Thermally activated asymmetric structural recovery in a soft glassy nano-clay suspension

Abstract

In this work we study the structural recovery of a soft glassy Laponite suspension by monitoring temporal evolution of elastic modulus under isothermal conditions as well as following step temperature jumps. Interestingly, evolution behavior under isothermal conditions indicates the rate, and not the path of structural recovery, to be dependent on temperature. The experiments carried out under temperature jump conditions however trace a different path of structural recovery, which shows strong dependence on temperature and the direction of change. Further investigation of the system suggests that this behavior can be attributed to the restricted mobility of counterions associated with Laponite particles at the time of temperature change, which do not allow the counterion concentration to reach the equilibrium value associated with the changed temperature. Interestingly this effect is observed to be comparable with other glassy molecular and soft materials, which while they evolve in a self-similar fashion under isothermal conditions show asymmetric behavior upon temperature change.