Multifunctional Biobased Benzoxazines: Synthesis, Copolymerization, and Thermal Stability Studies

In accordance with the principle of green synthesis, two biobased benzoxazines with high-purity bifunctional groups, diethylstilbestrol-laurylamine (D-la) and diethylstilbestrol-furfurylamine (D-fa), were prepared by the solution method from laurylamine/furfurylamine, diethylstilbestrol, and polyformaldehyde. The synthesis process is simple, and the post-treatment is convenient. The structures of the synthesized monomers were characterized by Fourier transform infrared (FT-IR) spectroscopies, 1H NMR, and 13C NMR nuclear magnetic resonance. Monomer thermal polymerization and copolymerization were studied and monitored by differential scanning calorimetry (DSC) and FT-IR. DSC showed that D-la had a very wide processing window (132 °C), and the curing temperature gradually decreased between 249 and 255 °C with the increase in its content. The thermal stability of D-fa was studied by thermogravimetric analysis and dynamic thermomechanical analysis, and the test results showed that D-fa had a higher residual carbon content (51%) compared with D-la and its copolymer. As the D-fa content increased, the residual carbon content and thermal stability also increased. Therefore, these two biobased benzoxazines featured excellent processability and thermal stability. This work has important reference values for designing biobased benzoxazines with high performance.