Gel and glass transition in fragile colloidal clays

Abstract

Dynamic Light Scattering (DLS) measurements were performed on colloidal suspensions of Laponite ® at different concentrations in the range C w = (1.5÷3.0)%. The slowing down of the dynamics induced by aging was monitored by following the temporal evolution of autocorrelation functions at different concentrations towards the gel and glass transition. Exploiting analogies with supercooled liquids approaching their glass transitions, an Angell plot for the structural relaxation times was drawn. Finally, the fragility of Laponite ® suspensions at different concentrations, in different solvents, at two salt concentrations and with the addition of a polymer was reported and discussed.

Physico‐Chemical Properties of Laponite®/Polyethylene‐oxide Based Composites

“…The aqueous dispersions of Lap revealed the very complex phase diagrams in dependence on concentration C Lap , presence of ionic additives, temperature, value of pH, technique used for dispersion preparation and time after preparation of Lap dispersion. In dependence of these factors thedifferent ergodic and non‐ergodic regimes (sol, liquid, repulsive, or attractive glasses, stable, or unstable gels) have been observed [29–31] . Note that in the ergodic regime the system is in equilibrium, it visits all of their possible states, and in this regime an observable‘sensemble averageequals the time average.…”

“…In dependence of these factors thedifferent ergodic and non-ergodic regimes (sol, liquid, repulsive, or attractive glasses, stable, or unstable gels) have been observed . [29][30][31] Note that in the ergodic regime the system is in equilibrium, it visits all of their possible states, and in this regime an observable'sensemble averageequals the time average. In contrast in the non-ergodic regime the system does not visit all of their possible states and thisregimeit is non-equilibrium.…”