Cation-Dipole Interaction-Induced Coacervate Underwater Adhesives in Natural Seawater

Significant progress has been made in wet adhesives for low salinity water, but exploration of general ionic adhesives for natural seawater is less developed because the high salinity could weaken interfacial bonding and shields electrostatic interactions, resulting in adhesion failure. Thus, the design of adhesives for natural seawater represents challenges less resolved. Herein, a cationic polyelectrolyte (PECHIA) containing imidazolacetonitrile unit was explored to prepare adhesives enabled by natural seawater. By combining the ion shielding effect with the “cation-dipole” interactions between PECHIA chains, aqueous solution of the PECHIA underwent coacervation and self-crosslinking in natural seawater, allowing for underwater adhesion to various substrates in seawater. The instantaneous lap-shear and tensile adhesion strengths are 47 and 119 kPa, respectively, while the cured adhesive shows ∼739 kPa tensile adhesion in natural seawater. The design of PECHIA enables wet adhesives viable for applications in the diversified scenarios of natural seawater.