Simply Formulated Dry Pressure-Sensitive Adhesives for Substrate-Independent Underwater Adhesion

Due to the long-standing challenge to realize underwater adhesion, there are a few commercially available underwater pressure-sensitive adhesives (PSAs), which are, however, ubiquitously used for dry adhesion. Herein, a dry underwater PSA is developed on the basis of a simple, low-cost, and easily commercial formulation, which only involves the copolymerization of butyl acrylate (BA) and acrylic acid (AA). By tuning the ratios between the hydrophobic BA unit and H-bonding AA unit, we optimize the viscoelastic properties of the PSA to maximize the underwater adhesion performance. The PSA exhibits high underwater bonding strength (e.g., >115 kPa) for diverse substrates (e.g., glass, metals, plastics), at the preload (e.g., 250 kPa) easily accessed by finger pressing. Moreover, the PSA exhibits dry adhesion capability, rendering it conveniently adhered to a backing material to form an underwater adhesive tape. The dry PSA can well-maintain its underwater adhesion performance even after long-term storage in air or incubation in water.