Synergy between dynamic covalent boronic ester and boron-nitrogen coordination: strategy for self-healing polyurethane elastomers at room temperature with unprecedented mechanical properties

Achieving mechanical robustness and highly efficient self-healing simultaneously at room temperature is always a formidable challenge for polymeric materials. Herein, a series of novel supramolecular polyurethane elastomers (SPUEs) are developed by incorporating dynamic covalent boronic ester and boron-nitrogen (B-N) coordination. The SPUEs demonstrate the highest tensile toughness (similar to 182.2 MJ m(-3)) to date for room-temperature self-healable polymers, as well as an excellent ultimate tensile strength (similar to 10.5 MPa) and ultra-high fracture energy (similar to 72 100 J m(-2)), respectively, owing to a synergetic quadruple dynamic mechanism. It is revealed that the B-N coordination not only facilitates the formation and dissociation of boronic ester at room temperature but also dramatically enhances the mechanical properties by the intermolecular coordinated chain crosslinking and intramolecular coordinated chain folding. Meanwhile, the B-N coordination and urethane hydrogen interaction also serve as sacrificial bonds, which rupture during stretching to dissipate energy and recover after release, leading to superior notch insensitiveness and recoverability. The SPUEs restore their mechanical robustness after self-healing at room temperature and the self-healing efficiency can be dramatically accelerated by surface wetting.

Automated summary

The novel supramolecular polyurethane elastomers (SPUEs) developed in this study achieved mechanical robustness and highly efficient self-healing at room temperature, demonstrating the highest tensile toughness for self-healable polymers and excellent ultimate tensile strength and fracture energy.