Spider Silk-Inspired Bio-Based Adhesive: Robust Adhesion Strength, Exceptional Flame Retardancy, and Full Recyclability

Reversible adhesives, viewed as alternatives for petroleum-derived counterparts, grapple with intricate and toxic preparation processes, while striking a balance between cohesive and interfacial adhesion energies to achieve robust adhesive strength and flame retardancy remains a challenge. Inspired by the heterogeneous structures of spider silk, a reversible ionic/hydrogen bond-induced heterogeneous structure was constructed to amplify cohesive force and flame retardancy while preserving interface adhesion. The resultant adhesives demonstrate an adhesion strength of up to 4.7 MPa, capable of supporting an 80 kg adult with a 0.0025 m² bonding area. Following closed-loop recycling by disassembly, the reused adhesive maintains 98% of its original strength. Additionally, these adhesives have a high limiting oxygen index value (∼46.0%), reduced peak heat release rate (∼49.4%), and reduced smoke production (∼75.0%) when applied to wood products and coatings. This work provides a straightforward and green approach to developing high-performance adhesives with full recyclability and multifunctionality.