Gallol-based constant underwater coating adhesives for severe aqueous conditions

Nowadays, constant and firm underwater adhesives are an essential topic for both biomedical and engineering fields. However, most of conventional underwater-implemented adhesives are lack of strength and durability, limiting their practical long-lasting underwater applications. Here, by taking advantage of the Gallol groups, a facile strategy was reported for the development of solid and persistent underwater coating adhesives based on the layer-by-layer (LBL) self-assembly technique. The TAPVA coatings comprise a low-cost, environment-friendly Poly(vinyl alcohol) (PVA) and naturally occurring tannic acid (TA). The adhesion strength of TAPVA coatings adhered on alloy surface was over 200 kPa underwater for 1 day and more than 100 kPa underwater for 60 days. Compared to previous work about catechol-based or Gallol-rich adhesives, the TAPVA coatings have a extensively tunable and excellent underwater adhesive strength (65.5 ± 8.0–667.1 ± 49.5 kPa) in wide ranges of pH (1.0–11.0) and (608.7 ± 46.8 kPa) at 20 °C in artificial seawater soaked for 14 days, which display robust and long-lasting adhesiveness. Moreover, the TAPVA coatings performed the outstanding underwater leak proof function. In this work, the coating adhesives implies promising applications for marine engineering, such as leakage prevention of ship hull damage.