Effect of hydrogen bonds on the polymerization of benzoxazines: influence and control

Abstract

This work aims to disclose the reason that prohibited the preparation of highly crosslinked polybenzoxazines. Based on experimental study and computer simulations, we found that the dominant –OH⋯N hydrogen bond (Type I –OH⋯N hydrogen bond) of polybenzoxazines blocked high-degree polymerization and resulted in a low crosslink density by decreasing the charge densities of corresponding hydroxyl groups on phenols. As a solution, by introducing additional hydrogen-bond acceptors, the formation of Type I –OH⋯N hydrogen bonds could be suppressed, which enables a high-degree of polymerization of benzoxazines. This novel insight about benzoxazine polymerization is anticipated to help researchers explore more types of polybenzoxazines with enhanced properties.