Advanced Polymers from Simple Benzoxazines and Phenols by Ring-Opening Addition Reactions

Simple benzoxazines were mixed and reacted with various phenolics such as phenol, p-nitrophenol, p-cresol, 1,3-dihyroxybenzene (resorcinol), 1,3,5-trihydroxybenzene (phloroglucinol), and N-(2-hydroxyphenyl)benzamide. The influence of these phenolic compounds on ring-opening polymerization temperature of benzoxazines was examined by DSC analysis. The cresol-based benzoxazine (C-a) and phenolics yielded polymers with molecular weight of around 1500 Da. Interestingly, for C-a/resorcinol-and C-a/phloroglucinol-based polymers, a second GPC trace was observed that corresponds to a few million daltons for mixing ratios of 4:1 and 5:1. Moreover, the mixtures of C-a and N-(2-hydroxyphenyl)benzamide gave poly(benzoxazine-benzoxazole)s through a new methodology eliminating the need of synthesis of ortho-amide benzoxazines. The obtained polymers were soluble and characterized in detail by ¹H NMR, ¹³C NMR, GPC, DSC, and TGA analyses.