Towards Solar-Driven Formation of Robust and Self-Healable Waterborne Polyurethane Containing Disulfide Bonds via in-situ Incorporation of 2D Titanium Carbide MXene

Waterborne polymers are vital for coating industry to reduce carbon emissions. However, formation of robust and self-healable films at ambient temperature remains a challenge owing to high energy cost of film formation pro-cess. This work reports a solar-driven film formation of waterborne polyurethanes (WPUs) containing disulfide bonds via in-situ incorporation of 2D titanium carbide (MXene) with ability to convert light to heat. Instead of directly mixed with WPUs, MXene is added to join the reaction with isocyanate-terminated pre-polymer before emulsification process. This approach not only prevents aggregation of MXene in water but stabilizes MXene against thermal degradation which is the key hurdle formassproductionofMXene/WPUcomposites.More importantly, our results show that mechanical performance of WPU films under visible light (100 mW/cm²)is overwhelmingly competitive with that processed in oven. Furthermore, the existence of disulfide bonds in PU chains enables fast self-healing of micro-cracks under natural visible light which could vanish completely within 40 min. The fractured specimens were repaired under natural visible light for 2 h, and the self-healing efficiency of tensile strength and elongation at break reached over 94.00%.