Highly Conductive Polyelectrolyte Membranes Poly(vinyl alcohol)/Poly(2-acrylamido-2-methyl propane sulfonic acid) (PVA/PAMPS) for Fuel Cell Application

In this study, chemically cross-linked PVA/PAMPS membranes have been prepared to be used in direct methanol fuel cells (DMFCs). The structural properties of the resultant membrane were characterized by use FTIR and SEM. Additionally, their thermal stability was assessed using TGA. Moreover, the mechanical properties and methanol and water uptake of membrane was studied. The obtained FTIR of PVA/PAMPS membranes revealed a noticeable increase in the intensity of adsorption peaks appearing at 1062 and 1220 cm−1, which correspond to sulfonic groups with the increasing proportion of PAMPS. The thermograms of these polyelectrolyte membranes showed that their thermal stability was lower than that of PVA membrane, and total weight loss gradually decreased with increasing the PAMPS. Additionally, the functional properties and efficiency of these polyelectrolyte membranes were significantly improved with increasing PAMPS proportion in these blends. The IEC of polymer blend membrane prepared using PVA/PAMPS ratio of 1:1 was 2.64 meq/g. The same membrane recorded also a methanol permeability coefficient of 2.5 × 10−8 cm2/s and thus, its efficiency factor was 4 × 105 greater than that previously reported for the commercial polyelectrolyte membrane, Nafion® (2.6 × 105). No significant increase in this efficiency factor was observed with a further amount of PAMPS. These results proved that the PVA:PAMPS ratio of 1:1 represents the optimum mass ratio to develop the cost-effective and efficient PVA/PAMPS blend membranes for DMFCs applications.

The Impact of Chemical-Mechanical Ex Situ Aging on PFSA Membranes for Fuel Cells

A proton-exchange membrane fuel cell (PEMFC) constitutes today one of the preferred technologies to promote hydrogen-based alternative energies. However, the large-scale deployment of PEMFCs is still hampered by insufficient durability and reliability. In particular, the degradation of the polyelectrolyte membrane, caused by harsh mechanical and chemical stresses experienced during fuel cell operation, has been identified as one of the main factors restricting the PEMFC lifetime. An innovative chemical-mechanical ex situ aging device was developed to simultaneously expose the membrane to mechanical fatigue and an oxidizing environment (i.e., free radicals) in order to reproduce conditions close to those encountered in fuel cell systems. A cyclic compressive stress of 5 or 10 MPa was applied during several hours while a degrading solution (H2O2 or a Fenton solution) was circulated in contact with the membrane. The results demonstrated that both composite Nafion™ XL and non-reinforced Nafion™ NR211 membranes are significantly degraded by the conjoint mechanical and chemical stress exposure. The fluoride emission rate (FER) was generally slightly lower with XL than with NR211, which could be attributed to the degradation mitigation strategies developed for composite XL, except when the pressure level or the aging duration were increased, suggesting a limitation of the improved durability of XL.

Preparation and Chemical Protective Clothing Application of Sulfonated Poly(2,6-dimethyl-1,4-phenyleneoxide)

The preparation of chemical protective clothing (CPC) materials with excellent protective performance and physiological comfort have always been a global challenge. The selective permeability of organic matter and water shown by polyelectrolyte membranes in fuel cells and other applications provides ideas for solving this problem. This research focused on sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), a polyelectrolyte membrane material with excellent performance, and carried out different counter-ion substitutions to prepare a series of membrane materials, and their mechanical properties, contact angle, permeability, and selectivity. The performance was tested and compared with Nafion, a typical commercial membrane. The results show that the SPPO membrane has the potential of CPC application and the performance of the membranes can be controlled by the simple method of adjusting the counter-ion exchange of the membrane material.

Preparation of Alkaline Polyelectrolyte Membrane Based on Quaternary Ammonium Salt–Modified Cellulose and Its Application in Zn–Air Flexible Battery

In this study, a type of alkaline solid polyelectrolyte (ASPE) membrane was developed via the introduction of microcrystalline cellulose (MCC) and its modified product (QMCC) into the polyvinyl alcohol (PVA) matrix. In this process, green NaOH/urea-based solvent was used to achieve a good dispersion of MCC in the PVA matrix; meanwhile, the OH− groups in the NaOH/urea-based solvent provided an alkaline environment for good ion conductivity. Compared to the MCC-incorporated ASPE, further improved conductivity was achieved when the MCC was modified with quantitative quaternary ammonium salt. TGA showed that the addition of QMCC improved the water retention of the matrix, which was beneficial to the OH− conduction in the system. Compared to the control (50 mS cm−1), a maximum conductivity of 238 mS cm−1 was obtained after the incorporation of QMCC in the PVA matrix. Moreover, the tensile strength of the polymer electrolyte were also significantly increased with the addition of QMCC. Finally, this developed ASPE membrane was used in assembling a flexible Zn–air battery and showed a promising potential in the development of flexible electronic devices.

Synthesis of Poly(2-Acrylamido-2-Methylpropane Sulfonic Acid) and its Block Copolymers with Methyl Methacrylate and 2-Hydroxyethyl Methacrylate by Quasiliving Radical Polymerization Catalyzed by a Cyclometalated Ruthenium(II) Complex

The first example of quasiliving radical polymerization and copolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) without previous protection of its strong acid groups catalyzed by [Ru(o-C6H4-2-py)(phen)(MeCN)2]PF6 complex is reported. Nuclear magnetic resonance (RMN) and gel permeation chromatography (GPC) confirmed the diblock structure of the sulfonated copolymers. The poly(2-acryloamido-2-methylpropanesulfonic acid)-b-poly(methyl methacrylate) (PAMPS-b-PMMA) and poly(2-acryloamido-2-methylpropanesulfonic acid)-b-poly(2-hydroxyethylmethacrylate) (PAMPS-b-PHEMA) copolymers obtained are highly soluble in organic solvents and present good film-forming ability. The ion exchange capacity (IEC) of the copolymer membranes is reported. PAMPS-b-PHEMA presents the highest IEC value (3.35 mmol H+/g), but previous crosslinking of the membrane was necessary to prevent it from dissolving in aqueous solution. PAMPS-b-PMMA exhibited IEC values in the range of 0.58–1.21 mmol H+/g and it was soluble in methanol and dichloromethane and insoluble in water. These results are well correlated with both the increase in molar composition of PAMPS and the second block included in the copolymer. Thus, the proper combination of PAMPS block copolymer with hydrophilic or hydrophobic monomers will allow fine-tuning of the physical properties of the materials and may lead to many potential applications, such as polyelectrolyte membrane fuel cells or catalytic membranes for biodiesel production.

Polyelectrolyte Membrane with Hydroxyapatite and Silver Nanoparticles as a Material for Modern Wound Dressings

Modern wound dressings not only play a covering role but also facilitate the function of the wound, contributing to a faster healing process. In this paper, we present a polyelectrolyte system with nanosized elements that could stimulate the growth of eukaryotic cells while providing antimicrobial properties, which may be recommended as a potential dressing material. The proposed platform consisted of polyethyleneimine, hydroxyapatite, and silver nanoparticles and was characterized using various macroscopic techniques. The constructed membrane scaffold was evaluated with immobilized WEHI 164 cells as a model system for cells sustained at the interface of bone and skin. Moreover, the bacteriostatic function of the designed membrane material was evaluated using different bacterial strains.

Dissipative Particle Dynamics Modeling of Polyelectrolyte Membrane–Water Interfaces

Previous experiments of water vapor penetration into polyelectrolyte membrane (PEM) thin films have indicated the influence of the water concentration gradient and polymer chemistry on the interface evolution, which will eventually affect the efficiency of the fuel cell operation. Moreover, PEMs of different side chains have shown differences in water cluster structure and diffusion. The evolution of the interface between water and polyelectrolyte membranes (PEMs), which are used in fuel cells and flow batteries, of three different side-chain lengths has been studied using dissipative particle dynamics (DPD) simulations. Higher and faster water uptake is usually beneficial in the operation of fuel cells and flow batteries. The simulated water uptake increased with the increasing side chain length. In addition, the water uptake was rapid initially and slowed down afterwards, which is in agreement with the experimental observations. The water cluster formation rate was also found to increase with the increasing side-chain length, whereas the water cluster shapes were unaffected. Water diffusion in the membranes, which affects proton mobility in the PEMs, increased with the side-chain length at all distances from the interface. In conclusion, side-chain length was found to have a strong influence on the interface water structure and water penetration rates, which can be harnessed for the better design of PEMs. Since the PEM can undergo cycles of dehydration and rehydration, faster water uptake increases the efficiency of these devices. We show that the longer side chains with backbone structure similar to Nafion should be more suitable for fuel cell/flow battery usage.