A Fully Bio-Derived Vitrimer from Lignin and Soybean Oil with Integrated Photothermal Conversion, Self-Healing, and Recyclability

To advance the high-value utilization of lignin and develop sustainable materials for clean energy applications, a fully bioderived polyimine vitrimer (VL) was synthesized through an energy-efficient room-temperature process by covalently integrating levulinic acid-modified lignin with a soybean oil-derived diamine. This design yields a material that combines robust mechanical properties (toughness: 7.1 MJ/m 3 ) with remarkable self-healing, recycling, and photothermal conversion capacities. The vitrimer can repair scratches within 10 min at 80 ° C and can be fully recycled with ∼90% strength retention after five reprocessing cycles. These dynamic features are governed by the cooperative exchange of hydrogen and imine bonds. Furthermore, the material demonstrates stable and efficient photothermal conversion, a direct result of the preserved π-conjugated and donor–acceptor structure of the lignin units. This photothermal capability not only enables applications such as photothermoelectric generation but also permits noncontact, light-triggered self-healing. This work transforms lignin from a byproduct into a core building block for advanced smart materials, providing a sustainable paradigm for developing multifunctional systems in energy and wearable technologies.