Proton-conductive inorganicorganic hybrid intermediate-temperature membranes were prepared from 3-glycidoxypropyltrimethoxysilane (GPTMS) and 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) by solgel process. To prevent the leaching out of phosphonic acid, triethylamine was used as catalyst to promote the reaction of HEDPA and GPTMS to immobilize phosphonic acid groups. Fourier transform infrared spectra revealed that phosphonic acid groups of HEDPA were chemically bounded to organosiloxane network as a result of the reaction of P?OH of HEDPA and epoxy ring of GPTMS. TG-DSC results indicated that the hybrid membranes were thermally stable up to 250 degrees C. The proton conductivity of the hybrid membranes increased with temperature from 30 to 130 degrees C. The proton conductivity of hybrid membrane with the molar ratio of GPTMS/HEDPA = 2/1 can reach up to 1.0 x 10-3 S/cm under anhydrous condition at 130 degrees C, which reveals that this membrane is a promising proton exchange membrane for intermediate-temperature proton exchange membrane fuel cell. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012