Thermal degradation of new copolymers from pyromellitic anhydride

Abstract

Abstract A series of new copolyimides has been synthesized from pyromellitic anhydride. Copoly(imide esters) and copoly(imide amides) were synthesized from bis( N -methylcarboxychloride)pyromellitimide with diols and amines, respectively. One copoly(imide amine) was obtained from bis( N -allyl)pyromellitimide and piperazine via the Michael reaction. The thermal degradation of the copolymides obtained was studied by direct pyrolysis mass spectrometry. Our results show that a selective β-CH hydrogen transfer reaction occurs in copoly(imide esters) containing 1,3-propyl and 1,6-hexane diols, while an intramolecular ester exchange process takes place in copoly(imide ester) with a neopentylglycol moiety. Copoly(imide amide) containing 1,6-hexane diamine decomposes by an N-H hydrogen transfer process, although extensive crosslinking is observed, while that containing piperazine decomposes by an α-CH hydrogen transfer. In contrast, copoly(imide amine) undergoes a very selective depolymerization process, yielding bis( N -allyl)pyromellitimide and piperazine.