A strong and tough supramolecular assembled β-cyclodextrin and chitin nanocrystals protein adhesive: Synthesis, characterization, bonding performance on three-layer plywood

The development of a biomass adhesive as a substitute for petroleum-derived adhesives has been considered a viable option. However, achieving both superior bonding strength and toughness in biomass adhesives remains a significant challenge. Inspired by the human skeletal muscles structure, this study reveals a promising supramolecular structure using tannin acid (TA) functionalized poly-β-cyclodextrin (PCD) (TA@PCD) as elastic tissues and chitin nanocrystals (ChNCs) as green reinforcements to strengthen the soybean meal (SM) adhesive crosslinking network. TA@PCD acts as a dynamic crosslinker that facilitates reversible host-guest interactions, hydrogen bonds, and electrostatic interactions between adjacent stiff ChNCs and SM matrix, resulting in satisfactory strength and toughness. The resulting SM/TA@PCD/ChNCs-2 adhesive has demonstrated satisfactory wet and dry shear strength (1.25 MPa and 2.57 MPa, respectively), toughness (0.69 J), and long-term solvents resistance (80 d). Furthermore, the adhesive can exhibit desirable antimildew characteristics owing to the phenol hydroxyl groups of TA and amino groups of ChNCs. This work showcases an effective supramolecular chemistry strategy for fabricating high-performance biomass adhesives with great potential for practical applications.