2-(4'-Hydroxyphenylbenzoyl)benzoic acid is readily available from phen
olphthalein by reaction with hydroxylamine. On treatment with hydrazin
e, 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'-difluor
odiphenyl 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 re
sulting polymers contain O-C and N-C linkages. Phenyl-substituted phen
olphthaleins have also been synthesized and converted to the correspon
ding phthalazinone polymers.