Synthesis and Polymerization of the Bio-Benzoxazine Derived from Resveratrol and Thiophenemethylamine and Properties of its Polymer

Resveratrol and 2-thiophenemethylamine have been employed in the synthesis of a novel tri-functional benzoxazine (RES-th) to develop the bio-benzoxazine monomer. The chemical structure of the synthesized monomer is confirmed by various characterization technics. The polymerization behavior is monitored by in situ Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The in situ FTIR results reveal distinct reaction mechanisms for the three oxazine rings presented in RES-th, with both ether and phenolic Mannich bridge structures observed in the products. The activation energy values of RES-th are calculated to be 119.05, 120.97, and 119.44 kJ mol⁻¹ by Kissinger, Ozawa, and Starink methods, respectively, which are all based on the heat flow curves at various heating temperatures. The thermal stability and flame retardancy of the resulting polybenzoxazine (poly(RES-th)) are investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The values of T_d5 and T_d10 of polybenzoxazine are found to be 356 °C and 399 °C, respectively, with a char yield of 66.3% at 800 °C. The prepared polybenzoxazine also demonstrates nonflammability characteristics with the values of heat release capacity (HRC) and total heat release rate (THR) of 18.65 J (g K)⁻¹ and 2.69 kJ g⁻¹, respectively. These findings suggest that the thermoset, poly(RES-th), is a promising candidate for fire-resistant applications.