A series of selectively sulfonated poly(arylene ether sulfone)-b-polybutadiene copolymers (SPAES-b-PB) were prepared based on carboxyl terminated polybutadiene (CTPB) and sulfonated poly(arylene ether sulfone) (SPAES) that was directly prepared by polycondensation of 4,4'-isopropylidenediphenol with different molar ratios of disodium 3,3'-disulfonate-4,4'-dichlorodiphenyl sulfone (SDCDPS) to 4,4'dichlorodiphenylsulfone (DCDPS), and subsequent selective postsulfonation of flexible PB block was carried out. Epoxidized modification of membranes was conducted by an in situ-generated peracid method. The content of sulfonic acid groups attaching to aromatic rings in SPAES was determined by H-1 NMR and was in good aggrement with the controlled ratios. The effect of sulfonated rigid blocks on the postsulfonation of PB blocks was studied by Fourier transform infrared spectroscopy. The glass transition temperature (T-g) and the temperature of the melting peak (T-m(p)) of membranes in acid form were studied by differential scanning calorimetry. Fenton's reagent test revealed that the selectively sulfonated SPAES-b-PB membranes had good stability to oxidation. The microstructure of rod-like rigid SPAES blocks and interpenetrating network of ions were observed by transmission electron microscopy. Complex impedance measurement showed that an epoxidized membrane with SPAES-40 exhibited the highest proton conductivity (1.08 x 10(-1) S/cm, 90 degrees C), which was due to the formation of obvious ionic networks. (c) 2006 Wiley Periodicals, Inc.