Equilibrium orientations of non-spherical and chemically anisotropic particles at liquid-liquid interfaces and the effect on emulsion stability

The effective stabilization of emulsions by solid particles, a phenomenon known as Pickering stabilization, is well known to be highly dependent on the wettability and the adhesion energy of the stabilizer employed at the liquid liquid interface. We present a user-friendly computational model that can be used to determine equilibrium orientations and the adhesion energy of colloidal particles at interfaces. The model determines the free energy profile of particle adsorption at liquid liquid interfaces using a triangular tessellation scheme. We demonstrate the use of the model, using a variety of anisotropic particles and demonstrate its ability to predict and explain experimental observations of particle behaviour at interfaces. In particular, we show that the concept of hydrophilic lipophilic balance commonly applied to molecular surfactants is insufficient to explain the complexity of the activity of colloidal particles at interfaces. In addition, we show the importance of the knowledge of the free energy adsorption profile of single particles at interfaces and the impact on overall free energy of emulsification of packed ensembles of particles. The delicate balance between optimization of adhesion energy, adsorption dynamics and particle packing is shown to be of great importance in the formation of thermodynamically stable emulsions. In order to use the model, the code is implemented by freely available software that can be readily deployed on personal computers. (C) 2015 Elsevier Inc. All rights reserved.