The blend membranes consisting of PVA and SPEEK were investigated for the purpose of maintaining low methanol permeability and little swelling ratio in direct methanol fuel cells (DMFCs). SPEEK with different sulfonation degree were prepared by sulfonation of PEEK. Blend membranes with various PVA content were prepared by solvent casting. Thermal stability, uptake behavior, methanol permeability, ionic exchange capacity (IEC) and proton conductivity of the blend membranes were determined as function of PVA content. The results of TGA show that the addition of PVA increases the weight loss of the membranes at the temperature ranging from 250 degrees C to 350 degrees C and shifts the weight loss onset temperature (T(oneset)) to lower direction. The uptake of blend membranes in water increases with the increase of PVA content, while the absorption of blend membranes in methanol solution show a decrease upon the PVA content, which can minimize the swelling ratio of electrolyte membrane in DMFC applications. The slightly lower ionic exchange capacity (IEC) and proton conductivity of the blend membranes indicate some interaction between SPEEK and PVA molecules. The lower methanol permeability of the blend membranes suggests its potential applications in DMFC. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.