Unprecedentedly tough, strong, water-resistant, and multifunctional lignin-based resin adhesives inspired by loose connective tissue, plant cell walls, and mussel foot proteins

Utilizing lignin as a complete substitute for petroleum-derived phenol to synthesize non-toxic lignin-based resin adhesives with bio-based aldehydes holds substantial significance for advancing sustainable development in the wood-based panel industry. Nevertheless, the poor bonding strength, toughness, and water resistance of phenol-free lignin-based resins hinder their practical application. Herein, inspired by the hyperbranched structures of loose connective tissue, borate chemistry of plant cell walls, and Fe 3+ -phenol coordination bonds of mussel foot proteins, a tough, strong, water-resistant, and multifunctional lignin-based resin adhesive is fabricated through introducing phenylboronic acid-grafted hyperbranched polyamide (HBPB), Fe 2 (SO 4 ) 3 , and furfural into the lignin matrix to construct lignin-based supramolecular networks. HBPB-induced microphase separation structure disperses mechanical stress and inhibits crack evolution. Meanwhile, hyperbranched phenylboronic ester bonds optimize the crosslinking strength and cohesive force. Furthermore, Fe 3+ -phenol coordination bonds facilitate the formation of hydrophobic structures to prevent moisture intrusion. Consequently, the fracture toughness, bonding strength, and wet bonding strength of the resin are 23.4, 6.1, and 5.4 times higher than those of the unmodified resin. Moreover, the resin exhibits excellent flame retardancy, recyclability, degradability, biosafety, and plant-growth promotion after degradation. This biomimetic design provides an effective approach to develop tough, strong, water-resistant, and multifunctional bio-based adhesives.