writer：Hongyan Yao,Pengju Feng,Peng Liu,Baijun Liu,Yunhe Zhang,Shaowei Guan,Zhenhu
keywords：sulfonated co-polyimide,crosslinking, proton exchange membrane
source：期刊
specific source：POLYMER CHEMISTRY,2015, 6, 2626-2635
Issue time：2015年
A series of novel highly sulfonated co-polyimides (SPI-20s) bearing cross-linkable hydrophobic tetrafluorostyrol side-groups have been successfully synthesized. The cross-linking reaction of the tetrafluorostyrol groups in the SPI-20s was performed at 260 degrees C without any additive. The glass transition temperatures of the cross-linked membranes were determined by differential scanning calorimetry and dynamic mechanical analysis and found to be higher than the SPI-20s proving the formation of cross-linked networks. There was no elimination of sulfonic acid groups during cross-linking reaction. The cross-linked membranes (Cured-SPI-20s) showed significantly enhanced performances, particularly high proton conductivity (0.103-0.179 S cm(-1) at 80 degrees C), low water uptake (31.2-53% at 80 degrees C) and swelling ratio (6.4-14.1% at 80 degrees C). Furthermore, the Cured-SPI-20s exhibited a greatly reduced methanol permeability (3.99-4.93 x 10(-7) cm(2) s(-1)), which was lower than that of Nafion 117 (2.94 x 10(-6) cm(2) s(-1)) at room temperature. The Cured-SPI-20 membranes also exhibited improved glass transition temperatures (254-277 degrees C), thermal stability (5% weight loss temperature exceed at 300 degrees C) and excellent oxidative stability, chemical resistance and mechanical properties. The results indicate that the Cured-SPI-20s were promising candidates as proton exchange membranes in fuel cell technology.