Effects of curing on structure and thermal characteristics of polybenzoxazine based on p-nitroaniline

Among the polybenzoxazines, nitroaniline based benzoxazine polymers are not popular for which the polymerization process overlaps with the beginning of the thermal degradation. Phenol and p-nitroaniline based benzoxazine monomer was synthesized and polymerized by applying different temperatures and curing periods systematically to investigate the effect of curing program on polymerization mechanisms via direct pyrolysis mass spectrometry, DP-MS technique. In order to get a better insight on the process, low energy DP-MS analysis was also performed and the results showed that the polymerization of nitroaniline based benzoxazine mainly proceed via attack of NCH2 groups to the phenol ring, contrary to the opposing reaction pathways suggested for benzoxazine based on aniline and the radicals generated by elimination of nitroaniline during curing and/or pyrolysis combined to form unsaturated linkages, resulting a very high char yield.