The Structure of Aqueous Solutions of a Hydrophilic Ionic Liquid: The Full Concentration Range of 1-Ethyl-3-methylinnidazolium Ethylsulfate and Water

Several structural features of aqueous solutions of the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate were analyzed in the entire concentration range using molecular dynamics simulation results. Different analysis tools developed in-house were applied to describe the size and connectivity of different water and ion aggregates as a function of the solution concentration. Four concentration ranges-x(H2O) < 0.5, 0.5 < x(H2O) < 0.8, 0.8 < x(H2O) < 0.95, and x(H2O) > 0.95-with four distinct structural regimes isolated water molecules, chain like water aggregates, bicontinuous system, and isolated ions or small ion clusters - were identified and discussed, including two different percolation limits: that of water in the ionic liquid network (around x(H2O) = 0.8) and that of the ionic liquid in water (around x(H2O) = 0.95).