Laponite-stabilised oil-in-water emulsions: viscoelasticity and thixotropy

Abstract

We have studied the breakdown and recovery of structure over time in Pickering emulsions under shear using a combination of rheology and confocal fluorescence microscopy. Oil-in-water emulsions were stabilised by laponite particles at particle and salt concentrations where the laponite dispersions form isotropic, thixotropic gels. The emulsions consist of a network of interconnected drops and particles clusters. The key result is that emulsion elasticity is sensitive to the structure of the laponite aggregates and the drop volume fraction. The stress required to break down the thixotropic laponite networks increases with the fraction of drops incorporated into the particle dispersions. At rest the network reforms, however, the presence of the drops can significantly slow recovery times.