The structure of aqueous solutions of a hydrophilic ionic liquid: the full concentration range of 1-ethyl-3-methylimidazolium 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(H(2)O)<0.5, 0.5<x(H(2)O)<0.8, 0.8<x(H(2)O)<0.95, and x(H(2)O)>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(H(2)O)=0.8) and that of the ionic liquid in water (around x(H(2)O)=0.95).