Catalytic polycyclodehydration of some poly-(o-hydrpxy)amides☆

A study has been made of the polycyclodehydration of poly-(o-hydroxy)amides into polybenzoxazoles in N-methyl-2-pyrrolidone medium in presence of acidic catalysts. Optimal conditions for the preparation of high-molecular weight polybenzoxazoles with high degrees of cyclization have been determined. It was found that the thermal stability of polybenzoxazoles synthesized by catalytic polycyclodehydration is practically on a par with that of analogous polymers prepared by thermal solid-phase polycydodehydration of poly-(o-hydroxy)amides, but the polybenzoxazoles dissolve more readily in strong acids and phenol solvents.