SYNTHESIS AND CHARACTERIZATION OF AROMATIC POLYIMIDE AND POLYAMIDE-IMIDE FROM 2,5-BIS(4-ISOCYANATOPHENYL)-3,4-DIPHENYLTHIOPHENE AND AROMATIC TETRACARBOXYLIC AND TRICARBOXYLIC ACIDS

Soluble polyimide having an inherent viscosity up to 1. 4 dL/g was synthesized by the high-temperature solution polycondensation of 2,5- bis(4-isocyanatophenyl)-3,4-diphenylthiophene with 3,3 prime ,4,4 prime -benzophenonetetracarboxylic dianhydride. The polycondensation of the tetraphenylthiophene diisocyanate with trimellitic anhydride afforded polyamide-imide with an inherent viscosity up to 0. 9 dL/g. These polymers showed limited solubility in organic solvents and had glass transition temperatures around 320 degree C.