'Rigid-flexible' strategy for high-strength, near-room-temperature self-healing, photo-thermally functionalised...

Lignin is the most abundant and only renewable aromatic polymer in nature. Herein, a flexible matrix and the rigid lignin were rationally integrated to prepare high-strength, near-room-temperature self-healing, processable lignin-reinforced polyurethane elastomers (LZPUs). Reversible hydrogen and oxime-amino ester bonds were introduced into the matrix to provide excellent dynamic properties and abundant ligands for lignin-matrix coordination bonds. Abundant metal coordination bonds were constructed between the matrix and lignin via the introduction of Zn²⁺, which not only effectively enhances the dispersibility and compatibility, but also provides an excellent energy dissipation mechanism for the LZPUs. One of the prepared elastomers, LZPUs, exhibited a high strength of 40.5 MPa, which is twice that of the blank sample and 1.6 times that of the sample without Zn²⁺. It maintained kinetic stability at mild temperature, but it exhibited a self-healing efficiency of 91.3 % in strength and 99.8 % in elongation at break after decoupling with trace ethanol (≈ 50 μL) at 35 °C. It exhibited a self-healing efficiency of 93.6 % in strength under 1 sun irradiation (0.1 W cm^-2) for 4 h. We believe this elastomer offering high mechanical properties with multi-functionality can be applied in flexible drives and photo-thermal power generation.