POLYMERS FROM 4-(4-HYDROXYPHENYL)PHTHALAZIN-1-ONE

2-(4'-Hydroxyphenylbenzoyl)benzoic acid is readily available from phenolphthalein by reaction with hydroxylamine. On treatment with hydrazine, 4-(4-hydroxyphenyl)phthalazin-1-one is formed in high yield. Under conditions conventionally used for the synthesis of poly(aryl ether)s the phthalazinone reacts with 4,4-difluorobenzophenone or 4,4'-difluorodiphenyl sulfone to yield high molecular weight linear polymers which are thermooxidatively stable and have Tg's approaching 300-degrees-C. The phthalazinone NH groups behave like phenolic OH groups and the resulting polymers contain O-C and N-C linkages. Phenyl-substituted phenolphthaleins have also been synthesized and converted to the corresponding phthalazinone polymers.