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

Sodium naphthenates (NaNs) are petrochemical anionic surfactants that stabilize 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 microstructure through a combination of small-angle X-ray scattering and cryoelectron microscopy. First, we will explicate the influence of surfactant and salt concentrations on micellar micromorphology of aqueous solutions of sodium dodecyl sulfate (SDS), a model, well-researched system. These trends will be compared with nanoscopic topography of draining SDS foam films, highlighting the striking similarity between intermicellar separations in bulk solutions and stratification step sizes in thin films. Next, phase behavior and microstructure of aqueous NaN self assemblies will be discussed, again highlighting the role of intermicellar correlations in dictating drainage of thin liquid films.