Phase Transitions in Soft Matter Induced by Selective Solvation

TL;DR

This paper reviews recent research on how selective solvation influences phase separation in polar mixtures, highlighting effects of antagonistic salts, strong selective solvents, and theories for ionic systems and polyelectrolytes.

Contribution

It provides a comprehensive overview of phase transition mechanisms driven by selective solvation, including new insights into mesophase formation and electrostatic effects on surface tension.

Findings

Antagonistic salts induce microphase separation at water-oil interfaces.

Strong selective solvents can trigger phase separation above a critical solute density.

Electrostatic contributions are essential for accurate surface tension calculations.

Abstract

We review our recent studies on selective solvation effects in phase separation in polar binary mixtures with a small amount of solutes. Such hydrophilic or hydrophobic particles are preferentially attracted to one of the solvent components. We discuss the role of antagonistic salt composed of hydrophilic and hydrophobic ions, which undergo microphase separation at water-oil interfaces leading to mesophases. We then discuss phase separation induced by a strong selective solvent above a critical solute density np, which occurs far from the solvent coexistence curve. We also give theories of ionic surfactant systems and weakly ionized polyelectrolytes including solvation among charged particles and polar molecules. We point out that the Gibbs formula for the surface tension needs to include an electrostatic contribution in the presence of an electric double layer.