Generation and stabilization of emulsions and foams with nanoparticles and surfactants
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Interactions between nanoparticles and surfactants are shown to improve the formation and stability of emulsions of dodecane-in-water and foams of carbon dioxide (CO2)-in-water. The initial work focuses on establishing a fundamental understanding of the interfacial properties of nanoparticle-surfactant combinations as novel dispersants for oil-in-water emulsions. Using the synergy between nanoparticles and surfactants, highly stable emulsions stabilized by with very low concentrations of amphiphiles are demonstrated. Additionally, amphiphilic polymers are grafted to nanoparticles to investigate their delivery to oil-water interfaces. Concepts developed in oil-in-water emulsion systems are then extended to design stabilizers for CO2-in-water foams. In this work, the first examples of viscous and opaque white foams stabilized solely with nanoparticles are demonstrated. This remarkable result was explained in terms of the nanoparticle interactions with the CO2 and water phases, which are tuned with small hydrophobic groups or amphiphilic polymers covalently grafted to the particle surfaces. Then the concept of nanoparticle-surfactant synergy is applied for the first time to CO2-in-water foams to create foams with both high stability and high viscosity. Finally, nanoparticles with grafted ligands on their surfaces are synthesized to give long-term colloidal stability in high salinity aqueous phases. These nanoparticles are then shown to improve CO2-in-water foam formation and stability. These new technologies may open new applications of nanoparticles in both seawater and reservoir brine.