Structure and Properties of Composite Perfluorinated Sulfonic Acid Membranes Modified with Cross-Linked Poly(vinyl alcohol)

The influence of the type of crosslinking agent for poly(vinyl alcohol) (PVA) (glutaraldehyde or epichlorohydrin) on the structure, morphology, thermal stability, and electrochemical properties of composite membranes based on the domestic perfluorinated sulfonic acid copolymer LSC, an analog of Nafion®, has been studied. The introduction of hydrophilic PVA has led to an increase in the moisture content of the membranes, which, taking into account the structural features, affects the proton conductivity. The presence of up to 5 wt % of cross-linked PVA in the composite membrane has not significantly changed the initial structure of LSC. The degree of crystallinity of the composite membranes upon the introduction of PVA has been slightly increased as compared to the original LSC membrane. With an increase in the amount of PVA in the composite, a domain surface morphology has appeared, its roughness being clearly increased. The increase in the PVA content in the LSC-PVA-GA samples has led to a noticeable increase in the temperature of thermal decomposition of sulfonic acid groups, while it has remained almost unchanged for the LSC-PVA-ECH samples.