Crosslinked composite membrane having a thin chitosan (CS) layer on microporous polysulfone (PSF) substrate was synthesized and assessed for its applicability in fuel cells. This composite (PSF/CS) was extensively characterized for morphology, intermolecular interactions, thermal stability, and physico-mechanical properties using SEM, XRD, FTIR, TGA and sorption studies, respectively. Since studies indicated a lack of interaction between the two polymers, efforts were made to enhance the interaction between polysulfone support and chitosan through surface modification of polysulfcone. This rendered a novel type of composite (SPSF/CS) derived by surface modification of polysulfone substrate prior to casting of chitosan layer on it. Proton conductivity of both the composites, PSF/CS and SPSF/CS, was determined and compared with respective values of commercial Nafion 117. These composites exhibited an increase in conductivity with an increase in temperature. The composite, SPSF/CS exhibited high Ion Exchange Capacity (IEC) and proton conductivity higher than Nafion 117 at temperature above 100 degrees C. The membrane also showed adequate geometrical and thermal stabilities and can therefore be considered as a potential alternative fuel cell membrane especially for high temperature operations. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.