Self-Healing and Recyclable Waterborne Polyurethane With Ultra-High Toughness Based on Dynamic Covalent and Hydrogen Bonds

The implementation of self-healing properties in waterborne polyurethane (WPU) materials plays a pivotal role in resource conservation and pollution mitigation. In this work, a strategy was devised to balance the self-healing and mechanical properties of WPU by incorporating bis(hydroxyethyl) disulfide (HEDS), an aliphatic disulfide, as a chain extender. The synthesized WPU constructed a dynamic molecular network through dynamic disulfide bonds (S  S). Meanwhile, a physical cross-linked network was formed by dynamic hydrogen bonds from carbamate groups. The synergistic effect of the dual dynamic bonds significantly contributed to the remarkable self-healing capability of WPU. Specifically, the optimal sample (SWPU-15) not only exhibited a tensile strength of 33.42 MPa and toughness of 162.19 MJ/m 3 but also achieved a healing efficiency of 81.9% when heated at 80°C for 4 h. Profiting from the abundant dynamic bonds, the SWPU-15 sample could be recycled through hot pressing or solvent treatment, with its tensile strength remaining above 20 MPa after recycling. This study provided a feasible approach for preparing environmentally friendly WPU with excellent performance and demonstrates promising prospects for potential applications.