation. This study combines an in-depth modeling and experimental approach to elucidate the temperature-dependent damping of these materials. Computational: Multiple Scattering Theory (MST) describes viscoelastic wave propagation through the composites to demonstrate negative effective mass density and a frequency band gap that moves with changing temperature. Previous MST codes scatter waves assuming constant stiffness in the local sonic resonator coating. Modifying the scattering model to allow the stiffness to vary with temperature and frequency allows the model to interact with arbitrary stiffness data, such as that which is measured experimentally. Specific bandgap engineering for acoustic waves occurs then through modifying this stiffness data. In future work, this will be combined with Molecular Dynamics (MD) simulations to gain fundamental insights into the interface between the dense metallic spheres and the variable stiffness surrounding shape memory matrix inside the local sonic resonators. In addition, utilizing a Peridynamic framework relaxes certain isotropy assumptions that helps motivate continuum models and refine MST with understanding gleaned from atomistic potentials and MD. Experimental: acoustic transmission through SMP acoustic metamaterials is an order of magnitude less than predicted by the conventional mass-density law. Versatile acrylic SMP coatings are synthesized around 5 to 15 mm lead and tungsten spheres and embedded into a hard epoxy matrix to create materials with tunable resonant frequencies across the audible spectrum. The glass transition temperature can be adjusted (between about -40 and 80 degrees C) and the stiffness of the resonators’ polymer matrix can be altered (between about 0.1 MPa and 1500 MPa). More specifically, this study characterizes the Tg and rubbery modulus (Er) of a crosslinked poly(alkyl (meth)acrylate-co-crotyl acrylate) polymer system with varying concentrations of crotyl acrylate and trimethylolpropane triacrylate (TMPTA) to control coating stiffness. Dynamic mechanical analysis (up to 300 Hz) and impedance tube tests (up to 10 kHz) will be used to confirm the predicted temperature-sensitive sound attenuation. Applications of this work include next generation noise-cancelling barriers in stealth, defense and industrial settings.
10:15 AM - V13.5
Synthesis and Characterization of a Poly(Styrene-Block-(Methylacrylate-Random-Octadecylacrylate)-Block-Styrene) Shape Memory ABA Triblock Copolymer.
Pengzhan Fei 1 , Kevin Cavicchi 1
1 Polymer Engineering, University of Akron, Akron, Ohio, United States
Show AbstractA new ABA triblock copolymer of poly(styrene-block-(methylacrylate-random-octadecylacrylate)-block-styrene) (PS-b-(PMA-r-PODA)-b-PS) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. A three-dimensional, physically crosslinked network was generated by the self-assembly of the triblock copolymer, where the bridging of the midblocks across the glassy PS domains generates “permanent” network of the shape memory polymer (SMP). The side chain crystallization of the polyoctadecylacrylate (PODA) side chains generates a second reversible network enabling shape memory properties. Shape memory tests by uniaxial deformation and recovery of molded dog-bone shape samples demonstrate that shape fixities above 96% and shape recoveries above 98% were obtained for extensional strains up to 300% when using rapid temperature jumps during strain fixing and recovery. A key advantage of this shape memory material is that it can be very easily shaped and remolded by elevating the temperature above the glass transition temperature of PS of the SMP, and after remolding the initial shape memory properties are completely recovered by eliminating the history of the previous deformation cycles. Dynamic mechanical tests show the combination of creep and stress relaxation occurs during long-term annealing which is detrimental to the shape fixity and shape recovery of this SMP. Efforts to increase resistance to creep and stress relaxation will be discussed.
10:30 AM - V13.6
3D Printable Shape Memory Polymers with Thermoset Properties.
Jonathan Reeder 1 , Taylor Ware 2 , Dustin Simon 2 , Walter Voit 2 1
1 Mechanical Engineering, The University of Texas at Dallas, Richardson, Texas, United States, 2 Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas, United States
Show AbstractCurrent 3D printing technology requires low molecular weight thermoplastic polymers which limits the desirable mechanical characteristics of a printed device. We seek to demonstrate a new method to 3D print custom shape memory polymers with thermoset properties using a combination of tuned polymer chemistry and ionizing radiation to post-crosslink thermoplastic precursors and dial in memory properties. Mnemosynation™ is the polymer manufacturing process we developed to enable mass production of complex thermoset shape memory polymer devices. This process transforms thermoplastic materials blended with unreacted multi-functional monomers into thermoset materials utilizing ionizing radiation. Ionizing radiation at doses from 5 to 200 kGy generates free radicals in polymer chains that favor crosslinking over scission. This is accomplished through careful selection of the monomer chemistries such that the free radicals created do not destroy the main chains of the polymers, but generate free radicals on side chains. The thermoplastic precursors are formed from combinations of linear acrylic monomers methyl acrylate, butyl acrylate and isobornyl acrylate. An incorporated radiation sensitizer, trimethylol propane triacrylate enables more efficient crosslinking by increasing the probability that generated free radicals chemically crosslink thermoplastic segments to form a network polymer. Atom transfer radical polymerization (ATRP) is used to provide a controlled process for varying the molecular weight of the resins or precursor thermoplastic chains to develop a suite of materials for rapid prototyping in a 3D printer and subsequent crosslinking with electron beams or γ-sources. Using Mnemosynation™, 3D printed devices are post-crosslinked to give them mechanical, environmental, and thermal properties that exceed those of current 3D printable materials. Materials have been developed with a controllable glass transition temperature (Tg) between 40°C and 100°C and a rubbery modulus (Er) between 0.1MPa and 15MPa. This application is of particular interest for the rapid manufacturing of medical devices in the event of catastrophic supply chain disruption.
10:45 AM - V13.7
Impact of Different Single Fiber Diameter and Variation of the Programming Temperature on the Shape-Memory Properties of Electrospun Scaffolds Prepared from Amorphous Polyetherurethanes.
Tilman Sauter 1 2 , Karl Kratz 1 , Andreas Lendlein 1
1 Centre for Biomaterial Development and Berlin-Brandenburg Centre for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Centre Geesthacht, Teltow, Brandenburg, Germany, 2 Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité, Berlin, Berlin, Germany
Show AbstractShape-memory polymers (SMPs) and composites thereof, which allow the adjustment of shape-memory properties by variation of physical parameters during the programming procedure, have been introduced recently as a promising class of active polymers. One example are amorphous polyetherurethanes (PEU) and their radio-opaque composites, where the switching temperature Tsw as well as the recovery behavior of actively moving scaffolds could be controlled by variation of the programming temperature Tprog from 25 °C to 70 °C [1-3].In this study we explored whether the adjustment of shape-memory properties in electrospun scaffolds consisting of fibers with different diameters can be influenced by application of different Tprog during programming. A PEU was chosen for this study, which was synthesized from methylene bis(p-cyclohexyl isocyanate) (H12MDI), poly(tetramethylene glycol) (PTMEG), and 1,4-butanediol (1,4-BD).PEU scaffolds were prepared by the electrospinning method using 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) as solvent. Scaffolds with different fiber diameters were achieved by variation of the mass flow rate and the conductivity, while the polymer concentration was kept constant. The resultant scaffolds were examined with respect to their thermal and mechanical properties by DSC, DMTA and tensile tests. For quantification of the shape-memory properties cyclic, thermomechanical tensile tests were performed on a tensile tester equipped with a thermochamber. Here a single-step shape-memory creation procedure (SMCP) was applied, where Tprog was varied. The recovery was examined under stress-free and constant strain conditions.PEU scaffolds with an average deposit thickness of 100 ± 20 µm and a porosity in the range of 70 to 80% scaffolds were obtained, where the single fiber diameter was around 1.5 µm and 0.6 µm, respectively. While DSC and DMTA results showed no difference in the thermal properties, tensile test measurements revealed an increased Young’s modulus (E) and a reduced elongation at break (εB) for scaffolds with 0.6 µm fibers. Excellent dual-shape properties were achieved for both PEU scaffolds with a high shape fixitiy rate Rf ≥ 97%, and a high shape recovery rate Rr = 88% for scaffolds with 0.6 µm fibers, whereas scaffolds with 1.5 µm fibers exhibited a lower Rr = 69%. Also the recovery stress maximum σmax achieved under constant strain conditions was found to increase with decreasing fiber diameter. Finally, it could be shown that Tsw for both electrospun scaffolds could be adjusted by variation of Tprog applied during SMCP.References:[1]Cui J, Kratz K, Heuchel M, Hiebl B, Lendlein A, Polymers for Advanced Technologies 2011, 22(1), 180-189[2]Cui J, Kratz K, Lendlein A, in Mater Res Symp Proc, Active Polym 2009, 1190, 93-98[3]Cui J, Kratz K, Lendlein A, Smart Mater Struct 2010, 19(6), 065019
V14: Encapsulation and Drug Release
Session Chairs
Thursday PM, December 01, 2011
Room 312 (Hynes)
11:15 AM - **V14.1
Reactive Polymers by Controlled Radical Polymerization: From Protein Dimers to Multivalent Cancer-Targeting Constructs.
Heather Maynard 1
1 Chemistry and Biochemistry, UCLA, Los Angeles, California, United States
Show AbstractProtein- and peptide-polymer conjugates are a class of materials widely used as drugs. Covalent attachment of polymer chains to proteins and peptides increases therapeutic potential. This talk will focus on our recent efforts to prepare multivalent protein and peptide constructs for this purpose. We have developed syntheses to produce homo- and hetero-telechelic polymers for reaction with biomolecules. One strategy involves modification of chain ends of polymers produced by reversible addition-fragmentation chain transfer (RAFT) polymerization via radical reaction with protein-reactive azo initiators. Depending on the chain transfer agent used, this can result in polymers with the same or different group at the chain ends. Another strategy is use of a bis-functionalized chain transfer agent to produce the homotelechelic polymer without post-polymerization modification. These materials have been employed to prepare dimeric protein conjugates, and this will be discussed. We have also prepared polymers with reactive side chains. In particular polymers with aldehyde groups have been prepared by both RAFT and atom transfer radical polymerization (ATRP). These polymers have been modified with peptides, model drugs, and oligo(poly(ethylene glycol)) (oligoPEG) groups. We are interested in these architectures because conjugate designs that control the number and presentation of proteins and peptides could exhibit higher biological activities than the corresponding monomeric conjugates or unmodified biomolecule. For example, we showed that multivalent integrin binding peptide polymers targeted glioblastoma cells (brain cancer cells) significantly better than the corresponding monovalent peptide. In this talk, synthetic strategies, as well as application of the resulting conjugates will be discussed.
11:45 AM - V14.2
Sub-Micro Silk Particles for Drug Delivery.
Thomas Scheibel 1
1 Biomaterials, Universität Bayreuth, Bayreuth Germany
Show AbstractSilk proteins are promising biopolymers for drug delivery due to their aqueous processability, biocompatibility, and biodegradability. A simple aqueous preparation method for silk particles with controllable size, secondary structure and zeta potential is established. The yield and morphology of the particles can be controlled by ionic strength and pH. A new model explains the process of particle formation based on intra- and intermolecular interactions of the silk domains, influenced by pH and kosmotropic salts. The reported silk protein particles can be loaded with small molecule model drugs by simple absorption based on electrostatic interactions. In vitro release of these compounds from the silk particles shows no burst release and depends on charge – charge interactions between the compounds and the silk.
12:00 PM - V14.3
Design Aspects of Drug Releasing Degradable Shape-Memory Polymers.
Christian Wischke 1 2 , Andreas Lendlein 1 2
1 Center for Biomaterial Development, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 , Berlin-Brandenburg Center for regenerative Therapies, Teltow Germany
Show AbstractModern concepts for biofunctional implants often comprise the controlled release of bioactive compounds to gain specific biofunctionalities. Here, the design of amorphous and semi-crystalline copolyester-based shape-memory polymer (SMP) networks as matrix for pharmaceutical applications is reported. Based on a description of the molecular basis for such multifunctional SMPs including the selection of building blocks, the polymer morphology, and the three dimensional architecture, a proposed general evaluation strategy was applied to characterize these materials including the effect of network properties and loading techniques on model drug release. Moreover, drug effects on thermomechanical properties of SMPs also in an aqueous environment and material properties during hydrolytic degradation were described. The three functionalities – as relevant for potential applications in minimally-invasive therapies as medical devices or pharmaceutical products – could be timely separated and were shown to be independent from each other, with first stimuli induced shape-memory effect, then continuous diffusion-controlled drug release, and finally material removal by hydrolytic degradation. Such materials enable various applications in modern medicine such as multifunctional drug carrier or implants for minimally-invasive therapies.References: [1] C. Wischke, A.T. Neffe, S. Steuer, A. Lendlein, J. Control. Release 2009, 138, 243.[2] A.T. Neffe, B.D. Hanh, S. Steuer, A. Lendlein, Adv. Mater. 2009, 21, 3394.[3] C. Wischke, A. Lendlein, Pharm. Res. 2010, 27, 527.[4] C. Wischke, A.T. Neffe, S. Steuer, E. Engelhardt, A. Lendlein, Macromol Biosci, 2010, 10, 1063.[5] C. Wischke, A.T. Neffe, S. Steuer, A. Lendlein, Eur. J. Pharm. Sci. 2010, 41, 136.[6] C. Wischke, A.T. Neffe, A. Lendlein, Adv. Polym. Sci. 2010, 226, 177.
12:15 PM - V14.4
Swelling and Release Properties of Functional κ-carrageenan Hydrogel Nanocomposites.
Ana Luisa Daniel-da-Silva 1 , Ana Salgueiro 1 , Sara Fateixa 1 , Joana Moreira 1 , Ana Estrada 1 , Ana Gil 1 , Tito Trindade 1
1 CICECO and Department of Chemistry, University of Aveiro, Aveiro Portugal
Show AbstractNatural polysaccharides are an important class of biomaterials for drug delivery. The incorporation of inorganic nanoparticles in polysaccharide hydrogels is currently being explored as a strategy to confer to the hydrogels novel functionalities valuable for specific bio-applications [1]. For example, an immediate benefit arising from the incorporation of magnetic nanoparticles into hydrogels is the magnetically driven drug transport which enables site specific drug delivery to be envisaged. The addition of gold nanostructures to thermosensitive hydrogels confers optical activity to the nanocomposites and the ability of triggered release upon light exposure [2]. The research communicated here aims to understand the role of inorganic nanofillers (Au and Fe3O4) on the swelling behavior and release mechanism of hydrogel nanocomposites, a topic that it is still not clear and is of relevance for the above mentioned applications.Hydrogel nanocomposites comprising a thermosensitive polymer matrix (κ-carrageenan) and dispersed nanophases with magnetic (magnetite nanoparticles) and/or optical properties (gold nanostructures of variable aspect ratio) have been prepared. The nanocomposites were extensively characterized by various techniques that allowed to acquire new insights regarding their morphological (SEM, TEM), optical (UV-Vis-NIR spectroscopy), thermal (DSC), rheological and magnetic properties. The effect of the morphology and load of the nanofillers on the swelling properties of the hydrogels and in the release kinetics and release mechanism of an encapsulated model drug was investigated. The mechanism controlling the release was seen to be determined by the strength of the gel network and the extent of gel swelling, both being affected by the incorporation of the nanofillers. Furthermore, it was found that the release rate and profile could be tailored using variable nanoparticles load. The implications of the incorporation of nanoparticles into hydrogels as a route for the design of drug delivery systems with tailored released behavior will be discussed.[1] A.M.G.C. Dias et al. Biotechnology Advances 29(2011) 142.[2] Hribar, K.C. et al. ACS Nano 5(2011) 2948.
12:30 PM - V14.5
On-Demand Drug Release by Electrically Actuatable Smart Nanoporous Membrane.
Gumhye Jeon 1 , Jinseok Byun 1 , Jin Kon Kim 1
1 Chemical Engineering, POSTECH, Pohang Korea (the Republic of)
Show AbstractPulsatile drug delivery is an ideal remedy of hormone-related disease and local pain relief of chronic diseases. The key issue in this area is to develop a smart nanoporous membrane whose pore is controlled by external stimuli. We fabricated electrically responsive nanoporous membrane based on polypyrrole doped with dodecylbenzenesulfonate anions (PPy/DBS) which was electropolymerized on the anodized aluminum oxide membrane. Open state of pore size was freely tunable as nanometer scale accuracy depending on kind of drugs. On and off states of the pores were reversibly controlled by volume change of PPy/DBS depending on electrochemical state (oxidation vs reduction states). The actuation of the pore size was experimentally confirmed by in-situ AFM and flux measurement. We also demonstrated successfully pulsatile (or on-demand) drug release demonstrated by using fluorescently labeled protein as model drug. This membrane showed a fast switching time (less than 10 s) and high flux of drug.
12:45 PM - V14.6
Smart Microgel Capsules and Model Colloids Tailored by Droplet-Based Microfluidics.
Sebastian Seiffert 1 2 3 , David Weitz 3
1 Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Berlin Germany, 2 Institute of Chemistry and Biochemistry, FU Berlin, Berlin Germany, 3 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractMicrometer-sized, stimuli-responsive polymer gel particles serve for a plethora of applications, including those as smart microcapsules, sensors, actuators, and delivery systems. These valuable materials can be produced with exquisite control through the use of droplet-based microfluidics. The key idea of this approach is to use emulsion droplets as templates for the particle synthesis and to control the size, shape, and monodispersity of the microgels by controlling the size, shape, and monodispersity of the pre-microgel droplets; this is readily achieved by droplet-based microfluidics. To extend this control to determining the material properties of the microgels, we combine droplet-based microfluidic templating with the use of functional, macromolecular precursor polymers [1]. This approach separates the polymer synthesis from the particle gelation and allows each to be controlled independently. In addition, it allows complex particle morphologies such as hollow [1], anisotropic [2], or multi-layered microgels [3] to be formed and used for encapsulation and controlled release purposes. We also use this approach to form microgels that are complexed with additives such as magnetic materials [2] or living cells [4].In addition to their utility for encapsulation purposes, these microgels can also serve as model systems to explore how changes in particle stiffness and size affect the thermodynamics and elasticity in strongly compressed colloidal and non-colloidal systems. While it is known that in dilute solution, the dynamics of colloidal microgels is strongly dependent on the particle size, it is unclear to what extent the dynamics of microgel systems are determined by the particle size if the system is densely packed. Our microfluidic approach allows us to prepare densely packed microgel systems that consist of particles with variable sizes. Studying the isotropic compressibility and shear elasticity of these systems shows that if a sufficient compression eliminates non-affine particle motion, the data obtained from colloidal-scale and granular-scale particles collapse on the same, macrogel-type master-curves and show a universal scaling independent of the particle size.[1] S. Seiffert, D. A. Weitz, Soft Matter 6, 3184 (2010).[2] S. Seiffert, M. B. Romanowsky, D. A. Weitz, Langmuir 26, 14842 (2010).[3] S. Seiffert, J. Thiele, A. R. Abate, D. A. Weitz, J. Am. Chem. Soc. 132, 6606 (2010).[4] D. Steinhilber, S. Seiffert, J. A. Heyman, F. Paulus, D. A. Weitz, R. Haag, Biomaterials 32, 1311 (2010).
V15: Stimuli-Responsive Hydrogels
Session Chairs
Thursday PM, December 01, 2011
Room 312 (Hynes)
2:30 PM - **V15.1
Self-Oscillating Polymer Gels as Novel Smart Materials.
Ryo Yoshida 1
1 Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo Japan
Show AbstractSo far stimuli-responsive polymer gels and their application to smart materials have been widely studied. On the other hand, as a novel biomimetic gel, we have been studying gels with an autonomous self-oscillating function, since firstly reported in 1996. We succeeded in developing novel self-oscillating polymers and gels by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the catalyst for the BZ reaction is covalently immobilized. In the presence of the reactants, the polymer gel undergoes spontaneous cyclic swelling–deswelling changes or soluble–insoluble changes (in the case of uncrosslinked polymer) without any on–off switching of external stimuli. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as biomimetic actuators and mass transport surface.
3:00 PM - V15.2
Active Ciliated Surfaces from Self-Oscillating Polymer Gels.
Pratyush Dayal 1 , Amitabh Bhattacharya 1 , Olga Kuksenok 1 , Anna Balazs 1
1 Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractUsing theory and simulations, we design active synthetic surfaces which are capable of replicating functionalities of biological cilia. In order to design such exquisite biomimetic systems we harness unique properties offered by polymer gels that undergo photosensitive Belousov-Zhabotinsky (BZ) reaction. Powered by internalized BZ reaction these polymer gels swell and de-swell autonomously by chemo-mechanical transduction and therefore are ideal materials for designing our system. In order to simulate the dynamics of the BZ cilia in surrounding fluid we have developed a nonlinear hybrid 3D model which captures all of the following processes: (a) elastodynamics of a polymer matrix (b) diffusive exchange of BZ reagents between the gel and the fluid (c) hydrodynamic interactions and (d) fluid-structure interactions. Here we show that the geometrical arrangement of cilia and the distribution of BZ activator in the fluid determine the dynamic response of the cilia. We further show that using light as an external stimulus we can sequentially modulate height of individual cilium and thereby create the “piano effect”. Finally, we demonstrate that the synchronized oscillations in the cilia result in development of the distinct flow patterns in the surrounding fluid. Our findings can be used to design active surfaces which can be remotely tuned depending upon the magnitude of external stimuli.
3:15 PM - V15.3
Coupling Chemomechanical Oscillators: Patterning BZ Hydrogels.
Matthew Smith 1 3 , Connor Slone 1 , Kevin Heitfeld 2 , Ryan Kramb 1 3 , Richard Vaia 1
1 , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 3 , National Research Council, Washington, District of Columbia, United States, 2 , Renegade Materials Corporation, Springboro, Ohio, United States
Show AbstractLiving organisms are adept at sensing and responding to their environment through chemical and mechanical means. Often, sensing and actuating functions involve the coupled response of biological oscillators. Self-oscillating hydrogels driven by the Belousov-Zhabotinsky (BZ) reaction can convert chemical signals into a mechanical response. Under appropriate conditions BZ gels exhibit sustained mechanical swell-deswell oscillations; and arrays of these gels have the potential to form networks of coupled oscillators. Precisely designed arrays are a promising avenue to forming actuators capable of complex autonomous motion and sensors with significant signal amplification capabilities. Key challenges to producing functional devices are developing effective BZ gel materials with robust patterning processes and characterizing the coupled oscillatory response across various geometric and chemical regimes. Here in, we discuss recent advances involving gel systems based on gelatin and polyacrylamide. This study contributes effective processing routes and a parameter space leading to coupled oscillations, while providing a foundation for exploring new soft actuator and sensor designs.
3:30 PM - V15.4
Inscribing Dynamical Patterns within Heterogeneous Self-Oscillating Gels.
Victor Yashin 1 , Seiichi Suzuki 2 , Ryo Yoshida 2 , Anna Balazs 1
1 Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Materials Engineering, The University of Tokyo, Tokyo Japan
Show AbstractGrafting the ruthenium catalyst to the network of swollen chemo-responsive polymer gel creates a new class of materials, which exhibit the autonomous, coupled chemical and mechanical oscillations induced by the ongoing Belousov-Zhabotinsky (BZ) reaction. In the course of the BZ reaction, the catalyst undergoes the periodic redox variations. The mechanical oscillations occur due to the hydrating effect of the oxidized Ru that causes the gel to swell and de-swell repeatedly. Previous theoretical studies of the authors (VVY and ACB) predicted that compartmentalization of BZ gels in a nonresponsive gel matrix would enable a researcher to create gel-based devices with the functionality inscribed by the configuration of the Ru-containing patches. Recently, two other authors (SS and RY) succeeded in fabricating the heterogeneous gels, which encompass the disk-shaped BZ patches. It was demonstrated experimentally for the first time that the direction of propagation of the chemo-mechanical waves in an array of the BZ patches can be controlled by varying the ruthenium content and size of the patches. Here, we present the results of computational modeling of such heterogeneous self-oscillating gels. Our computational approach is based on the Oregonator model for the BZ reaction kinetics, and the gel lattice spring model for the gel dynamics. We discuss how the catalyst concentration, patch size, and inter- patch distance affect the synchronization of oscillations in the neighboring BZ gels, and how the synchronization effects can be utilized to control the dynamical behavior of the entire system.
3:45 PM - V15: StimResHydr
BREAK
V16: Photosensitive Materials
Session Chairs
Thursday PM, December 01, 2011
Room 312 (Hynes)
4:15 PM - V16.1
New Fluorescent Singlet-Oxygen Responsive Materials.
Jingjing Zhang 1 , Syena Sarrafpour 1 , Damla Koylu 1 , Samuel Thomas 1
1 Chemistry, Tufts University, Medford, Massachusetts, United States
Show AbstractThis talk will describe a new structural platform for materials that are responsive to singlet oxygen and their potential in several applications. Singlet oxygen is an important molecule in both a number of biological processes, as well as in the decomposition of organic electronic materials such as pentacene and conjugated polymers. It also has the capability of being chemically amplified through photosensitization. We have developed a new class of acene-linked conjugated polymers that respond to singlet oxygen through interruption of energy transfer pathways. Before exposure to singlet oxygen, fluorescence from acene acceptors that are pendants on the polymer chain dominates, while after exposure to singlet oxygen—and subsequent endoperoxide formation—energy transfer is too slow to compete with fluorescence from the polymer backbone. The result is a ratiometric fluorescent response to singlet oxygen that shows 200x contrast in fluorescence recovery. Other important developments presented will be a new class of reactive red-emitting tetracenes, as well as application of these materials to biosensing and emissive thin films with photo-tunable color.
4:30 PM - V16.2
New Optical Fluorescent pH and Oxygen Sensors for Biosensing and Imaging.
Yanqing Tian 1 , Fengyu Su 1 , Xianfeng Zhou 1 , Cody Youngbull 1 , Roger Johnson 1 , Mark Holl 1 , Deirdre Meldrum 1
1 Center for Biosignatures Discovery Automation, Biodesign Institute, Arizona State University, Tempe, Arizona, United States
Show AbstractMeasuring pH and dissolved oxygen is important for monitoring drinking water quality, determining freshness of food, and understanding cell metabolism, cellular respiration rate, cell health, and diseases, including cancer. Herein, we report the syntheses and bioapplications of new fluorescence based optical pH sensors, oxygen sensors, and dual pH/oxygen sensors for intracellular and extracellular sensing.Probes for pH are derivatives of amino-naphthalimide. Probes for oxygen are platinum porphyrin derivatives. All these probes possess at least one methacrylate moiety, enabling them to be used in their monomeric and polymeric states. These probes and their nanoparticles were used for intracellular sensing. The pH probes were found to be suitable for cellular acidic compartment (lysosome) sensing, demonstrated using cell lines including: human brain glioblastoma U87MG cells, human cervical cancer HeLa cells, and human esophagus premalignant CP-A and CP-D cells under a confocal fluorescence microscope. The same monomeric probes were polymerized with 2-hydroxyethyl methacrylate and acrylamide to form pH, oxygen, and pH/oxygen dual sensing films for extracellular sensing. The chemical immobilization of these probes in the polymer matrices alleviated leaching problems of the physically doped sensors. The sensor thin films were applied to measure changes of pH and oxygen concentration during the growth of E. coli.
4:45 PM - V16.3
Photoswitchable Polymer Nanocomposites.
Vladimir Zaporojtchenko 1 , Christina Pakula 1 , Sri Wahyuni Basuki 1 , Thomas Strunskus 1 , Dordaneh Zargarani 2 , Rainer Herges 2 , Franz Faupel 1
1 Institute for Materials Science, Kiel University, Kiel Germany, 2 Institute for Organic Chemistry , Kiel University, Kiel Germany
Show AbstractIn this work photoswitchable molecules are combined with polymer nanocomposites [1] containing metal nanoparticles or carbon nanotubes to achieve different functional properties. This includes a new concept of light-controlled impedance switching. Photoswitchable metal/polymer nanocomposite films and nanosheet capacitors were prepared by physical vapor deposition of Au and Pt nanoparticles onto spin-coated polymer/chromophore blends with a thickness around 200 nm, followed by embedding of nanoparticles into the polymer. These blends consist of poly(methylmethacrylate) films doped with azo dyes molecules. A second type of nanocomposite films were made from these blends mixed with carboxyl functionalized multiwall carbon nanotubes (MWCNT-COOH). High dye concentrations were achieved by functionalizing the azo molecules with tails and branches thus enhancing solubility. The composites show completely reversible light controlled impedance switching with capacitance changes > 50 % upon alternating irradiation with UV and blue light, respectively. [2]. Reversible light controlled conductance switching is shown for metal/polymer and MWCNT/nanocomposite films near the percolation threshold. This is attributed to changes in the metal nanoparticle separations upon isomerization based on model experiments where analogous conductance changes were induced by swelling of the composite films in organic vapors and by tensile stress [3]. [1] F. Faupel, V. Zaporojtchenko, T. Strunskus, M. Elbahri, Adv. Eng. Mat. 12, 1177 (2010)[2] V. Zaporojtchenko. C. Pakula, S. W. Basuki, T. Strunskus, D. Zargarani, R. Herges, F. Faupel, Appl. Phys. A. 102, 421 (2011).[3] C. Pakula, V. Zaporojtchenko, T. Strunskus, D. Zargarani, R. Herges, F. Faupel, Nanotechnol. 21, 465201 (2010).
5:00 PM - **V16.4
Amplifying Fluorescent Polymers for Chemical- and Bio-Sensing.
Timothy Swager 1 , Carlos Cordovilla 1 , Jason Cox 1
1 Chemistry, MIT, Cambridge, Massachusetts, United States
Show AbstractThis lecture will describe the conceptual design and optimization of chemical/biological sensors based upon conjugated polymers (CPs). The ability of a CP to produce amplification in a fluorescence- or resistance-based chemosensor stems from its ability to transport optical excitations or electrical charge, respectively, over large distances. These transport properties provide the increased sensitivity and versatility of CPs over small-molecule chemosensors. By adding new functional diversity to CPs chemoresistive properties have been realized. In our fluorescence sensor schemes, the migration of an optical excitation increases the probability of an encounter with an occupied binding site. Block copolymer nanoparticles will be detailed that respond to enzymes. Other systems to be discussed will include host-guest conjugated polymer systems that respond to chemical signals based upon interrupted energy transfer processes. The latter has utility it the detection of secondary chemical signals associated with the detection of explosives.
5:30 PM - V16.5
An Overview on Light Sensing Organic Thin Film Transistor: From Basic Operating Properties towards High Performance, Selective Sensors.
Pasquale D'Angelo 1 , Thomas Anthopoulos 1
1 , Imperial College London, London United Kingdom
Show AbstractThe sensoristic approach based on OTFTs has recently been viewed as a focus of major interest because of their versatility, low cost and integration with microfluidics. In the simplest configuration of OTFT based sensors, the direct electrical detection of analytes is produced by the modulation of the device parameters due to the interaction of the device active layer with analytes [1] or light [2]. In particular, light sensing transistors (LS-OTFTs) represent an emerging application in view of the manufacturing of full organic Lab-on-Chip arrays for the selective detection of biomolecules or multifunctional, flexible, RGB sensors.LS-OTFTs basically exploit an organic semiconductive blend made of a donor-acceptor bulk heterojunction, acting as device channel in conventional TFT architectures. The as-prepared device shows an ambipolar behaviour whose OFF current is affected by the dissociation of excitons generated upon device light exposure.Key issues in terms of device operation and selectivity are the choice of the suitable donor polymer, to be combined with the acceptor organic material (generally fullerene derivatives) for the manufacturing of the active layer, and the engineering of the device architecture. In particular, device selectivity can be gained by changing the donor polymer and by coupling the device with suitable optical low-pass and high-pass filter, eventually hybrid or full organic, allowing thus the fabrication of flexible RGB filters. Sensor performances, such as the balance between the device p-type and n-type output currents, the strength of device parameter modulation, the lowest detectable power optical density and the sensor swiftness, are instead intimately correlated to the precursor concentrations, their mixing ratio, the post deposition treatment and the device architecture. In addition, LS-OTFT response can be enhanced introducing a short channel-low voltage operating OTFT acting as amplifier stage for the low LS-OTFT output OFF current, allowing the development of a light-biased current amplification stage.The first part of this talk will be focused on the analysis of LS-OTFT manufacturing and optimization process, showing how it is possible to obtain an OFF current modulation by two orders of magnitude in presence of selected monochromatic light (optical power density 100 µW/cm2), a low detectable optical power density of 2-3 µW/cm2 and a swiftness comparable the optical switching speed of commercial displays in the case of Bottom-Contac Top-Gate device with an organic dielectric barrier.Indeed, the second part of this talk will be focused on the testing of a TiO2-Dye high pass filter, coupled with a LS device for the selective detecting of visible light and a low-voltage operating OTFT to enhance the device current modulation. References [1] P.Stoliar et al. Biosens Bioelectron 2009, 24, 2935-2938.[2] T.D. Anthopoulos Appl Phys Lett 2007,91,113513.
5:45 PM - V16.6
Block Copolymer-Based Thermochromic Materials.
Yin Fan 2 , Joseph Walish 1 , Miriam Zachau Walker 1 , Steven Kooi 3 , Edwin Thomas 1 3
2 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Institute for Soldier Nanotechnology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThermochromic materials change color in response to temperature and find use in many applications, e.g. temperature sensors, quality security labels on food packages, decorations and toys etc. Our design of the thermochromic material is based on the Bragg stacks model. A Bragg stack shows structural color by reflecting light of certain wavelengths with its alternating layers of high and low refractive indices. The reflected color depends on and can be tuned by the thickness and refractive indices of the individual layers. We make use of block copolymers ' microphase separation to form the layered structure. A specific type of diblock copolymer, poly(styrene-b-2-vinylpyridine) (PS-P2VP) is chosen because of the chemical versatility of pyridines in the P2VP block, which provides a variety of tuning options for the optical properties. We refer to the critical solution behaviors of homopolymers PS and P2VP and have successfully made thermochromic materials with blue-shift or red-shift in color when heated. Two examples will be shown: PS-P2VP in acetic acid or cyclohexane. P2VP-acid systems show lower critical solution temperature (LCST) type behavior and the BCP-acid photonic material blue-shifts at increased temperatures; PS-cyclohexane system shows upper critical solution temperature (UCST) type behavior and the BCP-cyclohexane photonic material red-shifts at high temperature. The temperature dependence in both cases can be tuned by adjusting material property parameters. In sum, we have shown a model system for a thermochromic material with easy processing but high tunability.
V17: Poster Session: Multifunctional Polymer-Based Materials II
Session Chairs
Marc Behl
Rainer Haag
Tao Xie
Friday AM, December 02, 2011
Exhibition Hall C (Hynes)
9:00 PM - V17.1
Functional Nanostructured Porous Si/Hydrogel Hybrids: Synthesis, Characterization and Applications.
Ester Segal 1 2 , Naama Massad-Ivanir 1 , Giorgi Shtenberg 1 , Maksym Krepker 1
1 Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa Israel, 2 The Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa Israel
Show AbstractPorous Si (PSi) or SiO2 matrices have emerged as attractive and versatile scaffolds for the construction of complex functional nanostructures. These inorganic scaffolds provide a unique nano-scale host template for the incorporation of various polymeric materials. Specifically, the incorporation of hydrogels offers significant advantages due to their responsive behavior (volumetric changes) to different surrounding environments, ability to store and immobilize reactive functional groups, high optical transparency, and biological compatibility.Our work focuses on the design and synthesis of functional nanostructured porous Si(PSi)/hydrogel hybrids, and their application as sensors, biosensors, and drug delivery vehicles. We have recently demonstrated the use of these new hybrid nanomaterials as label-free optical biosensors for rapid bacteria detection (E. coli K12 as a model system). The hybrids combine an oxidized porous Si optical nanostructure (a Fabry-Pérot thin film) used as the optical transducer element and a hydrogel. The hydrogel, polyacrylamide, is synthesized in situ within the inorganic template and conjugated with specific monoclonal antibodies to provide the active component of the biosensor. Exposure of these modified-hybrids to the target bacteria results in “direct-cell-capture” onto the biosensor surface. These specific binding events induce predictable changes in the thin-film optical interference spectrum of the hybrid. Preliminary studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations, in the range of 103-105 cell/ml, within several minutes. These results suggest that attachment of bacteria onto the surface of the hybrid cause a detectable change in the intensity of the reflected light. Since, E. coli bacteria are large biological species, with typical dimensions of 0.8-2 µm, their presence on the surface scatters the light, resulting in a significant decrease in the intensity. The resulting intensity signals are proportional to the bacteria suspension concentration. The talk will describe the basic considerations in designing functional PSi/hydrogel hybrids, synthesis routes and new exciting applications of these nanomaterials.
9:00 PM - V17.11
Tuneable Adhesion through Novel Binder Technologies.
Marielle Wouters 1 , Marieke Burghoorn 1 , Pascal Buskens 1
1 , TNO, Eindhoven Netherlands
Show AbstractThe paper describes a crosslinking mechanism which enables bonding and debonding of adhesives and coatings. The crosslinking is based on Diels-Alder chemistry; the Diels-Alder compounds form a covalently crosslinked network at low temperatures that break at elevated temperatures. As a result, the binder exhibits good solvent resistance, adhesion, and mechanical properties at temperatures of use, and additionally it can debond at elevated temperatures for optimal positioning, adjustments or total debonding. Upon cooling the crosslinks are formed again and the properties of the original bond are maintained.The choice of crosslinker and binder material allows tailoring of the properties of the adhesive joint for different applications and processing conditions. At TNO, we have developed different Diels-Alder based binders for coatings and adhesives. In this paper we will focus on the design of a carrier tape for the semi-conductor industry.
9:00 PM - V17.12
Photophysics of Substituted Oligothiophenes and Ethylenedioxythiophenes.
Mamoun Bader 1 , Amjad Nazzal 2 , Mohamad Kazimi 2 , Wenfang Sun 3 , Yunjing Li 3
1 Chemistry, Pennsylvania State University, Hazleton, Pennsylvania, United States, 2 Physics, Wilkes University, Wilkes Barre, Pennsylvania, United States, 3 Chemistry, North Dakota State University, Fargo, North Dakota, United States
Show AbstractIn this paper we report on the photophysical properties, such as the UV-vis absorption spectra, triplet transient difference absorption spectra, triplet excited-state extinction coefficients, quantum yields of the triplet excited state, and lifetimes of the triplet excited state, of a series of oligothiophenes and ethylenedioxythiophenes endowed with a variety of electron donor/acceptor groups. The impact of the introduction of various structural modifications such as the presence/absence of various substituents and their relative positions on the optical characteristics of these materials is examined. These substituents include the tricyanovinyl, dicyanovinyl, bromo and alkyl groups. Twenty structurally related molecules were included in this study.
9:00 PM - V17.14
Photo- and Thermo-Sensitive Polymeric Micelles Assembled from Multifunctional Block Copolymers.
Wen-Chung Wu 1 , Chung-Hao Cheng 1 , Ching-Yi Chen 2
1 Department of Chemical Engineering, National Cheng Kung University, Tainan Taiwan, 2 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan
Show Abstract In this study, a series of new photo- and thermo-sensitive amphiphilic block copolymers was synthesized and the polymeric micelles of these copolymers self-assembled in aqueous solution were investigated. The photo-cleavable and thermo-sensitive moieties were incorporated into the hydrophobic and hydrophilic blocks of these copolymers, respectively. The photo-cleavable moiety shows hydrophobic-hydrophilic transition after UV irradiation, and the thermo-responsive moiety undergoes hydrophilic-hydrophobic transition when the temperature is higher than the lower critical solution temperature. Thus, the self-assembled nanostructures of these copolymers in aqueous solution could be manipulated either by the chemical structures of copolymers or by the external stimuli, namely UV irradiation or temperature change. The transformation of the self-assembled nanostructures from polymeric micelles to unimers triggered by UV irradiation or temperature change was investigated by monitoring the particle size and morphology of micelles. The particle size was measured by the dynamic light scattering, and the morphology was studied by the transition electron microscopy and/or atomic force microscopy. Through the dedicate adjustment of chemical structures, the thermal transition temperature was around body temperature. This indicates that this new series of amphiphilic block copolymers possesses the potential to be applied as nanocarriers for in-vivo treatment with the capabilities of both active and passive target delivery.
9:00 PM - V17.18
Superior Performances on Weather Stability and Water Resistance for Thermal Curable Conductive Film PEDOT:P(SS-NMA).
Hui-En Yin 1 , Chia-Fen Lee 4 , Wen-Yen Chiu 1 2 3
1 Department of Chemical Engineering, National Taiwan University, Taipei Taiwan, 4 Department of Cosmetic Science, Chia Nan University of Pharmacy and Science, Tainan Taiwan, 2 Department of Materials Science and Engineering, National Taiwan University, Taipei Taiwan, 3 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan
Show AbstractIn this research, Sodium 4-styrenesulfonate (SSNa) and N-(methylol acrylamide) (NMA) were copolymerized to form the thermal curable copolymer P(SS-NMA). Then, P(SS-NMA) was used as the polymeric template to carry out the oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) and yielded the thermal curable conductive dispersion, Poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate-N-(methylol acrylamide)) (PEDOT:P(SS-NMA)). The optoelectronic property and surface morphology for the PEDOT:P(SS-NMA) conductive thin films were investigated. The introduction of crosslinking structures into the conductive film improved the mechanical property and weather stability so as to resolve the drawbacks of the commercial products PEDOT:PSS.
9:00 PM - V17.19
High Contrast High Sensitivity Electron-Beam Resist.
Mehrsa Raeiszadeh 1 , Paul Kohl 1
1 Chemical and Biomolecular Engineering, Georgia Institute of Technolog, Atlanta, Georgia, United States
Show AbstractElectron beam lithography (EBL) is an established technique for the fabrication of small electronic device structures. EBL offers higher spatial resolution than optical photolithography because of the short wavelength of the electron beam. However, EBL has low throughput due to the sequential nature of the exposure, which can be mitigated to some extent by increasing the sensitively of the material to be imaged. Excessive exposure time can result in long write times for which beam drift or instability can occur. Thus, e-beam imageable materials with high sensitivity are of special interest. Epoxy-based polymers possess high e-beam sensitivity which comes from the chemical amplification mechanism where the e-beam generated acid catalyzes the epoxy crosslinking. Previously, a multifunctional epoxy crosslinked, aqueous-base developed, polynorbornene (PNB) dielectric (Avatrel 8000P) was introduced for packaging applications. Avatrel 8000P has a simple process procedure, high mechanical strength, and good thermal stability. The fluorinated alcohol and carboxylic acid groups on the PNB backbone provide solubility in aqueous base during developing, and cross-linkable sites for the multifunctional epoxy additives. The epoxy-based crosslinking of PNB can be initiated by an acid catalyst. In this work, the e-beam initiated reaction between PNB crosslinking sites and the multifunctional epoxy crosslinkers was investigated to explore the feasibility of the PNB as a highly sensitive electron-beam resist for nano scale fabrication. PNB formulations showed high electron-beam sensitivity and spatial resolution. The interaction of an electron beam with a PNB mixture including multifunctional epoxy crosslinker, photoacid generator (PAG) and sensitizer were investigated. The contrast, photodefinability, and electron-beam activation of the components in the PNB formulations were studied. Random crosslinking of the irradiated PNB polymer, by itself, was found to occur at relatively high electron-beam doses. The primary route to high sensitivity was through e-beam induced epoxy ring opening. Very high sensitivity was achieved when the epoxy crosslinking was catalyzed by e-beam activation of a PAG. The effect of the post-exposure bake and develop process on polymer sensitivity, contrast, and resolution was investigated. The exposure and film thickness were optimized for each formulation to achieve nanometer scale patternability. Structures with a critical dimension of 100 nm to 500 nm were fabricated and the resolution limitation of the formulations and LER of the structures were investigated. Contrast values as high as approximately 8 were obtained at doses as low as 0.38 µC/cm2 for formulation with additional PAG and multifunctional epoxy crosslinkers. This epoxy-based dielectric with simple processing procedure is extremely promising for the fabrication of high contrast patterns over large write fields.
9:00 PM - V17.2
Belousov-Zhabotinsky Reaction Induced Autonomous Self-Oscillatory Hydrogels.
Ye Zhang 1 , Ning Li 2 , Jorge Delgado 1 , Seth Fraden 2 , Irving Epstein 1 , Ryo Yoshida 3 , Bing Xu 1
1 Department of Chemistry, Brandeis University, Waltham, Massachusetts, United States, 2 Department of Physics, Brandeis University, Waltham, Massachusetts, United States, 3 Department of Materials Engineering, The University of Tokyo, Tokyo Japan
Show AbstractBelousov-Zhabotinsky reaction (BZ reaction) is well known as the classical example of non-equilibrium thermodynamics. Inspired by the natural materials with chemomechanical oscillation properties, we designed and fabricated chemo-responsive and chemomechanical-responsive hydrogels that oscillated in BZ reaction environment. By using BZ oscillating chemical reaction as theoretical modeling, we built the catalyst of BZ reaction-ruthenium complex into copolymer and supramolecular gelator to form hydrogels. The periodic oxidation and reduction of the anchored ruthenium ion in BZ reaction is possible to induce the corresponded hydrating and dehydrating effects in the hydrogels that finally result into its oscillatory volume change. All these efforts make the hydrogels self-oscillate without external stimuli. The overall aim of our research is to explore the possibility of utilizing hererogeneous chemoresponsive gels to produce multifunctional materials with the ability to convert the chemical energy of an oscillating chemical reaction into controllable mechanical forces.
9:00 PM - V17.20
Supramolecular Ionic Block Copolymers.
Longhe Zhang 1 , Nicole Brostowitz 1 , Robert Weiss 1 , Kevin Cavicchi 1
1 Polymer Engineering, University of Akron, Akron , Ohio, United States
Show AbstractSupramolecular polymers employ non-covalent intermolecular interactions to bind functional oligomeric or polymeric units together into effective macromolecular structures exhibiting different architectures. The introduction of non-covalent interactions can lead to unique self-assembly behavior useful for processing and smart materials, e.g., self-healing polymers. The majority of research on supramolecular polymers utilizes hydrogen bonding interactions to produce a polymer network. Hydrogen bonds, however, are temperature sensitive, highly directional and relatively weak in strength compared with other physical interactions, such as ionic bonds or metal complexes. The work described in this talk considers the use of ionic interactions to produce supramolecular polymers. Ionic interactions have dissociation energies an order of magnitude greater than hydrogen bonds. The electrostatic forces of ionic bonds can exceed the strong repulsive interactions between immiscible oligomeric chains and produce supramolecular block copolymers. The balance between association and dissociation of the ionic species and the interplay of temperature and stress can produce interesting thermal and rheological properties of physically bonded block copolymers. Controlled polymerization techniques were adapted for this research to synthesize well-defined end-functionalized polymers with chain-lengths below the entanglement molecular weights of the oligomers used. Telechelic and semi-telechelic polystyrenes (PS) with sulfonic acid or phosphonium end-groups were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP), respectively. Telechelic and semi-telechelic polyisobutylene (PIB) with primary amine end-groups were synthesized using living cationic polymerization. For all the end-functional polymers prepared, post polymerization organic transformations were required to achieve the desired end-functionality. Supramolecular PS-PIB block copolymers were prepared by solvent blending the functional oligomers. Infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) confirmed the formation of the ionic bond formed from the reaction of the sulfonic acid and primary amine. Differential scanning calorimetry (DSC) showed two distinct glass transition temperatures (Tg) from PS-rich and PIB-rich domains of a supramolecular block copolymer. SAXS and microscopy were used to determine the microstructure of the block copolymers, and dynamic and steady shear experiments were used to characterize the viscoelastic and flow behavior of the oligomers and supramolecular block copolymers.
9:00 PM - V17.21
Dynamics of Self-Associating Single-Chain Polymers in the Presence of Fluid Flows.
Charles Sing 1 , Alfredo Alexander-Katz 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractSignificant attention has been recently given to polymers that display self-associating behavior due to specific and long-lasting supramolecular interactions such as hydrogen bonds and metal-ligand binding. In concentrated solution or the bulk, these materials have been demonstrated to have interesting dynamic response that is intimately related to the time scale governing the associating interactions. In our research, we instead focus on the behavior of single chains in dilute solution. We demonstrate how the presence of self-interactions along the chain can govern the dynamics of the polymer, in particular when the presence of fluid flows is introduced. A combination of hydrodynamic and binder effects give rise to a regime of strongly non-monotonic extension behavior in shear flow.
9:00 PM - V17.23
Polydiacetylene – Based Biosensing: A Versatile Platform for Analysis of Biomolecular Recognition and Membrane Interactions.
Raz Jelinek 1 , Sofiya Kolusheva 1
1 , Ben Gurion University, Beer Sheva Israel
Show AbstractPolydiacetylene (PDA) is a conjugated polymer exhibiting remarkable chromatic properties, specifically undergoing dramatic color transformations and changes in fluorescence emission that are induced by varied external parameters, particularly biological molecules. In this presentation I will discuss our ongoing studies of PDA systems in diverse configurations and their applications in biosensing, diagnostics, and biological studies. Specifically, I will describe experiments carried out with lipid/PDA small and giant vesicles, PDA-based thin films assembled at the air/water interface, sol-gel-embedded PDA particles, and chemo-engineered living cells displaying PDA nanopatches upon their surface. In all those systems, the chromatic transitions of PDA provide unique analytical and signaling capabilities which we have exploited for diverse scientific and practical applications.
9:00 PM - V17.24
Three-Dimensional Characterization of Polymer Materials with X-Ray Fluorescence and Computed Tomography.
Brian Patterson 1 , George Havrilla 1 , Jeff Gelb 2 , Luke Hunter 2 , Jack Kasahara 2 , Arno Merkle 2 , Siew-Hock Lau 2 , Wenbing Yun 2
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 , Xradia, Inc., Pleasanton, California, United States
Show AbstractWhile multifunctional polymer based materials contain naturally complex micro- and nanostructures, their characterizations are especially challenging. Light- and electron-microscopy techniques are limited in their 3D imaging abilities for these materials, and often require the preparation of very small samples in order to visualize their internal structures. X-ray microscopy (XRM), on the other hand, is now routinely demonstrated to provide resolutions as high as 50 nm across a wide variety of different sample types. The coupling of this high-resolution imaging system with the technique of Zernike phase contrast now extends this platform to polymer samples, where the high penetrating power of an air-based x-ray microscope enables this characterization completely non-destructively. Thus, the multi-length scale XRM technique provides a non-destructive “zoom in” approach for characterizing the 3D morphology of polymer samples across the micron and nanometer length scales. Furthermore, the correlation of these results to confocal micro x-ray fluorescence (confocal micro-XRF) with resolution of ~30 um extends the non-destructive analysis to density information, complementing the morphology model provided by x-ray microscopy. While traditionally used for identifying and quantifying the elemental composition of a material, it can also be used for organic polymer materials to measure the density and variation in 3D.Here, we present the results of correlative imaging between confocal micro-XRF, micron-scale XRM, and nanometer-scale XRM as applied to a poly(styrene) foam. The micro-XRF system measures the 3D density (up to ~100 mg/cm3), while the XRM system visualizes the microstructure down to 50 nm feature sizes for measurement of the strut size and void distribution. Both techniques have kept the sample intact and preserved, allowing any future analysis to take place (such as re-characterization with the sample under compressive force).
9:00 PM - V17.25
Integration of Additive and Subtractive Processes for Three-Dimensional Sub-Wavelength Fabrication by Femtosecond Direct Laser Writing.
Wei Xiong 1 , Yunshen Zhou 1 , Jongbok Park 1 , Masoud Mahjouri-Samani 1 , Yang Gao 1 , Yongfeng Lu 1
1 Electrical Engineering, University of Nebraska, Lincoln, Nebraska, United States
Show AbstractAdditive nanofabrication by two-photon polymerization (2PP) has recently drawn increased attention due to its sub-wavelength resolution and three-dimensional (3D) structuring capability. However, besides additive processes, subtractive process is also required for many 3D fabrications. Method possessing both additive and subtractive fabrication capabilities was rarely reported. In this study, we achieved both additive and subtractive fabrications within a single framework of femtosecond direct laser writing through 2PP followed by multi-photon ablation. Two device structures were successfully fabricated including: periodic hole patterns with a diameter of 200 nm along sub-micron polymer fibres and micro-fluidic mesh channels with a diameter of 1 µm inside a polymer cubic. Integration of additive and subtractive processes are able to extend our capability of 3D fabrication in micro- and nanoscales and it is promising for a wide range of applications including integrated optics, MEMS, and micro-fluidics.
9:00 PM - V17.26
Diketopyrrolopyrrole (DPP)-Based Low Band Gap Polymers for Efficient Solar Cells.
Feng Liu 1 , Cheng Wang 1 , Dian Chen 1 , Lei Zhang 1 , Alejandro Briseno 1 , Thomas Russell 1
1 , University of Massachusetts Amherst, Amherst, Massachusetts, United States
Show AbstractFor bulk heterojunction (BHJ) photovoltaic devices to realize commercial applications, effective strategies to maximize the performance have to be developed and fundamentally understood. The development of low band gap polymers in the past decade enable enhanced absorption properties of the light harvesting semiconductor. In BHJ-type solar cells, the ability to control and optimize the active layer morphology is a critical issue to improve device efficiency. In this work, we synthesized a diketopyrrolopyrrole (DPP)-based low band gap polymer and blended it with phenyl-C71-butyric acid methyl ester (PCBM) to study their photovoltaic properties as well as thin-film morphology. We observed that DPP polymers are highly crystalline both in bulk and in thin film. Moreover, by incorporating units with long branching alkyl chains, the crystallinity of the polymer can be effectively reduced. In device fabrication, the high crystallinity polymer gives a better performance with efficiency, while the low crystallinity polymer performs worse. The morphology of the blended thin films was studied by both GISAXS and GIWAXS. In thin films, the polymer adopts an edge-on orientation and the blends show obvious phase separation without the need of post annealing treatment.
9:00 PM - V17.27
Molecular Modeling and Simulation of the Morphological Dynamics and Mechanics of Multifunctional Organic Polymer Membranes.
Luis Ruiz 1 , Sinan Keten 1
1 Mechanical Engineering, Civil & Environmental Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractOrganic building blocks inspired from biological systems are promising for fabricating nanostructured materials for a broad range of applications such as antimicrobials, biosensors and actuators, electronics, as well as adaptive biomaterials. Self-assembling cyclic peptide organic nanotubes have shown great promise for these applications due to their precise structural features, diverse chemical functionalization capabilities and exceptional stability arising from arrangement of hydrogen bonds into cooperative clusters. We carry out molecular simulations to investigate the mechanics of subnanoporous thin film polymer membranes employing organic nanotubes. Our investigations elucidate critical structural transitions arising from hydrogen bonding and electrostatic interactions that collectively function as tunable physical cross-links in hybrid polymer systems. We quantify the strength of physical cross-links as a function of molecular geometry, strain rates, as well as the ambient solvent environment at the nano-scale. Deformation and failure mechanisms arising from mechanical stress and interactions with water explain key experimental findings. We conclude with an outlook for the role of atomistic and multi-scale simulation methodology for providing new insight into nanodynamics of multifunctional organic polymers.
9:00 PM - V17.28
Modeling Nanoparticle Release from Responsive Microcapsules.
Hassan Masoud 1 , Alexander Alexeev 1
1 George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractWe use the dissipative particle dynamics to probe the release of nanoscopic particles from responsive hollow microcapsules. The capsules are immersed in a Newtonian fluid and their gel-like shells are modeled using a network of randomly connected elastic filaments. We show that capsule swelling results in a steady release of encapsulated nanoparticle, which is set by the diffusion time of particles through the network. For deswelling capsules, we show that a fluid flow generated by capsule shrinking leads to rapid particle release. This release, however, is limited due to decreasing mesh size of the deswelling shell. To gain control over the rapid release, we introduce solid microrods inside a deswelling capsule. The simulations disclose that the rods stretch the membrane during capsule deswelling and promote formation of large pores in the shell. These larger pores, in turn, allow massive and controllable release of nanoparticles. Thus, our findings reveal a new approach for regulating the release from stimulus responsive micro-carriers and will be especially useful for designing new drug delivery systems.
9:00 PM - V17.29
Facile Encapsulation of Organic Amines into Nano-Sized Hollow Particles and Their Release Behaviors in Various Environments.
Hana Choi 1 , Jong Myung Park 1
1 , POSTECH, Pohang Korea (the Republic of)
Show AbstractThe controlled release of active agents such as corrosion inhibitors is an essential part of increasing service time of steel products with organic coatings due to the so-called self-healing protection. For the manipulation of release control of the active materials, core-shell polymer particles loaded with organic amines as corrosion inhibitors were fabricated by using a sequential emulsion polymerization procedure with the following 4 stages; (1) a preparation of highly carboxylated polymer core latex, (2) a formation of the intermediate shell layer with medium hydrophilicity, (3) a formation of the outermost hydrophobic shell with chemical/physical stability and (4) a neutralization with an organic amine. Various types of organic amines were introduced into the core-shell particles by interaction of alkaline amines with carboxylic acid groups in the core latex. The morphologies of fabricated nanoparticles were observed by transmission electron microscope (TEM) and the encapsulated efficiency of each particle was measured by thermogravimetric analysis (TGA) and gas chromatography (GC). Monodisperse polymer capsules with an average particle diameter of 400-450 nm were synthesized. This study revealed that the chemical structures and physical/chemical properties of amines played an important role in determining the easiness and the degree of encapsulation of amine species into the core-shell particles. In addition, the release behaviors of encapsulated amines from nanoparticles were affected by the characteristics of organic amines. Different amounts of amines were released in various pH conditions depending on their ionization power and basicity. The released amines were investigated by ion chromatography (IC) and Fourier transform infrared (FTIR) spectroscopy.
9:00 PM - V17.3
Vapor-Based Synthesis of Dual-Responsive Hydrogel Coatings for Smart Nanovalves.
Yumin Ye 1 , Yu Mao 1
1 , Oklahoma State University, Stillwater, Oklahoma, United States
Show AbstractStimuli-responsive hydrogels are promising candidates for building new smart devices as they respond to environmental changes by altering a variety of properties, such as volume, surface wettability, permeability and mechanical properties. We report a novel approach of synthesizing responsive hydrogel coatings using a single-step, vapor-based method, which presents advantages over conventional liquid-based approaches in the simplicity, controllability, the solvent-free nature, and the capability to work on substrates with nanoscale features. The coating process exploits the thermal decomposition of the initiator in the vapor phase to start the copolymerization of monomer and crosslinker molecules, resulting in deposition of uniform nanocoatings on three-dimensional substrates. pH- and thermo-responsive poly(dimethyl amino ethyl methacrylate) (PDMAEMA) hydrogel films with swelling ratios up to 15.4 at 23 °C were synthesized. The swelling ratio dramatically decreased with the elevation of temperature and the increase of pH in the environment. Crosslinking degree was also found to affect the swelling of the hydrogel. Sub-50 nm PDMAEMA hydrogel films were coated along the sidewalls of the nanopores in the polycarbonate membrane to fabricate thermo-responsive nanovalves. Switch between the “open” and “closed” states of the nanopores was achieved by varying the temperature. The vapor-deposition process also enabled fine regulation of the flow by controlling the coating thickness. We expect a wide spectrum of potential applications of the vapor-based responsive hydrogel coating technique, such as controlled release, tunable transportation and separation, sensors and actuators.
9:00 PM - V17.30
Facile Synthesis of Hydrogel Hollow Microcapsules on a Superhydrophobic Surface.
Sung-rheb Cho 1 , Minyung Song 1 , Kyoung Duck Seo 2 , Sunae Hwang 1 , Dong Sung Kim 2 , Jonghwi Lee 1 , Suk Tai Chang 1
1 Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of), 2 Mechanical Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractWe have developed a one-step, template-free synthetic method for preparing hydrogel hollow microcapsules on a superhydrophobic surface. Aqueous microdroplets of hydrogel monomers and cross-linker solution are deposited on the superhydrophobic surface, which is situated under the hydrocarbon oil layer containing photoinitiators. During exposure to UV light, the aqueous microdroplets converted to hollow microcapsules with a polymerized hydrogel shell by diffusing the initiators into the oil/water interface. The hydrogel microcapsules are produced continuously with multiple aqueous droplets rolling on the tilted superhydrophobic surface under UV irradiation. The responses of the hydrogel microcapsules to environmental temperature, pH, ionic strength are examined. The method for the preparation of hydrogel hollow microcapsules on the superhydrophobic surface is simple and efficient, rendering to easy encapsulation of colloidal nanoparticles, drugs, or biological cells.
9:00 PM - V17.31
In Vivo Assessment of Poly (Ester Urea) Scaffolds that are Mechanically-Enhanced with Growth Factor Peptide-Crosslinks.
Fei Lin 1 , Laura Smith 1 , Shi-Wang Cheng 1 , Shi-Qing Wang 1 , Matthew Graham 3 , Kimberly Stakleff 2 , Matthew Becker 1
1 , Department of Polymer Science, Akron University, Akron, Ohio, United States, 3 , Akron Polymer Systems, Akron, Ohio, United States, 2 , Akron General Medical Center, Akron, Ohio, United States
Show AbstractBone defects are one of the most significant problems in orthopedic surgery. Polymeric scaffold substitutes have got instances of success for bone defect repair, due to their mechanical properties, biocompatibility, and biodegradability. In this study, two polymer scaffold systems: phenylalanine – (PHE) and leucine-based (LEU) poly (ester urea) were tested using a subcutaneous model in male Sprague Dawley rats. Bioactive ostegenic growth peptide (OGP) was also incorporated into the scaffold as tethered crosslinkers with two concentrations (0.5% and 1% mass). Mechanical experiments showed that the modulus of PHE based polymer increased with the peptide concentration after UV crosslink. As to both systems, they showed good biodegradability and there were no grossly visible inflammatory responses appreciated in any of the tissue specimens. Vascularization of the PHE with 1% OGP implant was grossly observed in two of four rats. These necropsy findings were confirmed by histological analysis and microscopic examination of the tissues stained by hematoxylin/eosin. The LEU scaffold did not demonstrate any biologic interaction.
9:00 PM - V17.32
The Aggregation-Induced Emission from Fluorescent Polymeric Micelles Self-Assembled from Amphiphilic Block Copolymers.
Wen-Chung Wu 1 , Jen-Ing Chen 1
1 Department of Chemical Engineering, National Cheng Kung University, Tainan Taiwan
Show Abstract The nanostructures and photophysical properties of the fluorescent polymeric micelles self-assembled from a series of new amphiphilic block copolymers were investigated in this work. A fluorescent pendent group with the special characteristic of aggregation-induced emission (AIE) was introduced in the hydrophobic block of the copolymers. This AIE fluorescent moiety could overcome the problem of aggregation-induced quenching for most conventional dyes when encapsulated in the core of polymeric micelles. The chemical attachment of AIE moiety in the side chain of copolymers enables the emission of AIE moieties as the fluorescent probe to trace the location of polymeric micelles, suggesting its potential application in the bioimaging. Furthermore, due to the spectral overlap between the emission of AIE moieties and the absorption of doxorubicin, a FDA-proved drug for cancer treatment, the Föster Resonance Energy Transfer (FRET) from AIE moieties to doxorubicin encapsulated in the micelle facilitates the indication of successful encapsulation of doxorubicin in the core of polymeric micelles. The photophysical properties of these fluorescent polymeric micelles were studied by the absorption and photoluminescence spectra. The efficient emission from the AIE moieties in the core of micelles was observed with higher quantum yield than the AIE moieties dissolved in the organic solvent. The confinement of AIE moieties in the core of micelles provides suitable environment for aggregation-induced emission. The encapsulation and release of doxorubicin in the micelles was studied by the FRET behavior. The occurrence of efficient FRET requires not only the good spectral overlap but also the close proximity between donor and acceptor. Thus, efficient FRET from donor (AIE moieties) to acceptor (doxorubicin) indicates the successful encapsulation of doxorubicin in the core of micelles. On the other hand, the gradual decrement of FRET suggested the release of doxorubicin from the micelles.
9:00 PM - V17.33
NMR Characterization of Canopy Dynamics in Nanoscale Ionic Materials.
Michael Jespersen 1 2 , Peter Mirau 1 , Ernst von Meerwall 3 , Phuong Ngo 2 , Rajiv Berry 1 , Richard Vaia 1 , Nikhil Fernandes 4 , Emmanuel Giannelis 5
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 , UES, Inc., Dayton, Ohio, United States, 3 Department of Physics, University of Akron, Akron, Ohio, United States, 4 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States, 5 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractNanoscale ionic materials (NIMs) are organic-inorganic hybrids in which a core nanoparticle is functionalized with a covalently attached corona and an ionically tethered oligomer canopy. NIMs exhibit liquid-like character in the absence of solvent under ambient conditions, offering unique combinations of size-dependent nanoparticle properties and liquid characteristics (e.g., plasmonic fluids). NIMs physical properties can be tuned by varying the canopy molecular weight and canopy loading. However, the relationship between the local and collective molecular dynamics and the macroscopic properties is not clearly understood, preventing rational material design and widespread incorporation into numerous applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMs prepared from silica nanoparticles. NMR relaxation studies show that the fast (ns) local dynamics of the canopy are insensitive to the presence of the silica nanoparticles unless the system is starved of canopy oligomers, indicating that local canopy-particle attractive interactions are necessary to reduce canopy chain relaxation rates. Canopy diffusion in the NIMs is slowed relative to the bulk oligomers, but not all canopy oligomers are slowed equally when the effective footprint of the canopy molecule is greater than the area per charge on the nanoparticle surface. Molecular crowding prevents all the canopy oligomers from reaching the charged nanoparticle, resulting in a strongly bound fraction of canopy oligomers at the surface and a weakly bound outer sphere The strong electrostatic coupling at the surface can be screened by addition of ions, which alters the dynamics by reducing the strongly bound population, offering a simple route to tuning the macroscopic properties of NIMs.
9:00 PM - V17.34
Active Layer Enhanced Conjugated Polymer Fluorescence for Sensing Applications.
Roy Aad 1 , Christophe Couteau 1 , Gilles Lerondel 1 , Laurent Divay 3 , Christophe Galindo 3 , Pierre Le Barny 3 , Corinne Sartel 2 , Vincent Sallet 2 , Vesna Simic 4 , Licinio Rocha 4
1 P2MN, University of Technology of Troyes, Troyes, Champagne-Ardenne, France, 3 , Thales Research and Technology - TRT, Palaiseau France, 2 , Groupe d'Etude de la Matière Condensée (GEMaC), Meudon France, 4 , CEA, Saclay France
Show AbstractWe present experimental results on the enhancement of the fluorescence of conjugated polymers by means of active optical structures. Conjugated polymers are organic semiconductors that present many interesting features making of them good candidates for various applications. More specifically, polymers can exhibit a fluorescence quenching effect and present a high quantum efficiency that makes them suitable for sensing. Fluorescence quenching is usually triggered by the capture of analytes by receiver sites present on the polymer chain. Thus, the quenching process is highly dependent on the molecular diffusion of the polymer layer. As a matter of fact, thick polymer layers exhibit low quenching efficiencies and slow response time. So, the thickness must be limited to a few nanometers (5~10nm) in order to enhance the sensing properties of the polymer. However, the decrease of the polymer thickness presents other problems. In the case of conjugated polymers, these last are usually optically excited in order to luminesce. Therefore, ultra-thin layers present low material densities and very weak excitation efficiencies which gravely reduce the polymer fluorescence. However, good sensing necessitates high fluorescence intensities along with the fast response times and high quenching efficiencies secured by the ultrathin layers. In this context, we have proposed the idea of photon recycling to enhance the excitation and thus the luminescence of conjugated polymers [1]. For this, we use zinc oxide (ZnO) based optical structures as a support layer for the polymer coating. ZnO is a widely studied material which is extremely known for his optical properties. ZnO is a wide-gap semiconductor emitting in the UV spectra, even at room temperature, at a wavelength of ~375nm. When these structures are pumped, the polymer/ZnO bi-layer is excited. The ZnO layer absorbs the light escaping the polymer light (~99% of the excitation light). The ZnO then luminesces, coupling the light in all directions (preferably in the guided mode), further exciting the polymer layer. In order for the process to work, the polymer and ZnO layer need to be optically adequate. In other words, the ZnO emission needs to be within the polymer absorption band. Various structures have been realized and studied, including polymer coated on ZnO slabs and ZnO nanowires. Their optical response is compared to that of the polymer coated on silica. Results show a colossal gain in polymer luminescence. Luminescence gains of over a 10-fold are observed. Moreover, a nonlinear optical behavior induced by the ZnO is observed. The origin of the gain and nonlinear optical response will be discussed.[1] R. Aad, S. Blaize, A. Bruyant, C. Couteau, and G. Lérondel, J. Appl. Phys. 108, 123111 (2010)
9:00 PM - V17.35
Polymeric Nanopore Membranes for Hydrophobicity-Based Separations by Conformal Initiated Chemical Vapor Deposition (iCVD).
Ayse Asatekin 1 , Karen Gleason 1
1 Department of Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractHigh-aspect ratio hydrophobic, cylindrical nanopores having diameters as low as 5 nm are rapidly fabricated using conformal vapor deposition of fluorinated polymeric layers into porous track-etched polycarbonate membranes. The resultant selectivity of these membranes for pairs of small molecules of similar size, but of different hydrophobicity, arises from solute-pore wall interactions emphasized by confinement. Increasing selectivity was observed as pore diameter decreased and as the surface of the pore became more hydrophobic. Cylindrical pores provided higher selectivity than bottleneck shaped pores having the same minimum diameter. A maximum selectivity of 234 was achieved between mesitylene and phloroglucinol by the best performing membrane. Membranes with small fluorinated pores exhibited an effective cut-off based on the polar surface area of the molecules, with limited correlation with solute size. This technology could lead to a new generation of membrane separations based on specific interactions.
9:00 PM - V17.36
One Pot Synthesis of Multifunctional Aramid Aerogels.
Chakkaravarthy Chidambareswarapattar 1 , Dhairyashil Mohite 1 , Zachary Larimore 2 , Hongbing Lu 3 , Chariklia Sotiriou-Leventis 1 , Nicholas Leventis 1
1 Chemistry, Missouri university of Science & Technology, Rolla, Missouri, United States, 2 Mechanical Engineering, Missouri University of Science & Technology, Rolla, Missouri, United States, 3 Mechanical Engineering, University of Texas, Dallas, Texas, United States
Show AbstractAerogels are quasi-stable, low-density, three-dimensional assemblies of nanoparticles, but they are commonly associated with poor mechanical properties. The most successful efforts to improve their mechanical properties involve cross-linking of the skeletal nanoparticles with polymers. However, post gelation cross-linking is time-consuming. Hence, it is reasonable to seek robust all-polymer aerogels among polymers known for their high mechanical strength. As a result, here we report the facile one-pot synthesis of a new class of Kevlar-like aerogels based on the rather underutilized reaction of multifunctional isocyanates and carboxylic acids. The resulting materials are up to 84% v/v porous with surface areas as high as 380 m2 g-1. The ultimate compressive strength per unit density is within 10% equal to that of Kevlar 49. The high specific energy absorption (37 J g-1) and Styrofoam-like thermal conductivity (0.028 W m-1 K-1) combined with thermal stability up to 350 oC render aramid aerogels multifunctional materials suitable for defense, civil and transportation related applications. Upon pyrolysis at 800 oC they can be converted to 80% (v/v) porous, electrically conducting carbons with surface areas as high as 474 m2 g-1.
9:00 PM - V17.37
From Flexible to Hard Polyurethane Aerogels: The Effect of Molecular Functionality vs. Molecular Rigidity.
Chakkaravarthy Chidambareswarapattar 1 , Jared Loebs 2 , Zachary Larimore 2 , Chariklia Sotiriou-Leventis 1 , Nicholas Leventis 1
1 Chemistry, Missouri university of Science & Technology, Rolla, Missouri, United States, 2 Mechanical Engineering, Missouri University of Science & Technology, Rolla, Missouri, United States
Show AbstractHigh performance polymer-based aerogels are not only interesting for their mechanical properties and their low thermal conductivity, but also as precursors to porous carbons. The prevalent design rule dictates that crosslinking at the monomer level decreases solubility and induces phase separation of nanoparticles with high surface to volume ratios. Hence hyperbranched structures based on trifunctional single aromatic core monomers should have enhanced interparticle connectivity and rigidity compared to those based on either difunctional or multiple aromatic core monomers. Here we report flexible to rigid hyperbranched polyurethane aerogels synthesized from tris(4-isocyanatophenyl)methane (TIPM) and 1,1,1-tris(4-hydroxyphenyl)ethane (HPE) in anhydrous acetone using dibutyltin dilaurate as catalyst. The resulting materials vary from highly flexible to more rigid as the monomer concentration increases. FTIR and 13C solid NMR confirm urethane formation. SEM shows that the flexible variety is macroporous with a beaded worm-like structure, while the rigid variety is mesoporous and nanoparticulate. The resultant flexible aerogels have the high porosity (92%) and having the surface area of 132 m2 g-1 while the rigid ones have the surface area as high as 256 m2 g-1. Hyperbranched polyurethane aerogels synthesized with trifunctional and difunctional monomers, phloroglucinol and resorcinol, respectively, have also been studied and it was found out that for the similar monomer concentration shrinkage and bulk density increases. All other material properties are also compared.
9:00 PM - V17.38
Hierarchically Structured Electronic Conducting Polymerized Ionic Liquids.
Millicent Firestone 1 , Sungwon Lee 1 , Scott Brombosz 1
1 Materials Science Division, Argonne National Laboratory, Lemont, Illinois, United States
Show AbstractProteins facilitate many key cellular processes, including signal recognition, ion transport, and energy transduction. The ability to harness this evolutionarily-optimized functionality could lead to the development of protein-based systems useful for advancing alternative energy storage and conversion. The future of protein-based materials (and ultimately devices), however, requires the development of materials that will stabilize, order and control the activity of the proteins. Furthermore, the full realization of the potential of protein-based functional materials in the fabrication of devices requires architectures that ensure assembly of the proteins into high density, ordered arrays for signal amplification and addressability, components for interfacing with traditional materials or device platforms, and a means to achieve adequate mechanical strength and chemical resistance without detriment to the biological components. Toward this end, our research has emphasized the design, synthesis and characterization of hierarchical, self-assembled, soft nanostructured architectures that fulfill these criteria. In this talk our efforts to prepare polymerized ionic liquids (poly(ILs)) that incorporate components that facilitate the interfacing and coupling of protein output (light-generated electron flow) to traditional device architectures will be presented. Specifically, these polymers have been modified in two ways so as to promote electrical communication between the encapsulated proteins and an external circuit. In the first approach, a hybrid material organizes Au nanoparticles in columns within a hexagonally perforated lamellar structured poly(IL) to serve as a conduction pathway or conduit. In the second approach, a thiophene moiety is incorporated into the ionic liquid monomer, yielding an electrically-conductive polymer.
9:00 PM - V17.4
Mussel-Inspired Polymer Coating of Nanoporous Alumina Membrane for Temperature-Controlled Mass Transport.
Jee Seon Kim 1 , Taek Gyung Kim 1 , Won Ho Kong 1 , Yoon Sung Nam 1 2 , Tae Gwan Park 1
1 Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractSurface modification of nanoporous inorganic materials with functional polymers has received increasing attention in recent years because of a wide range of applications, including nanofluidics, drug delivery, separation, and biosensors. There are two approaches available for the polymer coatings of nanoporous structures: direct coatings of pre-synthesized polymers and reactive polymer coatings. Direct coatings of pre-synthesized polymers (e.g., spin and dip coatings) often lead to nanoscale heterogeneity in surface topography. Reactive polymer coatings, based on the surface deposition of reactive initiators followed by surface graft polymerization, have been widely used to modify the surface of a planar substrate. In the application to three-dimensional nanostructures, the pre-activation of surfaces is essentially required to generate polymer chains selectively grafted to the surface. Multiple surface pre-treatment techniques are available: silanization, ion beam radiation, plasma graft pore-filling, chemical vapor deposition, electrochemical deposition, etc. Here we report a facile one-step method to coat the pore surface of an anodized aluminum oxide (AAO) membrane with a pre-synthesized functional polymer. Monodisperse poly(N-isoproylacrylamide) (PNIPAAm) with a molecular weight of 12 kDa is synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization, followed by the conjugation of catechol, a mussel-derived adhesive molecule, to one chain end of the synthesized PNIPAAm. The catechol-conjugated PNIPAAm is successfully grafted to the surface of nanopores by infiltration of polymer solution through a porous alumina membrane. The temperature-controlled conformational transition of the grafted PNIPAAm chain is correlated to the variations of contact angle and topography of the membrane surface. Our results show that the hindered diffusivity of dextran (40 kDa) through the 20-nm pores is determined by the surface wettability rather than the pore size. We expect that this simple coating approach can be extended as a general method for other polymer coatings to modify the surface of various nanostructured materials.
9:00 PM - V17.40
On the Flexoelectricity in Polyvinylidene Fluoride Films.
John Fu 1 , Sivapalan Baskaran 1 , Xiangtong He 1
1 Mechanical and Aerospace Engineering, The State University of New York, Buffalo, New York, United States
Show AbstractFlexoelectricity, which describes the linear energy coupling between the inhomogeneous elastic deformation and the induced electric polarization in solid crystalline materials and the splay and bend directing deformations and the induced electric polarization in liquid crystals, has been attracting scientific attention since Kogan and Meyer published their seminal papers in 1960s [1, 2]. The physical mechanism of the flexoelectricity in solid crystalline dielectrics is well known and its phenomenological model can be derived from the electromechanical energy coupling under equilibrium thermodynamics, whereas the flexoelectricity in liquid crystals is closely related to the geometrical asymmetry of the mesogen molecules or shape polarity but the relation between the flexoelectric coefficients and molecular structures is far from being understood. Theoretically, the flexoelectricity in polymers is similar to that in liquid crystals, which is largely dependent on the rotation of molecules; therefore, the flexoelectric responses of polymers are complicated and might be different under external perturbations, such as tensile stretching, bending, electric field poling, etc. In this report, we will discuss theoretical studies and experimental observation of the giant direct flexoelectric effect in certain polyvinylidene fluoride (PVDF) films under tensile stretching and bending conditions [3, 4]. Our experimental studies indicate that the physical mechanism behind the flexoelectricity in polymers might be more complicated than the one proposed for solid crystalline dielectrics.[1] Sh. M. Kogan, Sov. Phys. Solid State 5, 2069 (1964).[2] R. B. Meyer, Phys. Rev. Lett. 22, 918 (1969).[3] S. Baskaran, N. Ramachandran, X. He, S. Thiruvannamalai, H. Lee, H. Heo, Q. Chen, and J. Y. Fu, Phys. Lett. A 375, 2082 (2011).[4] S. Baskaran, X. He, Q. Chen, and J. Y. Fu, Appl. Phys. Lett., 98, 242901 (2011)
9:00 PM - V17.41
Electrostatic Chuck Consisting of Electrostatic Inductive Polymer Fibers for Handling of Curved Surface.
Kenji Sawai 1 , Radon Dhelika 1 , Wataru Takarada 2 , Takeshi Kikutani 2 , Kunio Takahashi 3 , Shigeki Saito 1
1 Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Tokyo Japan, 2 Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Tokyo Japan, 3 Department of International Development Engineering, Tokyo Institute of Technology, Tokyo Japan
Show AbstractElectrostatic Chuck (ESC) is a tool used to handle objects by employing electrostatic force. The most common application of ESC today includes handling of semiconductor wafer in industry; however, the targets that current industrial products can be used for are limited to only objects with flat surface because the attractive force reduces significantly for those with curved or rough surface, mainly due to the void formed in the interface at the contact of ESC and objects. An ESC that can handle curved surface will expand its applications to MEMS or optical parts handling. This study proposes a new type of ESC utilizing electrostatic inductive polymer fibers which have compliance in bending direction and transform according to the surface profile. The attractive force of this fiber-based ESC is theoretically investigated using mechanical model for each fiber. Additionally, a prototype of the ESC consisting of ten fibers arranged with an angle is developed to experimentally observe its attractive force for a curved surface. Samples for various rough surfaces, which are modeled after sinusoidal curves with different amplitudes, are also prepared. Then the attractive forces produced by the ESC are observed and compared to examine how the prototype works. The result shows the feasibility of fiber-based ESC application for curved surfaces with potential use in industry.
9:00 PM - V17.42
Optimization Study of Ag/BSA Nanoparticles Adsorption on Model Biological Surfaces.
Chandra Bhan 1 , Dharmaraj Raghavan 1
1 Chemistry, Howard University, Washington, DC, District of Columbia, United States
Show AbstractProtein conjugated nanoparticles have found broad utility in biomedical, sensing, and advanced imaging applications. A considerable amount of studies have been performed on addressing the physical, chemical, and biological characteristics of nanoparticles. However, limited work has been performed on the interaction of protein conjugated nanoparticles with model biological substrates. The objective of this work was to understand and optimize the adsorption of protein conjugated silver nanoparticles with model biological substrates (e.g. collagen). Surface Plasmon Resonance (SPR) technique was used to follow the Ag/BSA nanoparticles adsorption on to the model substrates. Factors that were varied to influence the nanoparticle adsorption include concentration of nanoparticles, ionic strength, pH, and chemistry of underlying substrates. Preliminary results indicate that the nanoparticles adsorbed on the substrate reached saturation at 8 ppm concentration. Nanoparticles retention was optimum at physiological pH than at acidic or basic pH conditions. Ionic strength of solution influences the retention of nanoparticles on model substrate. These observations are consistent with electrostatic interactions being the dominant force governing nanoparticles retention on collagen substrate. Studies are underway to investigate the adsorption of the nanoparticles on modified substrates of different functionalities. Funding: NSF (DMR-0213695)
9:00 PM - V17.43
Sacrificial Layer and Supporting Layer Techniques for the Fabrication of Ultra-Thin Free-Standing PEDOT:PSS Nanosheets.
Francesco Greco 1 , Alessandra Zucca 2 1 , Silvia Taccola 2 1 , Arianna Menciassi 2 1 , Paolo Dario 2 1 , Virgilio Mattoli 1
1 Center for MicroBioRobotics IIT@SSSA, Istituto Italiano di Tecnologia, Pontedera Italy, 2 Biorobotics Institute, Scuola Superiore Sant’Anna, Pontedera Italy
Show AbstractThe conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and its macromolecular complex with poly(styrene sulfonate) (PEDOT:PSS) have been extensively studied and successfully used in many different applications.[1] Among other interesting properties, the biocompatibility of PEDOT and PEDOT:PSS permitted their use in biomedical field, e.g. in the development of micro-electrodes for neural interfaces or in scaffolds for epithelial cells adhesion and proliferation controlled by electrochemical modulation of surface properties. [2-3] Aim of this work was to realize robust and flexible free-standing conductive nanofilms having very large surface area with typical nano-scale thickness (40-120 nm) by modifying existing approaches for nanostructured thin films assembly. [4] We tested and optimized two different fabrication methods for the obtainment of free-standing conductive nanosheets based on properly modified Supporting Layer and Sacrificial Layer techniques. As regards the Supporting Layer technique, free-standing single layer PEDOT:PSS or bi-layer PEDOT:PSS/PLA (Poly(lactic acid)) were realized that can be released in water by dissolving a poly(vinyl alcohol) supporting layer. On the other hand, free-standing LbL multilayer nanosheets embedding a conductive PEDOT:PSS layer were realized with a Sacrificial Layer technique. In this case, due to the use of a sacrificial cellulose acetate layer, the release is allowed in acetone. Here we describe the details of both the proposed fabrication methods and compare the properties of the realized nanosheets in terms of thickness, surface roughness and conductivity. Interestingly, the realized free-standing nanosheets, despite their low thickness, are very robust and compliant while maintaining their structure and functionality also after manipulation with pipettes and folding/unfolding in fluids. Adhesion of nanosheets onto tissues or on soft and rigid substrates has been tested as well as their electrochemical behaviour in Cyclic Voltammetry experiments. Possible applications are foreseen in the field of sensing and actuation, as well as in the biomedical field, e.g. as smart conductive substrates for cell culturing and stimulation. References[1] A. Elschner, S. Kirchmeyer, W. Lovenich, U. Merker, K. Reuter, PEDOT: Principles and Applications of an Intrinsically Conductive Polymer (CRC Press, Boca Raton, USA, 2010).[2]M. H. Bolin, K. Svennersten, X. Wang, I. S. Chronakis, A. Richter-Dahlfors, E. W. H. Jager, M. Berggren, Sens. Actuators, B 142 451 (2009).[3]K. Svennersten, M. H. Bolin, E. W. H. Jager, M. Berggren, A. Richter-Dahlfors, Biomaterials 30 6257 (2009).[4] P. T. Hammond, Adv. Mater. 16 1271 (2004).
9:00 PM - V17.44
Multilayer Superparamagnetic Polymer Nanocomposites.
Georgios Sotiriou 1 , Christoph Blattmann 1 , Sotiris Pratsinis 1
1 Particle Technology Laboratory, ETH Zurich, Zurich Switzerland
Show AbstractPolymer nanocomposites are prepared containing high volume fractions of nanoparticles with controlled size and crystallinity that were made by scalable flame aerosol technology [1]. Here a method is developed for synthesis of multi-layer polymer nanocomposite films overcoming the tendency of agglomeration of nanoparticles at high concentrations [2] and formation of non-uniform patches throughout such films. Filler nanoparticle characteristics are obtained by N2 adsorption and X-ray diffraction. By incorporating superparamagnetic maghemite nanoparticles [3] into the polymer matrix, the otherwise absent material property of superparamagnetism, can be induced into the resulting film. As a result, free-standing nanocomposite microstructures have been made by depositing the polymer nanocomposite films on a sacrificial layer. The filler film stays intact after polymer addition, resulting in high-filler content nanocomposites with homogeneous filler distribution or dispersion into the polymer as demonstrated by optical microscopy. These free-standing nanocomposite microstructures respond to an external magnetic film essentially mimicking the behavior of cantilevers. Using this method and with judicious selection of polymer & filler composition, morphology, size and crystallinity nanocomposite films can be made that are attractive for their antireflective properties, limited gas permeability, superparamagnetic performance, dielectric behavior, antiseptic properties, antifogging, hydrophobic or hydrophilic performance, mechanic behavior, dental prosthetics and hygiene, optics, luminescence and phosphorescence.References[1] Strobel,R., Pratsinis, S.E. Flame aerosol synthesis of smart nanostructured materials. J. Mater. Chem. 17, 4743-4756 (2007).[2] Suter, M., Ergeneman, O., Zürcher, J., Moitzi, C., Pané, S., Rudin, T., Pratsinis, S. E., Nelson, B. J. & Hierold, C. A photopatternable superparamagnetic nanocomposite: Material characterization and fabrication of microstructures. Sens. Act. B-Chem. 156, 433-443 (2011).[3] Teleki, A., Suter, M., Kidambi, P. R., Ergeneman, O., Krumeich, F., Nelson, B. J. & Pratsinis, S. E. Hermetically coated superparamagnetic Fe2O3 particles with SiO2 nanofilms. Chem. Mater. 21, 2094-2100 (2009).
9:00 PM - V17.45
Polymerization of Pyrrole on a Bi-Component Fiber.
Ferdinando Bruno 1 , Subhalakshmi Nagarajan 1 , Stephen Fossey 1
1 , US Army RDECOM Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, United States
Show AbstractElectrically conductive fibers continue to be at the forefront of research with applications in electromagnetic shielding, electrical display, rechargeable batteries, computers, protective coatings etc. Since a number of naturally occurring and synthetic fibers are insulating in nature, there has been significant research on integrating electronic conductors (such as metals and conductive polymers) on to fibers via processes including electroless plating, evaporative deposition, sputtering or carbonization. Here we report the synthesis of Polypyrrole (PPy) on a bi-component thermally responsive triangular shape fiber (such as nylon 6-6/polypropylene). PPy is one of the most widely studied conducting polymers because of its good environmental stability, ease of synthesis and high conductivity at room temperature. Using the fiber as a template, pyrrole was polymerized using ammonium persulfate as a catalyst at room temperature, resulting in the formation of a conjugated PPy on the nylon section of the fiber. Results on synthesis, characterization and electrical properties of the PPy fibers will be presented. The process compared to the electro spinning procedure is more durable less expensive more sensitive and more repeatable.
9:00 PM - V17.46
Effect of Solvent on Interactions between Functionalized Gold Nanoparticles and Polymers.
Rakhee Pani 1 , Yaroslava Yingling 1
1 , North Carolina State University, Raleigh, North Carolina, United States
Show AbstractPolymer-nanoparticle composite materials have potential use in chemical, biological, optical and microelectronic technology. The properties of these composites largely depend on the interfacial properties and spatial arrangement of the nanoparticles. The spatial distribution can be controlled using block copolymers. In this study, we investigate the interactions of polystyrene (PS), poly-(methyl methacrylate) (PMMA) and diblock copolymers PS-PMMA with ligand functionalized gold nanoparticle (Au NP) in polar and bad solvent. In our study, we represent nanoparticles with all-atom model in order to establish a deep understanding of the atomic interactions between polymers and nanoparticles. We found that PMMA will wrap around NP more efficiently in a bad solvent and interact with NP stronger than PS, which will directly affect the properties of nanocomposites.However, PS is more responsive to the presence of NP in polar solvent than in a bad solvent. Our results indicate that in the case of diblock PS-PMMA, PMMA interacts stronger with NP while PS interacts stronger within itself through pi-pi stacking interactions. Thus, PMMA has higher fraction of contacts compared to PS as observed in the diblock copolymer chains (PS–PMMA) with gold nanoparticle. The results of this study will provide a better insight into structural ordering of nanoparticles in these composites.
9:00 PM - V17.47
Engineering Multicatalytic Polymer-Cellulase Assemblies.
Ranjan Kamat 1 , Nisaraporn Suthiwangcharoen 3 , Vijay Challa 2 , Qian Wang 3 , Yao Lin 1 2
1 Polymer Program, University of Connecticut, storrs, Storrs, Connecticut, United States, 3 Department of Chemistry and Biochemistry and Nanocenter, University of South Carolina, Columbia, South Carolina, United States, 2 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractMulticatalytic enzyme assemblies such as cellulosomes, which uses cooperativity to drastically improved biological activities, have inspired researchers to develop artificial systems with similar or higher efficiency. A facile method to assemble multiple enzymes onto a synthetic scaffold is highly desired. Herein, we report a unique way to engineer multicatalytic enzyme assemblies by interfacial assembly of enzymes on polymer nanoparticles. The enzyme-polymer assemblies are hundreds nanometers in diameter, which can be controlled during the sample preparation. Catalytic domains of cellobiohydrolase I (CBHI), prepared from controlled proteolysis of CBHI, were used as the model enzymes in the study. We found that the enzymatic activities of the CBHI-polymer assemblies on their soluble substrate remain unchanged. Interestingly, in case of insoluble cellulose substrate, both surface adsorption and catalytic efficiency of the CBHI-polymer assemblies increased. The enhanced surface adsorption and catalytic effectiveness are attributed to the multivalent nature of the enzyme assemblies.
9:00 PM - V17.48
Superhydrophobic Nylon 6 Nanocomposite Fibers.
Hao Wu 1 , Mourad Krifa 1
1 , The University of Texas at Austin, Austin, Texas, United States
Show AbstractSuperhydrophobic surfaces have the potential to be used in many applications such as self-cleaning clothing, enhanced corrosion resistance surfaces and more recently energy transition materials for battery and fuel cell application. In this study, we propose a novel two-step method to produce superhydrophobic surfaces by a combination of electrospun nanocomposites with plasma disposition. Nylon6/nanoclay nanocomposite fibers with diameter around 200nm were obtained by electrospinning. The incorporation of nanoclay introduced a wrinkle structure on the fiber surface, which adds a second level of roughness for the superhydrophobicity. A layer of conformal fluorocarbon film was deposited on the fiber mat by inductively coupled plasma (ICP) deposition using C4F8. The morphology of fiber surfaces was observed with scanning electron microscope (SEM) and atomic force microscope (AFM). X-ray photoelectron spectroscopy (XPS) study was used for the evaluation of surface chemical changes. The effect of hierarchical surface roughness and plasma treatment hydrophobicity was tested by water contact angle goniometer.
9:00 PM - V17.49
Enhanced Surface Free Energy of Electrospun Polymer Nanofiber Surfaces.
Urszula Stachewicz 1 , Asa Barber 2
1 , Nanoforce Technology/Queen Mary University of London, London United Kingdom, 2 Department of Materials, Queen Mary University of London, London United Kingdom
Show AbstractElectrospun polymer nanofibers present a relatively new material with a large surface area to volume ratio that is extensively used in applications such as filtration and tissue engineering. The active surface functionality not only depends on the surface area of nanofibers available but also their inherent surface chemistry. We show in this work how the surface free energy of polymers is enhanced when processed by electrospinning. Quantitative analysis of individual electrospun nanofiber properties using a modified Wilhelmy balance method and supporting chemical spectroscopy indicates an enhanced expression of polar components at the nanofiber surface.Nanofibers in applications such as filtration, tissue engineering and composites require understanding of fiber surface behavior in order to define function and optimize the adhesion between the fibers whereas the interfacial adhesion between nanofibers and binding polymer critically define the mechanical performance of the whole composite.
9:00 PM - V17.5
Degradable Thermosensitive Hydrogels Based on Grafted Pectin or Chondroitin Sulfate.
Harshal Santan 1 2 , Stefan Kamlage 1 , Axel Neffe 1 2 , Andreas Lendlein 1 2
1 Center for Biomaterial Development, Berlin-Brandenburg Center for Regenerative Therapies and Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 Institute of Chemistry, University of Potsdam, Potsdam Germany
Show AbstractStimuli-sensitive materials can interact with their biological environment or can be remotely controlled to exhibit a functionality on demand, and are therefore of especial interest for regenerative medicine applications. Thermoreversible gelation of hydrogels is one example for stimuli-sensitivity which is relevant for biomedical applications such as injectable implants. Volume changes of the hydrogel during gelation should be avoided for an effective application, which was targeted through sol-gel-transitions based on a material showing a critical micellar concentration (CMC). Polyether-based triblock copolymers often exhibit reversible sol-gel transitions with increasing temperatures in aqueous solution. Here, grafting of the thermosensitive poly(ethylene glycol-b-propylene glycol-b-ethylene glycol)s (PEPEs) to pectin or chondroitin sulfate was performed combining thermosensitivity with degradability and, potentially, specific cell or protein interactions due to the biopolymer.PEPEs were monoaminated and grafted to the respective polysaccharide via EDC coupling. The grafting density was varied by the ratio of the components and the materials were characterized by NMR, IR, UV, TGA, and GPC. Temperature dependent behaviour of the systems was investigated by rheology and the critical micelle concentration and critical micelle temperature were determined. The gelation temperature was adjusted by the amount of PEPE grafted onto the polysaccharide as well as the concentration of the thermosensitive system in water. A concentration of 15 – 20 wt% of the grafted system in water led to gelation temperatures in the range of 28 – 36 °C. Degradability of the materials was studied in hydrolytic and enzymatic degradation tests.
9:00 PM - V17.50
Creating Superhydrophobic Polycarbonate Fiber Network from Hydrophilic Polycarbonate through Electrospinning.
Shuangwu Li 1 , Asa Barber 2
1 , Queen Mary, University of London, London United Kingdom, 2 , Queen Mary, University of London, London United Kingdom
Show AbstractSuperhydrophobic polycarbonate (PC) fibre surfaces have been successfully created from electrospinning process by increasing the surface roughness and apparent porosity through spacing between the electrospun fibres. Characterization and analysis of PC electrospun fibre and PC film surfaces were carried out to compare surface roughness with wetting contact angle. In this study, electrospun PC fibres can produce a superhydrophobic surface with a relatively high contact angle of 159°, but smooth PC film is hydrophilic and has a contact angle of 85°. Results show that the water contact angle increases with apparent surface roughness as described using a Cassie-Baxter model, where composite liquid-air-solid interface was formed and thus enhanced hydrophobicity of the surface. The changes in the surface roughness are therefore geometric rather than a function of a surface treatment applied to the polymer surface.
9:00 PM - V17.51
Modelling of Free Radical Polymerization of Azobenzene-Based Linear Polymers.
Danish Iqbal 1 , C. Melchert 1 , M. Behl 1 , A. Lendlein 1 , S. Beuermann 2
1 Center for Biomaterial Development, Institute of Polymer Research, Teltow Germany, 2 Institute of Chemistry, University of Potsdam, Potsdam Germany
Show AbstractAzobenzene-based liquid crystalline elastomers are an interesting class of multifunctional polymers.[1] The polymerization of linear polymers can serve as a model case for the prediction of the molecular chain length between two netpoints of elastomers. In this way, the predetermination of polymerization results is a highly desirable aim, especially for monomers, which require several synthesis steps. Modelling of polymerization reactions enables prediction of the polymer chain length.[2, 3] Although polymer chain lengths obtained by free radical polymerization could be predicted by various well established methods,[4, 5] this process had been tremendously simplified by the simulation package PREDICI (CIT GmbH, Rastede, Germany).[6]Here we report about the modelling of the free radical polymerization of the liquid crystalline monomer 6-[4-(4-heptyloxyphenylazo)phenoxy]hexyl¬acrylate and compare the obtained molecular weights with experimentally determined values. The linear polymers were synthesized by thermally-initiated free radical polymerization at various initiator concentrations using azobisisobutyronitrile (AIBN) as an initiator. Molecular weights of the polymers were determined by gel permeation chromatography (GPC) (Mn,exp). Model predictions for the number average molecular weight (Mn,sim), conversion and polydispersity index (PDIsim) on the basis of the kinetic model of butyl acrylate[7] were in reasonable agreement with the experimentally determined data, e.g. Mn,sim = 12,800 g.mol-1¬ / Mn,exp = 7,500 g.mol-1; PDIsim = 1.6 / PDIexp = 2.1. In conclusion it could be shown that the assumption of the kinetics of butyl acrylate provides a reasonable approximation even for acrylate-based monomers having larger substituents. [1] M. Behl, J. Zotzmann, A. Lendlein, Adv. Polym. Sci. 2010, 226, 1.[2] S. Beuermann, M. Buback, G. T. Russell, Maromol. Rapid Commun. 1994, 15, 647.[3] R. Siegmann, A. Jeličić, S. Beuermann, Macromol. Chem. Phys. 2010, 211, 546.[4] J. Cardenas, K. F. O’ Driscoll, J .Polym. Sci., Polym. Chem. Ed. 1976, 14, 883.[5] P.A. Clay, R.G.Gilbert, Macromolecules. 1995, 28, 552.[6] M. Wolkow, Macromol. Theory Simul. 1996, 5, 393.[7] W. Wang, A. N. Nikitin, R. A. Hutchinson, Macromol. Rapid. Comm. 2009, 30, 2022.
9:00 PM - V17.53
Nonlinear Melt Rheological Behavior of Sulfonated Polystyrene Ionomers.
Xiuying Qiao 1 2 , Robert Weiss 1
1 Department of Polymer Engineering, The University of Akron, Akron, Ohio, United States, 2 State Key Laboratory of Metal Matrix Composites, Shanghai Jiaotong University, Shanghai China
Show AbstractIonomers, relatively hydrophobic polymers with a small amount of ionic groups chemically attached to the polymer backbone, have attracted great attention due to the effects of ionic interactions on their physical, mechanical and rheological properties. Current and potential applications of ionomers include membranes (e.g., proton exchange, Li-ion batteries and reverse osmosis), packaging, blend compatibilization, thermoplastic elastomers, organogels, fluid modifiers and shape-memory or self-healing materials. The association and aggregation of the ionic species remarkably increases the stiffness and melt viscosity of the polymer. Most research on the rheological behavior of ionomers has focused on the linear rheological response. In this study, we measured the nonlinear melt rheological behavior of the lightly sulfonated polystyrene ionomers with different cations and sulfonation levels. This provided information on the microstructure changes that occurred in large deformation flows and on the structure recovery processes. When the sulfonation level was below 5 mol%, the association of the ion groups was relatively weak and easy to break at small strains, while for ionomers with a sulfonation level of 6.5 mol%, the ionic interactions produced elastic behavior and a yield strain. The sulfonated polystyrene ionomers exhibited shear-thinning behavior only when the sulfonation level and/or the Coulomb energy of the ion-pair were sufficiently low. Shear flows produced no stress overshoot behavior or stress growth, even for high shear rate. Although nonlinear deformation appeared to dissociate the ionic interaction, upon removal of a nonlinear deformation, the dissociated ionic interactions fully recovered, though longer times were required for the microstructure recovery as the prior deformation increased.
9:00 PM - V17.6
Multi-Layered Hydrogel Microparticles on a Superhydrophobic Surface.
Kyoung Duck Seo 1 , Min Jin Choi 1 , Sunae Hwang 2 , Jonghwi Lee 2 , Suk Tai Chang 2 , Dong Sung Kim 1
1 Mechanical Engineering, POSTECH, Pohang Korea (the Republic of), 2 Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractIn this research, we present a simple and mass producible fabrication method for multi-layered hydrogel microparticles on a concave superhydrophobic surface. Aqueous microdroplets of prepolymer solution containing a photoinitiator are dispensed on concave PDMS surface coated with an alky keton dimer (AKD). The microdroplets are then cured upon exposing to ultraviolet radiation. In this system, microdroplets will always settle at the lowest point due to the concave shape of the superhydrophobic surface. Therefore, the position of microdroplets is easily controlled without any additional manipulation and irrespective of their dispensed site on the surface. In this manner, Janus hydrogel microparticles composed of two different layers are automatically fabricated by merging two droplets in the trough. Multi-layered microparticles with a high order of complexity are also obtained by changing the number of droplets or the dispensing sequence. In addition, response to environmental conditions (i.e. temperature, pH) of microparticles is also investigated. These multi-layered hydrogel microparticles could be used in the fields of drug delivery, cell encapsulation, and microspheres for embolization.
9:00 PM - V17.7
Modeling Self-Oscillations of Chemo-Responsive Polyacrylamide-Based Gels.
Olga Kuksenok 1 , Peixi Yuan 2 , Dustin Gross 2 , Ralph Nuzzo 2 , Jeffrey Moore 2 , Anna Balazs 1
1 Chemical Engineering Dep, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 School of Chemical Sciences, University of Illinois-Urbana Champaign, Urbana, Illinois, United States
Show AbstractOscillating polymer gels undergoing the Belousov–Zhabotinsky (BZ) reaction provide an ideal medium for probing the mechanisms for chemo-mechanical and mechano-chemical transductions. Here, we focus on modeling and computer simulations of novel UV-curable polyacrylamide(PAA) gels with Ru catalyst grafted into the polymer matrix. As BZ reaction takes place, the Ru catalyst undergoes periodic oxidation and reduction, which in turn is accompanied by the periodic shrinking and swelling of the sample. This mechanical response of the PAA-based gels is distinctly different from that of more studied NIPAAm-based BZ gels, where oxidation of Ru, on the contrary, results in the swelling of the sample. We hypothesize that observed shrinking of the PAA gels upon oxidation of Ru is due to formation of additional crosslinks; these crosslinks break when Ru is in the reduced state. Here, we extend our recently developed three dimensional gel lattice spring model to account for formation and break-up of the additional cross-links. We confirm the validity of our computational model and justify our choice of model parameters by direct comparison between the simulation results and corresponding experimental studies. We isolate unique features of pattern formation in these novel PAA-based BZ gels and illustrate how these features can be affected by the gradients in sample’s properties. The findings from these studies could provide guidelines for creating robust active gels for robotic and microfluidic applications.
9:00 PM - V17.8
Novel Integration of Biochemical Interaction in Stimuli-Responsive-Hydrogel-Based Biphase Microfluidic System.
Ximin He 2 3 , Ankita Shastri 1 , Lauren Zarzar 1 , Philseok Kim 2 , Ronn Friedlander 3 , Lynn McGregor 1 , Yolanda Vasquez 3 , Michael Aizenberg 2 , Joanna Aizenberg 1 2 3
2 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States, 3 School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, United States, 1 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Show AbstractIncreasingly scientists are looking to nature and finding important inspiration in the unique mechanisms that organisms display for various adaptive and survival purposes. Here we describe a bio-inspired smart material designed for mimicking the adaptive ability of creatures in nature to change appearance by camouflage and also their ability to detect specific biomolecules and achieve transportation by complex chemical signal transduction mechanisms. This biomimetic device reports the dynamic mechanic signal to the local environment in the form of a variety of biological signals through the process of which functions such as color switching and biomolecule sorting are realized. When the platform is integrated with a novel microfluidic design, the system exhibits precise control of the bioluminescence reaction presenting switchable colors. Making further use of the responsive motion of the microstructures, the versatile system can present specific target-molecule recognition- sorting functions for a wide range of biomolecules including proteins, DNA, enzymes, etc. . With the high stability and specificity for a diverse array of target molecules, such a smart device can readily find use as a biosensor, a simple diagnostic tool of diseased indicators in solution, or even as a tool to quantitatively determine the extent of chirality achieved in the synthesis of a complex molecule.
9:00 PM - V17.9
A Novel Synthetic Route for Creating Thin-Film, UV-Curable Self-Oscillating Gels.
Peixi Yuan 1 , Olga Kuksenok 2 , Dustin Gross 1 , Ralph Nuzzo 1 , Anna Balazs 2 , Jeffrey Moore 1
1 School of Chemical Sciences, University of Illinois-Urbana Champaign, Urbana, Illinois, United States, 2 Chemical Engineering Department, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractUsing a methacrylate-modified ruthenium trisbipyridine monomer, we fabricate and characterize novel UV-curable self-oscillating gels that undergo the Belousov-Zhabotinsky (BZ) reaction. The photo-initiated polymer chemistry is realized by using acrylamide, a cross linking agent, a photo initiator and methacrylate-modified ruthenium. The photo-polymerization provides a highly efficient method for tailoring the shape of the self-oscillating gel particles. We demonstrate that these novel acrylamide-based gels exhibit high oscillation frequencies and display a relatively rapid propagation of chemical waves. Importantly, our investigations of the oscillatory properties of these acrylamide-based materials show that the oxidized state of the BZ gel particle has a smaller swelling ratio than the reduced state, which is opposite to the known swelling/deswelling properties of N-isopropylacrylamide (NIPAAm) based BZ gels. With the aid of computational modeling, we verified our hypothesis that the oxidized state of ruthenium is responsible for the formation of additional crosslinks in the network, which break when ruthenium is in the reduced state. We also demonstrate that pattern formation and propagation strongly depends on the thickness of the sample; specifically, traveling waves always originate at the thin ends of the sample. Our novel synthetic approach allows us to fabricate robust self-oscillating acrylamide-based BZ gels with readily tailored features and properties.