4-(4-Aminophenoxy)benzene-1,3-diamine-based covalent cross-linked sulfonated polyimide as proton exchange membranes in fuel cell

Hydrolytic and oxidative stabilities of sulfonated polyimide membranes are of significant concern when they are used as fuel cell polyelectrolyte membranes. To increase the hydrolytic and oxidative stabilities of sulfonated polyimide membranes, atriamine crosslinker, 4-(4-aminophenoxy)benzene-1,3-diamine, was synthesized, characterized, and successfully used to synthesize covalently cross-linked sulfonated polyimide membranes. 1,4,5,8-Naphthalenetetracarboxylic dianhydride, 2,2’-benzidine-disulfonic acid, 4-(4-aminophenoxy)benzene-1,3-diamine and 2-bis(4-(4-aminophenoxy)phenyl) hexafluoropropane-based cross-linked sulfonated polyimide membranes have been synthesized and compared with linear sulfonated polyimide membrane in terms of various fuel cell application parameters. Covalent cross-linking is a simple and efficient method to increase the lifetime of the polyelectrolyte membranes. The covalently cross-linked sulfonated polyimidemembranes show an ion exchange capacity of 1.426 1.441 meq.g-1, proton conduction of 0.026 – 0.031 S cm-1, and water uptake capacity 10.7 – 17.07%. As the triamine concentration is increases, both hydrolytic and oxidative stabilities of the membranes also increased. The linear sulfonated polyimide showed hydrolytic stability of 43 h, whereas hydrolytic stability of the cross-linked sulfonated polyimide membranes is increased up to 70 h.