Ultra-tough and sustainable epoxy adhesive enabled by microphase separation and dynamic chemical structure

Despite significant efforts in developing high-performance epoxy adhesives, an inevitable trade-off persisted among strong adhesion, high toughness and reprocessability. Here, an epoxy adhesive with high toughness and reprocessability was developed through microphase separation and dynamic chemical structure, effectively addressing the aforementioned challenge. Specifically, the asynchronous ring-opening reactions of aromatic amines and aliphatic amines with epoxy groups resulted in the formation of a phase-separated microstructure in the cured epoxy resin, thereby endowing it with high toughness. Furthermore, the dynamic chemical structure, realized through B-N coordination and dynamic bond exchange of borate esters, enabled epoxy adhesives to have decent environmental stability and reprocessability. Therefore, the acquired epoxy adhesives exhibited superior toughness with a work of debonding of 32927.77 N/m, high adhesive strength of 24.87 MPa, decent environmental resistance (water, extreme temperatures and various solvents) and reprocessability. This strategy of incorporating microphase separation and dynamic chemical structure is expected to provide novel insights into the design of high-performance epoxy adhesives and to facilitate advancements in sustainable polymer materials.