Versatile and robust poly(ionic liquid) coatings with intelligent superhydrophilicity/superhydrophobicity switch in high-efficient oil-water separation

Superhydrophilic/superhydrophobic surfaces with unique superiority have been applied for oil-water separation over a long time. Facing the increasingly complicated requirements in diverse separation fields, developing intelligent surfaces with switchable superhydrophilic/superhydrophobic properties are highly needed. In this work, versatile and robust poly(ionic liquid) (PIL) coatings were designed and a series of intelligent materials with switchable superwettabilities were generated for high-efficient oil-water separation. The PIL coatings were obtained by polymerization of PIL monomer on the roughened GO sheets, for which were realized by the immobilization of Fe3O4 nanoparticles. Three materials with different structures (cotton fabric (CF), nylon fabric (NF) and cotton ball (CB)) were chosen as the coating substrates. After "dip-coating" process, the PIL coated materials (PCMs) exhibited switchable superhydrophilic/superhydrophobic performances due to the anionresponsive behavior of PIL and the roughness enhanced effect. Thus, the PCMs showed high-efficient separation performances upon multiple oil-water separation cycles, and the separation could be switched between "water-removing" and "oil-removing" by anion exchange. Meanwhile, the PIL@CF had high permeate fluxes, which could separate layered water-oil mixtures rapidly under gravity; the PIL@NF had the highest separation efficiency; the PIL@CB possessed great potential to be used as efficient absorbents for water/oil adsorption and recycle.