Lignin-Derived Dual-Dynamic Covalent Adaptable Networks: From Solubilization-Enabled Fabrication to Recyclable Adhesives and Carbon Fiber Composites.

Lignin, a renewable biomass-derived aromatic polymer, is restricted by poor solubility and low accessibility of its active functional groups, which hinders its application in high-performance materials. Herein, a dynamic covalent chemistry strategy was proposed: lignin was solubilized in 1,3-propanediol via hydrogen bonding, and lignin-based covalent adaptable networks (CANs) were fabricated through synergistic ring-opening esterification, thiol-anhydride reaction, and thiol-ene click reaction, integrating dual dynamic mechanisms (anhydride-hydroxyl transesterification and anhydride-thiol thioester exchange) for dynamic responsiveness. The optimal sample (L1P1MT1, anhydride:thiol = 1:1) exhibits excellent performance: as an adhesive, it achieves a shear strength of 11.8 MPa on steel with stable bonding over -40°C to 40°C and in complex media, plus thermal debonding at 130°C; as a matrix, carbon fiber composites prepared via vacuum-assisted resin infusion (VARI) show superior tensile properties and can be fully degraded in 1 M NaOH at 25°C within 7 h. Recycled carbon fibers retain their original structure and performance, enabling closed-loop recycling. This work realizes high-value lignin utilization, providing a green route toward high-performance, sustainable CANs with broad prospects in adhesives and advanced composites, thereby advancing green materials development and the polymer circular economy.