A rubber-like, underwater superoleophobic hydrogel for efficient oil/water separation

Hydrogel has been widely applied in agriculture, oil/water separation, and tissue engineering due to its hydrophily and three-dimensional network structure. But its practical applications are restricted by their nonreversible deformation or poor mechanical property to a great extent. In this study, we prepared a rubber-like, interpenetrating-network poly(acrylamide-co-acrylic acid)/chitosan/methacryloxy propyl trimethoxyl silane modified SiO2 nanocomposite hydrogel (P(AM-co-AA)/CS/MPS-SiO2 nanocomposite hydrogel, SIPN-Gels) that exhibit feature underwater superoleophobicity, self-healing and low swelling ratio properties. The nanocomposite hydrogel has hierarchically porous structure and dense spherical papillae structures on its surface, which can improve oil-repellent capability and result in superoleophobicity and self-cleaning property. Besides, synergetic interactions of CS physical networks and MPS-SiO2 crosslinked P(AM-co-AA) covalent network endows the hydrogel with rubber-like mechanical property (high elasticity, fast self-recovery after large tensile or compression deformation), superior to most of reported underwater superoleophobic hydrogels. To apply this hydrogel for efficient oil/water separation, the obtained underwater superoleophobic hydrogel is further coated on a stainless-steel mesh as separator, we believe that the rubber-like nanocomposite hydrogel will inspire researchers to design flexible and wearable oil-repellent or oil/water separation materials.