Relation between the alpha-relaxation and the Johari-Goldstein Beta-relaxation of a component in miscible blends of two glass-formers

TL;DR

This paper investigates how the alpha- and Johari-Goldstein beta-relaxations of a component in glass-former mixtures change with composition, using the coupling model to predict their relationship and validating with experimental data.

Contribution

It establishes a theoretical link between alpha- and beta-relaxations in mixtures using the coupling model and confirms predictions with experimental results.

Findings

Predicted simultaneous changes of l and -relaxations agree with experimental data.

The coupling model effectively describes relaxation dynamics in glass-former mixtures.

The correspondence between  and -relaxations extends to binary blends.

Abstract

It is well known that the \alpha-relaxation of each component in a miscible mixtures of two glass-formers has its own dynamics, which change with the composition of the blend. Lesser known are the corresponding change of the Johari-Goldstein (JG) \beta-relaxation and its relation to the \alpha-relaxation. Previously, in neat glass-formers, the relaxation time \tauJG of JG \beta-relaxation was identified with the independent relaxation time \tau0 of the coupling model. The correspondence between \tau0 and \tauJG was supported by analysis of experimental data of many glass-formers. In this work, this correspondence between \tau0 and \tauJG of a component in binary mixtures and the relation between \tau0 and \tau\alpha of the coupling model are used to generate predictions of the simultaneous changes of \tau\alpha and \tau\JG of the component on varying the composition of the mixture. The predictions are in accord with the experimental data of the component 2-picoline in mixtures with either tri-styrene or ortho-terphenyl by T. Blochowicz and E.A. Rossler, Phys.Rev.Lett. in press(2004).