Reversible B–O Bonds-Based Epoxy Vitrimer with High Thermo-Mechanical 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 thermal-mechanical properties remain insufficient for engineering applications in reusable carbon fiber reinforced composites (CFRCs). Herein, we reported a high performance epoxy vitrimer containing boronic ester bond-based dynamic exchange networks, to which a small amount of N-donating imidazole was added for introducing the intermolecular N–B coordination interactions. The obtained vitrimer (E51-NBO-IMZ) possessed a high glass transition temperature (T_g) of 198^oC 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, the stress relaxation tests also indicated a lower activation energy (Ea=151.31 kJ/mol) of E51-NBO-IMZ vitrimer, suggesting a better dynamic exchange activity. Despite the high stability and thermal-mechanical properties, the self-repairing, recycling and degradation of the vitrimer and its CFRCs were successfully achieved under heating, stress or chemical environmental conditions, demonstrating outstanding potentials for practical applications.