Connecting Interfacial Properties to Emulsion Stability for Complex Particle-Laden Interfaces

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CBET 1437864Emulsions and foams occur in many processes of industrial and biological importance. The food, cosmetic, pharmaceutical, medicinal, polymer, and oil and gas industries routinely process emulsions and foams. One of the key requirements in making useful, long-lived products from emulsions and foams is to guarantee that they are stable by preventing the drops or bubbles from coalescing with each other, which can degrade product quality. This project will use a microtensiometer developed by the investigators to examine the physical and chemical properties of drop and bubble interfaces and determine how those properties influence the coalescence of two drops under carefully controlled conditions. Using the microtensiometer, the investigators will examine the coalescence process while simultaneously acquiring information about the interfacial characteristics of the drops. The influence of emulsifiers that can stabilize emulsions by adsorbing onto drop interfaces and preventing coalescence will be examined. Then, the team will explore the effectiveness of a novel stabilizer consisting of nanoparticles coated with surfactants. The results will provide new tools to scientists and engineers who formulate emulsions and foams and design systems to process them.A microtensiometer will be used to study the interfacial rheology of small drops and bubbles with radii between 50 and 150 micrometers. By monitoring the pressure inside the bubble and the interfacial area, the dynamic surface tension and interfacial elasticity of the interface can be determined. To access conditions where the adsorption of surfactants onto the interface is kinetically limited, the device will be modified by adding a convective flow past the interface. The microtensiometer will then be used to observe the coalescence of two drops or bubbles with identical curvature, composition and history, which will help eliminate ambiguities that occur in other coalescence measurements. The results will be used to ascertain the relationship between interfacial rheology and coalescence. The effects of particle-laden interfaces on coalescence will be characterized using a model system of surfactant-coated nanoparticles that readily adsorb onto interfaces.