Relationship among Phase Behavior, Micellar Structure and Thin Film Drainage in Aqueous Surfactant Solutions

Sodium naphthenates (NaNs) are petrochemical anionic surfactants that stabilize undesired petroleum emulsions and foams and pose significant environmental challenges when released into water bodies. Relatively little is known about the phase behavior and self-assembly (including micelle formation) as well as thin film drainage kinetics of aqueous NaN self-assemblies, impeding the development of strategies for NaN sequestration and petroleum foams and emulsions destabilization.
In this presentation, we will discuss experimental methodologies to elucidate surfactant phase behavior and self-assembly structure through a combination of small-angle X-ray scattering and thin film stratification studies. First, we will explicate the influence of surfactant and salt concentrations on micellar structure evolution and interparticle interactions of SDS solutions as a model system. These trends will be compared with nanoscopic topography of draining SDS foam films, elucidating the striking similarity between intermicellar separations in bulk solutions and stratification step sizes in thin films. Next, phase behavior and micelle structure of aqueous NaN self-assemblies will be discussed, again highlighting the role of intermicellar correlations in dictating drainage of thin liquid films.