Hydrogen bond dynamics at the glass transition

TL;DR

This paper investigates how hydrogen bonds influence the glass transition, revealing their varying impact on shear relaxation spectra in different materials and connecting these effects to a recent theoretical framework.

Contribution

It provides a quantitative description of hydrogen bond effects on relaxation spectra across multiple physical properties using a unified theory.

Findings

Hydrogen bonds cause a strong asymmetric rupture process affecting shear relaxation.

The influence of hydrogen bonds varies significantly between glycerol and PPE.

A recent theory successfully describes relaxation spectra in shear, dielectrics, and heat capacity.

Abstract

The glass transition in hydrogen-bonded glass formers differs from the glass transition in other glass formers. The Eshelby rearrangements of the highly viscous flow are superimposed by strongly asymmetric hydrogen bond rupture processes, responsible for the excess wing. Their influence on the shear relaxation spectrum is strong in glycerol and close to zero in PPE, reflecting the strength of the hydrogen bond contribution to the high frequency shear modulus. A recent theory of the highly viscous flow enables a quantitative common description of the relaxation spectra in shear, linear and non-linear dielectrics, and heat capacity.