Determine whether liquid-liquid phase separation is isocompositional or involves demixing

Determine whether the liquid-liquid phase separation observed in deeply supercooled water-glycerol solutions is isocompositional or accompanied by a net redistribution of glycerol and water between the transient liquid domains.

Background

The study combines wide-angle X-ray scattering (WAXS), ultra-small-angle X-ray scattering (USAXS), and X-ray photon correlation spectroscopy (XPCS) to show that a structural and dynamical transformation precedes detectable ice crystallization in a deeply supercooled 16.5 mol% water-glycerol solution. The observations are consistent with liquid-liquid phase separation (LLPS), potentially through spinodal decomposition, but the measurements primarily probe average liquid structure and mesoscale dynamics.

An unresolved issue is whether the separated liquid domains retain the original water-glycerol composition or whether the transformation produces compositional demixing with a net redistribution of water and glycerol. Resolving this distinction would clarify whether the observed LLPS is driven mainly by water-glycerol demixing or by an underlying liquid-liquid transition, and would require composition-sensitive measurements beyond those used in the study.