A Highly Effective Self-Healing Waterborne Polyurethane Vitrimer Containing Conjugated Schiff Base Bonds Driven by Photothermal

Abstract

Self-healing materials are the current focus of smart materials research. However, the implementation of self-healing materials remains limited by the challenge of balancing efficient healing properties with high mechanical strength. In this study, N, N′-(4-hydroxy-3-methoxybenzyl) aniline (VPSB) with π−π conjugated structures were prepared by introducing Schiff base bonds between aromatic rings. VPSB is then incorporated into the polyurethane system to synthesize a self-healing waterborne polyurethane vitrimer (VPSB-WPU) containing conjugated aromatic Schiff base bonds. This locally conjugated structure can convert absorbed visible light into thermal energy, which promotes the rapid breaking and formation of Schiff base bonds, resulting in an improved selfhealing effect. The results indicated that the topological network of the vitrimer exhibited an activation energy (E a ) of 60.69 kJ/mol and a freezing transition temperature (T v ) of 45.46 °C. After 3 min of visible-light irradiation, the film temperature increased from 6.4 to 91.5 °C, with a photothermal conversion efficiency of 92.13% and a film scratch-healing efficiency of 93.75%. After 25 min of irradiation, the fractured film's tensile strength after healing was 11.57 MPa. These results demonstrated that VPSB-WPU exhibited vitrimer properties and possessed excellent mechanical strength, photothermal conversion, and self-healing function. A balance between highly efficient healing properties and excellent mechanical strength was achieved by the VPSB-WPU vitrimer, making it highly promising for future applications in material self-healing.