Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules

Abstract

This thesis investigates new uses and benefits of colloidal particles adsorbing to the liquid-liquid interface of emulsion droplets. The first part of this thesis investigates morphology control of double emulsions of the water-in-oil-in-water (W/O/W) variety due to the use of interfacially adsorbing particles. W/O/W emulsions typically yield oil droplets containing a multitude of internal water droplets when scalable emulsification procedures are used. W/O/W emulsions containing a single internal aqueous core are preferred for some applications; but single core double emulsions usually require small-scale continuous processes that have low yields. As a result of the investigation into double emulsion morphology control, a readily scalable batch procedure for the production of single core droplets was developed that requires particulate emulsifiers of appropriate concentration and wettability as well as osmotically induced coalescence of the internal droplets. The second part of this thesis describes a different method of morphology control applied to pairs of immiscible droplets brought into contact in a liquid medium. It was found that colloidal particles adsorbing selectively to the different liquid interfaces can change the balance of interfacial tensions responsible for the wetting morphology of the two droplets. Therefore, particles can be used as “wetting modifiers” that allow for control of the equilibrium droplet configuration in a way that was previously considered achievable only with the help of surfactants. The third and final part of this thesis explores the use of particle stabilized emulsion droplets in a new strategy for microencapsulation. In collaboration with an industrial research sponsor, double walled microcapsules with polymer-particle composite shells were developed. The composite shells were formed by interfacial polymerization at the particle covered liquid interfaces. The developed microcapsules were characterized with regard to their potential benefits for the storage and sustained release of aqueous cargoes.