Synthesis and properties of novel aromatic poly(o-hydroxy amide)s and polybenzoxazoles based on the bis(ether benzoyl chloride)s from hydroquinone and its methyl-, tert-butyl-, and phenyl-substituted derivatives

Four series of poly(o-hydroxy amide)s were prepared by the low-temperature solution polycondensation of the bis(ether benzoyl chloride)s extended from hydroquinone and its methyl-, tert-butyl-, or phenyl-substituted derivatives with three bis(o-aminophenol)s. Most of the poly(o-hydroxy amide)s displayed an amorphous nature, were readily soluble in various polar solvents such as N,N-dimethylacetamide (DMAc), and could be solution-cast into flexible and tough films. These poly(o-hydroxy amide)s had glass transition temperatures (T_g) in the range of 152-185°C and could be thermally cyclodehydrated into the corresponding polybenzoxazoles approximately in the region of 200-400°C, as evidenced by the DSC thermograms. The thermally converted benzoxazole polymers exhibited T_gs in the range of 215-247°C and did not show significant weight loss before 500°C either in nitrogen or in air.