Preparation of novel sulfonated block copolyimides for proton conductivity membranes

In this article novel sulfonated block copolyimides with various diamine compositions and block chain lengths were synthesized by chemical imidization using a two‐pot procedure. The proton conductivities of the block copolyimide membranes were measured as functions of the relative humidity and temperature using four‐point‐probe electrochemical impedance spectroscopy. The proton conductivity of the membranes strongly depended on the block chain lengths and increased with an increase in the block chain lengths. The proton conductivity of NTDA‐BDSA‐b‐6FAP (112/48) as the block copolyimide membrane was approximately 0.35 S cm−1 which indicated a higher value when compared to that determined for Nafion®. Copyright © 2005 John Wiley & Sons, Ltd.