Instant and Strong Underwater Adhesion by Coupling Hygroscopicity and in Situ Photocuring

Designing underwater adhesives with short bonding time yet strong adhesion is in pressing demand in many applications such as underwater construction and medical healthcare. However, shortening the bonding time normally leads to premature bonding and thus weak adhesion. Such trade-off becomes more pronounced in the presence of interfacial water, which disrupts adhesive-adherend interactions. The adverse influence of interfacial water on adhesion can be alleviated by various dehydrating strategies; however, attaining high adhesion within a short bonding time still remains a challenge. Here, we present a facile approach that resolves this challenge by embedding a photoreactive monomer into a hygroscopic matrix. This engineered photocurable adhesive instantly absorbs the interfacial water and solidifies upon in situ photocuring (IPC), allowing for the construction of strong adhesive-adherend interactions and bulk cohesion within 10 s. The hygroscopic adhesive with significantly reduced bonding time demonstrates an impressive underwater adhesion strength up to 7.6 MPa, surpassing the state-of-the-art performances. The synergy of efficient adsorption of interfacial water with the IPC strategy could open new opportunities for the development of high-performance underwater adhesives.