One type of negatively charged alkoxysilane, that is, sulfonated 3-(mercaptopropyl)trimethoxysilane (SMPTS), has been developed from 3-(mercaptopropyl)trimethoxysilane (MPTS) and hydrogen peroxide. SMPTS is used to modify sulfonated poly(ether sulfone) (SPES) through in situ sol-gel process. The membranes with proper SMPTS dosage show enhanced ion exchange capacity (IEC), hydrophilicity, mechanical strength, chemical stability, and proton conductivity, which prove that SMPTS is an effective modifier for preparing proton-exchange hybrid membranes. With MPTS of 5-20%, the hybrid membranes exhibit IEC 1.34-1.50 mmol g(-1), thermal stability 264-316 degrees C, and proton conductivity 0.0015-0.0102 S cm(-1) and thus recommended for potential application in fuel cells. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 313-320, 2011