Underwater Adhesives Enabled by Interfacial Water Activation through Solvent Exchange and In Situ Silane Hydrolysis Cross-Linking

Interfacial water typically impairs underwater adhesion by preventing effective adhesive-substrate contact. Herein, a rationally designed copolymer adhesive, synthesized via free radical polymerization of hydrophilic/hydrophobic segments and silane coupling agents, is reported to overcome this challenge through a synergistic water-management mechanism. The introduction of silane groups transforms interfacial water from a barrier into a reactant: its consumption during hydrolysis disrupts the hydration layer, enabling other segments of the adhesive to displace water and establish intimate contact. Uniquely, the bulk curing kinetics are governed by a dynamic solvent exchange process. Initially, the rapid efflux of dimethyl sulfoxide (DMSO) induces phase separation to form a cohesive network and facilitates silanol condensation by solubilizing aqueous byproducts. As bulk water progressively replaces DMSO, the diminishing diffusion gradient and reduced capacity for byproduct removal lead to a self-limiting deceleration of the cross-linking rate, eventually reaching a stable equilibrium. This mechanism results in universal adhesion (0.42–1.98 MPa) on metals (Fe, SS304), glass and polymers (PMMA, PVC, PP), and a progressive strengthening profile that maximizes in ∼10 days,while maintaining 90% performance in harsh environments (acid/alkali/salt). For time-sensitive applications, sodium dodecyl sulfate (SDS)/carbon nanotubes (CNTs) incorporation enables rapid photothermal curing, achieving 60% stronger adhesion within 30 min of xenon irradiation (86% faster than conventional methods). The prepared adhesive combines autonomous long-term strengthening with on-demand rapid curing, addressing a critical limitation in most of conventional underwater adhesives exhibiting static adhesion strength or gradual deterioration over time. Systematic characterization confirms the adhesive and its mechanical properties through this innovative curing process. This work provides fundamental insights into interfacial chemistry manipulation and presents a versatile solution for marine engineering and industrial applications requiring robust, environmentally stable underwater adhesion.