Exploiting the reversible covalent bonding of boronic acids for self-healing/recycling of main-chain polybenzoxazines

In this work, a new strategy for the synthesis of self-healable/recyclable polybenzoxazine networks under mild conditions by exploiting dynamic B–O bond exchanges is presented. The process is based on mixing main chain polybenzoxazine precursors with phenyl boronic acid and heating up to 180 °C. The obtained polybenzoxazine films displayed good self-healing properties at low temperatures and very mild pressures in the absence of additives to promote the healing process. The recovery extent of the films was quantified by tensile tests. The stress relaxation and sweep frequency behaviour of the films were analyzed by rheological measurements. The spectral and thermal behaviors of the films were also investigated. Moreover, the networks showed higher hydrolysis stability than those of conventional boronic esters because of the intramolecular coordination of B–N in the linkages.