Effect of selective swelling on protons and methanol transport properties through partially sulfonated block copolymer membranes

The partially sulfonated polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene (SSEBS) and its membranes blended with a low molecular weight of hydrogenated dicyclopentadine (DCPD) as a selective swelling agent to the middle block were prepared for a possible application to DMFC. The characteristic properties such as proton conductivity and methanol permeability were compared with SSEBS and the blend membranes when they have the same ion exchange capacity (IEC). Using small-angle X-ray scattering (SAXS), morphological transition by the selective swelling were observed as water and methanol are absorbed. It was found that the addition of DCPD prohibits the morphology transition and reduces the methanol crossover. By means of selective blending with methanol-hating materials, it was shown that satisfactory membranes being with methanol tolerance for DMFC can be fabricated by controlling the nano-scaled morphology of proton conducting block copolymer membranes.