# Mean field approach to first and second order phase transitions in ionic liquids

## TL;DR

This paper uses a mean-field model to analyze phase transitions in ionic liquids, revealing how nano-structures form and influence the electrical double layer, with implications for their self-assembly and electrochemical properties.

## Contribution

It introduces a mean-field framework based on Onsager's relations to describe phase transitions and nano-structure formation in ionic liquids, linking them to experimental observations.

## Key findings

- Bulk nano-structures arise via type-I and II phase transitions.
- Type-I phase transition is induced by thermal fluctuations and depends on ion ratio.
- Insights relate to decaying charge layers observed in experiments.

## Abstract

Ionic liquids are solvent-free electrolytes, some of which possess an intriguing self-assembly property. Using a mean-field framework (based on Onsager's relations) we show that bulk nano-structures arise via type-I and II phase transitions (PT), which directly affect the electrical double layer (EDL) structure. Ginzburg-Landau equation is derived and PT are related to temperature, potential and interactions. The type-I PT occurs for geometrically dissimilar anion/cation ratio and, surprisingly, is induced by perturbations on order of thermal fluctuations. Finally, we compare the insights with the decaying charge layers within the EDL, as widely observed in experiments.