Water resistant sulfonated polyimides based on 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA) for proton exchange membranes

• Published in: Polymer (Guilford) 2007-10, Vol.48 (21), p.6210-6214
• Main Authors: Yan, Jingling, Liu, Changpeng, Wang, Zhen, Xing, Wei, Ding, Mengxian
• Format: Article
• Language: English
• Subjects: 4,4′-Binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA); Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Sulfonated polyimides; Water resistance
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2007.07.026

A series of sulfonated polyimides (SPIs) were synthesized in m-cresol from 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA), 4,4′-diaminodiphenylether-2,2-disulfonicacid (ODADS), and 4,4′-diamino-diphenyl ether (ODA) in the presence of triethylamine and benzoic acid. The resulted polyimides showed much better water resistance than the corresponding sulfonated polyimides from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and ODADS, which is contributed to the higher electron density in the carbonyl carbon atoms of BNTDA. Copolyimides S-75 and S-50 maintained their mechanical properties and proton conductivities after aging in water at 100°C for 800h. The proton conductivity of these SPIs was 0.0250–0.3565S/cm at 20°C and 100% relative humidity (RH), and increased to 0.1149–0.9470S/cm at 80°C and 100% RH. The methanol permeability values of these SPIs were in the range of 0.99–2.36×10−7cm2/s, which are much lower than that of Nafion 117 (2×10−6cm2/s).