Patchy Rough Colloids as Pickering Stabilizers

Abstract

A Pickering emulsion is a dispersion of immiscible fluids stabilized by colloidal particles. Pickering stabilizers are typically considered to be perfectly smooth and chemically homogeneous. The use of rough and heterogeneous colloids is expected to fundamentally alter the properties of the formed emulsions. In particular, we investigate the role of surface structuring on emulsification and the catastrophic phase inversion of Pickering emulsions. To gain deeper fundamental insights into this topic, we fabricate in large amounts patchy rough particles comprising a polystyrene core with organosilicate asperities. Their roughness is characterized with AFM and an estimate of their composition can be obtained from their oxidative mass losses upon combustion. The chemical heterogeneity of the particle surfaces is estimated by measurements of the surface patchiness. The degree of surface heterogeneity is used to calculate the particles’ contact angles at a water-decane interface, which are empirically measured by gel trapping technique. Systematic variations in emulsification shear rate, o/w ratio and particle type reveal the influence of particle heterogeneity on processing and formulation of emulsions. This work paves the way for a deeper understanding of the behavior of Pickering emulsions, where non-ideal, heterogeneous particles are present.