Intrinsic aging and effective viscosity in the slow dynamics of a soft glass with tunable elasticity

TL;DR

This study explores how the elastic modulus influences slow dynamics and aging in a soft glass, revealing that an effective viscosity governs these processes and remains unaffected by elastic perturbations or quench rates.

Contribution

It introduces a model linking effective viscosity to internal stress at the fluid-to-solid transition, advancing understanding of soft glass aging.

Findings

Effective viscosity is independent of elastic modulus and perturbations.

A simple model connects effective viscosity to internal stress.

Aging behavior is fully described by the evolution of effective viscosity.

Abstract

We investigate by rheology and light scattering the influence of the elastic modulus, $G_0$, on the slow dynamics and the aging of a soft glass. We show that the slow dynamics and the aging can be entirely described by the evolution of an effective viscosity, $\eta_{eff}$, defined as the characteristic time measured in a stress relaxation experiment times $G_0$. At all time, $\eta_{eff}$ is found to be independent of $G_0$, of elastic perturbations, and of the rate at which the sample is quenched in the glassy phase. We propose a simple model that links $\eta_{eff}$ to the internal stress built up at the fluid-to-solid transition.