Superstrong Water-Resistant underwater adhesives enabled by in situ coacervation through dense hydrogen bonds

Underwater adhesives that can provide strong and stable adhesion on various substrates are highly desirable for both daily and industrial uses. It remains challenging to achieve both high adhesion strength and long-term water-resistance at the same time. Herein, using commercially available materials, we report successful preparation of a novel type of underwater adhesives enabled by in situ coacervation through high dense hydrogen bonds (H-bonds). The formed poly(acrylic acid-co-benzyl methacrylate) [P(AA-co-BzMA)] could spontaneously complex with poly(vinyl pyrrolidone) (PVP) via strong and dense H-bonds, in cooperation with hydrophobic groups of BzMA to resist water. The resultant adhesives showed superstrong underwater adhesion with shear strength reaching as high as 9.29 MPa on glass substrates. The shear strength remained almost unchanged even after 60 days of immersion in water, demonstrating excellent water-resistant performance. The adhesives could be applied on various substrates in different environments including the artificial seawater, high humidity and acid solution for versatile applications.