Design of a Low-Temperature Ring-Opening Benzoxazine System Using a Supramolecular Hydrogen-Bond Structure

Phenolic derivatives capable of reducing the ring-openingtemperatureof benzoxazine resin have gradually emerged as valuable modules forbenzoxazine chemistry, not to mention their good compatibility, coreactivity,and network modifiability. However, the previously reported unsatisfactorypromotion effects, unclear reaction mechanisms, and unstable structurehave severely limited the development of benzoxazine/phenol systems.Herein, a supramolecular hydrogen-bonded system consisting of resorcinoland 2-aminopyridine benzoxazine (PH-2a) was developed. The PH-2a/resorcinolmixture system with an equivalence ratio of 1:1 exhibited a dramaticreduction in ring-opening peak temperature (T (p)) from 283 to 110 & DEG;C. Experimental combined with computationalinvestigations supported its supramolecular H-bond behavior. Basedon the cross-comparison of PH-2a analogues and other diphenols, thecritical roles of H-bonding interactions both in activating reactantsand inducing a directional reaction were revealed. These H-bonds withappropriate strengths can self-assembly form and close the distancebetween potential reaction sites, facilitating the direct productionof an adduct. In addition, the application potential of the PH-2a/resorcinolsystem was also prospected, which can promise network tailoring andlow-temperature cross-linking by the design flexibility of PH-2a andresorcinol derivatives, opening up possibilities for the preparationof advanced polybenzoxazine resins at low temperature.