Synthesis of poly(aryl ether benzoxozoles)

Abstract

Aromatic polybenzoxazoles (PBO) are a class of high temperature heterocyclic polymers which show excellent thermal stability. PBO's are generally prepared by step-growth polymerization of bis(o-aminophenols) and aromatic diacid derivatives. The use of PBO's has been limited as they are soluble only in strong acids and cannot be processed from organic solvents. The introduction of aryl ether linkages has also been shown to improve the solubility characteristics of rigid high temperature polymers (6). The authors recently demonstrated a novel approach for synthesizing aryl ether containing poly(phenylquinoxalines) based on pyrazine activated aryl fluoride displacement by phenoxides. Likewise, other heterocycles should activate aryl halide displacement, analogous to the pyrazine ring of the phenylquinoxaline moiety. They investigated oxazole activated fluoro displacement as a route to PBO's with aryl ether linkages, with the objective of extending the scope of heterocyclic activated halo displacements, as well as obtaining organic processable PBO.