Constituent Polymers Research Articles

Elasticity of Swollen and Folded Polyacrylamide Hydrogel Using the MARTINI Coarse-Grained Model.

One of the key advantages of using a hydrogel is its superb control over elasticity obtained through variations of constituent polymer and water. The underlying molecular nature of a hydrogel is a fundamental origin of hydrogel mechanics. In this article, we report a Polyacrylamide (PAAm)-based hydrogel model using the MARTINI coarse-grained (CG) force field. The MARTINI hydrogel is molecularly developed through Iterative Boltzmann inversion (IBI) using all-atom molecular dynamics (AAMD), and its quality is evaluated through the experimental realization of the target hydrogel. The developed model offers a mechanically high-fidelity CG hydrogel that can access large-scale water-containing hydrogel behavior, which is difficult to explore through AAMD in practical time. With the modeled hydrogel, we reveal that the polymer conformation modulates the elasticity of the hydrogel from a folded state to a swollen state, confirmed by the Panyukov model. The results provide a robust bridge for linking the polymer conformations and alignment to their bulk deformation, enabling the multifaceted and material-specific predictions required for hydrogel applications.

Thermochemical processing for the sustainable disposal of spent filter waste

High-efficiency particulate air filters are widely used for indoor air purification. Spent filter waste (SFW), which can trap infectious and toxic substances, is primarily treated via incineration. This method causes environmental concerns, particularly regarding the generation of carbon dioxide (CO2) and other air pollutants. To cope with these issues, this work proposes the pyrolysis of SFW using CO2 as a sustainable alternative to conventional incineration. The introduction of CO2 enhanced reactivity during pyrolysis, potentially offering a more sustainable process. The SFW consisted of filtered particles and two distinct filter/support layers, and the presence of toxic chemicals and primary polymer constituents was characterized. While CO2 had a minimal impact on enhancing syngas production, owing to its slow reaction rate during SFW pyrolysis, adding a nickel-based catalyst significantly improved CO2 reactivity. This resulted in a 649.7% increase in carbon monoxide (CO) production compared to that in pyrolysis under N2. The potential of this pyrolysis system for reducing CO2 emissions was evaluated against that of conventional incineration. Overall, this study presents a promising method for the pyrolytic conversion of SFW into combustible gases, particularly CO, while leveraging CO2 utilisation to mitigate global warming.

Understanding the influence of configurations and intermolecular interaction on thermomechanical and dynamics properties of polymer–clay nanocomposites via molecular dynamics simulations

AbstractPolymer‐clay nanocomposites (PCNs) have emerged as highly versatile structural materials that possess exceptional thermomechanical and dynamic properties, all the while retaining their inherent attributes of being lightweight and optically clear. The fabrication of nanocomposites involves the incorporation of carefully calibrated quantities of clay nanofillers into polymer matrixes. Current research expands upon existing coarse‐grained (CG) models of nanoclay and poly (methyl methacrylate) (PMMA) and utilize molecular dynamics simulations to methodically explore the thermomechanical characteristics of PCNs. Specifically, the effects of exfoliated and stacked configurations of nanoclays, as well as variations in intermolecular interactions between the nanoclay and polymer constituents were tested. Tensile and shear simulations, as well as interfacial behaviors, are conducted. The intermolecular interaction could have significant influences on Shear Modulus and Young's Modulus, and those influences have their characteristics due to different configurations and different force directions, such as in most cases, exfoliated structures exhibit higher mechanical modulus compared with stacked configurations at varying interaction strengths. Additionally, in the in‐plane direction, they demonstrate stronger resistance effects compared with the out‐of‐plane direction. The interaction between PMMA and nanoclay slows down the global dynamics of PMMA, with a stronger effect observed for higher interaction strength. The impact of nanoclay on the segmental dynamics of PMMA decreases as we move away from the nanoclay layers toward the pure PMMA matrix. These findings provide molecular insights into the arrangement of components in PCNs during deformation and highlight the significance of nanoclay and the interface in determining their mechanical and dynamic properties.Highlights Variation patterns of mechanical modulus with interactions and configurations. The property difference in mechanical modulus due to configurations. Positive correlation between polymer Tg and intermolecular interaction. Global and local confinement effects on molecular stiffness during tension. Dynamical heterogeneity behavior on different interactions and temperatures.

Design of Organic-Inorganic Hybrids and Application to Electrochemical Sensor for Detecting Food Poisoning Bacteria

Pathogenic Escherichia coli, Salmonella enterica, and Staphylococcus aureus are well-known as causative organisms of food poisoning. The ingestion of food and drinking water contaminated with these pathogens causes various symptoms such as diarrhea, abdominal pain, and vomiting, and in severe cases, hemolytic uremic disease. Current microbiological testing methods such as the polymerase chain reaction, enzyme-linked immunosorbent assay, and colony counting require skilled experimentalists and/or a complex and time-intensive culture process. In recent years, many studies have reported the development of biosensors that apply novel materials and technologies. Biosensors based on physical or chemical signals, such as optics, bioluminescence, and piezoelectricity, have been developed for the highly sensitive and rapid detection of pathogenic bacteria. Although methods based on these principles achieve highly sensitive and specific detection, they require expensive and bulky detectors, which limits their use in the field. Therefore, in order to prevent health hazards such as food poisoning and infectious diseases, it is necessary to develop new testing methods that can quickly detect food-poisoning bacteria.Electrochemical biosensors are particularly useful in fields where on-site inspection is required, because of their high sensitivity, rapid measurement, and ease of device miniaturization. Generally, biosensors use electrochemical reporters as labels to obtain electrochemical signals. In particular, metal nanoparticles have unique surface effects and catalytic functionality and are used in biosensor design to improve specificity, sensitivity, and simplicity. However, it is necessary to separate electrochemical cells for different labels or to fabricate a multiarray of electrodes that is selective for bacterial species when multiple bacterial species need to be detected simultaneously.Previously, we successfully developed organic-inorganic hybrids with a densely assembled structure of gold nanoparticles in a polyaniline matrix (AuNH).1 This fabrication method exploited the fact that the reduction of aurate by aniline and the oxidation of aniline by aurate occurred in the same reaction field, enabling the production of nanometer-scaled hybrids in a single process. Similarly, silver NH (AgNH) and copper NH (CuNH) were synthesized using silver nitrate and copper sulfate as metal sources.2 The hybridization of metal nanoparticles and conductive polymers is expected to endow various functions, such as environmental stability, electrical conductivity, and electrochemical activity.3 We investigated the characteristic electrochemical properties of the hybrids in detail and attempted to use them as electrochemical labels for detecting bacteria.4 The results of cyclic voltammetry revealed that NHs exhibit redox current derived from there constituent materials, either polymers or metal nanoparticles. Also, different NHs showed similar current sensitivities at different potentials in differential pulse voltammetry. This shows that these qualifications and quantifications can be achieved simultaneously. AuNH and CuNH did not interfere with each other in terms of electrochemical signals obtained on the same electrode. Therefore, antibodies were introduced into these NHs to act as electrochemical labels to target specific bacteria. AuNH was modified with anti-E. coli O26 antibody, and CuNH was modified with anti-Staphylococcus aureus antibody. Electrochemical measurements using screen-printed electrodes dry-fixed with NH-labeled bacterial cells enabled the estimation of bacterial species and number within minutes, based on the distinct current response of the labels. The development of this analytical technology will ensure the safety of food and drug production and contribute to the realization of a safe, secure, and comfortable lifestyle.[1] S. Itagaki, S. Tanabe, H. Ikeda, X. Shan, S. Nishii, Y. Yamamoto, Y. Sadanaga, Z. Chen, H. Shiigi, Analyst, 147, 2355 (2022).[2] S. Tanabe, S. Itagaki, K. Matsui, S. Nishii, Y. Yamamoto, Y. Sadanaga, H. Shiigi, Anal. Chem., 94, 10984 (2022).[3] S. Nakamura, A. Nakao, S. Itagaki, K. Matsui, S. Nishii, X. Shan, Y. Yamamoto, Y. Sadanaga, Z. Chen, H. Shiigi, Sensors and Materials, 35, 4761 (2023).[4] S. Itagaki, A. Nakao, S. Nakamura, M. Fujita, S. Nishii, Y. Yamamoto, Y. Sadanaga, H. Shiigi, Anal. Chem., 96, 3787 (2024).

Chitosan nanoparticles as drug carrier of gentamicin - density functional theory and molecular dynamics simulation studies

To the best of our knowledge, the detailed evaluation of the interaction of gentamicin with chitosan nanoparticles in the absence and presence of Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant followed by the evaluation of structural, dynamical, and thermodynamic properties was carried out for the first time which helped to understand the relative drug retention and release time in the model drug delivery system. Gentamicin being an unstable drug molecule demonstrated low efficacy against brucellosis as well as considerable toxicity, thus requiring frequent dosing in different forms including a single dose and combination with other antibiotics; however, no satisfactory result was observed. Chitosan is biodegradable and biocompatible which could help overcome drug delivery issues enabling the drug to reach the target site. Our study is based on the investigation of the chitosan-drug systems without and with the surfactant for the evaluation of the structural, dynamical, and transport properties using a combined approach consisting of density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The DFT results showed that increasing the size of the chain consisting of D-glucosamine facilitated its interaction with the drug molecule thus signifying the role of polymer for the drug accommodation. Furthermore, MD simulation results exhibited the interaction of chitosan nanoparticles with the drug molecules via H-bonding and hydrophobic contacts which were enhanced after the addition of the surfactant. The dynamics and thermodynamic data corroborated the structural properties of the drug-nanoparticle interaction which confirmed the perturbation of the simulation system after the addition of the surfactant. The investigation of another two simulation systems based on the polymer constituents, D-glucosamine pointed towards the significance of the polymerization which eventually resulted in nanoparticles thus providing a platform for drug adsorption. The gentamicin-chitosan nanoparticles were further characterized via transport properties in terms of drug diffusion coefficients which served to consider its use in the context of target drug delivery to treat brucellosis.

FACILE SYNTHESIS OF ACTIVATED CARBON/ALGINATE/CHITOSAN COMPOSITE BEADS AS RHEMAZOLE BRILLIANT BLUE R ADSORBENT

Developing composite beads composed of chitosan, alginate, and activated carbon for dye removal is essential due to their improved adsorption capabilities and environmental benefits. By utilizing natural resources efficiently for an effective dye removal process, this study developed an activated carbon/alginate/chitosan composite bead as Rhemazole Brilliant Blue R (RBBR) adsorbent. The surface shape of composites exhibits more protrusions, grooves, and asymmetric pores than activated carbon, which could improve dye adsorption capability. FTIR analysis verified that functional groups such as OH, NH, protonated amine, and carboxylate from the constituent polymers were enriched in the activated carbon/alginate/chitosan composite. These groups also function as active sites for adsorbents. It was aligned with the composite beads' Freundlich isotherm model, which shows that heterogeneous or many active sites contribute to adsorption and provide multilayer adsorption. The kinetic model of pseudo-second order fits well with the adsorption process, indicating that chemisorption is the rate-limiting step in RBBR adsorption. The optimum adsorption conditions were at pH 1, with an adsorbent dose of 0.08 g, RBBR dye concentration of 125 mg/L, and a contact time of 60 min. The composite beads also exhibit stability in acidic and basic solutions, with the effectiveness of being reused up to four times, providing a reusable adsorbent with versatility in various water treatment conditions. Hence, synthesizing activated carbon/alginate/chitosan composite beads presents a promising solution for sustainable wastewater treatment based on biodegradable and eco-friendly composite.

Molecular Dynamics Study of Adhesion-Related Structural Properties for PVDF-HFP Polymer Binders

The current lithium-ion battery (LIB) market is expanding rapidly. Binders are essential to maintaining the high capacity and longevity of batteries. These binders can be classified into organic binders used for cathodes and aqueous binders used for anodes. Among them, Poly(vinylidene fluoride) (PVDF) binder is a representative organic binder that offers excellent electrochemical stability. To solve low adhesive force and weak mechanical strength of conventional PVDF binders, hexafluoropropylene (HFP) is added to improve these properties. However, the present poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) binders still show lower adhesive force than other polymeric binders, and therefore further research works are necessary.In this study, we employ classical molecular dynamics (MD) simulations to investigate the structural properties of the PVDF-HFP copolymers. To create realistic disordered PVDF-HFP polymers, we develop a computational scheme that can randomly arrange the angles and sequences of the constituent polymer chains. By varying the ratio of randomly arranged PVDF-HFP copolymers to 0/100, 5/95, 10/90, 15/85, and 20/80, we build a solution model that mimics the HFP concentration of PVDF-HFP (0–20%, Sigma Aldrich) used in the actual experiments. N-methyl-2-pyrrolidone (NMP) used as solvents. To create a large-scale model, we utilize the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) and set parameters by using OPLS force field. This allows us to build a simulation model containing approximately 40,000 atoms consisting of 10 PVDF-HFP polymers and 1500 NMP monomers.After creating the simulation model, approximately eight steps of molecular dynamics simulation are performed by referring to the process of making the actual polymer film. In this process, NMP molecules are evaporated to produce a polymer film consisting only of PVDF-HFP polymers. Then we perform the adhesion analysis by applying forces to five polymer film models with different composition ratios in various conditions. Throughout these processes, we find the characteristic changes depending on the composition ratio. Finally, we will present the possible routes that can lead to the enhanced adhesive properties of PVDF-HFP, which is a key requirement to the development of high performance binders.

Additive manufacturing of highly entangled polymer networks.

Incorporation of polymer chain entanglements within a single network can synergistically improve stiffness and toughness, yet attaining such dense entanglements through vat photopolymerization additive manufacturing [e.g., digital light processing (DLP)] remains elusive. We report a facile strategy that combines light and dark polymerization to allow constituent polymer chains to densely entangle as they form within printed structures. This generalizable approach reaches high monomer conversion at room temperature without the need for additional stimuli, such as light or heat after printing, and enables additive manufacturing of highly entangled hydrogels and elastomers that exhibit fourfold- to sevenfold-higher extension energies in comparison to that of traditional DLP. We used this method to print high-resolution and multimaterial structures with features such as spatially programmed adhesion to wet tissues.

Nonlinear Poisson effect in affine semiflexible polymer networks.

Stretching an elastic material along one axis typically induces contraction along the transverse axes, a phenomenon known as the Poisson effect. From these strains, one can compute the specific volume, which generally either increases or, in the incompressible limit, remains constant as the material is stretched. However, in networks of semiflexible or stiff polymers, which are typically highly compressible yet stiffen significantly when stretched, one instead sees a significant reduction in specific volume under finite strains. This volume reduction is accompanied by increasing alignment of filaments along the strain axis and a nonlinear elastic response, with stiffening of the apparent Young's modulus. For semiflexible networks, in which entropic bending elasticity governs the linear elastic regime, the nonlinear Poisson effect is caused by the nonlinear force-extension relationship of the constituent filaments, which produces a highly asymmetric response of the constituent polymers to stretching and compression. The details of this relationship depend on the geometric and elastic properties of the underlying filaments, which can vary greatly in experimental systems. Here, we provide a comprehensive characterization of the nonlinear Poisson effect in an affine network model and explore the influence of filament properties on essential features of both microscopic and macroscopic response, including strain-driven alignment and volume reduction.

Behavioral and physiological responses of Girardia tigrina exposed to polyethylene microplastics.

Microplastic particles appear in great abundance and variety in freshwater ecosystems across the globe, spanning lakes and rivers, with increasingly frequent exposure of aquatic organisms. Studies on the mechanisms of any effects of plastic particles are still scarce, particularly in relation to the regenerative capacity of biota, for which there is no established model organism; however, planaria have shown sensitivity for assessing these risks to the aquatic environment. Thus, the present study aimed to investigate the behavioral and regeneration responses of the freshwater planaria Girardia tigrina exposed to polyethylene (PE) microplastics (MPs) incorporated into their food source. The greatest effect was observed on planarian regeneration, which was manifested at 10μg/mg liver. Planaria reproduction and fertility were affected at 50μg/mg liver; however, planaria locomotion was not affected at the concentrations evaluated. Mid-infrared absorption spectroscopy (FT-IR) was used to identify the constituent polymers, and ingestion of the polyethylene microplastic by the planaria was confirmed by infrared spectroscopy. The results highlight the potential adverse effects of exposure to polyethylene microplastic and show that the reproductive behavior and regeneration of a freshwater organism can be indicators of toxicity resulting from environmental pollution.

Effects of gamma, electron beam, and X-ray irradiation on the plastic components of a universal bone cement mixer medical device

Due to market and regulatory pressures, many healthcare manufacturers are considering alternatives to cobalt-60 gamma radiation, including accelerator-based electron beam (E-beam) and X-ray radiation for product sterilization. In this work, the effects of irradiation on a representative medical product, comprised of eight distinct polymer materials, were directly compared for three radiation technologies – cobalt-60 gamma, E-beam, and X-ray – at four dose levels (15, 25, 50, and 70 kGy). The objective was to determine how radiation effects (deleterious or beneficial) are influenced by source and dose level, with the specific goal of determining whether E-beam radiation and/or X-ray radiation could be viable alternatives to gamma radiation for device sterilization. The specific product considered is a single-use medical device for orthopedic surgery, the Stryker Instruments MixeVac III bone cement mixer, which is currently sterilized using gamma radiation from cobalt-60 sources. Following ASTM International standards and input from the manufacturer, we characterized the effects of the three radiation sources on product functionality as well as on the mechanical and optical properties of the constituent polymers. Results indicate that although measurable differences in properties between the standard gamma irradiated materials and the alternative E-beam and X-ray irradiated materials were observed, those differences were small. Statistically significant differences were noted in the case of yellowness index for polyvinyl chloride, high-density polyethylene, and polycarbonate, and in the case of tensile elongation at break for high impact polystyrene and polyvinyl chloride. In general, the results of this study support the viability of E-beam and X-ray radiation as alternative options to cobalt-60 gamma radiation for sterilization of Stryker single-use universal bone cement mixer medical devices.

Nanoplastics and Neurodegeneration in ALS.

Plastic production, which exceeds one million tons per year, is of global concern. The constituent low-density polymers enable spread over large distances and micro/nano particles (MNPLs) induce organ toxicity via digestion, inhalation, and skin contact. Particles have been documented in all human tissues including breast milk. MNPLs, especially weathered particles, can breach the blood-brain barrier, inducing neurotoxicity. This has been documented in non-human species, and in human-induced pluripotent stem cell lines. Within the brain, MNPLs initiate an inflammatory response with pro-inflammatory cytokine production, oxidative stress with generation of reactive oxygen species, and mitochondrial dysfunction. Glutamate and GABA neurotransmitter dysfunction also ensues with alteration of excitatory/inhibitory balance in favor of reduced inhibition and resultant neuro-excitation. Inflammation and cortical hyperexcitability are key abnormalities involved in the pathogenic cascade of amyotrophic lateral sclerosis (ALS) and are intricately related to the mislocalization and aggregation of TDP-43, a hallmark of ALS. Water and many foods contain MNPLs and in humans, ingestion is the main form of exposure. Digestion of plastics within the gut can alter their properties, rendering them more toxic, and they cause gut microbiome dysbiosis and a dysfunctional gut-brain axis. This is recognized as a trigger and/or aggravating factor for ALS. ALS is associated with a long (years or decades) preclinical period and neonates and infants are exposed to MNPLs through breast milk, milk substitutes, and toys. This endangers a time of intense neurogenesis and establishment of neuronal circuitry, setting the stage for development of neurodegeneration in later life. MNPL neurotoxicity should be considered as a yet unrecognized risk factor for ALS and related diseases.

Efficiently tuning the electrical performance of PBTTT-C14 thin film via in situ controllable multiple precursors (Al2O3:ZnO) vapor phase infiltration

Conjugated polymer-based organic/inorganic hybrid materials become the current research frontier and show great potential to integrate flexible polymers and rigid solid materials, which have been widely used in the field of various flexible electronics and optical devices. In this study, based on the multiple vapor phase infiltration (VPI) process, various precursor molecules (diethylzinc DEZ, trimethylaluminum TMA, H2O) are applied for the in situ modification of PBTTT-C14 films. The conductivity of the PBTTT-C14/Al2O3:ZnO (AZO) film is significantly enhanced, and the maximum value of conductivity is 1.16 S cm−1, which is eight orders of magnitude higher than the undoped PBTTT-C14 thin film. Here, the change of morphologies and crystalline states are analyzed via SEM, AFM, and XRD. And the chemical changes during the VPI process of PBTTT-C14 are characterized through Raman, XPS, and UV–vis. During the AZO VPI process, the formation of new ZnS matrix in the polymer subsurface can generate new additional electron conduction pathways through the crosslinking of polymer chains with inorganic materials, and the addition of Al2O3 can bring about the increase of average grain size of ZnO crystals, which is also benefit to the conductivity increase of PBTTT-C14 thin film. Generally, the synergistic effect between the inorganic and polymer constituents results in the significantly enhancement of the conductivity of PBTTT-C14/AZO thin films.

Extrusion and thermoforming of poly(butylene succinate–co‐butylene adipate)/poly(3–hydroxybutyrate–co–3–hydroxyhexanoate) bio‐based blends for the fabrication of disposable packaging

AbstractThermoformed fossil‐based disposable packaging is widely used in everyday life but it represents a serious environmental problem, as it is often incorrectly dispersed or destined to landfills. Bio‐based and biodegradable materials can constitute and effective solution to this issue. Two different blends of poly(butylene succinate‐co‐butylene adipate) (PBSA) and Poly (3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBH) were studied as constituents for disposable packaging production. The blends were produced via twin screw extrusion. Sheets were cast extruded and then thermoformed into trays. A rheological, thermal and mechanical characterization was performed on compounds and manufacts. Both blends presented a good processability and interesting properties for packaging application, which can be tailored by varying the percentage of constituent polymers.

Flexible switch matrix addressable electrode arrays with organic electrochemical transistor and pn diode technology

Due to their effective ionic-to-electronic signal conversion and mechanical flexibility, organic neural implants hold considerable promise for biocompatible neural interfaces. Current approaches are, however, primarily limited to passive electrodes due to a lack of circuit components to realize complex active circuits at the front-end. Here, we introduce a p-n organic electrochemical diode using complementary p- and n-type conducting polymer films embedded in a 15-μm -diameter vertical stack. Leveraging the efficient motion of encapsulated cations inside this polymer stack and the opposite doping mechanisms of the constituent polymers, we demonstrate high current rectification ratios (105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{5}$$\\end{document}) and fast switching speeds (230 μs). We integrate p-n organic electrochemical diodes with organic electrochemical transistors in the front-end pixel of a recording array. This configuration facilitates the access of organic electrochemical transistor output currents within a large network operating in the same electrolyte, while minimizing crosstalk from neighboring elements due to minimized reverse-biased leakage. Furthermore, we use these devices to fabricate time-division-multiplexed amplifier arrays. Lastly, we show that, when fabricated in a shank format, this technology enables the multiplexing of amplified local field potentials directly in the active recording pixel (26-μm diameter) in a minimally invasive form factor with shank cross-sectional dimensions of only 50×8 μm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu m}^{2}$$\\end{document}.

Rate-enhancing PETase mutations determined through DFT/MM molecular dynamics simulations

The PETase enzyme from the bacterium Ideonella sakaiensis can degrade polyethylene terephthalate (PET) back into its polymeric constituents at room temperature, making it an ecologically friendly tool for reducing PET pollution.

Waterborne polymers and coatings from bio-based butenolides.

In the quest for sustainable paints and coatings, bio-based resources for the polymeric binder constituents are key. Recently, we introduced poly-butenolides as bio-based acrylate replacement for solventborne and 100% solids (UV-curing) coatings. Here, we report the first step towards aqueous poly-butenolide dispersions, enabling the use of this novel binder technology platform in waterborne coatings.

Radical Attack and Damage Mitigation in Hydrocarbon-Based Ionomers

In an operating polymer electrolyte fuel cell (PEFC) radical intermediates are formed as a result of the interaction of H2 and O2 on the surface of the Pt-based electrocatalyst. Of the various radical intermediates, •OH is of particular concern owing to its high oxidative strength, E°(•OH,H+/H2O) = 2.72 V) [1]. In PFSA ionomers, •OH reacts relatively slowly with the polymer and has a lifetime on the order of microseconds. This leaves sufficient time for additives, such as Ce(III), to scavenge the radicals and thus mitigate radical induced damage of the ionomer. In hydrocarbon-based ionomers containing aromatic units, •OH reacts within nanoseconds with polymer constituents [2]. Radical scavenging can therefore not be effective.In the development of alternative antioxidant strategies for hydrocarbon-based ionomers, it is crucial to elucidate polymer degradation mechanisms triggered by radical attack. In addition to studying the initial reactions of primary radicals, i.e. •OH, it is equally important to characterize the nature of the formed polymer intermediates, their lifetime, stability and reactivity. Sufficiently long-lived intermediates can be repaired by suitable additives, thereby restoring the original ionomer [3]. In the fuel cell, the thus protected membranes show a much lower rate of degradation in an accelerated stress test (AST) at open circuit voltage (OCV) [4].In this contribution, we provide an overview of methods to study reaction of radicals with small-molecule model compounds and ionomer constituents [5, 6]. The interaction of ionizing radiation (MeV electrons or photons) with water leads to the formation of radicals, such as •OH, at known rates. Water radiolysis can therefore be used to study the kinetics of radical attack and follow-up reactions as a function of pH, electron density of the aromatic ring, and presence of additives. Examples relevant to the acidic conditions in the proton exchange membrane (see Figure, Panel a) as well as the alkaline conditions in an anion exchange membrane (AEM) will be given. Moreover, the use of suitable antioxidants to mitigate degradation through the repair of intermediates will be discussed. Fuel cell tests with hydrocarbon-based membranes containing polymer-bound antioxidants will be shown (see Figure, Panel b) and prospects for long-term stability of non-fluorinated ionomers assessed.Figure caption: a) Analysis of the effect of Ce(III) ions on the extent of degradation of 1 mM of 4-cumenesulfonate (4CS) and 4-(tert-butyl)phenylsulfonate (BPS) at pH 0 (1 M H2SO4) in 1 mM H2O2 upon exposure to a radiolytic dose provided by a 60Co-source of 800 Gy (corresponding to a cumulative amount of •OH of 0.22 mM). ‘Excess degradation’ indicates the difference to the extent of degradation in the absence of Ce(III) and H2O2. Data for BPS from [5]. b) Ohmic resistance of single cells (average of several experiments) with partially fluorinated membrane containing a tethered crown ether with and without Ce(III) metal center during an accelerated stress test. Ion exchange capacity at the end of test was measured to represent remaining membrane state of health. Conditions: open circuit voltage (OCV), H2/O2, 80 °C, 2.5 bara, and 100% R.H. [4].

The Potential of Double-Faced Polyester-Viscose Woven Fabric as a Porous Substrate for Direct-Coating and Multilayer Concept.

Textile-based sensors fabricated using the direct-coating method are the appropriate choice to meet the aspects of flexibility, non-invasiveness, and lightness for continuous monitoring of the human body. The characteristics of the sensor substrate are directly influenced by factors such as the type of weave, thread fineness, fabric density, and the type of polymeric constituent fibers. The fabric used as the sensor substrate, fabricated using the direct-coating method, must be capable of retaining the electrode paste solution, which has higher viscosity, on one surface of the fabric to avoid short circuits during the fabrication process. However, during its application, this fabric should allow the easy passage of analyte solutions with low viscosity as much as possible. Hence, an appropriate fabric construction is required to serve as the substrate for textile-based sensors to ensure the success of the fabrication process and the effectiveness of the resulting sensor's performance. The development of the structural design of the fabric to be used as a substrate for non-invasive biosensors with a multilayer concept is carried out by weaving and sewing processes utilizing polyester-viscose fibers. During the production process, variations are applied, such as weft yarn density, the characterization of wetting time, absorption rate, maximum wetted radius, spreading speed, and accumulative one-way transport index. The most suitable fabric for use as a substrate for non-invasive biosensors with a multilayer concept, such as in this research, is a fabric with a weft thread density of 70 strands per inch, along with the addition of an analyte transfer thread configuration.

Graphite reinforced polymers for sealing geothermal wells

The objective of this study is to develop high-temperature resistant polymers for sealing geothermal wells by reinforcing inexpensive rubber with surface-treated graphite particles. We respectively treated two types of graphite particles, small-size lamellar graphite (SFG15) and graphite nanoplatelets (GNP), with a mixture of sulfuric and nitric acids. Through surface treatment, carboxylic groups are shown to be formed on graphite surfaces, and their oxygen contents are considerable. Polymer nanocomposites were made by compounding treated graphite particles with ethylene propylene diene monomer (EPDM). Uniform dispersion of treated graphite within developed polymer nanocomposites was achieved. Direct heating of prepared EPDM nanocomposites shows that treated SFG15 and GNP both enhance the temperature resistance of EPDM by over 80 °C. Also, the addition of treated graphite to EPDM remarkably enhances its storage modulus. Among all additive types and concentrations, 3.0 wt% of treated SFG15 performs the best in enhancing the storage modulus (by up to 215.83%) and reducing tan δ, namely the loss factor. Adding treated graphite significantly enhances the specific heat capacity of EPDM and remarkably increases the heat energy required to melt it. The onset degradation temperature of EPDM-SFG15 nanocomposites is 30 °C higher than that of plain EPDM. With these enhanced thermal and mechanical properties, the prepared nanocomposites are a promising candidate for the constituent polymer of seals applicable in geothermal wells.