Catechol-free ternary random copolymers for strong and repeatable underwater adhesion

Ternary random copolymers consisting of chemical features of nonphenolic aromatic groups, cations, and polar side chains enabled excellent underwater adhesion. Dry adhesives for underwater adhesion are only occasionally reported, and bioinspired catechol-containing materials have been extensively developed for underwater adhesion but face chemical instability of oxidation in alkaline solutions. Here, we report a biomimetic dry underwater adhesive free of catechol chemistry, which is facilely prepared by ternary copolymerization of monomers consisting of chemical features of nonphenolic aromatic groups, cations, and polar side chains. Ternary copolymers present hydrophobicity, moderate Young's modulus and mechanical toughness, enabling effective hydration layer repellance and interfacial bonding in water. The peel strength to PET substrate can be optimized to 1025 N m −1 , and various substrate surfaces are able to adhere well underwater by varying the copolymer composition. Repeatable adhesion is achieved on account of the self-adhesion property. The tape-based adhesive also manifests long-term water resistance and storage stability under ambient conditions.