Symposium SF04—Progress in Materials Genomics, Synthesis and Characterization of Functional Polymers and Polymer Nanocomposites

Colloidal noble metal nanocrystals (NCs) have metal cores and organic or inorganic ligand shells and are known for their size- and shape-dependent localized surface plasmon resonances. In this talk, I will describe the use of these NCs as building blocks of assemblies with designer optical properties for 2D and 3D metamaterials. Chemical exchange of the long ligands used in NC synthesis with more compact ligand chemistries reduces the interparticle distance (d) and increases interparticle coupling. This ligand-controlled coupling allows us to tune through a dielectric-to-metal phase transition, seen by a 10¹⁰ range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies [1], and design assemblies that are strong optical absorbers [2] or scatterers [1,3]. We harness the solution-processability and physical properties of colloidal NCs to pattern NC superstructures for large-area metamaterials, demonstrating 2D extreme bandwidth quarter-wave plates [3] and optical sensors [4]. By exploiting the different chemical and physical properties of NC assemblies from bulk thin films, we construct NC/bulk bilayer heterostructures that, upon ligand exchange, fold into three-dimensional structures [5] providing a simple route to 3D metamaterials, demonstrating chiral structures that form broadband circular polarizers [6,7]. Combining superparamagnetic NCs and plasmonic NCs, we fabricate multifunctional, smart superparticles, that in suspensions, switch their polarization-dependent transmission in the infrared in response to an external magnetic field [8].
1. A. T. Fafarman, S.-H. Hong, H. Caglayan, X. Ye, B T. Diroll, T. Paik, N. Engheta, C. B. Murray, C. R. Kagan, “Chemically Tailored Dielectric-to-Metal Transition in the Design of Metamaterials from Nanoimprinted Colloidal Nanocrystals,” Nano Lett 13, 350-357 (2012).
2. W. Chen, J. Guo, Q. Zhao, P. Gopalan, A. T. Fafarman, Au. Keller, M. Zhang, Y. Wu, C. B. Murray, C. R. Kagan, “Designing Strong Optical Absorbers via Continuous Tuning of Interparticle Interaction in Colloidal Gold Nanocrystal Assemblies,” ACS Nano, 13, 7493-7501 (2019).
3. W. Chen, M. Tymchenko, P. Gopalan, X. Ye, Y. Wu, M. Zhang, C. B. Murray, A. Alu, C. R. Kagan, “Large-Area Nanoimprinted Colloidal Ay Nanocrystal-Based Nano-antennas for Ultrathin Polarizing Plasmonic Metasurfaces,” Nano Lett 15, 5254-5260 (2015).
4. W. Chen, G. Wu, M. Zhang, N. J. Greybush, J. P. Howard-Jennings, N. Song, F. S. Stinner S. Yang, C. R. Kagan, “Angle-Independent Optical Moisture Sensors Based on Hydrogel-Coated Plasmonic Lattice Arrays,” ACS Appl Nano Mater 1, 1430-1437 (2018).
5. M. Zhang, J. Guo, Y. Yu, Y. Wu, H. Yun, D. Jishkariani, W. Chen, N. J. Greybush, C. Kubel, A. Stein, C. B. Murray, C. R. Kagan, “3D Nanofabrication via Chemo-Mechanical Transformation of Nanocrystal/Bulk Heterostructures,” Adv. Mater. 30, 1800233 (2018).
6. J. Guo, J.-Y. Kim, M. Zhang, H. Wang, A. Stein, C. B. Murray, N. A. Kotov, C. R. Kagan, “Chemo- and Thermomechanically Configurable 3D Optical Metamaterials Constructed from Colloidal Nanocrystal Assemblies,” ACS Nano 13, 1427-1435 (2019).
7. J. Guo, J.-Y. Kim, S. Yang, J. Xu, Y. C. Choi, A. Stein, C. B. Murray, N. A. Kotov, C. R. Kagan, “Broadband Circular Polarizers via Coupling in 3D plasmonic Meta-Atom Arrays,” ACS Photonics, 8, 1286-1292 (2021).
8. M. Zhang, D. J. Magagnosc, I. Liberal, Y. Yu, H. Yun, H. Yang, Y. Wu, J. Guo, W. Chen, Y. J. Shin, A. Stein, J. M. Kikkawa, N. Engheta, D. S. Gianola, C. B. Murray, C. R. Kagan, Nature Nano, 12, 228-232 (2016).

Nanomaterials are considered as an important class that has found interest in various fields including electrical, optical, catalytical, and biomedical applications. In nanoscale, chemical, biological, and physical properties are all different from the properties of each atom or molecule of bulk materials. Meanwhile, gels also make up a crucial class of materials on account of their large free space between the networks and highly adjustable mechanical properties. Many hydrogel systems have been researched utilizing covalent cross-linking processes, including radical polymerization initiated by temperature, UV, and pH. It is important to understand the physical behavior of these gels, as they are being continuously introduced into various fields such as electrical, pharmaceutical, and biomedical applications.

On the basis of previous research about nanoparticles, gels, and chirality, we envisioned that a coordination-assembly complex might be able to couple with nanoparticles to form a chiral gel. The advantage of this method is that it does not require the use of a specific device or heating. Mechanical properties such as storage and loss modulus showed chirality-response along the chiral coordination direction. The aim of this research is to demonstrate unique features of the coordination system of cobalt oxide nanoparticles with cadmium salts to produce a structure that responds to the direction of chirality.

Interfacial assembly of shaped Ag nanoparticles (NPs) into two-dimensional structures provides a promising approach for generating nanomaterials with novel plasmonic properties. However, assembling such NPs at interfaces into 2D tunable non-close packed arrangements is challenging. In this talk, we propose the use of binary (hydrophilic and hydrophobic) ligands to manipulate the interactions between shaped Ag NPs and thereby to achieve the tunability of their assembly at an air-water interface. We demonstrate through both molecular dynamics simulations and experiments that the interactions between Ag nanocubes grafted with mixed hydrophilic/hydrophobic (PEG thiol/hexadecanethiol) ligands can be manipulated and their assembly can be controlled by changing the length and stoichiometry of the two ligands. We systematically explore the structural phases assembled from such grafted nanocubes by tuning the overall surface grafting densities and the length and number ratios of the two ligands, which reveals interesting phases of assembly. A fascinating finding of them is the formation of a novel checkerboard pattern of Ag nanocubes due to the interplay between the two ligands. We also show that Ag nanocubes at the air-water interface can experience multi-phase transitions in response to Langmuir-Blodgett compression. In addition, we study the orientational behavior of such nanocubes at the interface and highlight its importance on their assembly.

Hybrid NPs provide unique advantages which allow to exhibit multifunctional characteristics of including materials and modified properties. Various research fields require multifunctional structure for efficient operation such as carriers which can generate heat for improving efficiency of drug delivery and micro robots, which have magnetic properties, allows noninvasive manipulation for targeting biomaterials.
The FePt/Fe₃O₄ nanopaticles has strong potential for both magnetic and biological applications due to FePt surface, which is enable to immobilize with target molecules and magnetic property of Fe₃O₄. Though, there was issues such as aggregation of particels and not uniformed particles size generated from the previous chemical FePt synthesis methods, by applying ferrite phase, uniform hybrid phases of nanocubic can be obtained with low temperature condition. In this case, the cubic morphological NPs can exhibit multifunctional characteristics by surface functionalizing with two different desired materials as well as offering relatively large surface area. Though the considerable potential of FePt/Fe₃O₄ NPs, synthesis method still limited due to a long reaction time and high temperature.
Here, we optimized synthesis method for hybrid FePt/Fe₃O₄ nanocubes by growing Fe₃O₄ on the homogenous FePt seed structure with a short duration time and low temperature, using 1,2-hexadecanediol and 1-octadecene as the reducing agents. The phase of FePt/Fe₃O₄ components were controlled through the precursor ratios of Fe and Pt. The hybrid FePt/Fe₃O₄ nanocubes was characterized according to the ratio of precursor using TEM images, EDS mapping and XRD measurement. When Fe:Pt molar ratio was 4:1, complete hybrid FePt/Fe₃O₄ nanocubes, Fe₃O₄ phase is more prominent, was successful obtained.
Furthermore, we analyzed the properties of hybrid FePt/Fe₃O₄ nanocubes in magnetic and biocompatible perspective. The saturation magnetization value of hybrid FePt/Fe₃O₄ nanocubes increase according to the Fe precursor ratio. The highest measured saturation magnetization is equal to 26.5 emu g⁻¹ from VSM data and the measured hysteresis loops indicated an promising superparamagnetic property of synthesized nanocubes with no coercivity. Moreover, cytotoxicity test of hybrid FePt/Fe₃O₄ nanocubes was demonstrated for THP-1 (ATCC TIB-202D) cell line, representing commendable biocompatibilities.
In conclusions, we proposed hybrid FePt/Fe₃O₄ nanocubes synthesis method for growing Fe₃O₄ on homogenous FePt material by controlling precursor ratio and suitable reducing agents. This technique has advantage in avoiding the separate synthesis of seed material and in obtaining a controlled morphology of nanocubes. The synthesized FePt/Fe3O4 nanocubes can be widely used in various biomedical applications such as an MRI agent, hyperthermia, and multifunctional platform based on their high cell viability and multifunctional characteristic

The ability to synthesize functional polymer nano/microstructures with programmable shapes will benefit a wide range of applications such as particles for drug delivery with programmable pharmacokinetics, oriented fibers for efficient electrolytic capacitors and batteries, isoporous films for membrane separations, to name a few. Current synthesis approaches for polymer particles are laborious and insufficiently versatile. For example, driven by surface tension effects, polymer nano/microparticles are predominantly spheres and the obtainment of non-spherical shapes often require complete redesign of the synthesis procedure. Using a novel synthesis platform, where initiated chemical vapor deposition (iCVD) polymerization of divinylbenzene was performed in nematic liquid crystals (LC), we obtained a host of shape-controlled polymer particles ranging from nano spheres, hemispherical micro-domes, randomly oriented or directed macrogel, micro spheres, spheroids and micro discs simply by tuning the synthesis conditions such as the flowrates of monomer and LC alignment. That unprecedented versatility in shape control was enabled by a deep understanding of the mechanisms of reaction and transport in the dynamic LC, achieved using a novel assembly of in-situ long-focal range reflection-mode microscopy with the reactors. The in-situ imaging capability bridged a critical knowledge gap in liquid-templated polymerization, the mechanism of which remained elusive partially due to the depleting reactant concentrations and changing LC alignments over the course of polymerization. Applying the iCVD polymerization technique to LC, enabled continuous and controlled vapor-phase delivery to achieve concentrations below the structure-disrupting threshold of LC templates throughout the process with real-time monitoring. Nematic LC medium being a poorer solvent lead to the formation of nanospheres in bulk in contrast to microspheres obtained in conventional isotropic solvents used for precipitation polymerization of divinylbenzene. These precipitating nanospheres constituted as the building blocks, aggregating into shaped-macrogel clusters on the LC-solid interface. Guided by the LC-template near the interface, we obtained hemispherical domes in homeotropically aligned LC and, randomly oriented or directional clusters in two different hybrid templates. Further, we obtained microspheres, spheroids and unique disc-shaped particles desolvating from the macrogel clusters formed at the LC-solid interface at later stages. Additionally, we observed iCVD polymerization to cause lowering of LC-surface anchoring energy over the course of reaction. This is the first-time synthesis of such a wide variety of tunable shaped-polymeric particles have been demonstrated using a single synthesis platform compatible with a library of more than 70 functional monomers.

The Materials Genome Initiative (MGI) has heralded a sea change in the philosophy of materials design. In an increasing number of applications, the successful deployment of novel materials has benefited from the use of computational, experimental and informatics methodologies. Here, we describe the role played by computational and experimental data generation and capture, polymer fingerprinting, machine-learning based property prediction models, and how such methods will have to evolve to handle situations including homopolymers, copolymers and blend polymers. These efforts have culminated in the creation of an online Polymer Informatics platform (https://www.polymergenome.org) to guide ongoing and future polymer discovery and design [1-3]. Challenges that remain will be examined, and systematic steps that may be taken to extend the applicability of such informatics efforts to a wide range of technological domains will be discussed. These include strategies to deal with the data bottleneck, new methods to represent polymer morphology and processing conditions, and the applicability of emerging AI algorithms for materials design.
[1] Rohit Batra, Le Song and Rampi Ramprasad, “Emerging materials intelligence ecosystems propelled by machine learning”, Nature Reviews Materials (2020)
[2] Huan Doan Tran, Chiho Kim, Lihua Chen, Anand Chandrasekaran, Rohit Batra, Shruti Venkatram, Deepak Kamal, Jordan P. Lightstone, Rishi Gurnani, Pranav Shetty, Manav Ramprasad, Julia Laws, Madeline Shelton, and Rampi Ramprasad, “Machine-learning predictions of polymer properties with Polymer Genome”, Journal of Applied Physics (2020).
[3] Christopher Kuenneth, William Schertzer, and Rampi Ramprasad, Copolymer Informatics with Multitask Deep Neural Networks, Macromolecules (2021).

A common strategy to control the nanoparticle (NP) distribution in composites is to graft polymer chains onto the NP surfaces. Grafted polymer NPs can exhibit rich phase behavior due to complex interplays among chain conformational entropy, depletion effects, and enthalpic interactions. I will describe the use of a relatively new method, theoretically-informed Langevin dynamics (TILD) simulations, to determine the structure of polymer brushes on single grafted NPs and to calculate equilibrium phase diagrams for grafted NPs in solution and in polymer melts. The TILD method is sufficiently fast to allow simulations of tens of densely-grafted NPs, enabling simulation of NP-dense phases and self-assembled structures. In this talk I will focus on two systems. The first consists of PMMA-grafted NPs dispersed in a SAN homopolymer melt. The phase diagram is calculated from direct simulations of the NP-dense and NP-dilute phases. Adding small volume fractions of PMMA homopolymer to the composite shifts the phase boundary so that the PMMA-grafted NPs are more miscible in the polymer matrix, in qualitative agreement with experimental results from Composto and coarse-grained MD simulations from Jayaraman. The second system consists of NPs grafted with two immiscible polymers and dispersed in a selective solvent. In this case the polymers microphase separate on the surface of the particle. A Janus structure is obtained for sufficiently small NPs, while the polymers grafted to larger NPs tend to form disordered patchy structures on the NP surface. Janus-patterned NPs self-assemble in solution into double-walled vesicles when the volume fraction of solvophilic chains is between 0.2 and 0.3, similar to the range required for vesicle formation in diblock copolymers in selective solvent. These simulations establish the TILD method as an efficient tool for exploring complex NP-polymer phase behavior.

This work was performed at the Center for Integrated Nanotechnologies. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s National Nuclear Security Administration under contract DE-NA-0003525.

Polymeric electrolytes are a potential electrolyte material in the push towards all solid-state lithium-ion batteries, replacing the highly flammable liquids of the modern day. However, since the 1990s, the maximum ionic conductivity they can achieve has largely stagnated at approximately 10^-3 S/cm even at elevated temperatures, an order of magnitude below liquid electrolytes. Additionally, the highest performing polymer electrolytes are still based on polyethylene oxide (or other polyethers) with dissolved lithium salts. Our group seeks to modernize research into polymer electrolytes by taking a high throughput data driven approach which combines active machine learning with a high throughput instrument designed specifically to accelerate the pace and reliability of sample formulation and characterization. In this way we hope to further understand descriptors of ion conduction in polymeric materials, and ultimately increase the ionic conductivity of polymer electrolytes. Herein we will present our custom high throughput instrument and a growing database of polymer electrolytes formulated and characterized on the tool. Additionally, we will detail our active learning workflow and progress towards incorporation of multiple data streams such as molecular dynamics simulations, machine learned predictions, and experimental data with the common goal of boosting ionic conductivity in polymer electrolytes.

Metal substituted ferrite nanoparticles (Me_xFe_3-xO₄, Me = Mn, Co, Ni, and Zn, etc.) have been utilized in a variety of biomedical applications, including magnetic hyperthermia, drug delivery, and magnetic resonance imaging (MRI) contrast agents. Additional applications include magnetic induction for selective reduction of CO₂, high frequency inductors for energy conversion, and environmental remediation tools. In most these applications the likelihood of success is dependent upon the magnetic properties of these composite materials as well as ability to modify the surface with a strongly anchored polymeric brush that provides sufficient steric repulsion to insure colloidal stability.
The most significant magnetic properties include magnetic saturation and magnetic anisotropy. For these materials, those properties are most depended on the composition of the ferrite core. Therefore, by manipulating the atomic composition, materials can be intelligently designed to have the appropriate magnetic properties for a given application. Normally, to produce such materials is a rather Edistonian where multiple samples synthesized and characterized seeking the optimal composition. For this work we have utilized we use a combination of Density Functional Theory (DFT) and machine learning (ML) to learn the relationship between composition and magnetic performance of substituted ferrites. Magnetic saturations and anisotropies are calculated for ~1,000 substituted ferrite bulk structures (with x ranging from 0.0625 to 1) using DFT. Substitutions are made at the octahedrally coordinated Fe²⁺ sites. DFT values are input to machine-learning (ML) to correlate the magnetic properties to composition. Specifically, an XGBoost algorithm is used to correlate the magnetic performance to tabulated properties of the substituents, such as electronic properties, nuclear properties, atomic sizes, and redox energies. All of these "features" of the substituents are taken from established databases and do not require further calculations.
To produce multi-dopant ferrite nanoparticles, the 'Extended LaMer' and seed-mediated growth techniques were combined by first utilizing traditional thermal decomposition of metal acetylacetonates to produce seed particles, followed by a continuous injection of metal oleate precursors to increase the volume of the seed particles. With the choice of precursors for the seeding and dripping stage. Combining transmission electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and vibrating sample magnetometry, we conclude that the seed-mediated drip method is a viable method to produce multi-dopant ferrite nanoparticles, and the size of the particles was mostly determined by the seeding stage, while the magnetic properties were more affected by the dripping stage.
Finally, the effect of stabilizing polymer brushes on the surface of the nanocomposites will be discussed. Specially, calculations of the energetics between the particles accounting for the magnetic interactions are applied to determine the molecular weight of the stabilizing polymer brush. In addition, surface moieties for additional imaging, therapy, and targeting will be covered as avenues of investigation.

Motivated by the idea that 1D nanomaterials can be used as a template for polymer chain alignment, carbon nanotubes, have been widely used as nanofillers for reinforcing the mechanical properties of composite materials. Dispersing the CNT in polymeric matrix becomes a main issue to address in order to increase the efficiency of enhancement. Experimental works of our lab have shown the dispersion of CNT within polyacrylonitrile matrix can be significantly improved by non-solvent induced phase separation process. To systematically explore the mechanism behind this phenomenon, full atomistic simulation is used to study the energy profile in a CNT/PAN/DMF/Water system. To connect the simulation with the experimental work, a coarse-grain model using dissipative particle dynamic (DPD) method has been built to scale-up the simulated system. The DPD simulation was validated using experimental tools including SEM, SAXS and TGA. With the this mesoscale computational tool, we were able to develop a phase diagram for the CNT/PAN//DMF/Water system and investigate the blending behavior and solvation of CNT by a polymer. This system serves as a benchmark to understand the potential for using polymers to solvate nanofillers in composite processing. The result of this work will be presented.

Polymer nanocomposites (PNCs) are advanced materials that take advantage of both the properties of polymer matrix and nano-scale reinforcement. The interphase, the region between the matrix and the nano-filler, plays a critical role in determining and predicting the overall properties of PNCs. Here, we showcase the potential of the materials data infrastructure, such as the NanoMine database, which is a new materials data resource that collects annotated experimental data on PNCs, to assist fundamental materials understanding and therefore rational materials design. This specific case study is built around studying the relationship between the change in glass transition temperature () and the interfacial surface energy of the nanofillers and the polymer matrix in PNCs. We sifted through data from over 2000 experimental samples curated into NanoMine, used descriptors from the data in additional heuristic modeling tools to augment the dataset, and built a multilinear regression metamodel to predict PNC . Further analysis points to the importance of additional analysis of parameters from processing methodologies and continuously adding curated datasets to increase sample pool size. Overall, results demonstrate the power of using aggregated materials data to gain insight and predictive capability. The results also indicate the critical role of dispersion and the interphase properties, which are typically unknown. To bridge this gap, Molecular Dynamic simulations are used to assess the local polymer property changes resulting from the combined effect of interfacial polymer interactions with particles and particle-particle proximity. Approaches to scale the local mechanical properties of the interphase obtained from these simulations are discussed in order to use them as input for finite element analysis, to bridge the molecular and continuum length scales. The importance of molecular scale insight to understand and predict key features of the interphase and its impact on nanocomposite design is illustrated.

While data science is revolutionizing the study and design of hard materials, the promise of these approaches for soft and polymeric materials is manifesting more slowly. A Materials Genome approach to polymeric materials is challenged in part by the greater degree to which environmental conditions affect the salient structures and properties of soft matter as compared to hard/crystalline matter. From an experimental point of view, the dynamic and sensitive nature of soft materials makes it more challenging to amass sufficiently large and well-controlled experimental data sets to enable machine learning and data mining approaches. This talk will present a case study in merging highly-controlled experimental synthesis and characterization with machine learning strategies for the study and design of macromolecule-scaffolded nanomaterials. Our research focuses on a fluorescent nanomaterial with “genomic” properties: DNA-stabilized silver nanoclusters (Ag_N-DNAs) with atomic sizes and fluorescence colors selected by DNA sequence. These tiny fluorophores are finding applications in sensing and bioimaging, but it remains complex to understand how DNA ligands sculpt silver clusters. To answer this question and enable informed design of these macromolecule-based nanoclusters, we have developed high-throughput experimental synthesis and optical characterization of Ag_N-DNAs in order to establish a well-controlled data library that connects the optical properties of thousands of Ag_N-DNAs to the sequences of their DNA templates. Through a combination of statistical sampling and machine learning classification, we can extract the features of DNA oligomers that are discriminative for the fluorescence colors of Ag_N-DNAs, providing fundamental insights into how these macromolecules select the atomic sizes and shapes of few-atom silver clusters. The approach we have developed can be expanded to numerous sequence-encoded materials and provides a roadmap for developing machine learning approaches that exploit experimental data libraries to understand and design soft and polymeric materials.
This work is supported by NSF-CBET- 2025790.

Amphiphilic synthetic random heteropolymers can provide a bio-inspired means for augmenting and even mimicking bio-macromolecular function. The statistical distribution of chains makes analysis of particular molecules and motifs challenging experimentally. Through molecular dynamics simulations, we can provide nanoscale analysis of individual sequences to provide insight into how these synthetic polymers respond to their environments. Having previously shown multiple dynamic modes and heterogeneous surfaces for the chains in aqueous solution, we now characterize their statistically derived properties when electrostatic and polar interactions are changed through an introduction of organic solvents and small molecules. Environmentally-dependent driving forces to compact globular assembly or chain extension with significant activation barriers are observed when altering solvent. Additionally, we demonstrate that mixing solvents and small molecules alter not only the driving forces to assembly, but also introduce high energy interfaces that can stimulate changes in polymer conformation. Our characterization, leveraging analysis techniques from both polymer physics and protein sciences, enables predictable modification and processing of synthetic polymer assemblies. As native proteins and nucleic acids are, themselves, heteropolymers, our system also provides a synthetic perspective that relays behavioral relationships back to the biomolecules that inspire it.
This work was supported by the Defense Threat Reduction Agency contract HDTRA11910011.

Photons have multiple enabling advantages to control stimuli-responsive materials. In this seminar, I will discuss our groups effort to design and develop a new class of negative photochromic molecules termed DASA, their incorporation into materials and subsequent effort to unlock their potential to convert light directly into mechanical work.

The short time limit for preserving donated organs after collection leads to organ shortages, morbidity and mortality of transplant recipients. We have successfully rewarmed vitrified, cryopreserved (-140 °C – indefinite storage) biological samples, using radiofrequency (RF) excited iron oxide nanoparticles (IONPs) in cryoprotective agents (CPAs).¹ CPAs are aqueous (high concentration) solutions of salts, sugars, and organics such as DMSO and propylene glycol. We previously demonstrated that silica-shell coated IONPs form stable colloidal suspension in CPA and that their production is scalable. Unfortunately, these IONPs have limited saturation concentration.² Herein, we present a new small molecule phosphonate linker (PLink) biocompatible polymer (i.e. polyethylene glycol PEG) for coating IONPs that 1) is stable in CPAs, 2) improves saturation concentration, and 3) is inexpensive for scale-up (> 1g per batch).
PLink enables ligand attachment to commercial IONPs (Ferrotec Inc.) such as EMG-1200 (hydrophobic) and EMG-308 (hydrophilic) by displacing the initial coating. PLink contains a phosphonate anchoring moiety that has high affinity for iron oxide and a carboxyl chemical handle for ligand attachment. PLinked-PEG increases colloidal stability and decreases aggregation in water and CPAs from minutes (uncoated) up to 6 days. The heating properties of EMG-1200, specific absorption rate (SAR), increased from 20 to 150 W/g Fe, which we attribute to decreased aggregation as the PLink-PEG5000 replaced the initial hydrophobic coating. Heating is also preserved when the stability of the colloidal suspension is unaffected; as is the case in replacing EMG308s hydrophilic ligand with hydrophilic PEG. We successfully rewarmed cryopreserved HDF cells in CPA by tuning the concentration of coated IONPs, 1200PLink-PEG from 20-60 mg Fe/mL, and 308PLink-PEG from 8-25 mg Fe/mL and achieved higher viability then convective rewarming in a water bath.
Designing proper PLink-PEG coating with appropriate molecular weight and concentration leads to the formation of stable colloidal suspensions of IONPs in CPAs while preserving their heating ability. The simple coating method is both inexpensive and scalable, as needed for future manufacturing of PEG coatings for bulk cryopreservation and other biomedical IONP applications. In future experiments, PLink IONPs will be tested at higher saturation Fe concentration in CPAs, potentially increasing the heating rates and improving cryopreservation outcomes.
1. Manuchehrabadi, N.; Gao, Z.; Zhang, J.; Ring, H. L.; Shao, Q.; Liu, F.; McDermott, M.; Fok, A.; Rabin, Y.; Brockbank, K. G. M.; Garwood, M.; Haynes, C. L.; Bischof, J. C., Improved tissue cryopreservation using inductive heating of magnetic nanoparticles. Science translational medicine 2017, 9 (379).
2. Gao, Z.; Ring, H. L.; Sharma, A.; Namsrai, B.; Tran, N.; Finger, E. B.; Garwood, M.; Haynes, C. L.; Bischof, J. C., Preparation of Scalable Silica-Coated Iron Oxide Nanoparticles for Nanowarming. Advanced Science 2020, 7 (4), 1901624.

The bandwagon effect, where individuals adapt their behaviors to match with that of others, accounts for a range of societal events. Inspired by such, I will present our most recent experiment-scaling theory approach to extend this effect to abiological entities of polymers at the nanoscale curved surfaces. Using gold nanoparticles (NPs) and polystyrene-b-polyacrylic acid as a model system, we demonstrate that polymers can be designed to keep adsorbing onto NP surfaces already occupied by preceding polymers. As a result, single-patched nanoprisms are obtained for the first time at a high yield. Tunable by the fine balance of interpolymer interactions, the supramolecular bandwagoning effect further provides a variety of grafting symmetries, including double-patched and tri-patched prisms. Our grafting theories and Monte Carlo simulation accurately predict experimental observations at all levels—from particle-level patch pattern, nanoscopic size and shape of patches, to the self-limited assemblies into nano-bowties. We anticipate the composite diagram provides a novel guide to a priori pattern symmetry and nanoscale-precision morphologies of functional polymer patterns for the potential applications in plasmonics, catalysis, sensors, actuators, and data storage devices. Lastly, we demonstrate that the polymer patches can serve as “hinges” to connect NPs into reconfigurable open networks, with their rotational dynamics directly visualized under a liquid-phase electron microscope.

One of the promises of nanotechnology in its early developmental stages was the ability to make designer materials with precise control over individual building block composition and organization in 3D space. In recent years, material synthesis methods have advanced to be able to create a multitude of nanoparticles of varying sizes, shapes, and compositions, providing a vast array of building blocks to use as materials fabrication components. Additionally, processing methods have been developed to arrange these nanoparticles into ordered arrays, to dry them into thin films, and even to sinter them into more complex bulk materials. However, the fundamental promise of being able to build a material with controlled structure across the length scales of atomic crystal structure, nanoscale size, shape, and organization, and ultimately material microstructure and macroscopic form has been challenging to realize. A major advancement would therefore be a materials synthesis and processing route that could create free-standing, macroscopic materials or arbitrary three dimensional shapes with precisely controlled nanoparticle positions across the entirety of the material composition. Here, we demonstrate a nanoparticle-based building block called a “Nanocomposite Tecton (NCT)” that enables a self-assembly route to fabricating free-standing solids of arbitrary macroscopic shapes that can utilize a multitude of different nanoparticle compositions and shape, and also possess specifically programmed nanoscale particle arrangements and controlled microstructure. This talk will outline the key synthesis and processing steps that enable this method of making materials with programmed material structure across ~7 orders of magnitude in length scale, thereby realizing a long-standing goal of nanomaterials fabrication.

Advantageous properties that reveal themselves in the nanoscale have attracted focus across a wide range of research fields. A great challenge lies in developing materials that can extend effects at the nanoscale to macroscopic materials. Several methods to address this challenge include nanoparticle superlattices and thin film deposition methods that struggle to achieve sufficient thickness for application as a bulk material, or through the dispersion of active nanoscale materials into a polymer matrix that frequently struggles to incorporate a significant enough volume fraction of the functional inorganic phase. For inorganic functional nanomaterials desired for optoelectronic, thermoelectric, and similar applications that rely on transport of information quanta, the nanomaterials must be organized in a way such that both the particle-to-particle separation is sufficiently short and the inorganic phase forms a percolation path that spans the bulk composite volume.

Our work reports on a material system that forms a percolation networks of lead telluride (PbTe) nanoparticles (NPs) supported in a polymer matrix for mechanical reinforcement. PbTe NPs are semiconducting materials sought for applications in high energy photon sensing and shielding – due to its high effective atomic number – as well as thermoelectric applications for its attractive ZT figure of merit. The confinement effects displayed in PbTe NPs have promise for greatly reducing thermal losses by suppressing optical phonons which is possible to lead to high resolution photon sensing and enhanced thermoelectric power generation in a properly designed and optimized material. The aqueously dispersed PbTe NPs spontaneously self-assemble into percolating networks, which in turn swells to form a volume-spanning hydrogel, which achieves the goals of close particle-to-particle transport and percolation pathways through bulk volumes.

The hydrogel form of the PbTe nanostructured network is fragile with a short shelf-life due to water evaporation, and converting from hydrogel to an aerogel or xerogel either results in a brittle solid or collapsed structure. To solve this challenge, the PbTe NP network was infiltrated with one of a variety of hydrophilic monomers/polymers, and subsequently polymerized/crosslinked by UV initiation. The resulting functional PbTe+polymer nanocomposites were confirmed to retain stochastic networks from the assembled PbTe network, while the polymer reinforced the samples to prevent brittle fracture and support the network so it can percolate across macroscopic volumes. The nanocomposites’ mechanical properties were determined by the polymer selection and preparation method. The attenuation of the nanocomposite with neutral particle radiation was quantified and unexpectedly outperforms a simulated material of the same element distribution but homogenous composition. Explanations for these unexpected results are currently being investigated to be able to understand the potential improved interaction of high energy photons with nanostructured materials compared to amorphous devices.

Photochromic bipyridines typically appear in literature in the form of N,N’-disubstituted-4,4’-bipyridines, known as viologens. Following irradiation with UV light, a viologen undergoes one-electron transfer to form a blue-colored radical cation detectable by electron paramagnetic resonance (EPR) spectroscopy. Metal complexes with 2,2’-bipyridine ligands are also known to form photosensitizers. In this work, we investigated a new photo-responsive mechanism of metal-free 2,2’-bipyridines and its applications in photo-switchable polymers. The 2,2’-bipyridine derivatives synthesized in this study undergoes color change from light yellow to magenta upon UV irradiation with a new absorption peak at 550 nm. EPR spectroscopy did not show any detectable free radicals in the colored form, indicating a photochromic pathway that is different from viologens. Reversibility of the photochromism is highly tunable by changing the solvent environments and polymer structures when 2,2’-bipyridine derivatives are incorporated into polymer backbones. For example, when polyethylene glycol is copolymerized with the 2,2’-bipyridine derivatives, the semi-crystalline product appears to be magenta after UV irradiation. The colored state stays stable after removal of UV light. Heating and cooling without UV convert it back to the white semicrystalline solid, which also remains stable until being exposed to UV again. In this talk, we will discuss the tunability and reversibility of the photo-responsiveness of 2,2’-bipyridine derivatives and their polymers which are uniquely different from known photochromophores. The photochromism is attributed to the UV-induced staking of bipyridines, representing a new class of molecular photo-responses that can be adapted to various photo-switchable materials.

The need for high power density, flexible, pulsed power, and lightweight energy storage devices in advanced applications necessitates the use of polymer film-based dielectric capacitors. The maximum energy density of a dielectric capacitor is limited by the breakdown of the dielectric material at high electric fields, otherwise known as dielectric breakdown strength. Thus, for enhancing the energy density of the polymeric dielectric capacitors for advanced applications, the physics governing the dielectric breakdown of polymers needs to be understood and utilized in devising novel strategies to enhance the breakdown strength and energy density of polymeric dielectric capacitors. Theoretically, it has been shown that chain ends contribute adversely to the electrical breakdown of polymer dielectrics at high electric fields due to the free volume associated with them, resulting in low energy density in polymer capacitors. In this work, we experimentally demonstrate the role of chain ends indirectly and directly in the dielectric breakdown by using block copolymers (BCP) and cyclic polymer films respectively. The BCPs show an enhanced breakdown strength due to chain end segregation, resulting in energy densities of 5 J/cm³, which is higher than the industry standard of 1-2 J/cm³. Given the role of the chain ends is explored in the BCP films indirectly, we synthesized the cyclic polymers with high purity to explore the adverse effect of chain ends in the dielectric breakdown directly. The cyclic polymer films demonstrate ~50% enhancement in dielectric breakdown strength and as a result, the capacitive energy density in the cyclic polymer films increases by ~80% as compared to their linear counterparts. Interestingly, the cyclic polymer films show a higher refractive index and packing density as compared to their linear counterparts, which might be attributed to the elimination of chain end-based free volume. These novel insights into correlating the polymer structure and topology with electric properties and energy density will help design next-generation polymeric energy storage materials and devices.

Effective structural control of porous materials, by a selection of templating or template-free fabrication strategies, may produce materials with outstanding properties that are inaccessible in the bulk. However, existing preparative methods typically involve multiple, tedious steps that limit scalability. This trade-off between structural control and procedural simplicity for creating porous structures presents an outstanding challenge for researchers. Herein, a “burn-dry” process is introduced as a versatile, rapid strategy involving polymer-templated rapid thermal annealing (RTA) to fabricate porous networks of carbon-based materials. As a model system, we utilize a polystyrene/poly(vinyl methyl ether) blend loaded with reduced graphene oxide (rGO) particles to generate macropores on the size of phase separation, with the objective of understanding the impact of polymer mobility on templated rGO morphologies. We found that both particle loading and annealing rate contribute to kinetic trapping and network formation, and studied their impact on macropore formation using glass transition temperature as a measure of polymer mobility. Without changing the template composition and processing conditions, we demonstrate applicability of burn-dry to other carbon materials, such as graphene oxide, carbon black, carbon nanopowder, and multi-walled carbon nanotubes. The sequential templating and template degradation induced by RTA can be accomplished in less than 10 minutes. Although established in the semiconductor industry for doping inorganic materials, our use of RTA when coupled with polymer templates holds promise for large-scale fabrication of porous structures with its minimized thermal budget, high throughput, and optimized productivity/cost ratio. This work will serve as a powerful platform for the rapid templating of hard materials, and will inspire other simple, scalable approaches for creating porous structures. In addition, the impact of polymers on the electronic properties of all-carbon materials will be described.

Smart hydrogels are polymers that respond to an external stimulus (physical or chemical) by absorption or desorption of liquid. Therefore, they are interesting materials for sensing elements since the resulting volume change be related to the stimulus concentration or intensity [1,2]. The corresponding response is dependent on composition and chemical and mechanical properties of the material and can be tailored by adding metallic nanoparticles [3-5].
Here we are presenting a study on how embedded gold and silver nanoparticles influence thermo-responsive Poly(N-Isopropylacrylamid) (PNIPAAm) hydrogels. Thereby, we aim at determining if and how adding of prefabricated metallic nanoparticles can alter properties of smart PNIPAAm hydrogels, specifically with regard to sensor applications.
For sample fabrication, gold and silver nanoparticles of different diameters (15 nm and 50 nm) with polyvinylpyrrolidon (PVP) surface termination and dissolved in phosphate-buffered saline (PBS) solution (obtained from nanoComposix Europe) have been added to the pregel solution in varying concentrations. The hydrogels were subsequently polymerized at room temperature by free radical polymerization. Afterwards, samples were washed in deionized (DI) water for seven days (liquid exchange every 24 hours) to remove any chemical residues. Furthermore, plain PNIPAAm hydrogels of the same composition but without nanoparticles were fabricated as control samples.
Sample volume change has been studied by time and temperature dependent weight measurements to investigate the influence of nanoparticle type, concentration and diameter on the thermo-responsiveness. For the time-dependent measurements, samples stored in 20°C DI water were directly placed into 37°C DI water and their weight obtained every 2 minutes for the duration of 90 minutes. The temperature dependent response was studied in the range of 20°C to 40°C (region of volume-phase transition) by placing a beaker containing DI water and the sample onto a hot plate. The temperature was increased by 2°C every 70 minutes and at the end of each time interval, sample weight was measured. Furthermore, we employed an optical detection setup [6] to directly track the dynamic sample response and determine swelling and shrinking time constants in 1x and 0.25x PBS solution.
In these characterization measurements it is found that: (i) gold nanoparticles do neither influence the time- nor temperature-dependent hydrogel response, irrespectively of nanoparticles diameter and concentration; (ii) silver nanoparticles enhance the swelling response (faster and greater volume change) compared to plain hydrogels; (iii) polymerization time is strongly dependent on nanoparticle concentration in case of silver but independent for gold. These findings indicate that silver nanoparticles exert an influence already during the polymerization process leading to a change of the polymer network and resulting in the altered response. Further investigations are necessary to determine the exact causes and we will also study mechanical properties in stress-strain measurements to determine the nanoparticle influence.

[1] A. Richter et al.: Review on hydrogel-based pH sensors and microsensors. Sensors 8(1):561, 2008
[2] F. Ganji et al.: Theoretical description of hydrogel swelling: A review. Iranian Polymer Journal 19(5):375, 2010
[3] P. Thoniyot et al.: Nanoparticle–hydrogel composites: concept, design, and applications of these promising, multi-functional materials. Advanced Science 2(1-2):1400010, 2015
[4] S. Rafieian et al.: A review on nanocomposite hydrogels and their biomedical applications. Science and Engineering of Composite Materials 26(1):154, 2019
[5] C. Dannert et al.: Nanoparticle-hydrogel composites: from molecular interactions to macroscopic behavior. Polymers 11(2):275, 2019
[6] K. Rückmann et al.: A facile real-time optical characterization method for dynamic properties of smart hydrogels. Under review in Polymers, Dec. 2021

The discovery and investigation of new phenomena in polymer colloidal materials can be based on random or even designed structures that are capable of stimuli-responsive properties. Polymers can be designed from the macromolecular level where the processing conditions play a very important role in their eventual macroscopic properties. In this talk, we will focus on interfaces, particles, and microparticles mainly accessed by templating and layering to enable chemo-responsive properties observed by actuation and swelling. This will be based on polymer particles processes through non-lithographic methods. We hereby demonstrate the following systems: 1) Bilayer based folding origami-like structures via folding of reactive ion etched patterns and multilayer assemblies, 2) Colloidal particles by melt polymer extruded polymer layers capable of swelling and incorporation of dyes to enable controlled release, and 3) Fabrication of smart colloidally templated surfaces capable of controlled wetting and separation. We report the phenomena as well as the possibilities for actual applications.

Understanding the local nanoscale structure in heterogenous polymer nanocomposites and blends, particularly at and near interfaces, is critical in understanding the resulting bulk properties and completing the feedback loop for improved materials design. However, observing these structures has been a challenge as there are few to no techniques which can achieve nanoscale resolution, and provide information about the local atomic ordering, crystalline and amorphous, in polymeric materials which express heterogeneous structure on the nanoscale.
Four-dimensional scanning transmission electron microscopy(4D-STEM) a recently popularized nanobeam diffraction technique promises the needed resolution and structural information^[1]. However, beam damage and low scattering contrast from low Z elements has severely limited its application into the study of polymeric materials^[2]. Now, with the recent advances in high-speed direct electron detectors, and electron counting algorithms, coupled with energy filtration and cryogenic holders, which provide vast improvements in electron dose control and signal-to-noise ratio, there is potential for expanding this technique to characterize local structure in beam-sensitive polymer composites^[2]. In addition to experimental considerations, 4D-STEM produces large amounts of complex high-dimensional data requiring a processing algorithm to extract meaningful structural information^[1].
In this presentation we demonstrate a low-dose 4D-STEM technique and an accompanying processing routine for visualizing nanostructure in beam sensitive semicrystalline isotactic polypropylene and ethylene-octene copolymer (iPP/EOC) films with 5nm resolution. We use a two-step routine to map the amorphous phase distribution, and the crystalline structure. Our method is able to overcome the beam sensitivity, chemical and structural similarity, and low diffraction contrast limitations to image this multiphase polymer sample. This technique opens the door to direct observation of nanostructure in polymer blends and nanocomposites without heavy metal staining.
References:
[1] C. Ophus, Microsc. Microanal., 25(3), 563-582 (2019).
[2] K.C. Bustillo et al, Acc. Chem. Res. 54, 2543–2551 (2021).
[3]S.A. Rabiej, Eur. Polym. J. 27, 947–954 (1991).
[4] F.P.T.J. Van der Burgt et al, J. Macromol. Sci. - Phys. 41 B, 1091–1104 (2002).
[5] L. Godail and D.E. Packham, J. Adhes. Sci. Technol. 15, 1285–1304 (2001).

The role of the interactions between the polymer and a reinforcing inorganic phase are critical to the high performance of polymer nanocomposites. The strength of the interactions can control the local structure and properties of polymers at the nanoscale and lead to enhanced mechanical, thermal or electrical properties of the overall composite. However, changes in filler surface chemistry, casting solvent, and processing temperature, among other process variables responsible for determining polymer-surface interactions, can simultaneously lead to significant changes in the dispersion and structure of the nanocomposite fillers. To enable effective design of polymer nanocomposites, it is critical to study the impact of tuning polymer-surface interactions on polymer structure and dynamics in isolation while the inorganic phase maintains a stable dispersion and structure. Currently, one-dimensional systems are used, where a polymer film is deposited onto a planar substrate for analysis. However, the polymer volume interacting with the surface is extremely small, limiting the characterization techniques capable of probing the interfacial polymer.
To develop a system with a large volume of interfacial polymer and stable structure, we leverage evaporation induced self-assembly of sol-gel precursors and a structure directing agent to produce porous, sintered alumina and titania films. The films are 100s of nm thick with a tightly controlled and highly interconnected network with pore sizes approximately 5-10 nm in diameter. Polymers are then infiltrated into the porous network through solvent and/or thermal annealing treatments. Due to the small pore size, a significant fraction of infiltrated polymer interacts with neighbouring surfaces, and studies can directly probe changes in properties due to the surface interactions and confinement with high sensitivity. The resulting nanocomposite films lend themselves well to bulk and nanoscale characterization techniques including infra-red and Raman spectroscopy, time-domain thermoreflectance, nanoindentation, XPS, and AFM. To demonstrate the capability of these films we establish how the thermal and mechanical properties of confined PMMA and PS can be directly correlated to the extent of the hydrogen bonding between the polymer functional groups and surface hydroxyl groups using a combination of techniques. In summary, the use of the self-assembled composite films provides an approach to enable highly specific studies of the surface interactions that define polymer nanocomposites.

Barium Titanate (BTO) is a ferroelectric perovskite material that is widely studied and commonly used in state-of-the-art capacitors due to its high dielectric permittivity [1] [2] [3]. This value is generally understood to be ~5000 [2]. However, it has been reported that BTO exhibits a sharp increase in dielectric constant to over 15000 at a particle size of 70 nm [5], which is intriguing yet highly contested. Here we present an investigation of the dielectric constant of BTO across six particle sizes ranging between 50 nm and 500 nm. Dielectric constants of BTO nanoparticles were determined by incorporating surface-functionalized BTO into an ABS polymer matrix at high volume loadings with low levels of agglomeration. Nanocomposite pellets were then injection-molded into disc shapes and sputtered with gold to fabricate a dielectric parallel plate capacitor. The dielectric constant was then extracted from capacitance measurements and cross-validated with computational values obtained from a COMSOL finite element model of the nanocomposite. As the global search for improved systems of energy storage and power conditioning hastens, these results may prove valuable in the development of solutions that power the future.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
[1] Fan, H., Wei, R., Guanghua, L., Peng, S., Xiaoqing, W., Xiaofeng, C., “Structure and dielectric properties of barium titanate thin films for capacitor applications.” Ceramics International, 39 (2013).
[2] Arlt, G., Hennings, D., de With, G., “Dielectric properties of fine-grained barium titanate ceramic capacitors.” Journal of Applied Physics, 58 (1985).
[3] Briscoe, J., Dunn, S., “Piezoelectricity and Ferroelectricity. Nanostructured Piezoelectric Energy Harvesters”. SpringerBriefs in Materials (2014).
[4] Wada, S., Yasuno, H., Hoshina, T., Nam, S-M., Kakemoto, H., Tsurumi, T., “Preparation of nm-Sized Barium Titanate Fine Particles and Their Powder Dielectric Properties.” Japanese Journal of Applied Physics (2003).

In recent years, a significant effort towards developing new, sustainable materials that can serve as alternatives to synthetic and non-degradable polymers and polymer composites has been presented. Amongst the most promising solutions are biopolymers, with specific emphasis on polysaccharides like cellulose and chitin, used as both a matrix and a reinforcing filler. This constantly emerging trend is due to their renewability, abundance, biodegradability, and exceptional specific mechanical properties, due in part to the inherent hierarchical nature of such biological systems^[1].
Our recent work^[2,3] shows that biomass from plant and algal cells can also serve as a biopolymer matrix, comprised of a mixture of multiple biopolymers rather than solely the structural polysaccharides. Such biopolymer matrix materials can self-bind into cohesive bulk structures that achieve macroscopic mechanical properties comparable to commodity plastics. In this work, we examine the influence of nanofillers of different dimensions (spherical nanoparticles, nanoclay, nanocellulose) on the structure and mechanical properties across different length scales for spirulina-based bioplastics. The variable surface chemistry and surface to volume ratios provide tunable interactions between the filler and the biopolymer matrix.
In these bioplastic nanocomposites, we examine the microstructure using scanning electron microscopy (SEM) and X-ray diffraction. Thermal properties are tested with thermogravimetric analysis and differential scanning calorimetry. Finally, we assess the multi-scale mechanical properties of the nanocomposites with a combination of nanoindentation tests, probing the nanoscale properties, and 3-point bending tests, addressing their macro-scale performance.
References:
[1] S. Ling, W. Chen, Y. Fan, K. Zheng, K. Jin, H. Yu, M. J. Buehler, D. L. Kaplan, Prog. Polym. Sci. 2018, 85, 1.
[2] E. Roumeli, L. Bonanomi, R. Hendrickx, K. Rinaldi, C. Daraio, ArXiv Prepr. ArXiv190901926 2019.
[3] J. Fredricks, H. Iyer, R. McDonald, J. Hsu, A. M. Jimenez, E. Roumeli, J. Polym. Sci. 2021.

Located in the plant cell wall as the structural component responsible for the mechanical properties, cellulose is a unique raw material, highly attractive when targeting a variety of different applications. The use of cellulose-based materials for the production of a broad range of products such as paper, cardboard, construction materials and textiles dates back thousands of years. However, the isolation of nanoscopic forms of cellulose during the last decades has paved the way to a new spectrum of possible applications in the field of composite materials of industrial interest. Within the family of nanomaterials derived from cellulose, cellulose nanofibrils (CNFs) are distinguished by a very high aspect ratio. Their typical dimensions are: width in the range of 3–100 nanometers, length as high as 1 micrometer. Made of alternating crystalline and amorphous domains, CNFs are isolated from fibers by mechanical treatments generally preceded by chemical pre-treatments of the surface. These are often aimed at introducing a surface charge, which ensures a stable dispersion in aqueous media thanks to electrostatic repulsion.

Within the hierarchical structure of plant tissues, elementary fibrils of cellulose are organized in bundles embedded in an amorphous matrix (mainly consisting of lignin and hemicelluloses), giving rise to an extraordinary composite material. Thanks to this complex structure, natural fibres display impressive strength combined with high performance in terms of flexibility. Nanoscopic cellulosic materials show even superior properties due to a higher structural homogeneity, higher extent of crystallinity and extremely large specific surface area. These features make them promising candidates as low density reinforcing additives for composite materials. CNFs isolated from lignocellulosic biomass have a longitudinal Young’s modulus close to 100 GPa, as determined by both theoretical and experimental methods. Yet in order to exploit their mechanical properties in composite materials, further investigation of surface modification pathways leading to a better fibril/matrix interaction is needed, resulting in the optimization of the fibrils dispersion in the matrix. Specific challenges must be addressed when incorporating nanocelluloses in hydrophobic polymer matrices: cellulosic nanomaterials are hydrophilic and have a strong tendency for self-aggregation driven by surface hydrogen-bond interactions. Surface modification is therefore essential to improve the material’s compatibility with common polymer matrices.

In the current study, we aim to explore the potential of surface-modified CNFs as reinforcing additives. Nanocomposite materials containing a low amount of CNFs are obtained by melt processing as well as by curing coating formulations. To ensure compatibilization, different routes for chemical modification of the CNF surface are used, tuning the surface properties depending on the specific application. Avoiding covalent modification and favouring adsorption of compatibilizers in aqueous media, tailor-made functional block copolymers synthesized by controlled radical polymerization, as well as small hydrophobic molecules, are adsorbed onto water dispersed CNFs. Finally, the composite materials obtained are characterized with a focus on the mechanical properties, highly dependent on the effectiveness of the nanofibrils dispersion in the matrix.

Here I introduce a new class of steam-stable, tunable, self-supported solid sorbents for the separation of carbon dioxide from sources with widely varying CO₂ concentrations, including direct air capture (~400 ppm) and manufacturing emissions (1–10%) where steam regeneration enables efficient waste-heat integration. These polyamine sorbents are structured at the nanoscale via a polymer aerogel synthesis technique developed at PARC that uses controlled radical polymerization (CRP) to afford unprecedented control over the polymer aerogel pore network. Pore size and dispersity can be tuned using this technique, and the pore walls of the CRP aerogels are thinner than traditional aerogels, allowing greater access of the active amine sites to CO₂. Together, these design tools allow for the development of carbon dioxide sorbents that can exhibit optimized capacities, kinetics, and degradation resistance for a variety of deployment scenarios. The polymer aerogel technology is highly tunable, and the chemistry/structure/performance relationships of these new materials are complex, providing many possibilities for data-driven materials design.

Lignin – cross-linked natural phenolic polymer – based on its chemical structure could have a wide range of high-value applications. It has a high reactivity due to its aromatic nature and presence of various functional groups, and thus, could be used as high performance adsorbent. However, its sorption capacity and sorption rate needs to be further improved for industrial applications. In general, chemical modification, including crosslinking and functionalization, are necessary to impart sufficient absorption properties to it. Another approach is combination of biomacromolecules and inorganic carriers to form organic-inorganic hybrid materials. In that case, properties of inorganic sorbents could be upgraded by the valuable characteristics of organic polymer.
Hybrid materials based on lignin, and silica/carbon in different mass ratios were prepared by several synthetic approaches: via electrostatic attraction of modified lignin to aminosilica surface, by using sol-gel method, and by crosslinking of functional groups of lignin and inorganic carrier with different agents.
The peculiarities of different approaches to synthesis of lignin-based hybrid materials were studied and the influence of synthetic conditions on physicochemical properties of obtained composites were investigated by infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption/desorption, and scanning electron microscopy.
It was found that changing of pH of system, variations with carrier mass content, type of crosslinking agent applied, time of preparation are greatly affect of physicochemical characteristics of obtained materials, such as specific surface area, porosity, morphology, and thermal stability.
Synthesized hybrid composites were found to be effective as sorbents for the removal of heavy metal ions and synthetic dyes from aqueous solutions. Thus, obtained lignin-based composites are perspective materials for water remediation processes as well as metals recovering from aqueous solutions.
Acknowledgment: T. Budnyak would acknowledge the ÅForsk Foundation (19-676) and Formas Foundation (2020-02321) for the financial support of the research.

In this study, we demonstrate the colloidal synthesis of nearly monodisperse, sub-100-nm phase change material (PCM) nanobeads with an organic n-paraffin core and poly(methylmethacrylate) (PMMA) shell. PCM nanobeads are synthesized via emulsion polymerization using ammonium persulfate as an initiator and sodium dodecylbenzenesulfonate as a surfactant. The highly uniform n-paraffin/PMMA PCM nanobeads are sub-100 nm in size and exhibit superior colloidal stability. Furthermore, the n-paraffin/PMMA PCM nanobeads exhibit reversible phase transition behaviors during the n-paraffin melting and solidification processes. During the solidification process, multiple peaks with relatively reduced phase change temperatures are observed, which are related to the phase transition of n-paraffin in the confined structure of the PMMA nanobeads. The phase change temperatures are further tailored by changing the carbon length of n-paraffin while maintaining the size uniformity of the PCM nanobeads. Sub-100-nm-sized and nearly monodisperse PCM nanobeads can be potentially utilized in thermal energy storage and drug delivery because of their high colloidal stability and solution processability.

Electroplated gold alloy layers have been widely adopted as contact materials for electronic products and PCBs owing to their advantages of excellent high temperature oxidation resistance, low electrical contact resistance, and good solderability. However, a lot of voids originally formed on the thinly electroplated (10-50nm layer) gold surface reduce its corrosion resistance. To improve corrosion resistance by void on surface, sealing treatment can be performed. It well known that the gold surface layer exhibits high bonding with sulfur atoms. Therefore, an electrochemical measurement was performed after dipping it in thiol-based sealing solutions with various organic sulfur compounds for 60s at 50 degrees Celsius. When a positive constant voltage (+0.5 V) was applied to the sealed Au-Ni specimen with respect to the Pt/Ti electrode, chronoamperometry was measured to evaluate the corrosion resistance. Among the 15 sealing agents, 1-dodecanethiol, 1-octadecanethiol, benzothiazole and 2-methlbenzothiazole showed similar behavior to comparison sealing agents.

Polydiacetylene (PDA) is an attractive polymer material due to its unique chromatic and fluorogenic transitions by external stimuli as temperature, pH, solvent, ligand-receptor, etc. However, the irreversible optical transitions of PDA make it be used as a single-use disposable materials, limiting the application to biosensor. Our study suggests a systematic approach to manipulate the degree of reversible color transitions of PDA depending on the binding strength between PDA headgroups. The reversibility of PDA is closely related to hydrogen bond strength and ionic interactions between the headgroups of PDA. Three types of PDA vesicles were prepared by using carboxyl-terminated diacetylene monomer (PCDA), amine-terminated diacetylene monomer (PCDA-EDA; PCDA-ethylenediamine), and both monomers. The PDA composed of both carboxyl- and amine-terminated monomers (poly(PCDA/PCDA-EDA)) at a molar ratio of 1:1 exhibited noticeable chromatic reversibility with colorimetric response (CR) values between ca. 84-91% and ca. 24-61% under heating-UV irradiation cycles. The changes in the backbone structure and hydrogen bond strength influencing the reversible color transitions of PDA were confirmed by Raman and Fourier transform infrared (FT-IR) spectroscopies, respectively. Furthermore, structural characterizations such as dynamic light scattering (DLS) and scanning electron microscopy (SEM) showed that morphological changes of PDA are closely connected to their color response. These results demonstrate that the hydrogen bond strength and ionic interactions of PDA with different terminal functional groups play an important role in the controllable colorimetric reversibility of PDA, which can ultimately be applied to the development of recyclable PDA sensors.

Global carbon emissions are set to jump by 1.5 billion tonnes this year, while COVID 19 continues to put pressure on global energy demand. In response to this, international agreements on climate protection demand increased energy production from renewable sources. Such demand has led to unprecedented growth of renewably generated energy such as solar and wind, however much of this is extremely weather dependent. In addition, we don’t currently have an efficient method of storing the renewable generated energy safely and efficiently on a large scale making it often unreliable.¹

To solve this storage issue, hydrogen has been considered as an attractive clean energy carrier. By passing renewably generated energy through water and splitting it into its constituent molecules of oxygen and hydrogen, the hydrogen can be stored as clean energy for later use. However, being a flammable gas, hydrogen is generally stored in heavy highly pressurised gas cylinders limiting its efficiency.²

Metal-organic frameworks (MOFs) are a class of 3D nanoporous crystalline solids, comprised of metal centres bridged together by organic linkers. Their permanent porosity and superhigh surface areas (1000 to 10,000 m²/g) render MOFs as being perfect for gas storage, such as hydrogen. Using MOFs could enable extremely large volumes of hydrogen to be safely stored in tiny amounts of solid.³

However, a key limitation of MOFs preventing their system integration is their lack of processability, predominantly owing to their general insolubility and crystalline powdered form. The formation of hybrid composites containing polymers and MOFs represent a novel class of materials with diverse functionality and enhanced processability. However, approaches to fabricate such MOFs are limited by poor dispersion in polymeric matrices, resulting in MOF aggregation, which not only results in pore blocking, but also a reduction of the polymeric structural integrity.⁴

In this work, a novel type of liquid MOF was achieved through melting novel MOF/polymer nanocomposites. By addition of a long, flexible polymer chains to nano-sized MOFs, the large increase in entropy created in transitioning from the solid to liquid phase enabled melting at lower temperatures and prior to MOF decomposition (typically 200 – 500 ^oC). In addition, the molten MOF/polymer nanocomposites represent one of the first examples of a type 1 porous liquid nanoMOF.

By combination of synthesis and experimental characterisation, a selection of the MOF/polymer composites were examined to reveal their chemical and thermal stability, porosity, gas uptake, and of course, their dispersion and processability. Furthermore, a variety of methods were investigated for optimization of polymer coverage on MOF surfaces.
This work highlights a potentially a valid solution to the safe, efficient and reliable storage of hydrogen, which could revolutionize the global use of renewable energy.


1) Energy Agency, I. (2021). Net Zero by 2050 - A Roadmap for the Global Energy Sector. www.iea.org/t&c/
2) Wu, Y., Zhang, T., Gao, R., & Wu, C. (2021). Portfolio planning of renewable energy with energy storage technologies for different applications from electricity grid. Applied Energy, 287, 116562. https://doi.org/10.1016/J.APENERGY.2021.116562
3) Xuan Zhang, Zhijie Chen, Xinyao Liu, L. Hanna, S., Xingjie Wang, Reza Taheri-Ledari, Ali Maleki, Peng Li, & K. Farha, O. (2020). A historical overview of the activation and porosity of metal–organic frameworks. Chemical Society Reviews, 49(20), 7406–7427. https://doi.org/10.1039/D0CS00997K
4) Xiao-Min Liu, Lin-Hua Xie, & Yufeng Wu. (2020). Recent advances in the shaping of metal–organic frameworks. Inorganic Chemistry Frontiers, 7(15), 2840–2866. https://doi.org/10.1039/C9QI01564G

Calamatic mesogens consist of rod-shaped molecules which can have an orientational and a positional order with their long axes in each layer by self-alignment. Alignment and twisting of every layer as an angular displacement lead to the loss of positional order and maintain of orientational order, thereby forming the helical structure, and these chiral mesogens get to the cholesteric phase. In other words, they are called cholesteric liquid crystals (LCs). A helical pitch is denoted as the distance for the full helical turn of the cholesteric LCs, and this provides optical rotation and selective reflection of light. When the cholesteric LCs reflect the incident light in a visible spectrum, structural colors can be observed. Most of the liquid crystals are reactive to temperature change, so when they are heated up, the angular displacement between layers increases, and the pitch decreases. This indicates that the color shown by selectively reflected light from the cholesteric LCs is blue-shifted as temperature increases.
Meanwhile, cholesteric LCs are divided into two main types: nematic mesogens with chiral dopants or dopant-free chiral mesogens. Typically, those with chiral dopants are used for encapsulation with a solid shell due to their well-ordered helical structures. However, the host mesogens and dopants are expensive and relatively toxic, and they are also vulnerable to impurities. Therefore, we chose dopant free-chiral mesogens that are predominantly derived from plants as the encapsulants, which are non-toxic and low-cost. Despite relatively less-ordered helical structures compared with nematic mesogens with chiral dopants, dopant free-chiral mesogens still show brilliant structural colors and excellent temperature responsiveness. However, a systematic development on elaborate encapsulation technology for chiral mesogens has not been reported. Only bulk encapsulation without control of size and composition has been applied to optical usage of cholesteric LCs.
In this work, we present a microfluidic approach to fabricate a thermochromic cholesteric liquid crystal microcapsule with an alginate hydrogel that contains a cholesteryl ester as a core, and the use of the microcapsules as colorimetric temperature microprobes. Using a glass capillary microfluidic device, monodisperse oil-in-water-in-oil (O/W/O) double-emulsion droplets are produced. To secure the fluidity of the LC mixture, a volatile organic solvent is added into the mixture, which is used as the innermost phase of double-emulsion droplets. As the middle water phase, an aqueous solution of sodium alginate and a complex of calcium-ethylenediaminetetraacetic acid (Ca-EDTA) is used to enclose the LC core with a hydrogel. The double-emulsion droplets are collected in the oil phase containing acetic acid. During the incubation, the volatile solvent evaporates from the inner droplets, and it triggers the self-alignment of cholesteryl esters to form a helical structure. At the same time, acetic acid diffuses from the continuous acidic oil phase to the water droplets and leads to the ionic gelation of alginate. The resulting microcapsules show conspicuous thermochromic property with temperature change. Additionally, we can control the range and sensitivity of colorimetric temperature measurement by adjusting the composition of cholesteryl compounds in the core. Therefore, we anticipate that these thermochromic microcapsules would have great potential for temperature measurement at local microenvironments where the microcapsules can be injected, suspended, or implanted.

Polymer nanocomposites are widely used due to their ability to change the base fluid properties to the desired specifications with good precision. Although previous studies have focused on the physical phenomena of nanoparticles and their potential to improve these properties, it is also important to investigate the possibility to implement nanocomposites into commercial processing methods, i.e., additive manufacturing. In this study the rheological properties have been studied to determine whether a processing technique is feasible. The first objective is to investigate the relationship between the PDMS component ratio and concentration of graphene with viscosity. Then, to compare the experimental data with various empirical models and finally, the printability range of our samples is calculated by using established results. Our results have shown an increase in viscosity for graphene concentrations higher than 5wt.% and a good agreement with Chen’s and Batchelor’s models. Surprisingly, the lubrication effect was also observed at small concentrations, showing that the nanocomposite viscosity is less than the pure viscosity and decreases with an increase in graphene concentration. For a constant shear rate of 10 s^-1 numerous of our graphene-PDMS samples are within the printable range, making them suitable for applications like direct ink writing (DIW). Overall, our unique approach shows the importance of controlling the nanocomposite viscosity, which highly depends on the nanoparticle concentration.

Air-borne particulates, dusts, and powders from debris can penetrate, accumulate, and transport through both porous and non-porous surfaces and are serious surface operational and bodily threats to space planetary explorers. Additionally, these risks also affect the crew equipment for crew members such as rovers, space vehicles, and on-board instruments, sensors and electronic panels therein. The effect is more damaging amidst high-speed dust and debris esp. at sub-zero temperatures, or cycles of extensive temperature gradient that can cause substantial mechanical damages, and significant economic losses. The extreme environments encountered include crewmember time preparation and strict EVA protocols to protect against thermal, radiation, MMOD, atomic oxygen, both high and low pressures in inert and oxidizing or caustic atmospheres, regolith, and combinations thereof. To circumvent this issue, we have developed a dust-repellent coating system with exceptional mechanical and low-temperature durability that can resist the attachment of a wide range of solids, while at the same time, resist the wetting of both high and low surface tension liquids. Such non-toxic omniphobic coating system will be instrumental to tackle dust mitigation issues stemming from planetary surface exploration. A true omniphobic coating can augment dust-repellency by simultaneously repelling solids, as well as high and low surface tension liquids on smooth non-textured (glass, ceramics, alloys, metals), and porous textured surfaces (e.g. fabrics) at low temperatures. Such coatings can significantly expedite operations, decrease crew risks, and improve preparation for lunar and planetary surface missions. Durability of the coating has been designed based on our fundamental understanding of the sol-gel methodology and mechanisms of solid and liquid adhesion on smooth and textured solids as developed in our lab. Our coatings will utilize low surface energy functional polymers that are either directly, covalently attached on to the underlying substrate, or are embedded within a durable elastomer. Such coatings can prevent the attachment of regolith, high fidelity simulants, lunar dust on surfaces by utilizing interfacial slippage, i.e. a non-zero slip velocity at the solid-solid interface. The science goal is to help advance technology, facilitate operations, and protect optimum human performance towards the ARTEMIS mission and then create a proven pathway towards Mars by 2030s.

Supramolecular polymers (SMPs) are an exciting class of materials with a wide range of new properties owing to their dynamic behaviour. A current challenge in the field is to fully control selfassembly behaviour and properties of the resulting SMPs. The selfassembly behaviour of SMPs can be influenced by a variety of external forces, including by selective chemical modification of the monomers. Thionation of the monomers has been studied as an interesting tool to control the properties of SMPs. Previous investigations suggest stronger binding between thionated perylene diimides (PDIs), paired with changes in assembly due to steric effects of the sulphur. Initial work in our group has shown how low degrees of thionation can lead to careful control of the supramolecular polymerisation process.
Here we show the initial steps towards the synthesis of various perylene SMP monomers thionated to different degrees. Multiple routes were attempted, including approaches to directly thionate the perylene anhydride with subsequent addition of the synthesized trialkoxy amine, as well as the synthesis of a variety of well-soluble PDIs for a more efficient thionation. The thionation has been optimized using a modified microwave-assisted literature route. Following this approach, we are optimistic to obtain novel SMPs, based on thionated PDIs for further analysis and studies, with control over structure and function.

Nanoporous structures with three-dimensional continuous polymeric networks and interconnected nanoporous channel have been used as functional materials owing to their distinct properties. The nanoporous network materials were prepared from mixtures of poly(ethylene glycol) and the cross-linked polyurea-based organic network, followed by selective removal of the polymer part. Free-standing film of the network materials was prepared by casting the mixtures onto the glass plate followed by evaporation. It showed tortuous nanoporous channel with thin thickness and can be used as support for metal nanoparticles (MNPs). Small sized MNPs are dispersed homogeneously into bicontinuous nanopore without aggregation, developing a new type of catalytic nano-reactors with the size and(or) amount of MNPs quantitatively tunable by changing the concentration of the metal precursor solution. Due to the tortuous nanoporous structure, it facilitates the contacting efficiency of reactants and catalysts and it were used in liquid-phase catalytic semi-hydrogenation reaction of substituted alkynes under continuous flow conditions. Based on the adjustments of several experimental conditions to obtain the best catalytic performance under the continuous flow, the catalytic membrane nano-reactors showed excellent catalytic selectivity over batch operation under mild conditions.

The tight regulation of metabolite metabolism in the body is crucial for balanced physiological function. We have recently developed a micronscale electrochemical device based on an electron-transporting (n-type) conjugated polymer. When catalytic enzymes are immobilized on the n-type polymer surface, the device detects metabolites in bodily fluids with record-high sensitivity and selectivity but without the need for an electron mediator.^1-2 In this work, we investigate how the molecular structure of conjugated polymers modulates the adsorption of the enzyme, glucose oxidase. We investigate the interactions of the enzyme with five different n-type polymers presenting the same backbone but bearing different side chains using a combination of quartz crystal micro-balance, surface characterization techniques, and circular dichroism. We correlate surface properties (charge, wettability, chemistry, roughness, and features dimensions), dictated by the nature of the polymer side chains, to the enzyme adsorption behavior, as well as its conformation and orientation, which then govern the sensor performance. We find that the enzyme adsorbs more loosely on hydrophilic/polar surfaces, while hydrophobic surfaces tend to denature the enzyme structure to a higher degree. Our work provides design guidelines for the development of synthetic electronic materials that would maximize interactions with proteins crucial for the development of biosensors and biofuel cells.

Data-driven, machine learning (ML)-assisted approaches in materials research have been used to study structure-property relationships at atomic scale. Although data-driven approaches have accelerated screening process and new material discovery, such approaches were not easily applicable to soft material design process due to significantly larger size of polymer chains and their disordered natures. Herein, we report a data-driven approach to soft material design using experimental data with features representing macroscale structural characteristics. We trained a ML model using 25 datapoints collected from experiments, and the trained model was used to develop a data-driven soft material design system. The design system takes desired mechanical properties as input and returns synthetic recipes of soft materials. We demonstrated a soft material design process by synthesizing soft material samples using the recipe and characterizing them. The mechanical properties of the newly synthesized samples indeed exhibited our desired properties (log(property) prediction with root mean square error (RMSE) less than 0.42). We believe our approach is widely applicable to experimental laboratories to explore structure-property relationships of various soft material systems and towards laboratory automation.

How microbes interact with one another and their environment is a central, yet challenging question in biology. These interactions are especially relevant when microbial communities facilitate the degradation of polymers in surface coatings and insulation of the built environment. However, no studies have addressed the composition and effects of environmental microbial communities on military aircraft and vehicles. Therefore, our laboratories characterized the total (fungal and bacterial) microbiomes of surface-contaminated samples including 4 from military aircraft and 3 from military trucks. A combined ultra-deep DNA and RNA sequencing-based approach was used to capture both the genetic capability and expression profiles of the aircraft and trucks sampled. Transcriptionally active microbiomes, quantitated based on small subunit ribosomal RNA expression data extracted from aircraft metatranscriptomes, were dominated by fungi while the trucks were dominated by bacteria. The data were then mined for hydrolase enzymes such as lipases, esterases, cutinases, peptidases, and proteases, known to be key players in polyurethane polymer degradation. Thousands of putative hydrolase enzymes were recovered for further verification and validation, with selected candidates to be expressed and tested for polymer-degrading activities in high-throughput in cell-free assays with near-infrared carbon nanotube probe hydrolytic detection. Yet, hundreds of these putative hydrolase sequences were unable to be annotated using classic methods such as BLAST. We have implemented DeepGoPlus, a convolutional neural network machine learning approach to characterize novel hydrolases and investigate species-species and species-environment interactions among members of the microbial community through gene ontology biological process analyses. Additionally, we are investigating expression of biological pathways among aircraft sampling locations and between aircraft and trucks to determine if hydrolase expression and other enzymes vary in their expression patterns among aircraft sampling locations and between aircraft and trucks. These data will ultimately be used for the assessment of the biodegradation potential in microbial communities on polyurethane polymer surfaces and for environmental enzyme bioprospecting for industrial and bioremediation purposes.

Applications of electrospinning (ES) range from fabrication of polymer-based biomedical devices to light manipulation and energy conversion, and even to deposition of materials that act as growth platforms for nanoscale catalysis. One major limitation to wide adoption of electrospun materials is the ES hardware itself, which typically requires high-voltage electrical isolation and charged and flat deposition surfaces. In the past, fabrication of polymer structures or materials with precisely determined mesoscale morphology has been accomplished through modification of electrode shape, use of multi-dimensional electrodes or pins, deposition onto weaving looms, hand-held electrospinners that allow the user to guide deposition, or electric field manipulation by lensing elements or apertures. In this work, we demonstrate an ES system that contains multiple high voltage power supplies that are independently controlled through a control algorithm implemented in LabVIEW. The end result is what we term “multiplex ES” where multiple independently controlled high-voltage signals are combined by the ES fiber to result in unique deposition control. COMSOL Multiphysics® software was used to model the electric field produced in this novel ES system. Using the multi-power supply system, we demonstrate fabrication of woven fiber materials that do not require complex deposition surfaces. Time-varied sinusoidal wave inputs were used to create electrospun tori shapes. Parametric analysis of tori diameter was found to be rather insensitive to frequency used during deposition, while inner diameter was inversely proportional to frequency, resulting in overall width of the tori to be proportional to frequency. The amount of control possible in multiplex ES is limited by the time response of high-voltage power supply output in relation to changes in input signal. Power supply time constants were measured and minimized through the addition of resistors that altered impedance of the system and improved response time up to 63 %.

Polymer nanocomposites of bioactive molecules (e.g. enzymes) and robust polymeric network are ideal components of bioresponsive materials. Appropriate spatial distribution of enzymes in the nanocomposite allows simultaneous enzymatic catalysis and directional molecular flow as found in cell membranes. Tuning the environment surrounding the enzyme in nanoscale is also critical for understanding and harnessing the enzymatic response under flow. However, development of bio-nanocomposite with such controllable enzyme nanoarchitecture and mechanical strength for flow application is still quite challenging. We recently reported caging enzyme in nanoporous covalent framework membrane prepared from urea-bonded network/poly(ethylene glycol) mixtures. Key advantages were facile and scalable membrane preparation method, stable enzyme entrapment in the nanopore, and prolonged activity in batch reactions. Herein, we demonstrate precisely-controlled pressure-driven flow reaction catalyzed by enzymes in nanopores, taking advantage of the robust crosslinked framework and membrane formulation. Enzyme-embedded molecular network membranes were synthesized by pressurization and readily used for performing flow catalysis. The nanoconfined enzymes exhibited long-term activity, allowing rapid reaction screening with elaborate control on a wide range of experimental parameters. Systematic comparison of enzyme kinetics depending on reaction modes and pore sizes further revealed the effect of flow and nanoconfinement. We expect the system be extended to other enzymes and used for combinatorial flow biocatalysis with the aid of automated reaction control.

The porous structure of Metal-Organic Frameworks (MOFs) is well suited for incorporating drugs, which makes MOFs ideal nanocarriers in biology and medicine.^[1,2] However, challenges arise when applying nanoparticles in the human body. Targeted drug delivery, for example, requires stable nanoparticle suspensions with long circulation in the bloodstream and avoiding protein adsorption.^[2] A solution is the attachment of polyethylene groups to the outer surface of the particles (PEGylation), which helps improve the suspensions stability (“stealth effect”).^[2] A reliable surface modification strategy is the grafting-from method, in which a polymer grows from a before-attached surface initiator on the nanoparticle.^[3] Controlled radical polymerization (CLRP) strategies like Reversible-Addition-Fragmentation Chain-Transfer (RAFT), and Atom Transfer Radical Polymerization (ATRP) proved highly useful for a reproducible synthesis, controlled chain length, and low dispersity of the polymer chains on the particles.^[4] Disadvantages of the before mentioned methods, especially for biomedical applications, are the additional mediator removal and the contamination with traces of metal (ATRP) or thiol-based components (RAFT).^[5] To avoid these disadvantages, Nitroxide-Mediated Polymerization (NMP), an alternative CLRP method that shows a controlled polydispersity and chain length, can be employed.^[6] In addition, the NMP, allows the introduction of target groups, through nitroxide exchange reactions, which can specifically bind, for example, to tumor cells in the body.^[7]
In this presentation, I will introduce a new NMP based grafting-from method for the attachment of polymers on the surface of UiO-66-NH₂ MOF particles. I will describe the synthesis of UiO-66-NH₂ particles, the attachment of an NMP initiator on the nanoparticle surface, and the grafting-from polymerization of a Polyethylene glycol derivative from it. With DLS and absorbance measurements, I will show the reduced agglomeration and protein (HSA) adsorption tendency compared to unmodified nanoparticles. In addition, I will show the nitroxide exchange reaction to demonstrate the end group modification towards active targeting.
Regarding the formerly described stealth effects evoked by protein adsorption in the bloodstream, I will expand the described NMP by a screening technology based on Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements to find the MOF/Polymer combination with the lowest protein adsorption.
Therefore, I will synthesize a homogeneous crystalline surface coating of defined thickness from UiO-66-NH₂ particles on QCM-D chips using machine learning tools. The successful synthesis will be verified by XRD and ellipsometry. I will then show the modified NMP initiator attachment and polymerization on the UiO-66-NH₂ bound to the QCM-D surface. The successful polymerization will be verified by IR-spectroscopy. Finally, I will give an HSA flux over the MOF/polymer substrate and qualify and quantify the adsorbed HSA amount using QCM-D and MALDI.
This method will allow me to test various, e.g. polyethylene glycols for their properties and applicability in reducing the "stealth effect" for drug delivery.
[1] S. Begum, Z. Hassan, S. Bräse, C. Wöll, M. Tsotsalas, Accounts of chemical research 2019, 52, 1598.
[2] P. Horcajada, R. Gref, T. Baati, P. K. Allan, G. Maurin, P. Couvreur, G. Férey, R. E. Morris, C. Serre, Chemical reviews 2012, 112, 1232.
[3] M. Kalaj, K. C. Bentz, S. Ayala, J. M. Palomba, K. S. Barcus, Y. Katayama, S. M. Cohen, Chemical reviews 2020, 120, 8267.
[4] B. Tieke, Makromolekulare Chemie. Eine Einführung, Wiley-VCH, Weinheim, 2014.
[5] R. B. Grubbs, Polymer Reviews 2011, 51, 104; b) B. Lessard, A. Graffe, M. Marić, Macromolecules 2007, 40, 9284.
[6] J. Nicolas, Y. Guillaneuf, C. Lefay, D. Bertin, D. Gigmes, B. Charleux, Progress in Polymer Science 2013, 38, 63.
[7] H. R. Lamontagne, B. H. Lessard, ACS Appl. Polym. Mater. 2020, 2, 5327.

The design of magnetic nanoparticles for functional polymer nanocomposite materials is an expanding field with recent interest in therapeutic techniques like magnetic hyperthermia for biomedical applications, sequestration of transuranics for environmental remediation, and functional catalytic materials utilizing inductive heating. One area of great interest is the interest of the polymer-functionalized magnetic particles. For example, magnetic particle imagining (MPI) is an emerging novel imaging technique which derives from magnetic particle spectroscopy (MPS). This has proven to be a revolutionary nondestructive characterization technique due to its high sensitivity and contrast abilities of which can be used for precise tuning and measurements of particle systems. ¹
The interest of this study is to measure the influence of magnetic dipole-dipole interactions on hysteresis curves, signal intensity and the corresponding harmonic spectra which elucidates physical and structural properties of the particle and bound analytes valuable to the design and application of magnetic bioassays. Recent reports have shown that particle aggregation in the presence of an applied external field can lead to chain formation which has drastic effects on the collective behavior of the particle system.² This poses a major problem to applications involving targeted drug delivery using local heating and magnetic particle imaging. A recently proposed solution to controlling cluster formation is the surface modification of the particles with stabilizing hydrophilic polymers which has shown to be a promising method for controlling colloidal arrangement.² Rinaldi et al. recently demonstrated by theoretical modeling that magnetic dipole-dipole interactions between chains formed by aggregation under an applied field enhances the MPI signal.³ This suggests that the intensity of the signal and the higher odd harmonic frequencies emitted by the particles can be tuned by surface modification. Many potential interactions and relationships between the particle ligand system have yet to be evaluated, herein, this study aims to experimentally demonstrate this prediction by evaluating the influence of steric repulsion between stabilizing ligand on chain formation via MPS. Iron oxide nanoparticles are synthesized using a single pot thermal decomposition reaction. The surface of the iron oxide nanoparticles is modified by application of nitroDOPA terminated poly(ethylene glycol) of weights: 1000, 2000, 5000, and 10,000 g/mol. The resulting particles are characterized by high resolution transmission electron microscopy, dynamic light scattering, and X-ray diffraction to determine particle size, hydrodynamic diameter, zeta potential, and composition. In addition, vibrating sample magnetometry and field-cooled/zero-field cooled loops were performed to determine the saturation magnetization and blocking temperatures of the materials. MPS measurements of each sample were conducted to measure the hysteresis curves and relaxation behavior which can deepen the understanding of interparticle interactions under an applied field. The postulated results of this study include demonstration of the tunability of particle signal strength under surface modifications and further evaluation of the interactions between chains and clusters of particles under applied field. The implications of this are improved synthesis techniques that can generate higher contrast images for MPI applications and a deepened understanding of the parameters that modulate variations in theoretical particle behavior.
References
1. Löwa et al Nanomaterials (Basel) 2020, 10.
2. Saville et al J. Colloid Interface Sci. 2014, 424, 141-151.
3. Zhao et al Phys. Med. Biol. 2020, 65, 185013.

As a regenerated protein extracted from natural silk, silk fibroin (SF) offers great opportunities in manufacturing biocompatible/biodegradable products that are environmental benign and promising for biomedical applications. However, the lack of clarity concerning the complex assembly mechanism limits precise design of SF-based materials. To understand the mechanism of SF self-assembly on the molecular scale, we investigated the self-assembly dynamics of SF molecules at the interface of aqueous SF solutions and highly oriented pyrolytic graphite (HOPG) using in-situ atomic force microscopy (AFM). We find that SF grows into a single-layer two-dimensional (2D) periodic array (TDPA) on HOPG during the initial growth stage with building blocks that are composed of about seven β chains containing (GAGAGS)₄. As the concentration of the SF solution increases, another pathway involving a metastable intermediate phase is observed. In this pathway, unfolded SF monomers directly attach to the TDPA structure, forming layers of the metastable film. This phase gradually converts into the TDPA structure. In the meanwhile, the TDPA structure can also act as a template to directly form β-crystals of SF layer-by-layer without first forming the metastable phase. Taken together these in-situ AFM results resolve the mechanism by which SF β-crystals assemble and an oriented 2D SF composite film is achieved.

In recent times, inorganic nanoparticle/polymer composites have generated considerable recent research interest, and their structure, composition design, and properties have been discussed in multitudinous catalysis studies because of their significant enhancement of stability and catalytic performance compared to homogeneous catalysts. Transition Metal/Polymer nanocomposite fiber holds great promise in catalysis science field including electrocatalysis, organic catalysis academia, and industry due to their high producibility with cost efficiency, easy separation from target molecule, large surface areas, a substantial number of surface metal atoms leading to abundant active sites, flexibilities. Various chemical or physical activation of the macroscopic fiber with strong oxidants/acids/alkalis/salts or gases, plasma, UV lights were carried with various metal supporting methods, and nanofiber synthesis has been made to increase the surface area of fibrous catalysts. However, the preparation of catalysts with uniformity, high mechanical property, and productivity on a large scale has not been clearly presented. Herein, we report a simple fabrication approach of macroscopic carbon fiber which can further be applied as carbon cloth form of transition metal/polymer nanocomposite via spinning of polyacrylonitrile, polyacrylonitrile/sacrificial polymer blend fiber matrix with transition metals. The design of the catalytic active sites, adhesion, the morphology of the carbon matrix and metal particle fillers, mechanical properties by controlling the composition and heat treatment will be discussed.

A significant amount of research has been focusing on the development of sustainable alternatives to synthetic polymers and polymer nanocomposites. At the same time, additive manufacturing has been a disruptive technology for producing higher and higher volumes of plastic parts, especially those not easily produced with conventional manufacturing techniques. Yet, reports on using entirely biobased materials in 3D printing, without the use of non-degradable binders are scarce^[1,2].
Here, we present a series of polymer nanocomposite slurries, in which the polymer matrix is a mixture of natural biopolymers derived from biomass (spirulina cells), and a series of nanofillers, including spherical nanoparticles, nanoclay, and nanocellulose fibers, are evaluated as potential reinforcing agents. The selected fillers are also naturally derived and offer distinctly different aspect ratios due to their spherical, plate-like and fibrillar structures, respectively. By modulating the concentration of components as well as water content, we are able to tune the rheological properties of the slurries to enable optimal extrusion under ambient conditions. We can then use extrusion-based 3D printing to create multilayered structures and evaluate their micromorphology with scanning electron microscopy (SEM). We analyze the multi-scale mechanical properties of our nanocomposite structures with a combination of nanoindentation testing, probing the nanoscale properties, and compression tests, assessing their macro-scale performance. The effects of each type of nanofiller on the elastic moduli, hardness, compressive strength and toughness of the biopolymer-based structures are discussed.
References:
[1] Y. Jiang, J. R. Raney, Adv. Mater. Technol. 2019, 4, 1900521.
[2] J. Fredricks, H. Iyer, R. McDonald, J. Hsu, A. M. Jimenez, E. Roumeli, J. Polym. Sci. 2021.

With increasing energy consumption, the development of alternative energy sources is becoming increasingly popular. However, despite several advantages of nuclear power, unsafety use of nuclear energy poses many dangers to people and the environment, including the leakage of radioactive waste from tanks and the uncontrolled release of enormous amounts of radionuclides caused by nuclear accidents, such as those in Chernobyl and Fukushima. Among the harmful radionuclides leaked from nuclear power plants accidents, radioactive cesium (¹³⁷Cs) and strontium (⁹⁰Sr) have the most substantial toxic effects of emitting beta-particles and gamma rays. Both of radioactive Cs and Sr radioisotopes have half-life around 30 years, therefore, it is imperative to remove cesium from the environment and wastewater for sustainable environmental preservation. In this work, two types of cryogels were synthesized at -12 C by free-radical polymerization of acrylate-based precursors with allylamine at different proportions and modified by 5 M NaOH. Main ion exchange capacity of cryogels is based on presence of key monomers, methacrylic acid (namely AAC cryogel) and 2-acrylamido-2-methyl-1-propansulfonic acid (SAC cryogel). The morphological and physico-chemical structure of polymers were characterized by SEM/EDX, FT-IR, XPS, and swelling measurements. Cryogels were studied towards Sr²⁺ and Cs⁺ removal from aqueous solutions. The results demonstrated fast removal kinetics and high capacities with AAC cryogel being superior over SAC cryogel. The results show that binding capacities of AAC cryogel were reached 361.6 mg/g of Cs⁺ and 209.3 mg/g of Sr²⁺ whereas SAC polymer also was best for Cs⁺ with maximum capacity of 258.7 mg/g, while Sr²⁺ adsorption reached 210.5 mg/g. The cation removal mechanism was studied by XPS technique and it was found that ion exchange followed by complexation reactions is the main mechanism of cations removal.

Progress on wearable biosensing has paved the way for non-invasive biomonitoring via peripheral biological fluids such as sweat and interstitial fluid (ISF). As an alternative to blood sampling, ISF (a rich source of soluble bioanalytes that exhibit a similar composition to blood plasma) can be accessed without disrupting the skin’s stratum corneum.¹

Integrating biomimetic elements on polymeric electroconductive surfaces (displaying micro-/nano configurations capable of effectively recognizing biological analytes in a complex microenvironment) could enhance biosensor performance. Through the direct exposure of ISF to microneedles (MNs), biorecognition elements presented on an MN array can capture target biomarkers in situ, thus offering a promising technology for real-time monitoring of physiological information.^2-4

This presentation will cover our ongoing research on developing poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based conductive MN arrays and the integration of biorecognition elements as a minimally invasive platform for the early detection of sepsis biomarkers. Exploiting PEDOT:PSS for biosensing has attracted significant attention due to its inclusion in an exclusive family of intrinsically conducting polymers that present high electrical conductivity, appropriate size workfunction, and water processability.⁵

Two approaches to the fabrication of homogenously distributed PEDOT:PSS conductive MNs will be highlighted.

1. A customizable and straightforward method for the fabrication of high-aspect-ratio MN arrays, based on reverse-MN master mold designs, utilizing PEDOT:PSS and polysiloxane (PDMS) miscible solutions.

2. Direct electrospinning of PEDOT:PSS composite polymer blends for the design of hierarchical conductive nanofibers.

Conductive MN array functionalization via integration of biorecognition elements (for lactate and cortisol detection) as part of a bio-affinity electrochemical sensor, will also be described. In short, in situ synthesis and homogenous distribution of biorecognition at the surfaces of the conductive MN arrays were obtained through simultaneous spin-coating. Polyvinyl chloride (PVC) was added to the mixture to promote the formation of a polymer matrix that acts as an insulating layer (increasing the detection limit and selectivity of the developed biosensing platform).

Future work, as well as evolvement and optimization of this research, will exploit the assessment of such biosensors in vivo for the real-time monitoring of sepsis. The constant evolvement of ISF monitoring through MN-based platforms could make it feasible to detect sepsis-relevant markers at the onset of disease. Furthermore, the generation of comprehensive data sets could allow for the use of accurate closed-loop control systems—applicable to real-time drug monitoring and delivery.

1. Turner, J.G., et al. Hydrogel-Forming Microneedles: Current Advancements and Future Trends. Macromolecular Bioscience. 2021; 21(2):2000307
2. Koklu, A., et al. From Diagnosis to Treatment: Recent Advances in Patient-Friendly Biosensors and Implantable Devices. Chemical Reviews. 2021
3. Rawson, T.M., et al. Optimizing antimicrobial use: challenges, advances and opportunities. Nature Reviews Microbiology. 2021
4. Li, P., et al. Organic Bioelectronic Devices for Metabolite Sensing. ACS Nano. 2021; 15(2):1960-2004
5. Yang, Y., et al. Recent progress on PEDOT:PSS based polymer blends and composites for flexible electronics and thermoelectric devices. Materials Chemistry Frontiers. 2020; 4(11):313

Acrylonitrile butadiene styrene (ABS) is a thermoplastic polymer that is widely used in automotive parts, electronic devices, and additive manufacturing. The properties and performance of ABS can be significantly enhanced by dispersing carbon nanomaterials in the polymer. Here we present new knowledge on the relationships between the processing, structure, and properties of injection-molded ABS nanocomposites filled with carbon nanomaterials. The impact of the carbon dispersion technique on the mechanical properties of ABS nanocomposites will be discussed. Additionally, the effects of filler loading and filler dimension (0D, 2D, 3D) on the properties of ABS nanocomposites will be presented. We will also show the processing conditions, filler types, and filler loadings that result in simultaneous enhancements in the strength and strain at break of ABS. This presentation will advance the understanding of the processing-structure-property spectrum of ABS and ABS nanocomposites, as well as demonstrate feasible methods of manufacturing ABS nanocomposite applications with enhanced mechanical properties.

In this work, we report the synthesis of an α-diethoxyphosphoryldithio, ω-alkynyl heterobifunctional chain transfer agent (CTA) that can engage in the reversible addition-fragmentation chain-transfer (RAFT) polymerization of (meth)acrylic monomers and subsequently engage in orthogonal Hetero–Diels-Alder (HDA) and copper-catalyzed azide-alkyne cycloadditions (CuAAC) at the resulting linear polymer end groups. A broad scope of monomers were polymerized with our CTA and the corresponding kinetics of RAFT polymerization were characterized. Efficient, orthogonal polymer end group transformations and kinetics were confirmed via polymer-dye, polymer-polymer, and polymer-protein conjugations. Finally, we employed the heterobifunctional CTA in the RAFT synthesis of amphiphilic triblock copolymers, fabricated micellular nanoparticles via self-assembly in aqueous buffer, and demonstrated stoichiometric control over nanoparticle surface chemistry via component polymer end groups. To our knowledge, this RAFT system is the first to report direct access to heterotelechelic, linear polymers capable of highly efficient, regioselective end group transformations immediately following polymerization without the need for post-polymerization end group modification/installation. We believe that the highly modular nature of this platform makes it amenable to applications in nanomedicine and bioconjugate chemistry, among others.

In polymer nanocomposites, interfacial area can be thought of as sites of interactions for polymer chains. Dielectric and various other types of relaxation spectra of chains in region adjacent to the interface, called 'interphase', changes depending on the nature of these interactions. Extent and decay of these interactions govern interphase percolation and interphase properties relative to bulk or farfield properties.
These Interactions and hence interphase properties can be fundamentally different around an isolated particle, smaller clusters and bigger agglomerations owing to large difference in area of interaction sites around each of those. At the same time, presence of agglomerations in microstructure (MS) is anticipated to influence interphase (IP) percolation, hence dielectric permittivity and loss response. Highly agglomerated systems can have an overall reduced interface per unit volume fraction of nanoparticles and can result in overall poorer properties compared to microstructures with identical total volume fraction in well dispersed form. Degree of agglomeration depends on processing parameters such as mixing energy and mixing speeds. Knowing how agglomerations affect overall properties can help establish an important link in the process-structure-property prediction framework.
As a first step towards that goal, we have simulated a full factorial design of experiments (DoE) over MS and IP space, a total of 1540 points, using continuum scale finite elements analysis. Microstructure images to fill the design of experiments were generated through a random sequential adsorption based on a set of parameters learnt from TEM images of real microstructures. Specifically, we identified a set of three descriptors from which we can generate new microstructures that are statistically equivalent to the experimental images. These parameters include: (i) the total volume fraction (vf), (ii) vf locked inside agglomerations, and (iii) number of agglomerations. The space of admissible range of these parameters have been determined from the available TEM images. In addition, the IP space is spanned by types of interphases considered. Those were based on combination of interfacial interaction (attraction or repulsion) and loss characteristics (lossy or not). Thus, we have used combination of 308 grid points in MS space and five discrete grid points on IP dimension for a DoE with 1540 samples.
We can identify overall trends and explain variance in interphase percolation, dielectric permittivity and loss with respect to size and number of agglomerations for various levels of total volume fraction and across types of interphases. A baseline set of two-phase systems, without interphase, were also simulated and compared with above to understand the crucial role interphase plays for property prediction. We also see some potential of using this DoE to train a machine learning model for property prediction from microstructure images.

High mechanical strength along with unique optical properties in biomaterials are often attributed to the presence of chiral multilayer ordered structures with the complex hierarchical organization. One such example is cellulose nanocrystals (CNC)-based materials, which are characterized by selective reflection from the helical structures formed by CNCs when the chiral pitch is in the visible range, resulting in iridescent colored films. Several factors have been reported to affect optical properties of CNC materials, such as the CNC dimensions, density/packing fraction, chemical modifications of CNCs, helical pitch and handedness of the individual CNCs, the presence of co-solutes or other additives, humidity, and mechanical stretching. However, due to the multitude of factors that may influence the optical properties of CNCs, the delineation of structure-optical property relationships of CNCs has been a challenge. We use systematic multiscale molecular modeling and machine learning to gain insights into self-assembly and other structural mechanisms contributing to the stress-optical relations (SOR) of CNC-based materials. We used a combination of electronic structure calculations and all-atom and coarse-grained molecular dynamics simulations to predict the self-assembly of CNC as a function of surface chemistry and environment, structural order parameters, and optical properties, such as refractive indices, in-plane birefringence, and out-of-plane birefringence as a function of stress. We then examined the correlation and sensitivity of these properties to factors of interest, such as stretch ratio, morphology, surface functionalization, and wavelength. We used order parameters from simulation and experiment to train the machine learning model and to further advance the optimization of optomechanical properties. The results from our study will help discover the design rules of chiral natural materials with enhanced mechanical, optical, transport, and photonic functionalities relevant to light and matter manipulation and conversion.

Nanoporous membranes with two-dimensional materials such as graphene oxide have attracted attention in volatile organic compounds (VOCs) and H₂ adsorption due to their unique molecular sieving properties and operational simplicity. However, the agglomeration of graphene sheets and low efficiency remains challenging. Cellulose, the most prevalent biopolymer, is derived from plants and agricultural wastes. The capture and conversion of carbon from the atmosphere into biomass also produces oxygen as the byproduct. Emulating optimum natural systems following Murray’s law, we designed a novel and controllable 2D nanostructured hierarchical nanopore-spaced membranes (HNM) from cellulose, a class of micropore-dominated carbon spaced graphene oxide-based nanocomposites via controlled-pyrolysis and “doctor blade” coating method. Hierarchical carbon spheres, prepared following Murray’s Law using chemical activation incorporating microwave heating, act as spacers and adsorbents. Hierarchical carbon spheres preclude the agglomeration of graphene oxide, while graphene oxide sheets physically disperse, ensuring structural stability. The obtained HNM contain micropores that are dominated by a combination of ultramicropores and mesopores, resulting in high VOCs/H₂ adsorption capacity, up to 235 and 352 mg/g at 200 ppmv and 3.3 wt% (77 K and 1.2 bar), respectively. This work opens a new vista for the development of efficient sustainable 2D composites for applications in both human health and global climate.

Nanocellulose is a renewable and abundant biomaterial that has been gathering a steadily increasing interest during the past decades. The potential of the material has mainly been attributed to its remarkable mechanical properties, low density and nanoscale dimensions, which has contributed to it to be seen as a promising material choice in biocomposites, foam materials and cellulose nanopapers.
However, research focusing on using nanocellulose as a tool to control reactions is a topic which has been less highlighted as a potential application.
Previous research has been particularly scarce when it comes to using aqueous nanocellulose dispersions during the synthesis of metallic oxides, especially when considering that properties of nanocellulose, such as dimensions, surface charge and functionalities can be accurately tuned, resulting in a highly varied behavior when dispersed in water as well as when interacting with ions.
Zinc oxide (ZnO) is an inorganic oxide that can be synthesized by using mild, water-based synthesis protocols and is seen as a potential material choice in applications ranging from solar cells to antibacterial devices. However, previous research has shown that the properties of ZnO are heavily affected by the morphologies it forms, indicating that the ability to control the particle nucleation and growth is of paramount importance.
Here, it is suggested that nanocellulose could be used as a versatile tool to tailor the morphology of inorganic oxides, such as ZnO, in order to either promote or suppress some of their inherent properties. Although it has been shown that cellulose can have some effects on the morphology of ZnO-particles, there are still not certain which aspects cellulose can affect when it comes to nucleation and growth of ZnO-particles. The incorporation of nanocellulose during the formation of inorganic particles, such as ZnO, also allows for the preparation of unique hybrid materials where the cellulosic material provides the structural properties and the tailored ZnO-particles provides the specific functional properties.
The results in this study shows that the inclusion of bacterial cellulose into an aqueous synthesis protocol can both increase the yield as well as decreasing the particle size of ZnO, which indicates that cellulose can function as a nucleating agent during the formation of ZnO. It is additionally revealed that the presence of cellulose can alter the formation of nanostructures as hierarchical ZnO-particles are formed, which indicates that cellulose also can affect the growth mechanisms during the formation of ZnO.

While polymer electrolyte membrane fuel cells (PEMFCs) have surged as promising eco-friendly power sources due to their high energy conversion efficiency and zero emission, their susceptibility to oxidative stress and degradation by in-situ generated hydrogen peroxide, hydroxyl radicals, and reactive oxygen radical species has prevented their widespread use. In order to alleviate such detrimental processes particularly on PEMs, addition of antioxidants has received a great deal of attention as the mitigation strategies as they directly transform the detrimental radical species into innocuous components. However, unprecedented adverse effects from the use of antioxidants has been often observed in PEM due to migration, agglomeration, dissolution of antioxidants within the distinctive chemical environment, leading to its accelerated chemical degradation. Recent research and applications activities with the antioxidants for the development of enduring PEMs toward long-term fuel cell applications include novel design strategies of antioxidant such as position control, anchoring, and electrochemically stable radical scavenging phase. In this talk, our recent results from these activities will be presented.

Light-mediated polymerization has emerged as a powerful tool in the synthesis of advanced materials. The spatial and temporal control imparted by light makes it an appealing external source of energy for initiation. While much of the work previously reported on photocontrolled and photoinitiated systems has focused on the radical or cationic polymerization of vinyl monomers, expanding the scope to the synthesis of degradable polymers like polyesters and polypeptides could lead to materials that are both biocompatible and degradable. The polymerization of N-carboxyanhydrides (NCAs) affords access to a vast array of synthetic polypeptides with tunable molecular weights, functionalities, and architectures. The use of light to achieve spatiotemporal control over these polymerizations could expand their applicability to a variety of areas, including 3D printing and photolithography. Moreover, modern advances in photopolymerization can be extended to other classes of monomers that lead to degradable polymers, including radical polymerization of cyclic ketene acetals (CKAs). By copolymerizing CKAs with electron-deficient monomers, it is possible to achieve copolymers with a uniform distribution of degradable ester linkages along their backbone.

Nowadays, elastomers have been widely used in various areas of applications including electronics, automotive industry, and biomedical applications. Elastic vitrimers, thermoset elastomers crosslinked by dynamic covalent bonds, can overcome the challenges associated with current elastomers and allow recyclability of such material while remaining its thermal and chemical stability. In our study, we synthesized boronic ester-based vitrimers that exhibit tunable dynamics and mechanical performance by variation of boronic ester structure in the polymer network. For this purpose, dynamic elastic networks with boronic esters were formed by reacting diol-containing tetra-arm poly(amidoamine) and boronic acid terminated tetra-arm poly(ethylene glycol) which possess different substituents adjacent to boronic ester moieties. Varying the substituent adjacent to the boronic ester unit will significantly impact the binding strength of boronic ester in dynamic crosslinked networks and therefore affect the dynamics and mechanical performance of resulting vitrimers. The presence of electron-rich substituent in polymer structure noticeably decreases the bonding strength, provides faster relaxation, and results in elastic vitrimers with prominent recyclability and malleability at lower temperatures. On the other hand, boronic ester-based vitrimers with electron-poor substituents noticeably suppress the dynamics of boronic ester exchange, increasing the apparent activation energy and relaxation time while enhancing the mechanical strength of fabricated elastic vitrimers. The developed pathway may serve as a guide for the rational design of elastomers with well-tunable mechanical stiffness and recyclability.

Perfluoroalkyl Substances (PFAS) are used throughout the world in products such as greasy food packaging, outdoor apparel, wristwatch bands, cookware, and smartphone screens. However, they are carcinogenic, bio-accumulating, and cause birth defects. Given their phase-out by 2023, new sustainable polymers are needed that offer similar surface-active properties as PFAS. In this talk I will discuss my group's work developing nanoscale polydimethylsiloxane (PDMS) brushes, i.e. single chains of PDMS covalently tethered to a substrate. Unlike unfunctionalized PDMS, which exists as a liquid at room temperature (commonly known as silicone oil), or crosslinked PDMS, which is an elastomer with highly tunable mechanical properties (commonly known as silicone rubber), PDMS brushes exhibit properties of both liquids and solids. One of their myriad properties is omniphobicity, the ability to repel many different types of liquids, one of the key surface properties that PFAS were thought to uniquely exhibit. Another property is easy release or anti-fouling performance, again a characteristic typically reserved for PFAS-containing surfaces. In this talk I'll discuss how PDMS brushes may be designed to exhibit these PFAS-replacing properties and give examples of the various industries in which we've demonstrated their feasibility. Among others, these include the formulation of a PFAS-free yet oil-repellent fabric finish, grease resistant paper, ice-release coatings, and open-channel microfluidic devices. The brushes are both biodegradable and, for example, paper coated with them remains recyclable, indicating that PDMS brushes are a strong candidate for PFAS replacement.

Polymers with programmed functionalities have been invented to autonomously detect and repair the mechanical damage. Although the traditional self-healing ability will theoretically increase material lifetime and safety, the lack of a self-assessment mechanism raises challenges in practical implementation. The conventional self-healing polymers provide no information about their mechanical and functional status, making it difficult to evaluate if the damage has been repaired and whether the self-healing ability is still in place to resist the next mechanical impact. In this work, we report a multifunctional material system that not only self-heals the mechanical damage but also reports its structural integrity in real-time. Microcapsules containing aggregation induced emission (AIE) luminogens-embedded healing reagents are incorporated into a polymeric material. The self-healing function is correlated with an evolution in emission wavelength, where the damage occurrence, healing process, and full recovery are characterized by distinctive fluorescence colors. This integrated self-healing and self-assessment ability significantly increases the sustainability and reliability of a wide range of polymeric materials and demonstrates a general concept of designing mutual communications among diverse stimuli-responsive functionalities.

Polymers can be infiltrated with inorganic precursors from vapor or solution resulting in high performing functional nanostructures. In the case of block-copolymers, the infiltration can be achieved selectively by selective interaction of only one type of domains with inorganic precursors. The dimensions of the block copolymer templates define the structural features of the formed hybrid or all-inorganic structures. Also, nanostructures can be obtained using porous polymers. We will present in detail the effect of polymer swelling and different types of infiltrations on the final composition and properties of nanostructures.
We will demonstrate that polymer infiltration can enable synthesis of a broad range of materials with interesting catalytic, sensing, and optical properties. We will show that this approach can be used to synthetize both three-dimensional heterostructures and conformal coatings. We will provide examples of catalytically active nanoparticles on porous supports with advanced thermal stability synthetized using the polymer templates. We will demonstrate a general platform toward fabrication of all-inorganic antireflective coatings. We will discuss the effect of polymer removal on the crystalline phase of the synthetized inorganic heterostructures.

Many kinds of stimuli-responsive polymer gels that exhibit reversible swelling-deswelling change in response to environmental changes have been developed. New functional gels called “intelligent” or “smart” gels have been created, and their applicationsto bio- or biomimetic materials such as actuator (artificial muscle), drug delivery systems, tissue engineering, purification or separation systems, biosensor, shape memory materials, molecular recognition systems, etc. has been exploited. Other than stimuli-responsive function, one of characteristic and important behaviors in living systems is autonomous oscillation such as heartbeat. However, there are few studies on polymer and gel systems undergoing self-oscillation under constant condition without any on-off switching of external stimuli. If such autonomous systems can be realized by using completely synthetic polymers, unprecedented biomimetic materials may be created. From this viewpoint, we developed “self-oscillating” polymer gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart muscle. The self-oscillating gels were designed by utilizing an oscillating reaction called the Belousov-Zhabotinsky reaction, as a chemical model of the TCA cycle in living systems. We have systematically studied these self-oscillating polymer gels since they were first reported in 1996 (JACS). Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems such as biomimetic actuators, mass transport systems and functional fluids. Recently, amoeba-like motion with autonomous sol-gel oscillation was realized. In the BZ reaction, the external addition of an oxidant is required to initiate the oxidation process; in living systems, it is realized by intracellular moieties such as ubiquinone. For further evolution of self-oscillating polymers into autonomous bio-inspired materials, a design imparting macroscopic physical property changes via built-in oxidation systems is key. We achieved an amoeba-like autonomous sol-gel oscillation without the external addition of oxidants by introducing an oxidizing moiety in a self-oscillating triblock terpolymer and coupling the oscillation of macroscopic physical properties with that of the microscopic structure due to spontaneous oxidation. The achievement reported here can pave the way to the creation of artificial life systems. In this talk, our recent progress on the self-oscillating polymer gels is summarized.

With the increasing usage of electronic gadgets in various fields, the problem of electromagnetic interference (EMI) has become eminent. To suppress this interference, lightweight materials, that are easy to fabricate, design, integrate and process are in great demand. Metals were the predominant choices earlier; however, they are being replaced by polymer nanocomposites due to their non-corrosive nature. Moreover, the properties of polymers can be tuned easily to achieve desired properties. In the present study, we have grown copper sulphide ‘flowers’ on graphene oxide by a facile one-pot hydrothermal technique, during the process GO sheets are partly reduced to yield rGO-CuS hybrid. The growth time of the “flower-like” structure was optimised based on structural (XRD) and morphological analysis (SEM). Then, as-prepared particles were dispersed in PVDF using melt blending. The bulk AC electrical conductivity and EMI shielding ability of the prepared composite was assessed, and it was found that the nanocomposites exhibited an EMI shielding effectiveness up to -25 dB manifesting in 86 % absorption of EM waves at a thickness of only 1 mm. Moreover, it was also observed that the addition of hybrid nanoparticles has a better effect on EM shielding performance compared to when the nanoparticles are added separately in terms of both total shielding effectiveness as well as absorption performance.

Self-organization of nanomaterials is not only driven by thermodynamics, but more frequently, is influenced by local metastable local states that inevitably exist during many nonequilibrium processes. The experimental factors that drive the system into these metastable states are many, such as liquid evaporation, anisotropic particle-particle interactions, particle -interface interactions and external applied mechanical forces. Tracking these assembly process thus requires developing in situ characterization techniques. In the talk, I will illustrate several examples of self-assembled metastable structures that involve spherical nanoparticles and nanorods using in situ real space optical microscopy imaging and q-space small angle x-ray scattering technique. I will show the experimental conditions that lead to the formation of two-dimensional crystals and gels during evaporation process and dynamical crystal formation in a shear cell.

Batteries represent a future growth area for energy storage, with lithium-ion batteries (LiBs) continuously and most rapidly growing due to their targeted use in electronic vehicles (EVs). It calls for efforts to develop strategies for the reuse, recycling, and recovery of batteries to avoid the build-up of waste in landfills since even the most long-lived EV battery has a limited lifetime of up to 20-years, including their reuse for 2nd lifetime. At the same time, it is well established that the most frequently used functional elements, i.e., metals and natural graphite, are limited. Global geological exploration predicts that a shortage of the relevant elements may occur within 25 years, and some are listed as critical raw materials for the EU. Resource-efficient recycling strategies are therefore required, which allow for continuous raw material supply in the future. This represents a cornerstone for the sustainable battery market. Macromolecules, such as cellulose, are potential candidates for recovery of relevance in recycling LiBs due to their remarkable adsorption capacities, low toxicity, and being environmentally sustainable. In addition, modification of the size, morphology, and surface of cellulose and protein with functional molecules can reach to recover various metals. Therefore, a mild but efficient process was used in this study to extract and recover valuable metals from spent LiBs with macromolecules. Our proposed leaching method shortened the extraction time (more than 50%). It also improved the leached percentage of valuable metal elements with fewer chemicals. The proposed metal recovery process with macromolecules shortened the precipitation time of relevant metal ions from the leachate. Overall, it is shown that recovery of the LiBs can be facilitated and carried out in a more selective and energy-efficient manner using our proposed soft method.

Background: Targeting for the materials in 5G technology, thermal conductivity of polymers and polymer composites has been spotlighted. However, despite a long history of theoretical study on polymers’ thermal conductivity, a general prediction model is still not available due to the facts that properties of polymers are influenced by many complex factors. In order to efficiently search around an enormous chemical structure in material space, we impose a framework based on Bayesian inference integrating with machine learning models by using the PoLyInfo database.

Methods: In the Bayesian molecular design process that generated a library of virtual chemical structures, we specified a higher region of glass transition temperatures and melting temperatures as alternative design targets, for which sufficient data were given to obtain reliable prediction models. Furthermore, an ML framework referred to as “transfer learning” was introduced to obtain a thermal conductivity model with the given small data set. For the given target property to be predicted from the limited supply of data, models on physically related proxy properties were pre-trained using an adequate amount of data, which captured common features relevant to the target task of predicting thermal conductivity. Re-purposing such machine-acquired features for the target task produced an outstanding achievement in the prediction accuracy even with the exceedingly small data set. We used the transferred thermal conductivity model to screen promising candidates over the virtual library that was produced by targeting the glass transition and melting temperatures, then proceeded with laboratory synthesis and experimental characterization of the thermophysical properties.

Results: Three chemical structures were selected from a list of 1,000 designed candidates on the basis of criteria involving synthetic accessibility and ease of processing, which are required for the practical use of enhanced newly designed polymers with high thermal conductivity. Then, the monomers of these candidates were synthesized and polymerized using retrosynthetic routes designed by synthetic chemists. The synthesized polymers exhibited a glassy state, and two of them were crystallized by annealing. We also observed the change in the crystal system resulting from additional chemical reaction during annealing. Their thermal conductivities reached 0.18 - 0.41 W/mK within non-composite thermo-plastics in amorphous and semi-crystalline states.

Conclusions: The experimentally confirmed properties of the computationally designed polymers are highly consistent with the predicted values from ML.

References: S. Wu, et al., npj Computational Materials 5, 66 (2019).

Machine learning as applied to polymer science has recently shown immense progress---mostly in areas where there are existing large datasets or where datasets can be generated quickly. However, there are numerous interesting problems where the dataset sizes are too small or the need to understand the physics behind the machine learning prediction is essential. Here, we aim to tackle both of these problems by incorporating domain knowledge into machine learning models. Specifically, using a toy system of polymers in different solvent qualities, we compare several methods for incorporating theory into machine learning using a simple, imperfect but easily interpretable theory. We also explore the intersection these methods with different machine models including random forest and Gaussian process regression.

The development of biomaterials and biomedical applications is relying on systems comprising functional nanocomposites, soft materials and/or polymer systems which in turn are fundamentally based on epoxides, cyclic esters, and cyclic carbonates among others due to introduced biocompatibility and biodegradability. Therefore, controlled high-throughput polymerization procedures are crucial to providing new high-quality polymer materials at time scales to accelerate the data-driven discovery.
Anionic ring-opening polymerization (ROP) of epoxides, cyclic esters, and cyclic carbonates with strong bases such as potassium tert-butoxide (KOtBu) or potassium bis(trimethylsilyl)amide (KHMDS) is typically performed as batch reaction, leading to broad dispersity and poor control over the molecular weight (M_n) mainly because of insufficient initiator efficiency and transesterification reactions.
We now present that combining a sterically hindered strong base such as KOtBu or KHMDS with a primary alcohol and using a continuous-flow apparatus can afford control and reliability over the ROP and, remarkably, enable the controlled polymerization of traditionally low-activity monomers such as δ-valerolactone and ε-caprolactone in milliseconds. These reactions exhibit characteristics capable of producing narrow dispersity with predictable molecular weights and can rapidly generate well-defined block copolymers at residence times below 0.1 s. With reaction rates that are orders of magnitude higher than the fastest rates reported for urea anions, these reaction conditions offer great potential to expand the breadth of materials accessible.

Polyurethanes (PUs) have found application as biomaterials and in the biomedical field due to their biocompatibility and physical properties which can be tailored over a wide range. In academic research and industry, PUs are commonly synthesized in batch/extrusion processes often involving multiple steps. However, conducting polymerizations under continuous flow conditions affords distinct advantages over batch experimentation and has increasingly been employed by the research community for chain-growth polymerizations to accelerate materials discovery and to finely tune material properties. Our work now expands on the reported advances by demonstrating the utility of continuous flow for polyaddition reactions of PUs. Various reactor configurations enable the on-demand organocatalytic synthesis of linear polyurethanes with tailored soft to hard segment ratios and under residence times of 3-5 min at room temperature. Implementing in-line analytics for real-time process monitoring increases the control over monomer conversion and minimizes batch-to-batch variations. Theoretical and experimentally determined molecular weights and material compositions were in good agreement and demonstrate reliability and reproducibility of the processes. Thus, these systems enable the straightforward preparation of libraries of commercially relevant PU materials and we demonstrate how the glass transition temperature can be modulated by composition. Finally, we discuss developed process control mechanisms aiming at increasing process automation and the underlying challenges due to employing reactive solutions.

Natural gas plays a significant role in the global energy mix, and global natural gas demand has grown steadily in recent years. However, more than 40% of global natural gas reserves are highly sour, i.e. the percentage of CO₂ and H₂S is significant. Their production and transport can be a challenge, due to its corrosiveness in the presence of water, leading to pipelines damages and H₂S toxicity. Therefore, the produced natural gas must be treated and sweetened in order to meet the standard pipeline specifications for transport and processing. The bulk removal of H₂S and CO₂ from natural gas remains an energy intensive separation challenge using the conventional amine absorption technology. Alternatively, membrane-based technologies have gained great industrial attention over the past decades due to their relatively energy-efficient and environment-friendly footprint. Designing novel structures and optimizing membrane performances for enhanced sour gas separations have been the subjects of intensive research in the Aramco Research Center-Boston during the past years. This talk will discuss the impact of polymer structures on the resulting permeation properties and high-pressure separation performance. Particular attention will focus on synthesizing novel glassy polymers (e.g. 6FDA-based co-polyimides), modifying rubbery polymers (e.g. poly(amide-b-ether) copolymers), and controlling their structures, which result in enhanced sour gas separation performance under industrially relevant feed streams and testing conditions (e.g. 20% H₂S-containing sour gas feed at feed pressure up to 800 psi). These studies emphasize the observation that membrane separation performance is strongly related to chemical structure and the testing conditions, highlight the importance of exploring and designing better polymeric materials for the actual industrial gas process.

Complex microscale colloids are material platforms for a wide range of sensing scenarios and can be tuned and configured by a variety of chemical and physical phenomena. In particular, the soft boundaries of colloids produce various synergetic effects by exploiting self-assembling polymers. First, I will present the state-of-the-art in the programmed design of anisotropically shaped polymer particles driven by phase-separation upon solvent evaporation from interface-engineered emulsions. In particular, two different topics: 1) block copolymer (BCP) particles with reversible shape-changing property activated by wavelength-selective light irradiation, and 2) full-color reflective photonic polymer particles capable of a dynamic color change will be discussed. First, the key to achieving light-responsive shape transitions of BCP particles is the design and synthesis of surfactants containing photo-cleavable groups (i.e., nitrobenzyl esters and coumarin esters) or photo-isomerizable groups (i.e., spiropyran) that modulate the amphiphilicity and interfacial activity of the surfactants in response to light of a specific wavelength. These light-induced changes in surfactant structure modify the surface and wetting properties of BCP particles, affording both shape and morphological transitions of the particles. Next, dendronized brush block copolymers are used to achieve highly ordered axially stacked lamellae with large domain size, allowing a near-perfect photonic multilayer. The photonic ellipsoids are functionalized with magnetic nanoparticles organized into bands on the particle surface to produce real-time on/off coloration by magnetic field-assisted activation.

Advanced electronic and communication devices require multifunctional miniaturization, high frequency band operating frequency and broadband. However, since electromagnetic waves emitted from these devices may adversely affect the operation of devices. To cope with EMI originated various electrical devices and components, development of high-performance electromagnetic interference shielding materials is urgently needed. However, there are only limited EMI shielding methods available which simultaneously satisfying high shield effectiveness, lightweight and flexibility. In order to fabricate such an ultra-thin multifunctional shielding material, we developed a high-performance shielding material using the flexibility of the nanofibers and the electrical conductivity by doping PEDOT on the electrospun PVDF nanofibers. The developed EMI shielding membrane is light-weighted, highly flexible, and conductive, providing high shielding effectiveness of ~ 40 dB at a thickness of 14 mm. Thus, considerably high specific shielding effectiveness per density (16232 dB cm2/g) can be achieved. The excellent EMI shielding effectiveness is attributed to the favorable porous structure in the hybrid nanofiber membrane. In addition, the resultant PVDF-PEDOT core-shell nanofiber membrane shows a reasonable mechanical strength and excellent flexibility. Furthermore, hydrophobic surface property can also useful for self-cleaning of the membrane surface. Consequently, the EMI shielding method introduced in this work can be used useful for various applications necessitating flexible and light-weighted EMI shielding materials.