Polyelectrolyte Membranes Research Articles

Regenerable Polyelectrolyte Membrane for Ultimate Fouling Control in Forward Osmosis.

This study demonstrated the feasibility of using regenerable polyelectrolyte membranes to ultimately control the irreversible membrane fouling in a forward osmosis (FO) process. The regenerable membrane was fabricated by assembling multiple polyethylenimine (PEI) and poly(acrylic acid) (PAA) bilayers on a polydopamine-functionalized polysulfone support. The resulting membrane exhibited higher water flux and lower solute flux in FO mode (with the active layer facing feed solution) than in PRO mode (with the active layer facing draw solution) using trisodium citrate as draw solute, most likely due to the unique swelling behavior of the polyelectrolyte membrane. Membrane regeneration was conducted by first dissembling the existing PEI-PAA bilayers using strong acid and then reassembling fresh PEI-PAA bilayers on the membrane support. It was found that, after the acid treatment, the first covalently bonded PEI layer and some realigned PAA remained on the membrane support, acting as a beneficial barrier that prevented the acid-foulant mixture from penetrating into the porous support during acid treatment. The water and solute flux of the regenerated membrane was very similar to that of the original membrane regardless of alginate fouling, suggesting an ultimate solution to eliminating the irreversible membrane fouling in an FO process. With a procedure similar to the typical membrane cleaning protocol, in situ membrane regeneration is not expected to noticeably increase the membrane operational burden but can satisfactorily avoid the expensive replacement of the entire membrane module after irreversible fouling, thereby hopefully reducing the overall cost of the membrane-based water-treatment system.

Enhanced anti-ultraviolet, anti-fouling and anti-bacterial polyelectrolyte membrane of polystyrene grafted with trimethyl quaternary ammonium salt modified lignin

A polyelectrolyte membrane with anti-ultraviolet, anti-fouling, and antibacterial abilities was prepared using trimethyl quaternary ammonium salt grafting lignin (QAL) and polystyrene (PS) at different ratios. Contact angle measurements indicated that the addition of QAL into the PS blending membrane altered the hydrophilicity by trimethyl quaternary ammonium groups and phenolic hydroxyl groups of QAL. Furthermore, the phenylpropane structural unit in the lignin formed double bonds by conjugating with carbonyl groups and formed p-π by conjugating with phenolic hydroxyl of side chains. For this reason, the produced composite membranes displayed high potential and commercial importance for absorbing ultraviolet light. The ultraviolet transmission values of all the PS/QAL blending membranes were close to zero ranging from 200 to 400 nm. The QAL5-PS membrane had less variation in the gas transmission rate (−6.388 cm3/m2/day/atm) than that of PS membrane (−32.9 cm3/m2/day/atm) after 5 circles of bovine serum albumin (BSA) fouling. The inhibition zone of the QAL5-PS membrane was 10.4 ± 0.06 mm, and almost zero for the neat PS membrane, indicating a much better antibacterial performance of the QAL-PS composite membranes than that of pure PS membranes.

Stabilized nanosystem of nanocarriers with an immobilized biological factor for anti-tumor therapy.

ObjectiveThe inadequate efficiency of existing therapeutic anti-cancer regiments and the increase in the multidrug resistance of cancer cells underscore the need to investigate novel anticancer strategies. The induction of apoptosis in tumors by cytotoxic agents produced by pathogenic microorganisms is an example of such an approach. Nevertheless, even the most effective drug should be delivered directly to targeted sites to reduce any negative impact on other cells. Accordingly, the stabilized nanosystem (SNS) for active agent delivery to cancer cells was designed for further application in local anti-tumor therapy. A product of genetically modified Escherichia coli, listeriolysin O (LLO), was immobilized within the polyelectrolyte membrane (poly(ethylenimine)|hyaluronic acid) shells of ‘LLO nanocarriers’ coupled with the stabilizing element of natural origin.Methods and resultsThe impact of LLO was evaluated in human leukemia cell lines in vitro. Correspondingly, the influence of the SNS and its elements was assessed in vitro. The viability of targeted cells was evaluated by flow cytometry. Visualization of the system structure was performed using confocal microscopy. The membrane shell applied to the nanocarriers was analyzed using atomic force microscopy and Fourier transform infrared spectroscopy techniques. Furthermore, the presence of a polyelectrolyte layer on the nanocarrier surface and/or in the cell was confirmed by flow cytometry. Finally, the structural integrity of the SNS and the corresponding release of the fluorescent solute listeriolysin were investigated.ConclusionThe construction of a stabilized system offers LLO release with a lethal impact on model eukaryotic cells. The applied platform design may be recommended for local anti-tumor treatment purposes.

Phosphonic acid functionalized poly(pentafluorostyrene) as polyelectrolyte membrane for fuel cell application

Abstract In this paper we introduce polyelectrolyte membranes based on phosphonated poly(pentafluorostyrene) (PPFS) and their performances in a fuel cell. The polyelectrolytes were obtained via partial phosphonation of PPFS varying the phosphonation degree from 17 to 66%. These membranes showed a high resistance to temperature (Tdecomp. = 355–381 °C) and radical attack (96–288 h in Fenton's test). A blend membrane consisting of 82 wt% fully phosphonated PPFS and 18 wt% poly(benzimidazole) is compared to the 66% phosphonated membrane having similar ion-conductivity (σ = 57 mS cm−1 at 120 °C, 90% RH). In the fuel cell the blend showed the best performance reaching 0.40 W cm−2 against 0.34 W cm−2 for the 42 wt% phosphonated membrane and 0.35 W cm−2 for Nafion 212. Furthermore, the blend maintained its operation at potentiostatic regime (0.5 V) for 620 h without declining in its performance. The highest power density of 0.78 W cm−2 was reached for the blend with a thickness of 15 μm using humidified oxygen (RH > 90%) at the cathode side. The switch from humidified to dry gasses during operation reduced the current density down to 0.6 A cm−2, but the cell maintained under operation for 66 h.

Porous Boron Carbon Nitride Nanosheets as Efficient Metal-Free Catalysts for the Oxygen Reduction Reaction in Both Alkaline and Acidic Solutions

Carbon materials have become a hot topic as potential substitutes for Pt/C catalysts for the oxygen reduction reaction (ORR). However, most of them exhibit their catalytic activities only in alkaline solutions, which severely limits their application in polyelectrolyte membrane fuel cells. To address this issue, here porous boron carbon nitride (BCN) nanosheets are fabricated by a facile and efficient polymer sol–gel method, which involves the annealing of polyvinylic akohol (PVA), boric acid, guanidine, and poly(ethylene oxide-co-propylene oxide) (P123) gel mixtures. The as-prepared porous BCN nanosheets possess a high surface area of 817 m2/g and display impressive ORR catalytic performance in both alkaline and acidic media, rivalling that of commercial Pt/C and other recently reported carbon materials. Importantly, the resulting metal-free catalysts exhibit much greater durability and higher methanol tolerance in both alkaline and acidic environments. This study provides a new insight into metal-free ORR catalysts that are practicable in industrial fuel cells.

High-Resolution Coarse-Grained Model of Hydrated Anion-Exchange Membranes that Accounts for Hydrophobic and Ionic Interactions through Short-Ranged Potentials.

Molecular simulations provide a versatile tool to study the structure, anion conductivity, and stability of anion-exchange membrane (AEM) materials and can provide a fundamental understanding of the relation between structure and property of membranes that is key for their use in fuel cells and other applications. The quest for large spatial and temporal scales required to model the multiscale structure and transport processes in the polymer electrolyte membranes, however, cannot be met with fully atomistic models, and the available coarse-grained (CG) models suffer from several challenges associated with their low-resolution. Here, we develop a high-resolution CG force field for hydrated polyphenylene oxide/trimethylamine chloride (PPO/TMACl) membranes compatible with the mW water model using a hierarchical parametrization approach based on Uncertainty Quantification and reference atomistic simulations modeled with the Generalized Amber Force Field (GAFF) and TIP4P/2005 water. The parametrization weighs multiple properties, including coordination numbers, radial distribution functions (RDFs), self-diffusion coefficients of water and ions, relative vapor pressure of water in the solution, hydration enthalpy of the tetramethylammonium chloride (TMACl) salt, and cohesive energy of its aqueous solutions. We analyze the interdependence between properties and address how to compromise between the accuracies of the properties to achieve an overall best representability. Our optimized CG model FFcomp quantitatively reproduces the diffusivities and RDFs of the reference atomistic model and qualitatively reproduces the experimental relative vapor pressure of water in solutions of tetramethylammonium chloride. These properties are of utmost relevance for the design and operation of fuel cell membranes. To our knowledge, this is the first CG model that includes explicitly each water and ion and accounts for hydrophobic, ionic, and intramolecular interactions explicitly parametrized to reproduce multiple properties of interest for hydrated polyelectrolyte membranes. The CG model of hydrated PPO/TMACl water is about 100 times faster than the reference atomistic GAFF-TIP4P/2005 model. The strategy implemented here can be used in the parametrization of CG models for other substances, such as biomolecular systems and membranes for desalination, water purification, and redox flow batteries. We anticipate that the large spatial and temporal simulations made possible by the CG model will advance the quest for anion-exchange membranes with improved transport and mechanical properties.

Molecular dynamics study of confined structure and diffusion of hydrated proton in Hyfion® perfluorosulfonic acid membranes

In polyelectrolyte membranes, hydrated protons and proton conductive channels have cooperative effect on proton conductivity, the mechanism of which is believed to involve the structure of hydrated proton being deformed to adapt the confining channel. To investigate the dependence of the structural and dynamical properties of hydrated protons in Hyfion® perfluorosulfonic acid membranes with various water uptake values on the channel size, a series of molecular dynamics simulations based on an all-atom force field were conducted. The water uptake dependence of the hydrated proton diffusivity determined from our simulations was consistent with the experimental results in literature, which verified the simulation systems. A probability distribution of the hydrated proton complex is proposed to characterize the confinement effect of the proton conductive channel on the hydrated proton structure in the membranes with different morphologies. By means of local structural properties and pair-potential energies, a reasonable hydrogen bond criterion was employed to characterize the structures of the hydrated proton complexes. It was found that the nanochannels confined the structure of the hydrated proton complex and that confined complexes of H9O4+, H7O3+ and H5O2+ were dominant. Weakening the confinement by increasing the channel size was beneficial for the formation of the H9O4+ complex, the probability distribution of which gradually became plateau. Thus, H9O4+ can be considered the stable structure of the confined hydrated proton complex in polymer electrolyte membranes. This work is helpful in understanding the relationship between the structure of the confined hydrated proton and the proton conductive channel. It also provides potential guidance for improving the membrane performance in fuel cell.

Spray-assisted biomineralization of a superhydrophilic water uptake layer for enhanced pervaporation dehydration

The membrane surface wettability is one of the most important factors influencing the solution-diffusion-controlled pervaporation process. In this work, a novel conceptual methodology for the construction of a superhydrophilic water uptake layer is proposed to overcome the limitation of trade-off effects. Rapid implementation of this strategy is possible by spray-assisted biomineralization of calcium carbonate (CaCO3) onto a (poly(acrylic acid)/poly(ethyleneimine))n/polyacrylonitrile ((PAA/PEI)n/PAN) membrane. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a hierarchical lotus CaCO3 layer with calcite crystals on the outermost layer. The water contact angle dramatically decreased from 74° to 4.2° after biomineralizing CaCO3 micro-nano-particles. In the pervaporation separation of ethanol/water mixtures, the water content could be enriched from 5wt% to 98.8wt% while the permeate flux reached 1317g/(m2h), which is almost five times that of a pure polyelectrolyte membrane without biomineralizing CaCO3. This suggests that the CaCO3 water uptake layer plays a very important role in achieving high flux. These results indicate that biomineralization of micro-nano-particles is a facile strategy to fabricate a superhydrophilic surface and, in turn, improve the membrane performance.

Immobilization of the Pyrroloquinoline Quinone Dependent Alcohol Dehydrogenase with Polyelectrolyte Membranes on the Glassy Carbon Electrode

Introduction Quinoproteins containig pyrroloquinoline quinone (PQQ) catalyze a dehydrogenation of the primary and the secondly hydroxyl group in alcohols or sugars. These are interesting not only in their role in physiological function but also in biotechnological approaches in the fields of bioelectronics, such as biofuel cells and biosensors. In a previous study, PQQ alcohol dehydrogenase from Pseudomonas putida KT2440 (PpADH) was overexpressed in the methylotrophic yeast Pichia pastoris for a bioanode [1]. This enzyme has broad substrate selectivity towards various alcohols and aldehydes, and can catalyze the two-step oxidation of alcohols. Thus, it is expected to develop a new bioanode that the two-step oxidation of ethanol to acetate using only PpADH. Immobilization of enzymes on electrodes is critical for the development of the enzymatic bioanode. Some polymeric materials were utilized for the modification of the enzyme electrodes so far. In this study, we have optimized the immobilization of PpADH on the glassy carbon electrodes using polyelectrolyte membranes. Experimental Recombinant PpADH was heterologously expressed in P. pastoris and purified as described previously [1]. Cationic polymers; polyethyleneimine (PEI) and poly (diallyldimethylammonium chloride) (PDDA) and an anionic polymer; poly(sodium 4-styrenesulfonate) (PSS) were used to immobilize purified PpADH on the glassy carbon electrodes (GCE). Three types of single polyelectrolyte modified electrodes were prepared; PEI (A), PDDA (B), and PSS (C). 0.5 wt % PEI, PDDA, or PSS and 9 µM the enzyme aqueous solution were dropped onto a pretreated GCE. After drying at least an hour at room temperature, the single polyelectrolyte modified electrodes with PpADH were obtained. Further, four types of multi polyelectrolyte modified electrodes were prepared by combining different polyelectrolytes; electrode (A) with PSS (D), electrode (B) with PSS (E), electrode (C) with PEI (F), and electrode (C) with PDDA (G). All electrochemical measurements were performed using a conventional three-electrode cell containing GCEs modified with PpADH and polyelectrolytes as working electrodes, a platinum wire as a counter electrode, and an Ag/AgCl (3 M NaCl) electrode as a reference electrode. Cyclic voltammetry (CV) was performed in the 50 mM CHES buffer (pH 9.0) containing 1 mM CaCl2, 30 mM ethylamine, and 100 µM aminoferrocene as an electron mediator (Fig 1). Results and Discussion The cyclic voltammograms of aminoferrocene exhibited reversible responses at -80 mV (E1/2) without substrate for all polyelectrolyte modified electrodes. The catalytic currents of ethanol oxidation by PpADH were observed for electrodes (A), (B), and (C). However, when the number of the cycles was increased, the catalytic currents were decreased. This result suggested that PpADH was removed from the electrodes. To prevent the release of PpADH, the modified electrodes with PpADH were prepared by combining different polyelectrolytes. Catalytic currents of ethanol oxidation of PpADH were also observed in electrodes (D), (E), (F), and (G). Figure 2 shows the current densities of these electrodes. While the current density of electrode (F) was the lowest in all electrodes, the current densities of the other electrodes were about the same (18 µA/cm2) at 0.3 V of the first cycle. However, the catalytic current of electrode (D) at the fifth cycle was considerably decreased to 35 % (6.4 µA/cm2). The catalytic currents of (E) and (G) electrodes slightly decrease to 73 % (13.2 µA/cm2) and 89 % (17.2 µA/cm2), respectively. The current density of electrode (G) was the highest in all electrodes at the fifth cycle. These results indicated that the electrostatic interaction between PSS and PDDA is effective to immobilize PpADH on the electrodes. The order to add PSS and PDDA is also important. PSS and PpADH should be added on the electrode firstly and then PDDA should be added after drying. Reference [1] K. Takeda et al., Bioelectrochemistry 94 (2013) 75-78 Figure 1

In Situ Growth and Characterization of Metal Oxide Nanoparticles within Polyelectrolyte Membranes.

This study describes a novel approach for the in situ synthesis of metal oxide-polyelectrolyte nanocomposites formed via impregnation of hydrated polyelectrolyte films with binary water/alcohol solutions of metal salts and consecutive reactions that convert metal cations into oxide nanoparticles embedded within the polymer matrix. The method is demonstrated drawing on the example of Nafion membranes and a variety of metal oxides with an emphasis placed on zinc oxide. The in situ formation of nanoparticles is controlled by changing the solvent composition and conditions of synthesis that for the first time allows one to tailor not only the size, but also the nanoparticle shape, giving a preference to growth of a particular crystal facet. The high-resolution TEM, SEM/EDX, UV-vis and XRD studies confirmed the homogeneous distribution of crystalline nanoparticles of circa 4 nm and their aggregates of 10-20 nm. The produced nanocomposite films are flexible, mechanically robust and have a potential to be employed in sensing, optoelectronics and catalysis.

In Situ Growth and Characterization of Metal Oxide Nanoparticles within Polyelectrolyte Membranes

AbstractThis study describes a novel approach for the in situ synthesis of metal oxide–polyelectrolyte nanocomposites formed via impregnation of hydrated polyelectrolyte films with binary water/alcohol solutions of metal salts and consecutive reactions that convert metal cations into oxide nanoparticles embedded within the polymer matrix. The method is demonstrated drawing on the example of Nafion membranes and a variety of metal oxides with an emphasis placed on zinc oxide. The in situ formation of nanoparticles is controlled by changing the solvent composition and conditions of synthesis that for the first time allows one to tailor not only the size, but also the nanoparticle shape, giving a preference to growth of a particular crystal facet. The high‐resolution TEM, SEM/EDX, UV‐vis and XRD studies confirmed the homogeneous distribution of crystalline nanoparticles of circa 4 nm and their aggregates of 10–20 nm. The produced nanocomposite films are flexible, mechanically robust and have a potential to be employed in sensing, optoelectronics and catalysis.

Water Diffusion Dependence on Amphiphilic Block Design in (Amphiphilic-Hydrophobic) Diblock Copolymer Membranes.

Polyelectrolyte membranes (PEMs) are applied in polyelectrolyte fuel cells (PEFC). The proton conductive pathways within PEMs are provided by nanometer-sized water containing pores. Large-scale application of PEFC requires the production of low-cost membranes with high proton conductivity and therefore good connected pore networks. Pore network formation within four alternative model diblock (hydrophobic_amphiphilic) copolymers in the presence of water is studied by dissipative particle dynamics. Each hydrophobic block contains 50 consecutively connected hydrophobic (A) fragments, and amphiphilic blocks contain 40 hydrophobic A beads and 10 hydrophilic C beads. For one amphiphilic block the C beads are distributed uniformly along the backbone. For the other architectures C beads are located at the end of the side chains attached at regular intervals along the backbone. Water diffusion through the pores is modeled by Monte Carlo tracer diffusion through mapped morphologies. Diffusion is highest for the grafted architectures and increases with increase of length of the side chains. A consistent picture emerges in which diffusion strongly increases with the value of ⟨Nbond⟩ within the amphiphilic block, where ⟨Nbond⟩ is the average number of bonds between hydrophobic A beads and the nearest C bead.

Chitosan/Chondroitin Sulfate Membranes Produced by Polyelectrolyte Complexation for Cartilage Engineering.

Membranes made of chitosan (CHT) and chondroitin sulfate (CS) are herein presented using a polyelectrolyte complexation sedimentation/evaporation method. The membranes present high roughness and heterogeneous morphology induced by salt crystals. Exposing the membranes to different salt concentrations induces saloplastic behavior, as shown by an increasing water absorption and decreasing stiffness while exposed to increasing concentrations of salt. Establishing contact between two parts of a cut membrane leads to their self-adhesion and maintenance of their stretching ability. The membranes sustain the adhesion of ATDC5 prechondrocyte cells, inducing their rearrangement in cellular aggregates typical of chondrogenesis, and the expression of cartilage markers. Impregnated TGF-β3 remains loaded after 14 days of incubation, releasing only 1.2% of its total loaded mass. CHT/CS polyelectrolyte membranes are here shown as suitable candidates for the biomedical field, namely, for cartilage regeneration.

Development of Novel Phosphorylated Cellulose Acetate Polyelectrolyte Membranes for Direct Methanol Fuel Cell Application

Development of Novel Phosphorylated Cellulose Acetate Polyelectrolyte Membranes for Direct Methanol Fuel Cell Application

Novel approach for the preparation of ionic liquid/imidazoledicarboxylic acid modified poly(vinyl alcohol) polyelectrolyte membranes

This paper first time describes the preparation of the novel ionic proton exchange membrane (ILPEM). Ionic liquid, 1-butyl-3-methylimidazol-3-ium hexafluorophosphate, has immobilized into 4,5-imidazoledicrarboxyic acid (IDC) modified PVA matrix. ILPEMs optimized by measuring the swelling properties at varying cross-link time. Membranes were characterized to evaluate functional groups, % swelling, gel content, molecular weight between cross-link, cross-link density, thermal stability and proton conductivity. The single cell performances of the membrane evaluated using a microbial fuel cell set-up (Biogenerator). Ionic membranes exhibited higher thermal stability, and proton conductivity of the membrane obtained was in order of 2.8–3.6mScm−1. The Biogenerator equipped with ILPEM showed maximum current density of 1260mAcm−2 and power density of 245mWcm−2, which was higher than any of the existing conventional cathodic microbial fuel cell.

Is Fine-Grained Simulation Able to Propose New Polyelectrolyte Membranes?

An extensive understanding in the molecular motions that occur in Nafion® should lead to important development of improved proton exchange membrane for use in fuel cells (PEMFC). As water molecules are added in the system, changes within the Nafion® chain definitely take place. To visualize such a process, molecular dynamics is especially useful. Can information gained at this level of details be useful to propose new molecules, with ultimately better physical properties, such as higher proton conductivity? For this purpose, we first computed non-bond parameters stemming from the study of the trifluorosufonic acid. They are inserted in the pcff force field. We then applied the procedure developed in our lab to extract the glass transition temperature of Nafion® with different water uptakes. The plasticization effect is first confirmed, fostering a molecular analysis. The particular behavior of the sulfur-sulfur distance is revealed, guiding the design of new monomers.

Improvement in the performance of low temperature H2–O2 fuel cell with chitosan–phosphotungstic acid composite membranes

Free-standing chitosan/phosphotungstic acid polyelectrolyte membranes, prepared by ionotropic gelation on alumina porous supports, were employed as proton conductor in low temperature H2–O2 fuel cell. A drying step on glass substrate was introduced in the fabrication procedure to reduce shrinkage and consequent corrugation. Membranes were tested with electrodes prepared according to different procedures and with two different Pt loadings, namely 0.5 and 1 mg cm−2. Both the investigated kinds of electrodes allowed to get very promising power peaks of 550 mW cm−2 in spite of the different Pt content. The polarization curves and the electrochemical impedance spectra suggest that water management is crucial in determining the overall cell performance.

Layer-by-layer self-assembly of polycation/GO nanofiltration membrane with enhanced stability and fouling resistance

Polyelectrolyte multilayering is a good technique used to fabricate nanofiltration (NF) membranes. However, the stability and fouling resistance of the polyelectrolyte membranes should be improved for industrial application. In this study, graphene oxide (GO) nanosheets were assembled with polycation to form a multilayer on a polyacrylonitrile substrate via a layer-by-layer self-assembly strategy. The migration and rearrangement of the polyelectrolyte chain were restricted because of the confinement effect of a neighboring GO nanosheet layer. Therefore, the anti-swelling property of the polycation/GO multilayer membrane was enhanced, which resulted in a more stable performance. The fouling resistance of the multilayer membrane was also improved because of the anti-fouling capability of the GO nanosheets. The polycation/GO multilayer membrane was used to remove dye from water. During the separation of methyl blue molecule from water at 5 bar, the flux and retention rate of the obtained multilayer membrane could reach 6.42 kg m−2 h−1 bar−1 and 99.2%, respectively. Compared with a pure polyelectrolyte multilayer membrane, the separation performance, stability, and fouling resistance of the polycation/GO membranes were significantly enhanced. The polycation/GO multilayer membrane can be potentially used to fabricate NF membranes because it is cost efficient and GO nanosheets can be produced in a large scale.

Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane.

Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

Structural and conformational properties of polybenzimidazoles in melt and phosphoric acid solution: a polyelectrolyte membrane for fuel cells

In this work, a single chain conformational analysis of poly[2,2′-(p-phenylene)-5,5′-bibenzimidazole (PBI) and poly(2,5-benzimidazole) (ABPBI) in melt as well as in PA was performed using classical molecular dynamics simulations.