Dynamically and structurally heterogeneous 1-propanol/water mixtures

Vasileios Moschos; Antonela Ananiadou; George Floudas

doi:10.1063/5.0170504

Dynamically and structurally heterogeneous 1-propanol/water mixtures

J Chem Phys. 2023 Oct 28;159(16):164903. doi: 10.1063/5.0170504.

Authors

Vasileios Moschos¹, Antonela Ananiadou¹, George Floudas^{1

2

3}

Affiliations

¹ Department of Physics, University of Ioannina, 45110 Ioannina, Greece.
² Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
³ University Research Center of Ioannina (URCI)-Institute of Materials Science and Computing, 45110 Ioannina, Greece.

PMID: 37877491
DOI: 10.1063/5.0170504

Abstract

1-propanol/water mixtures over the whole composition range (0 < XV ≤ 1; XV is the 1-propanol volume fraction) are shown to be structurally and dynamically heterogeneous. By combining structural (x-ray diffraction), thermodynamic (differential scanning calorimetry) and dynamical probes (dielectric spectroscopy) we construct the pertinent phase diagram. It consists of liquid 1-propanol, liquid water, hexagonal ice and different hydrates, the latter sharing the same lattice. The phase diagram can be discussed in terms of four regimes, all having in common a droplet arrangement of the minority component. When water droplets are strongly confined by 1-propanol (regime I, 0.92 < XV ≤ 1; "soft" confinement), water is unable to crystallize. It has dynamics reminiscent to the ultra-viscous water phase known as high-density liquid (HDL). When water droplets are moderately confined (regime II, 0.75 < XV ≤ 0.92) water can crystallize via homogeneous nucleation. Strikingly, the homogeneous nucleation temperature is at 205 K, well within "no-man's land." The result is in line with earlier reports that soft confinement is the key to enter into the "no-man's land". When 1-propanol is the minority component (regimes III and IV), the structure and the dynamics are dominated by the 1-propanol/water interface with the formation of hydrates. The corresponding dynamical features suggest a link between hydrate formation and the two metastable phases of ultra-viscous water, HDL and low-density liquid.