Time-dependent Re-Aggregation of Colloidal Laponite Clay Suspensions

Abstract

We study a synthetic clay suspension of laponite by measuring transient electric birefringence (TEB) and dynamic light scattering (DLS) over time. Experiments show a strong dependence on stirring of the sample for anomalous TEB behaviour, consistent with the effect being caused by competing optical contributions from single clay platelets and aggregates. Stirring must take place shortly before measurements, as samples will in the order of days reach an equilibrium where the anomalous effect is only observable by double pulse TEB measurements. Shaking a sample again after it is measured, does not reproduce the same time evolution, sample reaches equilibrium earlier. DLS show aggregates increasing in size and ratio with regard to platelets, supporting the TEB measurements.