Achieving strong, stable, and durable underwater adhesives based on a simple and generic amino-acid-resembling design.

Developing underwater adhesives is important in many applications. Despite extensive progress, achieving strong, stable, and durable underwater adhesion via a simple and effective way is still challenging, mainly due to the conflict between the interfacial and bulk properties. Here, we report a unique bio-inspired strategy to facilely construct superior underwater adhesives with desirable interfacial and bulk properties. For adhesive design, a hydrophilic backbone is utilized to quickly absorb water for effective dehydration, and a novel amino acid-resembling functional block is developed to provide versatile molecular interactions for high interfacial adhesion. Moreover, the conjunction of these two components enables the generation of abundant covalent crosslinks for robust bulk cohesion. Such a rational design allows the adhesive to present a boosted underwater adhesion (3.92 MPa to glass), remarkable durability (maintaining high strength after one month), and good stability in various harsh environments (pH, salt, high temperature, and organic solvents). This strategy is generic, allowing the derivation of more similar adhesive designs easily and triggering new thinking for designing bio-inspired adhesives and beyond.