A study of the effect of L-histidine on the polymerization of benzoxazines and properties of their thermosets

The cleavage of the oxazine ring of benzoxazine resins generally requires high energy during the ring-opening polymerization, which leads them to be processed at a much higher temperature than the traditional thermoplastics. In this paper, a bio-based substance, L-histidine, has been used as the catalyst to lower the ring-opening polymerization of the well-commercialized benzoxazine resin (BA-a) based on aniline and bisphenol-A. The catalytic effect of L-histidine on the polymerization behaviors of benzoxazine resin (BA-a) has been monitored by differential scanning calorimetry and in situ Fourier transform infrared spectroscopy. In addition, L-histidine has also been found to be a good property modifier for BA-a-derived thermosets. The thermal properties of resulting polybenzoxazines have been investigated by thermogravimetric analysis and dynamic thermomechanical analysis. Notably, the thermoset derived from BA-a with adding only 5 mol% L-histidine exhibits excellent thermal stability in consideration of high T g (206 °C), high T d10 temperature (319 °C) and high chair yield value (40%), making this thermosetting resin a promising material for high-performance applications.