Chapter 10. Pickering Emulsions Stabilized by Polymer Colloids

Abstract

Pickering emulsions are multiphasic liquid mixtures that are stabilized by solid particles. The strong attachment of particles to the interface makes these emulsions very stable. Additional functionality can be imparted to the emulsion by using particles with useful catalytic, electrical, photonic and magnetic properties. We highlight the most recent developments in polymer colloid-stabilized Pickering emulsions. Pickering emulsions are compared to conventional emulsions that are stabilized by molecular surfactants, focusing on the difference in thermodynamics of the formation of these two different emulsions. Pickering emulsions stabilized with anisotropic polymer particles with homogenous compositions, such as ellipsoids, microrods and thin sheets, are discussed in the second section. In the third section, we highlight recent advances in using Janus particles as solid surfactants for Pickering emulsions. The behavior of Janus particles at liquid–liquid interfaces, the thermodynamics of the formation of Pickering emulsions with Janus particles and the effect of Janus balance on emulsion stabilization are discussed. The fourth section discusses Pickering emulsions based on microgels, a unique class of polymer colloids. These microgels enable the preparation of stimuli-responsive Pickering emulsions as well as high internal phase emulsions for applications in cargo delivery and energy storage devices. The section highlights Pickering emulsions stabilized with polymer-grafted particles and recent developments in preparing Pickering emulsions stabilized by biopolymer colloids such as cellulose nanocrystals, proteins and fat crystals. The chapter concludes by presenting some of the outstanding questions that must be addressed to enable utilization of polymer colloids as effective and functional materials for emulsion stabilization.