The glass transition of glycerol in the volume-temperature plane

TL;DR

This study investigates how both volume and temperature influence the slowing dynamics of supercooled glycerol near the glass transition, revealing that volume changes have a more significant impact than temperature.

Contribution

It demonstrates that volume and temperature are equally important control variables, with volume having a greater effect on glassy dynamics, and links fragility to density-temperature scaling.

Findings

Both volume and temperature significantly affect glycerol's dynamics.

Dynamics are more sensitive to fractional volume changes than temperature.

Fragility correlates with density-temperature scaling across liquids.

Abstract

We assess the relative importance of spatial congestion and lowered temperature in the slowing dynamics of supercooled glycerol near the glass transition. We independently vary both volume, V, and temperature, T, by applying high pressure and monitor the dynamics by measuring the dielectric susceptibility. Our results demonstrate that both variables are control variables of comparable importance. However, a generalization of the concept of fragility of a glass-former shows that the dynamics are quantitatively more sensitive to fractional changes in V than T. We identify a connection between the fragility and a recently proposed density-temperature scaling which indicates that this conclusion holds for other liquids and polymers.