Compositional effect on the properties of sulfonated and nonsulfonated polymer blend membranes for direct methanol fuel cell

Various morphologies of blend membranes were prepared by changing drying condition and composition and their effect on the proton conductivity and the methanol crossover were discussed for direct methanol fuel cell. To obtain high proton conductivity but low fuel loss, highly sulfonated poly(arylene ether sulfone) (IEC=1.9 meq/g for sPAES55, synthesized with 55 mol% sulfonated monomer) was blended with nonsulfonated poly(ether sulfone) (IEC=0 meq/g for RH2000®, provided from Solvay) in solution blending manner. The blend ratio of sPAES55 and RH2000 was varied as 5 to 5, 6 to 4, 7 to 3, and 8 to 2 and three different temperatures (-42, -20, and 80 °C) were applied during the drying step to control the rate of phase separation. The effect of the blend ratio on the morphology, proton conductivity, and methanol permeability of the blend membrane was analyzed in combination with the drying process and finally the most desirable blend membrane for direct methanol fuel cell was proposed.