Effects of Ion Solvation in a Mixture of Polar Solvent and Polymer

The effect of the strong electrostatic field near ions dissolved in polar liquids causes substantial deviations from the standard theory of ion solvation based on linear-dielectric response theory. We consider this problem in a mixture of polar solvent and polymer by developing a polymerized Stockmayer-fluid (dipolar molecule) simulation method that accounts for the chain statistics and molecular polarization at the molecular scale. Our molecular dynamics simulations suggest that the dielectric constant of the mixture follows Landau-Lifshitz-Looyenga's formula, instead of the number fraction-weighted average. We also show that the ions in the polymer-rich phase tend to be solvated preferentially by polar solvents, tightly bound to the solvent molecules. However, the ion-solvent affinity decreases as the solvent content increases. We discuss how these two competing effects yield a qualitative difference in the simulated solvation energy from the conventional energy expression.