Design of amphiphilic-function-aiding biopolymer adhesives for strong and durable underwater adhesion via a simple solvent-exchange approach

Achieving strong and durable underwater adhesion in an easy way is highly demanded for practical applications. Despite extensive progresses, developing high-performance underwater adhesives by leveraging low-cost and sustainable biopolymer materials remains a hard task. Here, we report a simple one-pot strategy to construct a superior underwater adhesive through designing an amphiphilic function (established by thioctic acid and epoxy connector) in commercial biopolymer system. This amphiphilic-function-aiding biopolymer adhesive (AFBA), prepared in ethanol solution, can harness solvent exchange to trigger hydrophobic aggregation and phase transition in water, thereby yielding hydrophobic repulsion for effective dehydration, high structural stability for bulk cohesion strengthening, and versatile molecular interactions for interfacial adhesion enhancement. As such, AFBA exhibits a strong yet durable underwater adhesion (constantly increasing from 560 to 729 KPa to wood substrate after storing 30 days) and remarkable tolerance to various harsh environments (seawater, acidic, and alkaline solutions), allowing for underwater applying as a sealant to repair damage. Moreover, this simple strategy is generic that can derive a family of AFBAs with excellent underwater adhesion. This work may provide a promising pathway for engineering high-performance adhesives, and also open up a new direction to overcome the limitations of hydrophilic biopolymers in underwater application.