Proton conductivity in siloxane and ormosil ionomers prepared using mild sulfonation methodologies

Mild sulfonation procedures have been developed for preparation of proton (H+) conducting siloxane and ormosil ionomers. Method A involves mild oxidation (with 3-chloroperoxybenzoic acid) of mercapto (SH) sidechains in siloxane polymers to yield sulfonic acid (SO3H) groups. Method B involves the formation of copolymers of a methacrylate-containing siloxane and a novel protected styrene sulfonated precursor (NISS, 1,2,3,4-tetrahydro-1-naphthylideneamino p-styrenesulfonate), with subsequent deprotection by ultraviolet irradiation and acidification. Proton conductivities of materials from these two routes have been studied as functions of temperature and of relative humidity. Conductivities follow an empirical Arrhenius law and increase markedly in moist atmospheres. Conductivities at elevated temperatures are at least as high as those for Nafion® membranes under similar conditions.