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Reference: Jackson, George., (1986). Phase separation in solutions of large spherical particles. DPhil. University of Oxford.Citable link to this page:


Phase separation in solutions of large spherical particles

Abstract: The effect of large size ratios of solute to solvent onthe critical properties and phase behaviour of binarymixtures of spherical particles is investigated using anaugmented van der Waals equation of state. The equationused is essentially a van der Waals equation with animproved hard sphere repulsive term.Molecular dynamics and constant-pressure Monte Carlosimulations of binary mixtures of hard spheres withdifferent diameter ratios and mole fractions are undertakento check the adequacy of the hard sphere equation. Goodagreement is found, even for systems with large differencesin size. Furthermore, many of the hard sphere mixturesexhibited a transition from a fluid to a solid phase at highdensities.Phase boundaries are calculated for model mixturescomprising spheres of different sizes between which thereare long-ranged attractive forces. Particular attention ispaid to the case in which the ratio of sizes is infinite.The systems show a wide variety of behaviour that includesliquid-liquid and gas-gas immiscibility, and the formationof negative azeotropes. Calculations investigating theeffect of different attractive interactions between thesmall and large spheres show that as the magnitude of thisinteraction is increased, liquid-liquid immiscibilitybecomes the dominant feature of the phase diagram atmoderate temperatures. The extent of liquid-liquidcoexistence is greatest at large size differences. Thesemodel systems are shown to reproduce some of the behaviourof aqueous solutions of surfactants if it is assumed thatthe large spheres are models of the micelles and the smallspheres models of the solvent molecules.The properties of binary lattice mixtures ofbifunctional molecules whose ends are chosen to mimicsurfactant and solvent molecules are also brieflyinvestigated, to determine the effect of the asymmetricsurfactant molecule on the phase separation. Closed-loopsemerge in the phase diagrams as the surfactant character ofone of the species is increased.

Type of Award:DPhil Level of Award:Doctoral Awarding Institution: University of Oxford Notes:The digital copy of this thesis has been made available thanks to the generosity of Dr Leonard Polonsky


Rowlinson, J. S. (John Shipley)More by this contributor



Prof. John RowlinsonMore by this contributor


 Bibliographic Details

Issue Date: 1986Identifiers

Urn: uuid:9db7de2e-b365-4433-8e14-746efb32c070

Source identifier: 603839376 Item Description

Type: Thesis;

Language: eng Subjects: Phase transformations (Statistical physics) Particles Molecular dynamics Van der Waals forces Tiny URL: td:603839376


Author: Jackson, George. - institutionUniversity of Oxford facultyMathematical and Physical Sciences Division - - - - Contributors Rowlin



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