Electrostatic Barrier to the Production of Charged Latex Particle-Stabilized Emulsions

A new trend of Pickering emulsions is their use as precursors for creating novel functional colloidosomes. A prerequisite for the formation of such desirable colloidosomes from Pickering emulsions is the controlled formation and stabilization of oil-in-water and water-in-oil emulsions with colloid particles. Unfortunately, our current fundamental understanding of emulsions stabilized with colloidal particles, especially with ionizable latex particles, is still far from satisfactory and often fails to predict reliably the stability and the type of Pickering emulsions. To improve predictions for Pickering emulsions, our research suggests two widely neglected electrostatic effects in Pickering emulsions through investigating emulsifications with charged-polystyrene particles. We firstly argue the energy barrier to particle adsorption at the interface can also be created by the image charge repulsion across the interface in addition to repulsions from the charged interface as well acknowledged. Also, we propose effects of dipole-interaction on the preferred emulsion types to interpret the observations that particles with a macroscopic three-phase contact angle greater than 90⁰, defined as hydrophobic, can stabilize oil in water emulsions in contradiction to the conventional expectations for hydrophobic particles.  Both proposed effects will provide new insights into current fundamental understanding of Pickering emulsions.