Proton conductive membrane plays a decisive role in polymer electrolyte membrane fuel cell systems. To prepare polymer electrolyte membranes for direct methanol fuel cell(DMFC), a series of novel sulfonated polyimides(SPI) were synthesized from sulfonated diamine,2,5-bis(4-aminophenoxy)benzene sulfonic acid (S-TBDA) with 3,3′,4,4′- benzophenone tetracarboxylic dianhydride (BTDA) and non-sulfonated diamine(ODA) via direct polymerization in this study.The sulfonation degree of the polymers was controlled by changing the molar ratio of the monomers. The obtained SPI membrane was then characterized with FTIR and the influence of sulfonation degree on proton conductivity, methanol permeability and other properties were investigated.With the increase of sulfonation degree,the proton conductivity and methanol permeability increased gradually.The proton conductivity of the SPI membranes ranged from 3.9×10 -3 to 3.4×10 -2 S·cm -1 and the methanol permeability was less than 1×10 -7 cm2 ·s -1.The experiment result indicated the potential of such proton conductive membrane for fuel cell applications.
