Irreversible Aging Dynamics and Generic Phase Behavior of Aqueous Suspensions of Laponite

TL;DR

This study investigates the irreversible aging dynamics of aqueous Laponite suspensions, revealing salt-dependent energy barriers and universal aging behavior regardless of salt concentration.

Contribution

It demonstrates the self-similar aging behavior of Laponite suspensions and quantifies how salt concentration linearly decreases energy barriers to low energy states.

Findings

Aging behavior is self-similar across different salt concentrations.

Salt reduces the energy barrier to reach low energy states linearly.

Irreversible aging prevents rejuvenation to initial states.

Abstract

In this work we study the aging behavior of aqueous suspension of Laponite having 2.8 weight % concentration using rheological tools. At various salt concentration all the samples demonstrate orientational order when observed using crossed polarizers. In rheological experiments we observe inherent irreversibility in the aging dynamics which forces the system not to rejuvenate to the same state in the shear melting experiment carried out at a later date since preparation. The extensive rheological experiments carried out as a function of time elapsed since preparation demonstrate the self similar trend in the aging behavior irrespective of the concentration of salt. We observe that the exploration of the low energy states as a function of aging time is only kinetically affected by the presence of salt. We estimate that the energy barrier to attain the low energy states decreases linearly with increase in the concentration of salt. The observed superposition of all the elapsed time and the salt concentration dependent data suggests that the aging that occurs in low salt concentration systems over a very long period is qualitatively similar to the aging behavior observed in systems with high salt concentration over a shorter period.