A slippery oil-repellent hydrogel coating

Development of oil-repellent coatings that are anti-fouling with water alone is highly desirable, yet still challenging. Herein, to address this challenge, we fabricate a slippery oil-repellent hydrogel coating that exhibits oil repellency when exposed in the air as well as underwater. In the air, water wets the slippery oil-repellent hydrogel coating surface completely, while organic liquid drops such as toluene can slide off the water wetted coating surface easily. When immersed in water, the slippery oil-repellent hydrogel coating surface exhibits excellent underwater superoleophobic property with all oil contact angles more than 159 degrees and oil adhesive forces less than 1 mu N. The hydrogel coating keeps its oil repellency after long-term outdoor storage, thermal treatment, knife scratching and other treatments. Exploiting its water-attracting and oil-repelling property, the slippery oil-repellent hydrogel coated copper mesh and filter paper are demonstrated as reusable membranes to separate oil-water mixtures with separation efficiency more than 97%. Graphic abstract