UV-resistant and light-controlled self-healing lignin-based waterborne polyurethane elastomers for photothermal welding

Exploiting inexpensive, bio-derived lignin as a partial replacement for petroleum-based polyols offers a sustainable pathway to high-value lignin applications. However, prior studies have mainly focused on lignin's reinforcing effects in elastomers, neglecting its potential photothermal properties. Lignin-modified waterborne polyurethane elastomers (LWPUxAy) were synthesized, demonstrating UV resistance, enhanced mechanical robustness, rapid light-controlled self-healing, and photothermal weldability. LWPUxAy exhibited exceptional mechanical properties (51.9 MPa tensile strength, 768.8 % elongation) and a significantly enhanced photothermal conversion efficiency due to Ag + ligand bonding. Upon near-infrared (NIR) irradiation (1.25 W/cm 2 ), LWPUxAy rapidly reached a surface temperature exceeding 160 °C within 35 s. The synthesized LWPUxAy demonstrated rapid, light-controlled self-healing and notable welding performance under near-infrared (NIR) irradiation (0.6 W/cm 2 , 5 min). Furthermore, LWPUx effectively blocked the entire UV spectrum within the 200–400 nm range. Bio-derived lignin was incorporated into light-responsive polyurethane elastomers, resulting in enhanced tensile strength and self-healing efficiency.