Curable benzoxazine/siloxane hybrid networks from renewable phenolics and glycerol

Siloxane bearing benzoxazines from renewable phenolics such as vanillin and coumarin were prepared and reacted with glycerol by silyl ether exchange reactions to yield processable, soft, and curable bio-hybrid gels. Moreover, these benzoxazine-based gels were cured below 200 °C favored by the catalytic effect of hydroxyl groups present on glycerol moieties to yield bio-hybrid polybenzoxazines. All the synthesized intermediates, gels, and ultimate networks were characterized by ¹H, ¹³C NMR, FTIR, and UV–Vis analyses. The curing behavior and thermal stabilities of the monomers, glycerol-based gels and related polybenzoxazines were investigated by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). Moreover, the activation energies of polymerization of benzoxazine monomers were determined by DSC using the Kissinger and Ozawa methods.