Poly(vinylbenzyl sulfonic acid)-grafted poly(ether ether ketone) membranes

Abstract

In this study, an aromatic hydrocarbon based polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)-grafted poly(ether ether ketone) (PEEK-g-PVBSA), has been prepared by the simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a PEEK film and subsequent sulfonation. Each chemical conversion was monitored by FT-IR and SEM–EDX instruments. The physicochemical properties including IEC, water uptake, proton conductivity, and methanol permeability of the prepared membranes were also investigated and found that the values of these properties increase with the increase of degree of grafting. It was observed that the IEC values of the prepared PEEK-g-PVBSA membranes with 32%, 58%, and 80% DOG values were 0.50, 1.05, and 1.22meq/g while the water uptakes were 14%, 20%, and 21%, respectively. The proton conductivities (0.0272–0.0721S/cm at 70°C) were found to be somewhat lower than Nafion 212 (0.126S/cm at 70°C) at a relative humidity of 90%. However, the prepared membranes showed a considerably lower methanol permeability (0.61–1.92×10−7cm2/s) compared to a Nafion 212 membrane (5.37×10−7cm2/s).