K. Miyatake, N. Asano, Masahiro Watanabe
Dec 15, 2003
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Journal of Polymer Science Part A
Abstract
A series of novel sulfonated polyimides (equivalent weight per sulfonic acid = 310–744 g/equiv) containing 10–70 mol % 1,5-naphthylene moieties were synthesized as potential electrolyte materials for high-temperature polymer electrolyte fuel cells. The polycondensation of 1,4,5,8-naphthalene tetracarboxylic dianhydride, 4,4′-diamino-2,2′-biphenyldisulfonic acid, and 1,5-diaminonaphthalene gave the title polymer electrolytes. The polyimide electrolytes were high-molecular-weight (number-average molecular weight = 36.0–350.7 × 103 and weight-average molecular weight = 70.4–598.5 × 103) and formed flexible and tough films. The thermal properties (decomposition temperature > 260 °C, no glass-transition temperature), stability to oxidation, and water absorption were analyzed and compared with those of perfluorosulfonic acid polymers. The polyimide containing 20 mol % 1,5-naphthylene moieties showed higher proton conductivity (0.3 S cm−1) at 120 °C and 100% relative humidity than perfluorosulfonic acid polymers. The temperature and humidity dependence of the proton conductivity was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3901–3907, 2003