last update: July 05, 2000
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STC-ERSP Program Details Principal Investigator: Keith E. Gubbins and Carol. K. Hall Project Title: Molecular Simulation and Thermodynamics for CO2-Surfactant Systems (#8) Phone/Fax: (919) 513-2262 (KEG) and (919) 515-3571 E-mail: keg@ncsu.edu and hall@turbo.che.ncsu.edu Research Plan Connectivity Outreach Components Requested Budget Allocation - Year 1 Research Plan Overall objectives Gubbins and Hall plan to develop a molecular-level understanding of CO2-based systems using molecular-level computer simulations and theory. Objectives will be to understand the relationships between molecular architecture and properties, and the resulting phase diagrams and other thermodynamic and interfacial properties of bulk mixtures. Reliable molecular models will be developed for mixtures containing a variety of kinds of species in CO2 solvents, including small polar molecules (water, ethanol, etc.), simple hydrocarbons (methane, ethane, etc.), fluorinated molecules (F2, CF4, etc.), chain molecules and CO2-philic surfactants. Included in these objectives will be the development of simple models that mimic the kinetics of micelle formation and subsequent solubilization of a third component under a variety of operating conditions. Relation to overall objectives of the Center The ability to predict the effect of molecular architecture and intermolecular forces on the interfacial and bulk thermodynamic behavior of these CO2-based systems is essential to the design of systems for specific applications in environmental science, polymer chemistry, separation science and materials science. Approach and Year 1-Year 5 timelines Years 1-2: Develop realistic intermolecular potentials for pure CO2, and for CO2 interactions with a range of small and large solute molecules. Carry out molecular simulation studies for a wide range of binary mixtures, using Gibbs Ensemble and Semi-Grand Ensemble Monte Carlo simulations with histogram reweighting, and where necessary configurational bias. Develop square-well chain surfactant models and use these to study the kinetics of micelle formation in square well solvents. Validate models by comparison with experimental results wherever possible. Test theoretical methods (SAFT and Generalized Flory Dimer Theory) against simulation and experimental results Years 2-4: Carry out molecular simulations for ternary mixtures involving CO2 mixed with surfactants and a third component. Test these results against experiment. Test theoretical results against both simulations and experimental results. Add a third square well component to square well surfactant/solvent systems and monitor its solubilization. Years 2-5: Develop molecular simulation methods, and also theories, for prediction of micelle formation and critical micelle concentration, for a range of binary and ternary mixtures, using both realistic potentials and square well potentials. Systematically explore the influence on micelle formation of varying molecular parameters, such as chain length, polarity, types of chemical groups in surfactants, etc. Validate against experimental methods. Thrust area of this proposal Thrust Area B: Molecular Thermodynamics and Computer Simulations Connectivity Collaborators, multi-institutional, multi-disciplinary components The models and methods will be developed in partnership with Berkowitz. Additional collaboration is expected with Rubinstein (UNC-CH), with Wignall (ORNL), Cochran (ORNL) and Cummings (ORNL), and with Johnston (UTX). Close cooperation is expected with the experimental group of Kabadi (NCA&T), who will measure phase equilibria and thermodynamic properties for our model systems, and with the experimental groups of DeSimone (UNC-CH), Carbonell (NCSU) and Samulski (UNC-CH). The simulation and theoretical work will be designed to be complementary to the experimental studies. Related work in other thrust areas See preceding section Sharing of resources (students, supplies, equipment, etc.) The computer facilities, and some software will be shared with the groups of Rubinstein (UNC-CH) and Berkowitz (UNC-CH). Outreach Components Suggested K-12 Outreach Ideas Gubbins and Hall plan to explore the idea of preparing a video demonstrating molecular level visualization of the behavior of CO2 based mixtures and micellar solutions, which would be suitable for teacher workshops. These would be designed to be suitable for high school students. Requested Budget Allocation - Year 1 Personnel salaries
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