(13c) Probing Surfactant-Nanoparticle Interactions at Fluid-Fluid Interfaces

An emulsion is a type of colloid that consists of one liquid being dispersed in another immiscible liquid. The interface between the two immiscible phases can be stabilized by both surfactants and nanoparticles. Upon sufficient coverage of nanoparticles, the presence of a tightly packed colloidal network structure at the fluid-fluid interface provides enhanced mechanical rigidity and viscosity to the interfacial film. The surfactant-nanoparticle interactions play a critical role in determining the stability of the interfacial film. Our research aims at probing the fundamental mechanisms governing the surfactant-nanoparticle interactions at fluid-fluid interfaces and the consequence of surfactant-nanoparticle interactions on surfactant partitioning at such an interface. We will measure interfacial tension and elasticity to quantify the response of the interface to these interactions. The effect of particle morphology and wettability on the surfactant-nanoparticle interactions will be determined. Hydrophilic, partially hydrophobic, and hydrophobic silica nanoparticles will be used to quantify the effect of wettability on surfactant-nanoparticle interactions. The influence of the mode of nanoparticle addition on surfactant partitioning at the fluid-fluid interface will be determined. Non-ionic and ionic surfactants will be used to determine the influence of surfactant type on interactions with nanoparticles. To complement the experimental observations, molecular simulation results will be presented to shed light on the extent of interfacial adsorption of surfactant and nanoparticles. In addition, it will be demonstrated how the presence of such nanoparticles modify the interfacial structuring of the two liquids.