Polyamide Copolymers Containing Hexafluoroisopropylene Groups

New copolymers containing imide and different heterocyclic units such as oxadiazole, benzoxazole, or pyridazine, together with hexafluoroisopropylidene groups, have been synthesized by solution polycondensation of appropriate aromatic diamines with diacid chlorides incorporating preformed imide rings and hexafluoroisopropylidene bridges. In the case of oxadiazole-imide copolymers and pyridazine-imide copolymers, aromatic diamines containing preformed oxadiazole or pyridazine, respectively, have been used, while in the case of benzoxazole-imide copolymers the benzoxazole unit was formed during the polycondensation reaction between bis(o-hydroxy-amine)s and the above-mentioned diacid chlorides. Also, copolyimides containing pendant cyano groups have been prepared from aromatic diamines containing cyano substituents with the same diacid chlorides. Solubility, film-forming ability, thermal stability, and electrical insulating properties of all these compounds are discussed and compared with those of related polymers which do not contain hexafluoroisopropylidene groups, and with those of other heterocyclic polymers previously reported.