Synthesis and degradation of aromatic polyamides containing nitro groups

Abstract

Various aromatic polyamides (aramids) which contain a nitro group at the amino substituted ring were synthesized and their thermal properties and degradation mechanisms were studied. Our present work showed that the nitro group in ortho position to the amide bond acts as an excellent leaving group for intramolecular nucleophilic displacement via the enol form to yield poly-(benzoxazole)s. Thermal decomposition of ortho-substituted aramids proceeds via a two-stage mechanism, whereas unsubstituted aramids decompose in one step. The first step represents the loss of HNO2 and the second step is due to degradation of the resulting benzoxazole polymer. Model compound and high-temperature FT-IR studies of these materials also give supportive evidences for the cyclization reaction.