Ultra-Strong, Humidity-Tolerant Thermoset Based on Dynamic Covalent Bond Integration Strategy via Boron−Nitrogen Bidentate Coordination

Abstract

Dynamic covalent polymers, especially those containing boronic ester bonds, face an inherent contradiction between reversibility and robustness, as water poses a severe threat to their mechanical properties. Herein, we propose a scalable dynamic covalent chemistry, namely, interlocking imine bonds of the bis-Schiff base (Salen) and aryl boronic ester bonds to form sNCB linkages. Benefiting from the internal boron−nitrogen bidentate coordination, the sNCB linkage overcomes the inherent defect of boronic ester bonds, exhibiting strong hydrolysis/thermal stability. When we design the cross-linked network to contain merely 8 wt % of sNCB linkages, the mechanical robustness of the original polymer can be significantly enhanced, producing an ultrastrong and moisture-resistant material (PETX) with ∼102 MPa tensile strength. Moreover, PETX can still undergo multiple reprocessing and even achieve self-healing. The sNCB linkages also provide PETX with a range of structural health monitoring functions. Our work presents a promising strategy for producing high-strength, stable, and sustainable materials.