An equation for the description of volume and temperature dependences of the dynamics of supercooled liquids and polymer melts

TL;DR

This paper discusses a new equation that accurately models how temperature and volume influence the relaxation dynamics of supercooled liquids and polymer melts, fitting experimental data with minimal parameters.

Contribution

It introduces a novel expression that satisfies the scaling law for relaxation times and effectively fits experimental data across various glass-forming liquids and polymers.

Findings

Accurately fits experimental relaxation data over extended temperature and volume ranges.

Reconciles correlations between isochoric fragility, isobaric fragility, and the scaling exponent g.

Provides a minimal-parameter model for supercooled liquid and polymer melt dynamics.

Abstract

A recently proposed expression to describe the temperature and volume dependences of the structural (or alpha) relaxation time is discussed. This equation satisfies the scaling law for the relaxation times, tau = f(TV^g), where T is temperature, V the specific volume, and g a material-dependent constant. The expression for the function f is shown to accurately fit experimental data for several glass-forming liquids and polymers over an extended range encompassing the dynamic crossover, providing a description of the dynamics with a minimal number of parameters. The results herein can be reconciled with previously found correlations of the isochoric fragility with both the isobaric fragility at atmospheric pressure and the scaling exponent g.