The talk explores the formulation and destabilization of particle-stabilized single Pickering emulsions, focusing on oil-in-water (O/W) and water-in-oil emulsions (W/O), along with stabilization of double emulsion of oil-in-water-in-oil (O/W/O) water-in-oil-in-water (W/O/W) which have potential applications in medicine, food, and materials research. By utilizing hydrophilic and hydrophobic particles as stabilizers, the wettability of particles is tuned to control emulsion properties such as stability, droplet size, and type.
The first part investigates using colloidal scale particles (hematite ellipsoids) in stabilizing emulsions. Adding oleic acid to hematite ellipsoids stabilized emulsions induces transitional phase inversion, changing emulsion types from oil-in-water to water-in-oil. Interestingly, this modification results in the formation of non-spherical emulsion drops. Optical microscopy confirms the transition, revealing the unique surface structure of emulsion drops at varying oleic acid concentrations.
Next is a single-step method for creating various types of emulsions by varying particle surface wettability, the initial location of particles (water or oil) and changing oil-to-water volume ratio (φoil). The transition from oil-in-water to water-in-oil and the formation of double emulsions are achieved by varying φoil and particle wettability and their location. The results conclusively establish that the differential wettability of particles is the key to the design of Pickering double emulsions. The versatility of the proposed strategy is demonstrated by developing double emulsions using several model colloidal systems.
Further, we have explored natural and biodegradable emulsifiers, specifically plant latex, for emulsion stabilization. Latex dispersions, comprising colloidal particles and surface active components, are used as a sustainable and versatile interface stabilizer. Latex constituents reduce oil-water interfacial tension, forming stable single, double, and multiple emulsions across immiscible liquid systems.
Ultimately, we will address the destabilization of Pickering emulsions by adding different solutes. Interfacial instabilities induced by solutes across the oil-water interface offer a robust route for emulsion destabilization. Various solutes and stabilizers, including particles of different shapes and sizes, are tested, demonstrating a general method for inducing destabilization by transiently perturbing the oil-water interface. The approach works for oil-in-water and water-in-oil emulsions with different non-polar solvents but fails when the solute is insoluble in one of the phases. This study introduces a novel approach to destabilize particle-stabilized emulsions, expanding the understanding of Pickering emulsion destabilization mechanisms.