High Pressure Nmr Studies of the Dynamics of Fluids and Fluid Mixtures (Supercritical, Dimethyl-Sulfoxide, Diffusion)
Baker, Ellen S.
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Permalink
https://hdl.handle.net/2142/70265
Description
Title
High Pressure Nmr Studies of the Dynamics of Fluids and Fluid Mixtures (Supercritical, Dimethyl-Sulfoxide, Diffusion)
Author(s)
Baker, Ellen S.
Issue Date
1984
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Abstract
This thesis deals with several related but specific projects which examine the transport and relaxation properties of a number of fluids and fluid mixtures as a function of temperature and pressure. The common denominator of these projects is the use of pressure as an essential variable in studies of the dynamic structure of fluids. The use of pressure allows the determination of the effects of density on the properties of the fluid, independent of thermal effects.
The pressure dependence of the spin-lattice relaxation times and self-diffusion coefficients of water in aqueous dimethylsulfoxide solutions is examined in order to determine the effects of small amounts of DMSO on the long range hydrogen bonded structure of water. The observation of increased motional freedom of H(,2)O with the initial application of pressure in mixtures up to 0.1 DMSO mole fraction indicates that DMSO does not destroy the overall hydrogen bond network. The decreased pressure dependence of the rotational-translational coupling in solutions for x(,DMSO) (LESSTHEQ) 0.2, as compared to pure water, indicates that DMSO enhances the water structure at low concentration. The pressure dependence of the intramolecular and intermolecular proton dipolar relaxation rates of H(,2)O in the DMSO-d(,6)-H(,2)O mixtures is also reported.
Pressure is an essential variable for the study of transport in supercritical compressed gases. The study is important for both theoretical and practical reasons. The pressure dependence of the self-diffusion coefficients in ethylene and toluene-d(,8) is determined. The data are necessary for the design of industrial extraction processes, and for the determination of the applicability of current theories of transport in dense fluids. The density dependence of diffusion in compressed supercritical ethylene is well described by the molecular dynamics results of Alder, Gass, and Wainwright for hard spheres. The greatest discrepancies occur for densities less than the critical density, and can be attributed to the effects of attractive forces. Since the densities of supercritical toluene-d(,8) are not known, the data are compared to the predictions of four approximative methods suggested for the estimation of diffusion in dense fluids.
Viscosity is another important transport property of liquids. The viscosities of liquid hexafluorobenzene are determined as a function of temperature. The data are successfully analyzed in terms of the rough hard sphere theory, which accounts for the effects of coupling between the rotational and translational motions of the molecules.
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