Synthesis and Characterization of a Phosphonated Graft Copolyimide

Abstract

Abstract.A new synthesis route of phosphonated multi-block, branched copolyimide is proposed in this research. The synthesis and characterization of the series of new phosphonated graft copolyimides were prepared by combination of one-step high temperature polymerization and phosphonation method by lithiation and reaction with excess diethylchlorophosphate. The phosphonate ester product was converted to the phosphonic acid by hydrolysis. A branched polyimide structure was achieved by coupling the two polyimides with 3, 3'-diaminobenzidine. A phosphonated branched copolyimide with 32 % mol phosphonation exhibited high thermal stability, with a decomposition temperature in nitrogen of ~475°C. Proton exchange membranes prepared from these copolyimides had proton conductivity of 0.02 -0.03 S/cm at 100% humidity over a temperature range of 40 -100C.