Aging of rotational diffusion in colloidal gels and glasses

TL;DR

This study investigates how rotational diffusion in aging colloidal suspensions evolves, revealing distinct dynamical behaviors in gels and glasses through light scattering measurements.

Contribution

It demonstrates that rotational dynamics exhibit ergodic to non-ergodic transitions and can distinguish between colloidal gels and glasses during aging.

Findings

Rotational relaxation times scale with ergodicity-breaking time.

Two master curves describe rotational dynamics for gels and glasses.

Rotational behavior provides a signature to differentiate colloidal states.

Abstract

We study the rotational diffusion of aging Laponite suspensions for a wide range of concentrations using depolarized dynamic light scattering. The measured orientational correlation functions undergo an ergodic to non-ergodic transition that is characterized by a concentration-dependent ergodicity-breaking time. We find that the relaxation times associated with rotational degree of freedom as a function of waiting time, when scaled with their ergodicity-breaking time, collapse on two distinct master curves. These master curves are similar to those previously found for the translational dynamics; The two different classes of behavior were attributed to colloidal gels and glasses. Therefore, the aging dynamics of rotational degree of freedom provides another signature of the distinct dynamical behavior of colloidal gels and glasses.