Reversible B–O bond-based epoxy vitrimers with high thermomechanical and dynamic properties enhanced by intermolecular B–N coordination

Abstract

The development of recyclable and self-repairable vitrimer materials featuring reversible B–O bonds has garnered increasing attention. However, their stability and thermomechanical properties remain insufficient for engineering applications in reusable carbon fiber-reinforced composites (CFRCs). Herein, we report a high-performance epoxy vitrimer containing boronic ester bond-based dynamic exchange networks, to which a small amount of N-donating imidazole has been added for introducing intermolecular N–B coordination interactions. The obtained vitrimer (E51-NBO-IMZ) possessed a high glass transition temperature (T_g) of 198 °C and tensile modulus of 3.71 GPa. Compared to the system without imidazole, it exhibited significantly improved solvent resistance due to the stabilization effect of N–B coordination on the B-center atoms. Moreover, stress relaxation tests also indicated a lower activation energy (E_a = 151.31 kJ mol⁻¹) of the E51-NBO-IMZ vitrimer, suggesting better dynamic exchange activity. Despite the high stability and improved thermomechanical properties, the self-repairing, recycling and degradation of the vitrimer and its CFRCs were successfully achieved under heating, stress or chemical environmental conditions, showing outstanding potential for practical applications.