Polymer electrolyte hybrid membranes prepared by radiation grafting of p-styryltrimethoxysilane into poly(ethylene-co-tetrafluoroethylene) films

In order to prepare a polymer electrolyte hybrid membrane with both high proton conductivity and high thermal stability, an aromatic vinyl monomer having a trimethoxysilyl group, namely p-styryltrimethoxysilane, was first grafted into poly(ethylene-co-tetrafluoroethylene) (ETFE) film by γ-ray preirradiation. The p-styryltrimethoxysilane-grafted film was then sulfonated to attach sulfonic acid groups onto the aromatic rings of the graft chains, and finally hydrolyzed and condensed to introduce silane-crosslinking between the graft chains. Thus, a crosslinked proton-conducting polymer electrolyte hybrid membrane was obtained. The preparation conditions for grafting and sulfonation, and the properties of the resulting polymer electrolyte membrane, such as ion exchange capacity, proton conductivity, water uptake, and thermal stability were investigated with respect to its application in fuel cells. It is concluded that the properties of the new p-styryltrimethoxysilane-grafted polymer electrolyte hybrid membrane are comparable to Nafion, and are superior to a styrene-grafted membrane.