Mussel-inspired catechol-based strategy has been widely used in development of underwater adhesives. Nonetheless, the properties of the adhesives were still severely limited under harsh environments. A facile approach was proposed...

Anisotropic poly(vinyl alcohol) hydrogels with significantly enhanced mechanical properties are prepared by a freezing–thawing under drawing (FTD) method.

The mussel-inspired catechol-based strategy has been widely used in the development of adhesives.

No abstract

Hydrogel adhesives have been widely used in wet environments. Nonetheless, strong and stable persistent adhesion remains a challenge. Here, we report a facile yet powerful strategy to construct high-strength hydrogel adhesives for durable adhesion in a saline environment. Such a hydrogel consists of two polymer networks: a hydrophobic-associated polyacrylamide network of covalent and noncovalent cross-links and an alginate network cross-linked by divalent cations in saline. Meanwhile, polydopamine nanoparticles formed through in-situ self-polymerization are distributed evenly throughout the system to provide underwater adhesion. A low and controllable swelling rate and high compressive strength of hydrogels can be achieved via this multiple interaction strategy. Ultimately, this strategy contributes to the persistent underwater adhesion of hydrogels, and the decreasing rate of lap-shear adhesion strength of hydrogels is only 24.79 ± 8.01% after saline immersion for up to 21 days. Moreover, good cytocompatibility of hydrogels is helpful for their application in the biomedical field.