Water-in-Oil Microemulsions: Counterion Effects in AOT Systems and New Fluorocarbon-based Microemulsion Gels

WATER-IN-OIL MICROEMULSIONS: COUNTERION EFFECTS IN AOT SYSTEMS AND NEW FLUOROCARBON-BASED MICROEMULSION GELS FEBRUARY 2010 XIAOMING PAN, B.S., TSINGHUA UNIVERSITY Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Surita R. Bhatia Microemulsions have important applications in various industries, including enhanced oil recovery, reactions, separations, drug delivery, cosmetics and foods. We investigated two different kinds of water-in-oil microemulsion systems, AOT (bis(2-ethylhexyl) sulfosuccinate) microemulsions with various counterions and perfluorocarbon-based microemulsion gels with triblock copolymers. In the AOT systems, we investigated the viscosity and interdroplet interactions in Ca(AOT)2, Mg(AOT)2 and KAOT microemulsions, and compared our results with the commonly-studied NaAOT/water/decane system. We attribute the differences in behavior to different hydration characteristics of the counterions, and we believe that the results are consistent with a previously proposed charge fluctuation model. Perfluorocarbons (PFCs) are of interest in a variety of biomedical applications as oxygen carriers. We have used triblock copolymer Pluronic F127 to modify the rheology of PFC-based microemulsions, we have been able to form thermoreversible PFOB (perfluorooctyl bromide)-based gels, and have investigated the phase stability, rheology, microstructure, interactions, and gelation mechanism using scattering, rheometry, and microscopy. Finally, we attempted to use these data to understand the relationship between rheology and structure in soft attractive colloids.