Aggregation and Phase Separation of Hydrophobic Solutes in Water: a Combined Density Functional Theory and Simulation Approach
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Biography
Prof. Egorov obtained his B. Sc. degree in Physical Chemistry from St. Petersburg University in Russia, and Ph.D. degree from the University of Wisconsin-Madison, where he worked under Prof. James Skinner. He was a post-doctoral research fellow in the group of Prof. Bruce Berne at Columbia University. Since 1999, Prof. Egorov has been on faculty at the Chemistry Department of the University of Virginia. His research activity is in the broad area of Theoretical Soft Matter, including supercritical fluids, colloids, polymers, liquid crystals, and active matter. Theoretical methods employed in his research range from integral equation theory and density functional theory to mode-coupling theory. The accuracy of the developed approaches is confirmed by detailed comparisons with Monte Carlo and Molecular Dynamics simulation results. To highlight some of the research accomplishments of Prof. Egorov, a few representative examples are given. Supercritical fluids are a subject of active ongoing research due to their significant promise as environmentally friendly solvents. Prof. Egorov has developed an accurate theoretical approach to describe local density enhancements of supercritical solvents in the vicinity of strongly attractive solutes based on inhomogeneous integral equation theory. The theory was successfully applied to analyze experimental results on reaction equilibrium constants in supercritical solvents. In addition, Egorov has developed an accurate mode-coupling theory of diffusion in supercritical fluids. In the technologically important field of liquid crystals, Prof. Egorov has put forward an accurate density functional theory of isotropic-nematic phase transition of semiflexible polymers and their binary mixtures, both in the bulk and under confinement. Finally, for colloid-polymer mixtures, an accurate density functional theory of the polymer-induced potential of mean force between colloids has been formulated, which allowed Egorov to construct accurate phase diagrams of these binary mixtures. The latter achievement is of particular importance for the proposed collaboration with Prof. Wilding at Bristol, which will focus on the theoretical studies of aqueous solutions of hydrophobic solutes.
Project Summary
Water is undoubtedly the most important solvent on earth. It plays a crucial role in a wide variety of biological, chemical, and physical processes, many of industrial importance. For example, amphiphilic molecules (comprising both hydrophobic and hydrophilic units) tend to aggregate in aqueous solution into mesoscopic micellar structures, which is essential for detergent applications. Somewhat surprisingly, the propensity to aggregate or phase separate is often observed to increase with temperature, with e.g. aqueous solutions of triethylamine or nicotine exhibiting lower critical solution temperature. In a series of recent papers by the host (Prof. Wilding) and his colleagues significant progress has been made towards providing a new theoretical framework to rationalize hydrophobic solvation by demonstrating that the physics of water near an isolated extended hydrophobic solute is controlled by a surface phase transition called critical drying. This novel idea has been successfully confirmed by employing a combination of molecular simulations and density functional theory. In order to apply this new perspective to explain the unusual temperature dependence of the hydrophobic effect, it needs to be extended beyond the case of an isolated hydrophobe. In particular, one would need to compute the attractive ‘depletion potential’ which arises between a pair of hydro/solvophobic particles when their highly compressible depletion layers overlap. Prof. Egorov is well positioned to formulate a density functional theory for such depletion attraction potential, which will next be used to construct the phase diagrams for an effective one component system, integrating out the solvent degrees of freedom. Our expectation is that colloidal aggregation and concomitant phase separation will be enhanced with increasing temperature. Provided this is indeed the case, the result will need to be confirmed by Monte Carlo computer simulations, due to the unavoidable approximation in the density functional formalism, such as its intrinsically mean-field nature.
Professor Egorov is hosted by Professor Nigel Wilding, School of Physics.
Details of Professor Egorov's lectures and seminars will be listed on our Events page in due course. You can also contact Professor Egorov's host for further information.
