A series of proton-conducting semi- interpenetrating polymer networks (semi-IPNs) have been successfully prepared from [poly- (vinyl alcohol) and poly(2-acrylamindo-2-methyl-1-propanesulfonic acid)] blends by incorporating plasticizer variants. The resulting semi-IPNs exhibited excellent hydrolytic and oxidative stability with high proton conductivity of 0.1 S cm(-1) at 25 degrees C. (c) 2006 The Electrochemical Society.