Reversible tuning of the hydrophobic–hydrophilic transition of hydrophobic ionic liquids by means of an electric field

Abstract

In this work, we demonstrate for the first time that hydrophobic ILs can be strikingly tuned to be hydrophilic under a strong external electric field, with the use of nonequilibrium molecular dynamics (MD) simulations and atomic force microscopy (AFM) experiments. With increase of the electric field strength, the cation–anion and water–water interactions are both attenuated. The cations and anions gradually evolve from an IL interface to a water medium, leading to surprisingly hydrophilicity with high intersolvent mixing. This novel hydrophilic mixing process can be reversibly tuned to phase separation by reversing the electric field. These simulations suggest that the driving force of this hydrophobic–hydrophilic transition derived from a different tuning effect for the cations and the anions.