Levich Institute Seminar Announcement, 04/17/2007
Mudd Building, Room 825
500 West 120th Street
Professor Athanassios Panagiotopoulos
Department of Chemical Engineering
"Simulations of Phase Transitions and Micellization in Ionic Systems "
[This is a CCNY/Columbia NSF-IGERT Soft Materials seminar to be held at Columbia University - 500 W. 120th Street, 825 Mudd Building]
This presentation starts with a brief historical overview of simulation studies of phase transitions in fluids dominated by coulombic interactions. It then summarizes recent work in the author's group on modeling phase transitions in ionic and charged polymer systems. The unifying characteristic of these fluids is the close interplay between microstructure and macroscopic properties and the existence of strong interactions or multiple relevant length scales. A fine-lattice discretization approach is used for the computations, combined with multihistogram reweighting. The fine-lattice approach allows close approximation of continuum systems with significant computational savings. Systems with short-range interactions in addition to the Coulombic forces show a wealth of behavior including tricriticality, ionic criticality and conventional (non-ionic) criticality. Polyelectrolyte phase diagrams indicate that the existence of two separate length scales results in a finite critical density extrapolated to infinite chain length. Mixtures of charged colloids and salts show non-monotonic dependence of the critical parameters on salt content and an interplay between the critical lines of the pure salt and colloid that can lead to discontinuous critical lines. Finally, we have recently developed a simple model for ionic surfactants that shows promise in reproducing the critical micelle concentration and aggregation properties of these systems.