Novel bisphenol A-based sulfonated poly(arylene ether sulfone) (bi A-SPAES) copolymers were successfully synthesized via direct copolymerization of disodium 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone, 4,4'-dichlorodiphenylsulfone, and bisphenol A. The copolymer structure was confirmed by Fourier transform infrared spectra and H-1 NMR analysis. The series of sulfonated copolymers based membranes were prepared and evaluated for proton exchange membranes (PEM). The membranes showed good thermal stability and mechanical property. Transmission electron microscopy was used to obtain the microstructures of the synthesized polymers. The membranes exhibit increased water uptake from 8% to 66%), ion exchange capacities from 0.41 to 2.18 meq/g and proton conductivities (25 degrees C) from 0.012 to 0.102 S/cm with the degree of sulfonation increasing. The proton conductivities of bi A-SPAES-6 membrane (0.10-0.15 S/cm) with high-sulfonated degree are higher than that of Nafion 117 membrane (0.095-0.117 S/cm) at all temperatures (20-100 degrees C). Especially, the methanol diffusion coefficients of membranes (1.7 x 10(-8) cm(2)/s-8.5 X 10(-7) cm(2)/s) are much lower than that of Nafion 117 membrane (2.1 x 10(-6) cm(2)/s). The new synthesized copolymer was therefore proposed as a candidate of material for PEM in direct methanol fuel cell. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 304-312, 2009