Synthesis of a renewable bisguaiacol amide and its hydrogen bonding effect on enhancing polybenzoxazine performance

The development of bio-based phenols to replace bisphenol A (BPA) is an ongoing challenge in the polymer industry. In this work, we recommend a renewable bisphenol, bisguaiacol amide (BGA), which is synthesized from vanillic acid and vanillyl amine, to realize superior material performance to its benzoxazine resin. To demonstrate the important role of the amide group in BGA, an analogous bisphenol, bisguaiacol ester (BGE), is synthesized from vanillic acid and vanillyl alcohol for comparative investigation. A series of cytotoxicity tests confirm that the two renewable bisphenols are significantly safe for humans when compared to BPA. Furthermore, material performance comparisons between their benzoxazine resins, poly(BGA-fa) and poly(BGE-fa), reveal that the former is superior to the latter in terms of the storage modulus (2.0 vs. 1.8 GPa), Tg (170 vs. 152 °C), thermal stability (Td10% = 363 vs. 339 °C) and tensile strength (78 vs. 63 MPa). It can be inferred that the hydrogen bonds provied by amide group are responsible for the improved properties. The results from the comparative study provide a robust way to develop new biobased polymers of high performance.