Biomimetic development of a strong, mildew-resistant soy protein adhesive via mineral–organic system and phenol-amine synergy

Plant-derived protein adhesives have attracted extensive research interest in recent years as effective alternatives to nonrenewable and nonbiodegradable formaldehyde-based adhesives. However, owing to their insufficient bonding strength and poor mildew resistance, it has been challenging for biopolymer adhesives to achieve strong and durable adhesion performance. Inspired by insect cuticles, we report a green and versatile strategy for the fabrication of a strong, mildew-resistant, antibacterial soy protein (SP)-based adhesive via phenol-amine synergy and biomineralization reinforcement. Gallic acid (GA), as a phenolic glue molecule, was co-assembled with hydroxyapatite (HAP) through Ca2+–phenolic coordination bonds to prepare GA-functionalized HAP ([email protected]) nanoparticles. Moreover, ε-polylysine (PL) with abundant amino groups was used for grafting to the phenolic [email protected] nanoparticles through a Schiff base reaction. Owing to multiple cross-linking and the inorganic–organic hybrid system, the wet shear strength of the SP/PL/[email protected] adhesive increased considerably to 1.09 MPa, 127% higher than the unmodified SP adhesive. The cationic PL polymer endowed the protein adhesive with desirable antifungal and antibacterial properties, synergistically with the phenolic components in [email protected] In addition, the resultant adhesive exhibited enhanced flame retardation, thermal stability, and water resistance. This simple and versatile strategy could lead to advances in the development of high-performance biopolymer materials for biological and engineering applications including adhesives, hydrogels, and films.