Materials descriptors for advanced water dissociation catalysts in bipolar membranes.

The voltage penalty driving water dissociation (WD) at high current density is a major obstacle in the commercialization of bipolar membrane (BPM) technology for energy devices. Here we show that three materials descriptors, that is, electrical conductivity, microscopic surface area and (nominal) surface-hydroxyl coverage, effectively control the kinetics of WD in BPMs. Using these descriptors and optimizing mass loading, we design new earth-abundant WD catalysts based on nanoparticle SnO synthesized at low temperature with high conductivity and hydroxyl coverage.

Tunable thermoplastic elastomer gels derived from controlled-distribution triblock copolymers with crystallizable endblocks.

Thermoplastic elastomers (TPEs), a commercially important category of triblock copolymers, are employed alone or upon physical modification with a midblock-selective oil (to form TPE gels, TPEGs) in a broad range of contemporary technologies. While most copolymers in this class of self-networking macromolecules possess glassy polystyrene endblocks and a rubbery polydiene or polyolefin midblock, we investigate TPEGs fabricated from a novel controlled-distribution copolymer with crystallizable polyolefin endblocks and a random-copolymer midblock. According to both electron microscopy and small-angle scattering, the morphologies of these TPEGs remain largely invariant up to 40 wt% oil and then transform considerably at higher oil levels.

Preventing the spread of life-threatening gastrointestinal microbes on the surface of a continuously self-disinfecting block polymer.

Highly persistent, drug-resistant and transmissible healthcare pathogens such as Clostridioides difficile (C. difficile) and Candida auris (C. auris) are responsible for causing antibiotic-associated fatal diarrhea and invasive candidiasis, respectively.

Surface Mechanical Properties and Topological Characteristics of Thermoplastic Copolyesters after Precisely Controlled Abrasion.

Due to the high probability of surface-to-surface contact of materials during routine applications, surface abrasion remains one of the most challenging factors governing the long-term performance of polymeric materials due to their broad range of tunable mechanical properties, as well as the varied conditions of abrasion (regarding, , rate, load, and contact area). While this concept is empirically mature, a fundamental understanding of mechanical abrasion regarding thermoplastics remains lacking even though polymer abrasion can inadvertently lead to the formation of nano-/microplastics. In the present study, we introduce the concept of precision polymer abrasion (PPA) in conjunction with nanoindentation to elucidate the extent to which controlled wear is experienced by three chemically related thermoplastics under systematically varied abrasion conditions.

An integrated materials approach to ultrapermeable and ultraselective CO polymer membranes.

Advances in membrane technologies that combine greatly improved carbon dioxide (CO) separation efficacy with low costs, facile fabrication, feasible upscaling, and mechanical robustness are needed to help mitigate global climate change. We introduce a hybrid-integrated membrane strategy wherein a high-permeability thin film is chemically functionalized with a patchy CO-philic grafted chain surface layer. A high-solubility mechanism enriches the concentration of CO in the surface layer hydrated by water vapor naturally present in target gas streams, followed by fast CO transport through a highly permeable (but low-selectivity) polymer substrate.

Anion-Specific Water Interactions with Nanochitin: Donnan and Osmotic Pressure Effects as Revealed by Quartz Microgravimetry.

The development of new materials emphasizes greater use of sustainable and eco-friendly resources, including those that take advantage of the unique properties of nanopolysaccharides. Advances in this area, however, necessarily require a thorough understanding of interactions with water. Our contribution to this important topic pertains to the swelling behavior of partially deacetylated nanochitin (NCh), which has been studied here by quartz crystal microgravimetry.

Morphological Studies of Solution-Crystallized Thermoplastic Elastomers with Polyethylene Endblocks and a Random-Copolymer Midblock.

Styrenic thermoplastic elastomers (TPEs) in the form of triblock copolymers possessing glassy endblocks and a rubbery midblock account for the largest global market of TPEs worldwide, and typically rely on microphase separation of the endblocks and the subsequent formation of rigid microdomains to ensure satisfactory network stabilization. In this study, the morphological characteristics of a relatively new family of crystallizable TPEs that instead consist of polyethylene endblocks and a random-copolymer midblock composed of styrene and (ethylene-co-butylene) moieties are investigated. Copolymer solutions prepared at logarithmic concentrations in a slightly endblock-selective solvent are subjected to crystallization under different time and temperature conditions to ascertain if copolymer self-assembly is directed by endblock crystallization or vice versa.

Toward Universal Photodynamic Coatings for Infection Control.

The dual threats posed by the COVID-19 pandemic and hospital-acquired infections (HAIs) have emphasized the urgent need for self-disinfecting materials for infection control. Despite their highly potent antimicrobial activity, the adoption of photoactive materials to reduce infection transmission in hospitals and related healthcare facilities has been severely hampered by the lack of scalable and cost-effective manufacturing, in which case high-volume production methods for fabricating aPDI-based materials are needed. To address this issue here, we examined the antimicrobial efficacy of a simple bicomponent spray coating composed of the commercially-available UV-photocrosslinkable polymer -methyl-4(4'-formyl-styryl)pyridinium methosulfate acetal poly(vinyl alcohol) (SbQ-PVA) and one of three aPDI photosensitizers (PSs): zinc-tetra(4--methylpyridyl)porphine (ZnTMPyP), methylene blue (MB), and Rose Bengal (RB).

Rapid and Repetitive Inactivation of SARS-CoV-2 and Human Coronavirus on Self-Disinfecting Anionic Polymers.

While the ongoing COVID-19 pandemic affirms an urgent global need for effective vaccines as second and third infection waves are spreading worldwide and generating new mutant virus strains, it has also revealed the importance of mitigating the transmission of SARS-CoV-2 through the introduction of restrictive social practices. Here, it is demonstrated that an architecturally- and chemically-diverse family of nanostructured anionic polymers yield a rapid and continuous disinfecting alternative to inactivate coronaviruses and prevent their transmission from contact with contaminated surfaces. Operating on a dramatic pH-drop mechanism along the polymer/pathogen interface, polymers of this archetype inactivate the SARS-CoV-2 virus, as well as a human coronavirus surrogate (HCoV-229E), to the minimum detection limit within minutes.

Mesophase characteristics of cellulose nanocrystal films prepared from electrolyte suspensions.

Cellulose nanocrystals (CNCs) exhibit a cholesteric mesophase above a critical concentration in aqueous suspensions. Above this concentration, CNCs self-organize into left-handed helicoidal structures that can be preserved in dried, stratified films. In this systematic study, we have prepared optically-active CNC films cast from different electrolyte suspensions and investigated, via circular dichroism and other techniques, the effects of counterion type (six mono/divalent salts, including those responsible for promoting "salting-out" and "salting-in" in the Hofmeister series) and ionic strength on mesomorphic behavior and cholesteric arrangement.

Cellulose nanofibers and the film-formation dilemma: Drying temperature and tunable optical, mechanical and wetting properties of nanocomposite films composed of waterborne sulfopolyesters.

Hypothesis: Waterborne sulfopolyesters have gained considerable interest as coating materials due to their excellent film-forming and optical properties. Their commercial use has been limited, however, due to their fragile nature. Incorporating cellulose nanofiber (CNF), a sustainable biopolymer, into the polymer matrix is expected to enhance the mechanical integrity of the nanocomposite as these two components synergistically interact.

Photodynamic Coatings on Polymer Microfibers for Pathogen Inactivation: Effects of Application Method and Composition.

A substantial increase in the risk of hospital-acquired infections (HAIs) has greatly impacted the global healthcare industry. Harmful pathogens adhere to a variety of surfaces and infect personnel on contact, thereby promoting transmission to new hosts. This is particularly worrisome in the case of antibiotic-resistant pathogens, which constitute a growing threat to human health worldwide and require new preventative routes of disinfection.

Network topology and stability of homologous multiblock copolymer physical gels.

The mechanical properties of physical gels generated by selectively swelling a homologous series of linear multiblock copolymers are investigated by quasistatic uniaxial tensile tests. We use the slip-tube network model to extract the contributions arising from network crosslinks and chain entanglements. The composition dependence of these contributions is established and considered in terms of simulations that identify the probabilities associated with chain conformations.

Optimization of the Rubber Formulation for Footwear Applications from the Response Surface Method.

Impact force remains the primary cause of foot injury and general discomfort with regard to footwear. The footwear industry traditionally relies on modified elastomers (including natural rubber) whose properties can be physically adjusted by varying the constituents in the rubber formulations. This work aims to investigate the effect of filler/plasticizer fractions on shock attenuation of natural rubber soles.

Quantitative Calorimetric Studies of the Chiral Nematic Mesophase in Aqueous Cellulose Nanocrystal Suspensions.

Aqueous suspensions of cellulose nanocrystals (CNCs) can spontaneously form a chiral nematic mesophase at a critical concentration (*). Unfortunately, no current analytical technique permits rapid detection of *. Herein, we introduce a facile and accurate approach to assess * rapidly (<2 h) from a small sample volume and compare our results with those obtained by conventional methods.

Shear-Dependent Structures of Flocculated Micro/Nanofibrillated Cellulose (MNFC) in Aqueous Suspensions.

Cellulosic nanomaterials constitute a topic of growing commercial interest for numerous applications, many of which demand a working knowledge of the rheology of the materials. We demonstrate here that aqueous suspensions of micro/nanofibrillated cellulose (MNFC) exhibit complex shear behavior governed primarily by fibrillar floc dynamics. Regimes corresponding to structure formation, persistence, and breakdown are quantitatively differentiated.

Ionic complexation of endblock-sulfonated thermoplastic elastomers and their physical gels for improved thermomechanical performance.

Thermoplastic elastomers (TPEs) composed of nonpolar triblock copolymers constitute a broadly important class of (re)processable network-forming macromolecules employed in ubiquitous commercial applications. Physical gelation of these materials in the presence of a low-volatility oil that is midblock-selective yields tunably soft TPE gels (TPEGs) that are suitable for emergent technologies ranging from electroactive, phase-change and shape-memory responsive media to patternable soft substrates for flexible electronics and microfluidics. Many of the high-volume TPEs used for these purposes possess styrenic endblocks that are inherently limited by a relatively low glass transition temperature.

Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl Content.

The sol-gel transition of a series of polyester polyol resins possessing varied secondary hydroxyl content and reacted with a polymerized aliphatic isocyanate cross-linking agent is studied to elucidate the effect of molecular architecture on cure behavior. Dynamic rheology is utilized in conjunction with time-resolved variable-temperature Fourier-transform infrared spectroscopy to examine the relationship between chemical conversion and microstructural evolution as functions of both time and temperature. The onset of a percolated microstructure is identified for all resins, and apparent activation energies extracted from Arrhenius analyses of gelation and average reaction kinetics are found to depend on the secondary hydroxyl content in the polyester polyols.

Thermoplastic Elastomer Systems Containing Carbon Nanofibers as Soft Piezoresistive Sensors.

Soft, wearable or printable strain sensors derived from conductive polymer nanocomposites (CPNs) are becoming increasingly ubiquitous in personal-care applications. Common elastomers employed in the fabrication of such piezoresistive CPNs frequently rely on chemically cross-linked polydiene or polysiloxane chemistry, thereby generating relatively inexpensive and reliable sensors that become solid waste upon application termination. Moreover, the shape anisotropy of the incorporated conductive nanoparticles can produce interesting electrical effects due to strain-induced spatial rearrangement.

Self-Assembly of a Midblock-Sulfonated Pentablock Copolymer in Mixed Organic Solvents: A Combined SAXS and SANS Analysis.

Ionic, and specifically sulfonated, block copolymers are continually gaining interest in the soft materials community due to their unique suitability in various ion-exchange applications such as fuel cells, organic photovoltaics, and desalination membranes. One unresolved challenge inherent to these materials is solvent templating, that is, the translation of self-assembled solution structures into nonequilibrium solid film morphologies. Recently, the use of mixed polar/nonpolar organic solvents has been examined in an effort to elucidate and control the solution self-assembly of sulfonated block copolymers.

Dielectric and Resistive Heating of Polymeric Media: Toward Remote Thermal Activation of Stimuli-Responsive Soft Materials.

Stimuli-responsive soft materials are becoming increasingly important in a wide range of contemporary technologies, and methods by which to promote thermal stimulation remotely are of considerable interest for controllable device deployment, particularly in inaccessible environments such as outer space. Until now, remote thermal stimulation of responsive polymers has relied extensively on the use of nanocomposites wherein embedded nanoparticles/structures are selectively targeted for heating purposes. In this study, an alternative remote-heating mechanism demonstrates that the dielectric and resistive thermal losses introduced upon application of an alternating current generate sufficient heat to raise the temperature of a neat polyimide by over 70 °C within ≈10 s.

Hierarchical Self-Assembly of Toroidal Micelles into Multidimensional Nanoporous Superstructures.

Materials with controlled porosity play a prominent role in industrial and domestic applications. Although a rich array of methods has been developed to tune the pore size over a broad range (from <1 nm to >1 μm), the fabrication of functional materials with a fully open porous structure with sub-100 nm pore size has remained a significant challenge. Herein, we report the hierarchical assembly of block copolymer toroidal micelles with an intrinsic cavity into multidimensional nanoporous superstructures (pore size 85-90 nm) by modulation of interparticle interactions.

Incorporation of Metallic Species into Midblock-Sulfonated Block Ionomers.

Block ionomers can, in the same fashion as their neutral block copolymer analogs, microphase-order into various nanoscale morphologies. The added benefit of a copolymer possessing a charged species is that the resultant block ionomer becomes amphiphilic and capable of imbibing polar liquids, including water. This characteristic facilitates incorporation of metallic species into the soft nanostructure for a wide range of target applications.

Photodynamic Polymers as Comprehensive Anti-Infective Materials: Staying Ahead of a Growing Global Threat.

To combat the global threat posed by surface-adhering pathogens that are becoming increasingly drug-resistant, we explore the anti-infective efficacy of bulk thermoplastic elastomer films containing ∼1 wt % zinc-tetra(4- N-methylpyridyl)porphine (ZnTMPyP), a photoactive antimicrobial that utilizes visible light to generate singlet oxygen. This photodynamic polymer is capable of inactivating five bacterial strains and two viruses with at least 99.89% and 99.

Communication: Molecular-level description of constrained chain topologies in multiblock copolymer gel networks.

Network characteristics in physical gels composed of solvated block copolymers varying in molecular design are examined here by dynamic rheology and computer simulations. In two triblock copolymer series, one with chain length (N) varied at constant copolymer composition (f) and the other with f varied at constant N, we discern the dependence of equilibrium network metrics on both N and f. Increasing the block number in a linear multiblock series at constant N and f escalates conformational complexity, which dominates network connectivity classified according to a midblock conformation index.