Phase diagram of a solution undergoing inverse melting

TL;DR

This study maps the phase diagram of an inverse melting solution, revealing fluid and solid phases and their transitions, using calorimetry, rheology, and X-ray diffraction to understand the system's complex behavior.

Contribution

It provides the first detailed phase diagram of an inverse melting solution, highlighting the transition between fluid and solid phases at varying concentrations.

Findings

Two fluid phases separated by a solid phase at high concentration

Solid phase region diminishes with decreasing concentration

First order phase transition observed between fluid phases

Abstract

The phase diagram of $\alpha$-cyclodextrin/water/4-methylpyridine solutions, a system undergoing inverse melting, has been studied by differential scanning calorimetry, rheological methods, and X-rays diffraction. Two different fluid phases separated by a solid region have been observed in the high $\alpha$-cyclodextrin concentration range ($c$$\geq$150 mg/ml). Decreasing $c$, the temperature interval where the solid phase exists decreases and eventually disappears, and a first order phase transition is observed between the two different fluid phases.