Proton conduction in new polymer hydrogel films consisting of crosslinking partially phosphorylated poly(vinyl alcohol)s

Abstract

New polymer hydrogel films based on partially phosphorylated poly(vinyl alcohol)s (P-PVAs) have been prepared, and proton conduction in these hydrogel films has been investigated. These hydrogel films (GP-PVA films) consist of P-PVA crosslinked by glutaraldehyde and have different degrees of crosslinking and phosphorylation (DP). The proton conductivities of a series of GP-PVA hydrogel films increased with increasing crosslinking degree and DP and the temperature dependence of the proton conductivities became small. In particular, a GP-PVA hydrogel film with high crosslinking and DP had very little temperature dependence and exhibited a conductivity of ca. 4.0×10^-2 S cm^-1 at 40°C. These results were attributed to the fact that a large hydration region was formed by contacts between hydration regions around phosphoric acid groups. Namely, proton conduction took place in the large hydration region and was independent of segment motion of the polymer backbone, leading to high proton conductivity and low temperature dependence.