# Salt-induced microheterogeneities in binary liquid mixtures

## TL;DR

This study investigates how antagonistic salts induce microheterogeneities in binary liquid mixtures, revealing that competition between short-range and long-range interactions creates characteristic length scales, with experimental and theoretical analysis near phase transitions.

## Contribution

It demonstrates that microheterogeneity formation results from competing interactions and provides a quantitative model fitting SAXS data without specific assumptions, clarifying the underlying mechanism.

## Key findings

- Microheterogeneities are generated by competing short-range and monopole-dipole interactions.
- Experimental SAXS data are accurately fitted by derived correlation functions.
- Near the phase transition, critical-like behavior is observed in the microheterogeneity structure.

## Abstract

The salt-induced microheterogeneity (MH) formation in binary liquid mixtures is studied by small-angle X-ray scattering (SAXS) and liquid state theory. Previous experiments have shown that this phenomenon occurs for antagonistic salts, whose cations and anions prefer different components of the solvent mixture. However, so far the precise mechanism leading to the characteristic length scale of MHs remained unclear. Here, it is shown that MHs can be generated by the competition of short-ranged interactions and long-ranged monopole-dipole interactions. The experimental SAXS patterns can be quantitatively reproduced by fitting to the derived correlation functions without assuming any specific model. The dependency of the MH structure with respect to ionic strength and temperature is analyzed. Close to the demixing phase transition, critical-like behavior occurs with respect to the spinodal line in the phase diagram.