Volume Effects on the Glass Transition Dynamics

TL;DR

This paper investigates how available volume influences the glass transition dynamics, revealing that increased volume enhances volume-dependence of relaxation times, challenging traditional free volume theories.

Contribution

It demonstrates that increasing available volume strengthens volume effects on relaxation dynamics, providing new insights into the mechanisms of the glass transition.

Findings

Increased volume correlates with stronger volume-dependence of relaxation times.

Results challenge free volume interpretations of the glass transition.

Modifications affecting volume alter the ratio of activation enthalpies.

Abstract

The role of jamming (steric constraints) and its relationship to the available volume is addressed by examining the effect that certain modifications of a glass-former have on the ratio of its isochoric and isobaric activation enthalpies. This ratio reflects the relative contribution of volume (density) and temperature (thermal energy) to the temperature-dependence of the relaxation times of liquids and polymers. We find that an increase in the available volume confers a stronger volume-dependence to the relaxation dynamics, a result at odds with free volume interpretations of the glass transition.