Simulation and measurement of water-induced liquid-liquid phase separation of imidazolium ionic liquid mixtures

The miscibility of ionic liquid (IL) pairs with a common cation (1-ethyl-3-methylimidazolium [CCim]) and different anions (bis(trifluoromethylsulfonyl)amide [TFSI], acetate [OAc], and chloride [Cl]) was investigated at a wide range of water concentrations at room temperature. Molecular simulations predicted that the addition of water to the [CCim][TFSI]:[CCim][OAc] and [CCim][TFSI]:[CCim][Cl] mixtures would induce a liquid-liquid phase separation and that water addition to the [CCim][OAc]:[CCim][Cl] mixture would not produce a phase separation. The effect of water on the phase behavior of the IL mixtures was verified experimentally, and the IL and water concentrations were determined in each phase. Of particular importance is the analytical methodology used to determine the species' concentration, where H NMR and a combination of F NMR, Karl Fischer titration, and ion chromatography techniques were applied.