Dynamics of binary mixtures with ions: dynamic structure factor and mesophase formation.

Dynamic equations are presented for polar binary mixtures containing ions in the presence of preferential solvation. In one-phase states, we calculate the dynamic structure factor of the composition accounting for ion motion. Microphase separation can take place for sufficiently large solvation asymmetry of the cations and the anions. We show two-dimensional simulation results of the mesophase formation with an antagonistic salt, where the cations are hydrophilic and the anions are hydrophobic. The structure factor S(q) in the resultant mesophase has a sharp peak at an intermediate wavenumber of the order of the Debye-Hückel wavenumber. As the quench depth is increased, the surface tension nearly vanishes in mesophases due to an electric double layer.