Dynamic properties of water molecules in ionic liquid/water mixture with various alkyl chain length

This work investigated the alkyl chain length dependence of dynamic properties of water molecules in imidazolium-based ionic liquid (IL)/water mixtures. The microscopic (i.e., self-diffusion coefficients of water molecule and ILs) properties of these systems suggested that the movement of IL/water mixtures decreases with increasing alkyl chain length of the IL. In contrast, the self-diffusion coefficient ratios (Dwater/Danion or Dwater/Dcation) at a water concentration extrapolated to 0 mol% (i.e., the value of a pure IL) increased as the alkyl chain length of the IL increased. This finding indicates that the water molecules in the IL/water mixtures move more independent of the IL as the alkyl chain length of the IL increases. Based on these results, we propose a plausible model for water molecules in a space within the IL.