Multi-branched cage molecules synergistically physically and chemically crosslink transparent, robust, and reusable adhesive by mimicking gecko setae

The protection of marine equipment against complex media environments encounters multifaceted coupling factors, posing significant challenges to achieving durable environmental resistance and robust interfacial adhesion for critical applications such as submarine optical components, cross-sea bridges, and deep-sea operational devices. In this work, inspired by the gecko setae structure, based on the multi-branched molecular structure design characteristics of cage-like structures (n = 1, 2, 3) in synergy with the special zigzag hydrogen bond arrays of thiourea/urea, three types of tough adhesives with high transparency, mechanically robust interfacial adhesion, self-healing, and the ability to maintain strength for reusability are controllably fabricated. The unique molecular design of the multi-branched cage-like structures is effectively integrated through physical/chemical crosslinking actions with high-density quintuple hydrogen bond arrays of supramolecular polyurethane, showcasing strong adhesive strength (22.45 MPa; 406 % enhancement). Interestingly, the synergy between the initial interfacial wet adhesion work dominated by interfacial tension and the energy change terms (enthalpy change) brought by the physical/chemical properties of cleverly designed adhesives controlling viscous forces during curing is demonstrated through observations of dynamic wetting behavior of adhesive melts, innovatively establishing the evolutionary laws of adhesive spatial network structures and interfacial adhesion mechanisms. Additionally, the adhesive’s resistance to high and low temperatures and marine conditions is simulated for bridge pier protection, offering technical support for enhancing the protection of marine engineering components.