Synthesis and Properties of Sulfonated Polyimide/Polybenzimidazole Cross-Linked Membranes for Fuel Cell Applications
A series of cross-linked proton exchange membranes with the ion exchange capacities (IECs) of 0.70 - 1.52 meq/g have been prepared via the reaction of the anhydride-terminated sulfonated polyimide oligomers (SPI-3, SPI-5 and SPI-7, here the figure refers to the averaged block length) and the polybenzimidazole with pendant amino groups (H2N-PBI) in dimethylsulfoxide (DMSO) during the membrane cast process. The prepared cross-linked membranes showed high tensile strength (55 - 80 MPa) and good water stability (> 2 months in deionized water at 100 °C). Fenton’s test revealed that all the cross-linked membranes displayed significantly better radical oxidative stability than the corresponding pure SPIs. This is attributed to the presence of the highly oxidative-stable PBI component in the cross-linked membranes. The proton conductivities of the cross-linked membranes increased with increasing temperature and relative humidity. The cross-linked membrane prepared from the longest oligomer (SPI-7) displayed the highest proton conductivity which is comparable to that of Nafion 117.
Jinglong Bu, Pengcheng Wang, Liqun Ai, Xiaoming Sang, Yungang Li
Z. J. Xia et al., "Synthesis and Properties of Sulfonated Polyimide/Polybenzimidazole Cross-Linked Membranes for Fuel Cell Applications", Advanced Materials Research, Vols. 287-290, pp. 2516-2521, 2011