Stabilisation of water-in-water emulsions by montmorillonite platelets

The formation of water-in-water emulsions from the aqueous two phase system containing polyethylene oxide and pullulan, stabilised by montmorillonite platelets, was investigated. A novel approach of preparing the emulsions at non-equilibrium polymer concentrations was successfully utilised to control viscosity during mixing and allow the use of low energy emulsification methods. Polyethylene oxide adsorbed to the platelets much more strongly than pullulan favouring the formation of pullulan-in-polyethylene oxide emulsions which remained stable for a period of weeks. Polarising microscopy and small angle light scattering were used to show that droplets were most likely stabilised against coalescence by the adsorption of randomly oriented aggregates of platelets and against creaming by the formation of chains of droplets bridged by the adsorbed aggregates. Montmorillonite platelets were therefore shown to stabilise water-in-water emulsions and their preference for emulsion type was driven by the adsorption of the polymers to the particle surface.