Weak Acceptors Abnormally Reinforce Urethane Networks while Enabling Glassy-State Healability

Abstract

Hydrogen bonds are versatile motifs for designing repairable materials. The current preconception is that while weak hydrogen bonds lead to rapid exchanging dynamics beneficial for healing, they compromise mechanical properties by reducing the overall cohesion of the material. Herein, we overturn this preconception by designing a proximal acceptor cooperative effect (PACE): placing a weak acceptor adjacent to conformationally flexible urethane units generates an acceptor–urethane interaction that cooperatively stabilizes urethane–urethane hydrogen-bonding conformations, thereby reinforcing urethane–urethane cohesion while simultaneously introducing a labile dynamic interaction. As a proof of concept, we leverage thioether, a weak acceptor, to construct glassy poly(thioether–urethane) networks. Thioether not only reinforces urethane–urethane hydrogen bonds but also forms thioether–urethane hydrogen bonds that retain appreciable mobility far below the glass-transition temperature (Tg). Consequently, the optimized network achieves a record-high tensile strength of 79.5 MPa (the highest reported for intrinsic glassy-state repairable polymers) and a Young's modulus of 3.3 GPa, while delivering 100% strength recovery within 70 min at room temperature under a compression force of 40 N, despite a Tg of 62.7 °C. Moreover, the hydrophobic thioether groups impart notable moisture resistance, enabling the material to retain >90% of both strength and modulus after 120 h at 80% relative humidity. This work provides a novel and generalizable strategy to overcome the long-standing compromise between mechanical robustness and glassy-state healability in polymers.