To fulfill the principles of green chemistry, renewable magnolol and furfurylamine were taken to synthesize benzoxazine under microwave irradiation using poly­(ethylene glycol) (PEG) as the solvent. The reaction was monitored by the yield of target compound under varied conditions. Only in 5 min, the yield of target benzoxazine monomer (M-fa) could be high up to 73.5% in PEG 600 system, indicating the desired advantage of microwave irradiation for benzoxazine synthesis. After the chemical structure of M-fa was confirmed, its polymerization behavior, processability, and thermo-mechanical properties were carefully evaluated. The cured resins presented a high glass transition temperature of 303 °C and exceedingly good thermal stability with 5% and 10% weight-loss temperature higher than 440 and 463 °C, respectively, and a char yield of 61.3%. In addition, M-fa demonstrated viscosity lower than 1 Pa·s during the temperature range from 100 to 194 °C, which indicated its good processability. This work provided us a strategy for the synthesis of high bio-based content high-performance thermosets under environmental-friendly conditions, that is, microwave-assisted heating method and green solvent.

In this work, several bio-based main-chain type benzoxazine oligomers (MCBO) were synthesized from eugenol derivatives via polycondensation reaction with paraformaldehyde and different diamine. Afterwards, their chemical structures were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance Spectroscopy (1H-NMR). The curing reaction was monitored by Differential Scanning Calorimetry (DSC) and FT-IR. The polybenzoxazine films were prepared via thermal ring-opening reaction of benzoxazine groups without solvent, and their thermodynamic properties, thermal stability, and coating properties were investigated in detail. Results indicated that the cured films exhibited good thermal stability and mechanical properties, showing 10% thermal weight loss (Td10%) temperature as high as 408 °C and modulus at a room temperature of 2100 MPa as well as the glass transition temperature of 123 °C. In addition, the related coatings exhibited high hardness, excellent adhesion, good flexibility, low moisture absorption, and outstanding solvent resistance.