Predicting nonlinear physical aging of glasses from equilibrium relaxation via the material time

TL;DR

This paper demonstrates that the physical aging of glasses can be predicted from equilibrium relaxation data using the material-time concept, validated through experiments and simulations, advancing understanding of out-of-equilibrium glassy states.

Contribution

It provides the first direct validation of the material time concept for predicting glass aging from equilibrium relaxation behavior.

Findings

A successful prediction of glass aging from linear relaxation data.

Validation of the material time concept through experiments.

Confirmation via computer simulations of a binary liquid mixture.

Abstract

The noncrystalline glassy state of matter plays a role in virtually all fields of materials science and offers complementary properties to those of the crystalline counterpart. The caveat of the glassy state is that it is out of equilibrium and therefore exhibits physical aging, i.e., material properties change over time. For half a century, the physical aging of glasses has been known to be described well by the material-time concept, although the existence of a material time has never been directly validated. We do this here by successfully predicting the aging of the molecular glass 4-vinyl-1,3-dioxolan-2-one from its linear relaxation behavior. This establishes the defining property of the material time. Via the fluctuation-dissipation theorem, our results imply that physical aging can be predicted from thermal-equilibrium fluctuation data, which is confirmed by computer simulations of a binary liquid mixture.