Hyper cross-linked poly(ionic liquid)s with special anions as “smart materials” for switchable oil-water separation

Abstract

Smart materials with superhydrophobic-superlipophobic switchability can selectively penetrate one phase (oil or water) through the surface, and the other is trapped. In this study, several super wetting materials were fabricated based on the modulation of Friedel–Crafts alkylation and ion exchange on hyper cross-linked poly(ionic liquid)s (HCPILs) properties. They showed high oil-water separation efficiency in different complex environments. These synthetic HCPILs exhibit different hydrophilicity or lipophilicity when containing various anions. In particular, the HCPIL with a hexafluorophosphate (HCPIL-PF6) or a bis(trifluoromethylsulfonyl)imide (HCPIL-TF2N) possesses a switchable super wetting property due to its unique surface structure and chemical composition. They can be freely switched between hyperhydrophilicity and hyperlipophilicity according to the corresponding solvent changes and are suitable for separating many oil-water mixtures, especially the emulsions. The respective separation flux of the oil-water mixture or lotion is up to 9450 L/m2·h and 800.32 L/m2·h. Besides, they have strong durability and stability in harsh environments such as high concentrations of salt, acid, and basic solutions. After dozens of cycles, they can maintain efficient oil-water separation efficiency and exhibit a high underwater oil contact angle or underoil water contact angle. Such smart materials have great potential in various practical applications, providing a significant idea for future continuous production.