Abstract: Sulfonated poly(ether imide) (SPEI) and poly(ether sulfone) (PES) blend membranes for application in the direct methanol fuel cells (DMFC) were successfully prepared by solution blend technique. The structure and performance of the obtained blend membranes were characterized using TGA, AFM, and SEM. The results showed that the blend membranes had higher thermal stability, lower swelling property, and good mechanical strength both in dry and wet states at ambient conditions. The morphology of blend membranes showed that its structure became more compact than that of pure SPEI, which might lead to decrease the methanol diffusion. The proton conductivity and the methanol permeability were determined by A.C. impedance spectrometry and diaphragm diffusion, respectively. The results showed that the SPEI/PES (mass ratio of 50/50) membrane still exhibited adequate conductivity (5.5 mS·cm-1) for application as proton exchange membranes. Meanwhile, the methanol permeability of the blend membranes decreased dramatically and was only 5% of that of Nafion 112 membrane. This tremendous reduction of methanol crossover could indicate a potential feasibility as a promising electrolyte for DMFC.

Key words: Sulfonated poly(ether imide), Poly(ether sulfone), Proton exchange membrane, Conductivity, Direct methanol fuel cell