Polymer blend membranes composed of a proton conducting component and a methanol barrier component were prepared for direct methanol fuel cells. Sulfonated poly(arylene ether sulfone) copolymer with 60 rnol% sulfonation (sPAES-60) was synthesized via a poly-condensation reaction from 3,3'-disulfonated-4,4'-dichlorodiphenyI sulfone (SDCDPS), 4,4'-dichlorodiphenyl sulfone (DCDPS), and 4,4'-biphenol (BP) for the proton conducting component. Poly(ether) sulfone copolymer (RH-2000, Solvay) was used to compensate for the mechanical and chemical weakness of sPAES-60 and to reduce the methanol permeability. By varying the drying condition and the concentration of the casting solution (10, 15, 20 wt%), blend membranes having various phase separated morphologies were obtained. The morphology was characterized by SEM, EDAX, and AFM. In this paper, the effect of the drying conditions on the phase separation and morphology of the blend membranes was investigated. (c) 2007 Elsevier B.V. All rights reserved.