Polymerization of an AB-Type Benzoxazine Monomer toward Different Polybenzoxazine Networks: When Diels–Alder Reaction Meets Benzoxazine Chemistry in a Single-Component Resin

We report a new AB-type benzoxazine monomer, containing both maleimide and furan groups, which exhibits diversified polymerization mechanisms rather than the common single linear polymerization or ring-opening polymerization that leads to cross-linked structures. In addition, the polybenzoxazine obtained directly from the thermally activated polymerization shows higher thermal stability and lower flammability than the one based on the main-chain-type precursor. This is observed as an exception in benzoxazine chemistry because the other reported thermosets derived from main-chain-type benzoxazines generally possess higher performance compared with ones from monomers. More importantly, the varied polymerization mechanisms discovered in this single-component AB-type benzoxazine have cast new light on both benzoxazine chemistry and the Diels–Alder reaction.