A Dragonfly Wing-InspiredMXene-Reinforced Soy ProteinAdhesive with Balanced Strength, Toughness, and Multifunctionality

Abstract Replacing petroleum-derived wood adhesives with soy protein isolate (SPI) offers a sustainable alternative, yet the practical application of SPI is severely hindered by its intrinsic poor water resistance and mechanical fragility. To overcome these drawbacks, we developed a high-performance biomimetic adhesive by embedding MXene-Ag nanostructures into a rigid SPI framework, replicating the efficient energy-dissipating architecture of dragonfly wings. This multiscale hierarchical architecture significantly enhances both strength and toughness. The interfacial bonding is robustly fortified through a dual-cross-linking strategy: alongside Schiff base and hydrogen bonds, the incorporation of 3-carboxyphenylboronic acid (CPBA) triggers the formation of dense amide and borate ester covalent networks. Consequently, the engineered adhesive exhibits exceptional water resistance and mechanical performance, achieving a dry shear strength of 2.01 MPa and a wet shear strength of 1.19 MPa (108.8% enhancement over pure SPI), meeting the requirements for interior use. Additionally, its fracture toughness reaches 0.359 J (a 312.6% increase). Furthermore, the synergistic effects of the composite matrix endow the adhesive with exceptional multifunctional properties, including prolonged mildew resistance for up to 110 days and enhanced fire resistance, evidenced by a 52.05% reduction in the peak heat release rate. This work provides a scalable and robust platform for designing multifunctional, biobased structural adhesives.