This article reports on the synthesis and structural characterization of films containing hydrogenated poly(butadiene-styrene) block copolymer/ethylene-propylene terpolymer/polypropylene, hydrogenated poly(butadiene-styrene) block copolymer/ethylene-propylene terpolymer/polystyrene, and hydrogenated poly(butadiene-styrene block copolymer/ethylene-propylene terpolymer/silica) crosslinked with peroxides and heterogeneously sulfonated. Sulfonation of the different polymeric systems gives rise to materials with high proton conductivity and great dimensional stability, suited for application in a variety of electronic devices. (C) 2004 Wiley Periodicals, Inc.