A truly bio-based benzoxazine derived from three natural reactants obtained under environmentally friendly conditions and its polymer properties

Abstract

The majority of the published bio-based benzoxazine research has focused almost exclusively on different phenolic and amine compounds, while the aldehyde portion of the oxazine ring remains the same. These materials have been labeled as fully bio-based even though only two of the three raw materials are derived from renewable resources. In this study, we synthesize a truly bio-based benzoxazine in which all three reactants necessary to synthesize a benzoxazine are from renewable sources for the first time. The bio-originated compounds sesamol, furfurylamine, and benzaldehyde are used to synthesize a truly bio-based benzoxazine by a solventless method. Unlike almost all 1,3-benzoxazine resins reported in the literature thus far, the current paper reports oxazine ring-substituted benzoxazines, further providing a great opportunity for the molecular design flexibility of benzoxazine resins over the already very rich variation of 1,3-benzoxazine compounds. The structure of the 7-(furan-2-ylmethyl)-6,8-diphenyl-7,8-dihydro-6H-[1,3]dioxolo[4′,5′:3,4]benzo[1,2-e][1,3]oxazine monomer is characterized by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and 1D and 2D ¹H and ¹³C nuclear magnetic resonance spectroscopy. The polymerization behavior of the benzoxazine monomer is studied by differential scanning calorimetry (DSC), and the thermal stability of the polybenzoxazine is evaluated by thermogravimetric analysis (TGA). The corresponding polymer has a high thermal stability with 5% and 10% weight loss temperatures of 317 and 332 °C, respectively, a char yield of 46%, and a heat release capacity of 201 J g⁻¹ k⁻¹. Polymers that show a high char yield, a high degradation temperature and a heat release capacity below 300 kJ g⁻¹ are considered good anti-flammable materials.