Chemical modification of copolyimides with bulky pendent groups: Effect of modification on solubility and thermal stability

Two novel copolyimides bearing bulky pendent groups have been prepared by chemical modification of a copolyimide precursor containing carboxylic acid groups. The incorporation of the bulky groups was achieved by esterification of the copolyimide containing carboxylic acid groups with 4-tert-butylbenzyl alcohol. By controlling the carboxylic acid/alcohol ratio, two different degrees of modification were obtained The actual composition of the modified polymer was estimated by H-1 NMR. They showed better solubility than the copolyimide precursor where 100% modification yielded the copolyimide with the highest solubility properties. Thermal analyses indicated that the incorporation bulky pendent groups has a moderate effect on decreasing the thermal degradation temperature and the glass transition temperature. (C) 2007 Published by Elsevier Ltd.