New opportunity for sustainable benzoxazine synthesis: A straight and convenient one-pot protocol for formaldehyde-free bio-based polymers

Abstract Polybenzoxazine is an interesting class of high-performance polymers with potential applications in both the scientific and industrial fields. Due to its remarkable properties along with environmental concerns, different benzoxazine monomers are being synthesized in order to afford more sustainable alternatives for polymeric materials development. Here, we report a microwave-assisted and formaldehyde-free methodology for the synthesis of a cardanol-based benzoxazine. The reaction use cardanol and HMTA as starting materials with the efficient microwave-assisted heating, affording the desired product in a matter of minutes and high yields, in a reaction system completely absent of organic solvents. Monomer characterization was performed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance Spectroscopy (1H and 13C NMR) and differential scanning calorimetry (DSC). The obtained thermoset was studied by thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), showing good thermal and mechanical properties. The results indicate the successful protocol for the development of highly bio-based monomer under solvent- and formaldehyde-free conditions, starting form cardanol, an agro-industrial residue.