Fully biobased unsymmetric bisphenols from condensation of lignin-derived monophenols for non-isocyanate polyurethane synthesis

Transforming renewable biomass and CO₂ to the high value-added non-isocyanate polyurethanes (NIPUs) was of great significance to the development of sustainable chemistry. Herein, a series of unsymmetric bio-based bisphenols featured with chalcone structure were designed and synthesized by Claisen-Schmidt condensation of lignin-derived monophenols (vanillin and syringaldehyde) and plant methyl ketones (zingiberone, raspberry ketone, and piceol), these phenols and ketones are value-added chemicals from biorefinery process of biofuels. The unsymmetric bio-based bisphenols were consequently transformed into bis-epoxides, bis(cyclic carbonate)s, and finally polyhydroxyurethanes (PHUs). With eco-friendly proline as the catalyst, bio-based bisphenols were prepared in excellent yields (76% − 95%). More than 90% isolated yields of bis(cyclic carbonate)s were obtained from bis-epoxides. All of the bis(cyclic carbonate)s were cured with long-chain amine, i.e. Priamine^TM 1074, and the result PHUs, a kind of NIPUs, have thermal stability comparable to bisphenols A-based network according to DSC and TGA. The attempts to one-pot-two-step synthesis of PHUs also exhibited better thermal properties, which bis-epoxides directly conducted successively with carbon dioxide and 1,6-hexamethylenediamine. The bio-based bisphenols appeared to be a promising substitute to bisphenols-A with the aim at synthesizing environmentally friendly PHUs. Therefore, this study provided a valuable route in utilization of carbon dioxide and functional aromatics from fuel process into fully biobased polymeric materials.