Polymerization of p-cresol, formaldehyde, and piperazine and structure of monofunctional benzoxazine-derived oligomers

By using a secondary amine, e g. piperazine, a Mannich base polymer, having similar structure to the traditional polybenzoxazine, is synthesized. Unlike all the reported polybenzoxazines that are colored, the white polymer shows good thermal property that is close to the degradation temperature of the polybenzoxazine derived from difunctional benzoxazine monomers. 31P NMR spectroscopy in combination with facile phosphorus derivatization and previous model compound studies are utilized to clarify the structures of piperazine-based systems as well as the main chain and end group of traditional polybenzoxazines.