The nonlinear physical aging-susceptibility of a glass forming melt

TL;DR

This paper introduces a high-resolution oscillatory method to analyze physical aging in glass-forming melts, revealing complex susceptibilities and aging fingerprints with unprecedented detail using Fourier analysis of rheological responses.

Contribution

It presents a novel temperature oscillation-based approach to measure high-order aging susceptibilities in complex systems, surpassing traditional methods.

Findings

Accessed up to sixth harmonics in glycerol's relaxation

Detected aging fingerprints within three orders of magnitude in temperature resolution

High-order susceptibilities fit well with the Tool-Narayanaswami-Moynihan formalism

Abstract

A high-resolution, temperature oscillation-based probe of physical aging in complex systems is introduced. The Fourier analysis of the measured responses allows one to extract a high-order aging-related complex susceptibility that is not accessible via traditional temperature-jump and -ramp procedures. To demonstrate the potential of this oscillatory approach, we analyze the periodic time evolution of glycerol's structural relaxation using shear rheology as a vehicle. Thereby, we access up to the sixth harmonics and detect aging fingerprints within a resolution range of three orders of magnitude for temperature amplitudes of up to 4 K. The high-order aging coefficients and susceptibilities obtained for glycerol are described well by the Tool-Narayanaswami-Moynihan formalism.