Green and ultrastrong polyphenol lignin-based vitrimer adhesive with photothermal conversion property, wide temperature adaptability, and solvent resistance

Lignin, a natural adhesive in plants, has received extensive attention from both academia and industry. However, limited by the reactivity and heterogeneity of industrial lignin raw materials, lignin-based adhesives are not competitive in terms of adhesive performance and reusability. Here, a green and facile method is reported for a polyphenol lignin (Phenol-lignin)-based, ultrastrong, reusable, wide temperature adaptability, and solvent-resistant vitrimer adhesive with molecular designs of lignin extending beyond those in nature. The fabricated Phenol-lignin-based vitrimer exhibits the world's highest wood lap shear strength of 12.87 MPa among the vitrimer adhesives. Even in extreme environments, such as boiling water (100 degrees C), liquid nitrogen (-196 degrees C), and organic solvents, the Phenol-lignin-based vitrimer-bonded wood sheets can still maintain a high level of strength. In addition, due to the good light-to-heat conversion performance of lignin, Phenol-lignin-based vitrimer can be repaired by infrared laser irradiation. The recycled adhesive retained 93.1 % of its strength. This new lignin material will be incorporated into not only industrial adhesives but also various green material systems in the future.