Water vapour transport mechanism in naphthalenic sulfonated polyimides

• Published in: Journal of membrane science Vol. 223; no. 1; pp. 127 - 139
• Main Authors: Piroux, F., Espuche, E., Mercier, R., Pinéri, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-09-2003; Elsevier
• Subjects: Chemical Sciences; Copolymer; Polymers; Sulfonated polyimides; Water permeation; Water sorption; Water sorption; Copolymer; Water permeation; Sulfonated polyimides; water permeation; sulfonated polyimides; water sorption; copolymer
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/S0376-7388(03)00315-6

The morphology and the water transport properties of a large series of sulfonated copolyimides synthesised with a naphthalenic dianhydride, a sulfonated diamine and various non-sulfonated diamines were studied. For a sulfonated diamine content in the total diamine amount higher than 30%, the copolymers are composed by a continuous ionic phase and a dispersed non-sulfonated phase. The water sorption isotherms are of BET type II for all the copolymers and they result from the contribution of both the sulfonated and non-sulfonated phases. For the sulfonated phase, a two step sorption mechanism has been identified. It consists at low activity in sorption on ionic sites but also in unrelaxed holes formed during the triethylammonium/H
+ ionic exchange and at high activity in a clustering process. The contribution of the non-sulfonated phase to the transport phenomenon can be modulated by the hindrance brought by the non-sulfonated diamine and by its more or less hydrophobic character.