Self-healing and recyclable thermosetting polyurethanes based on dynamic imine and phenol-carbamate bonds

Thermosetting polyurethanes are widely used in various fields owing to the outstanding mechanical performances, excellent heat resistance, and solvent resistance. However, the poor recyclability and self-healing performance of the traditional thermosetting polyurethanes due to the inherent irreversible cross-linked network largely limited their application. To solve these problems, a high-strength, self-healing, and recyclable thermosetting polyurethane containing imine bonds and phenol-carbamate bonds was successfully prepared. First, a trifunctional chain extender (YAOH) bearing imine bond and phenolic hydroxyl groups was synthesized. Subsequently, polyurethanes featuring a dynamic reversible cross-linked network comprising hydrogen bonds, imine bonds, and phenol-carbamate bonds were synthesized via solution polymerization using YAOH as a chain extender. The obtained LYA4 polyurethane demonstrated excellent mechanical strength (the fracture stress was 15.85 MPa), outstanding stretch ability (1193 %), remarkable toughness (72.79 MJ/m 3 ), good fatigue resistance and thermal stability. Furthermore, LYA4 polyurethane also exhibited excellent self-healing properties and recyclability. The stress self-healing efficiency was achieved as high as 100 % when LYA4 polyurethane was healed at 100 °C for 12 h. Additionally, the material could be recycled multiple times under acidic conditions. After three recycling cycles, the mechanical strength of LYA4 polyurethane was maintained at 7.97 MPa. This research proposed a simple method to prepare thermosetting polyurethanes with high self-healing and recoverable properties, demonstrating various potential applications.