Glyoxal-Based Bi-Oxazine Benzoxazines: Formaldehyde-Free\nBiothermosets

Natural\nabundant resources and safe chemicals are attractive feedstocks\nfor achieving circular sustainability. A wide variety of biophenols\nand greener amines offered interesting avenues in the evolution of\nthe upcoming class of phenolic thermosets, polybenzoxazines (PBZ).\nHigh dependence on formalin as a starting material for monomer synthesis\nhas prompted exploration of alternative safe chemicals. In this study,\nwe designed a family of glyoxal-based benzoxazine (BZ) monomers to\nsynthesize formaldehyde-free biothermosets, leveraging a proximity\nand promiscuity oxazine–oxazine dependent polymerization. The\nbi-oxazine functionality at the reactive C<sub>2</sub> center in the\nmonomers demanded significantly low temperature for ring-opening polymerization\nwith high polymerization enthalpy favoring an ease in polymer growth,\novercoming challenges posed by earlier generation BZ monomers. Current\nwork demonstrates the proof-of-concept for a highly efficient methodology\nfor formaldehyde replacement in benzoxazine chemistry and holds promise\nfor the exploration of a new platform chemical, glyoxal, toward the\nnext generation of benzoxazine with unique reactivities.