Lignin-reinforced photothermal polyurethane elastomers with tunable mechanics, shape memory, and antibacterial...

Balancing the mechanical properties and multifunctionality of polyurethane elastomers presents a significant challenge. Herein, a sustainable strategy for fabricating high-performance polyurethane elastomers (MEPU) was developed by integrating two lignin derivatives, chemically modified lignin (MLOH) and unmodified enzymatic lignin (EL). MLOH, prepared via selective conversion of phenolic hydroxyl and carboxyl groups to alcohol hydroxyls, serves as a reactive chemical crosslinker, enhancing network formation and microphase separation. EL acts as a physical crosslinker, reinforcing intermolecular interactions. Notably, both MLOH and EL function as photothermal conversion agents, endowing MEPU with excellent photothermal properties. The resulting MEPU exhibits tunable photothermal conversion and mechanical performance, which can be optimized by adjusting the MLOH/EL ratio. Specifically, the optimal formulation M₅E₅PU displays exceptional mechanical properties, including tensile strength of 37.8 ± 2.0 MPa, elongation at break of 795.5 ± 26.4%, toughness of 125.6 ± 8.0 MJ/m³, and superior photothermal conversion, reaching 101.8 °C after 2 min near-infrared (NIR) irradiation. Leveraging its excellent photothermal properties, M₅E₅PU demonstrates a suite of NIR-triggered functionalities, including remarkable shape memory, fatigue resistance, self-healing, and complete antibacterial activity against both E. coli and S. aureus within 5 min. Therefore, this work offers a novel platform for developing multifunctional bio-based robust photothermal elastomers and promoting high-value utilization of lignin.