COLL 149 |
| Edgar J. Acosta, Department of Chemical Engineering, University of Oklahoma, 100 East Boyd, Sarkeys Engineering Center, room T-334, Norman, OK 73019, Erika Szekeres, School of Chemical Engineering and Materials Science, University of Oklahoma, 100 East Boyd Street, Sarkleys Energy Center, Room T-335, Norman, OK 73019, Jeffrey H. Harwell, College of Engineering, University of Oklahoma, 202 W. Boyd, Carson Engineering Center, Room 107, Norman, OK 73019, Brian P. Grady, Chemical Engineering and Materials Science, University of Oklahoma, 100 East Boyd EC Room T-223, Norman, OK 73019, and David A Sabatini, Institute of Applied Surfactant Research, University of Oklahoma, 100 East Boyd Street, Sarkeys Energy Center, Room T-335, Norman, OK 73019. |
| Dr. Adamson proposed some important ideas on how oil-swollen micellar solutions could be modeled (A.W. Adamson, “Model for Micellar Emulsions,” J. Colloid Interface Sci. (1969), 29(2), 261-7). In this presentation we describe a critical scaling approach to model microemulsion phase behavior including oil-swollen micellar solutions (Type I microemulsions), bicontinuous phases (Type III microemulsions) and reverse micelle phases (Type II microemulsions). This model uses a statistical approach to describe the microemulsion system as a system formed by virtual oil and water droplets coexisting at all conditions. The net curvature (inverse of oil radius minus inverse of water radius) of the virtual droplets describes the local curvature of the surfactant membrane. When initially applying the model we made certain commonly used assumptions regarding the molecular arrangement of the surfactant, oil and water; with these assumptions we were able to reproduce the macroscopic phase behavior of microemulsions including solubilization, interfacial tension and phase transition boundaries. Here we compare the model predictions of the droplet size to estimates obtained through small-angle neutron scattering experiments. It was found that the main inaccuracy of the model arose from the assumption that the area-per-molecule of the surfactant was constant. Thus, we introduce a correction to the model to account for the changes in the surfactant area per molecule as a function of the surfactant membrane curvature. |
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Symposium in Memory of Arthur W. Adamson
2:00 PM-5:40 PM, Monday, March 29, 2004 Marriott -- Orange County 4, Oral
Division of Colloid and Surface Chemistry |