An in situ encapsulation strategy for enhancing the stability of hydrogels in both air and water through surface-confined copolymerization

Air-drying and water-swelling are significant limitations of conventional hydrogels, hindering their potential applications. In this study, we present a facile, versatile and in situ encapsulation strategy aimed at overcoming these drawbacks and enhancing the stability of hydrogels in both air and water. Our method involves creating a flexible and hydrophobic polymer coating through surface-confined copolymerization of triethoxyvinylsilane (VETS) and 2, 2, 3, 4, 4, 4-hexafluorobutyl methacrylate (HFMA), along with the infusion of a hydrophobic oil layer through hydrophobic interactions. By adjusting the monomer ratio, polymerization time, and oil viscosity, we successfully anchored a flexible double-hydrophobic-coating to the hydrogel surface without compromising its mechanical properties. This double-layer-coating acts as an effective barrier, significantly reducing water evaporation within the hydrogel and preventing water diffusion and penetration from the external environment. Remarkably, the encapsulated hydrogel retains over 75.0 % of its weight after a 7-day air-drying test and exhibits non-swelling behavior in diverse aqueous environments for 150 days. Moreover, our strategy is applicable to various hydrogel types and shapes, demonstrating its universality in enhancing resistance against both drying and swelling. Therefore, the proposed approach offers valuable insights into the surface functionalization of hydrogel and broadens the application of next-generation hydrogels in real-world settings, spanning wet and dry environments.