Thermally Triggered Injectable Underwater Adhesives

A novel bioinspired underwater adhesive based on the injectable aqueous solution of a graft copolymer with a thermoresponsive backbone is reported, which turns into a sticky hydrogel just below body temperature. With this topology, the collapse of the backbones upon the thermal transition leads to the formation of a percolating network of strong hydrophobic domains. Similar to pressure-sensitive adhesives (PSAs), the hydrogel goes through fibrillation and extensive energy dissipation in large deformations, giving it an edge over conventional chemical hydrogels, which are typically elastic and inherently nonsticky. This capability comes from the hydrophobic nanoscaffold, which resists large deformations to minimize its contact with water. Since hydrophobic interactions are not weakened in water, the behavior of the hydrogel is maintained in aqueous medium. Chemistry-insensitive adhesion of this hydrogel offers a major advantage over current injectable adhesives, which rely on in situ chemical crosslinking reactions with tissues.