Self Termination of Ring Opening Reaction of p-Substituted Phenol-Based Benzoxazines: An Obstructive Effect via Intramolecular Hydrogen Bond

The ring opening polymerizations of p-substituted phenol-based benzoxazines are self-terminated as soon as dimers form. The polymerization of benzoxazine monomers does not proceed according to the theoretical mechanism even though the conditions, temperature, molar ratio, solvent polarity, and reactant ratio are varied. The speculated mechanism, involving the unique structure of a dimer with inter and intramolecular hydrogen bonds, is applied to explain an obstructive effect on ring opening polymerization. In this article, we clarify an important case which the stereo structure of the compound controls the reaction and prevents the polymerization expected from the theoretical mechanism.