Self‐Contained Underwater Adhesion and Informational Labeling Enabled by Arene‐Functionalized Polymeric Ionogels

Abstract Adhesives and water exhibit a conflicting correlation as indicated by the failure of most synthetic adhesives in submerged and humid environments. Development of instant, strong, reversible, and long‐lasting adhesives that can adhere to wet surfaces and function in underwater environments presents a formidable challenge, yet it is of paramount importance in biomedical and engineering applications. Herein, viscoelastic and moldable ionogels are developed based on synergistic engineering of aromatic substituents, fluorinated counterions, ionic building blocks, and 3D cross‐linked networks. The molecular design and structural engineering result in a facile synthesis, two bonding methods (glue‐ and tape‐type), and the combined mechanisms of enhanced adhesion and cohesion. The high underwater adhesion strength of over 8.9 MPa is among the best‐performing tape‐type underwater adhesives reported to date. A combination of excellent durability, reliability, deformation resistance, salt tolerance, water proof, antiswelling, and self‐healing properties demonstrates the “self‐contained” underwater adhesion. Furthermore, the extended π‐conjugation of the aromatic pendant groups confers a new functionality to the ionogels – visible fluorescence, enabling intriguing applications such as underwater labeling, information encryption, and signal transmission. This study shines lights on the fabrication of ionogel‐based adhesives and provides their future perspectives in underwater sealing, self‐repair, crack diagnosis, and informational labeling.