Bio-based dicoumarin-containing benzoxazine resin: Synthesis, photo-thermal polymerization and thermal stability

With the increasing awareness of environmental protection, considerable efforts are now devoted into bio-derived material fabrication. Through utilization of renewable biomass aligning with green chemistry principles, various sustainable materials have been prepared. In the current study, an innovative benzoxazine monomer containing dual coumarin moieties was successfully prepared through Mannich condensation using 4-methylumbelliferone (bio-phenolic precursor) and 7-amino-4-methylcoumarin (bio-amine component). The molecular architecture integrates photoreactive coumarin moieties, enabling dual photo-thermal curing capability. Structural validation via 1 H/ 13 C NMR and FT-IR spectroscopy confirmed the monomer integrity. Real-time UV–Vis spectroscopy monitoring indicated an 81 % conversion of the [2π + 2π] cycloaddition reaction following 2 h of UV irradiation (λ = 365 nm). The photopolymerized benzoxazine precursor shows a 5.4 °C curing temperature depression comparing to unphotopolymerized monomer. Complementary in-situ FT-IR analyses and DSC elucidated thermal-initiated ring-opening polymerization, demonstrating temperature-dependent conversion profiles. The polybenzoxazine prepared through photo-thermal polymerization shows higher thermal stability than solely thermal polymerized one. Through molecular design, this work realizes photo-thermal synergistic curing of bio-based benzoxazine resins, proposing an innovative approach to develop thermosetting materials that integrate low-energy processing, high heat resistance, and environmental sustainability.