An experimental and theoretical study of binary nematogenic mixtures
An experimental and theoretical study of binary nematogenic mixtures
The theme that runs consistently through this thesis is concerned with the experimental and theoretical treatment of binary nematogenic mixtures. A general introduction to the liquid crystalline state of matter is given in chapter one. In chapter two we have attempted to deal with binary mixtures at both a theoretical and experimental level. The first section is concerned with developing a general theory for binary nematogenic mixtures including scalar interactions. This theory is then applied to rods and spheres and also rods and disc like molecules. Reasonable qualitative agreement between experiment and theory is found for a binary mixture of hexafluorobenzene (solute) and Phase V (solvent). In chapter three we compare the phase behaviour of rods and spheres including scalar interactions using two molecular field models. The first is based on the Humphries James and Luckhurst (HJL) theory of multicomponent mixtures. This model allows a continuum of molecular orientations. The second is a modified HJL theory in which we impose a quantization of molecular orientations. A direct comparison of the phase behaviour highlights the differences in the two models. On a slightly different note but one which is pertinent to binary nematogenic mixtures, the orientational ordering of two `quasispherical' solutes in Phase V is studied in chapter four. The `quasispherical' molecules are tetraethyltin and tetra-n-butyltin which are found to be highly ordered by the non-spherical potential of the solvent. In chapter five the molecular dynamics of a monomer (solvent) in a monomer-polymer mixture is investigated. A 5.4% w/w concentration of the polymer is seen to have dramatic effects on the spin lattice relaxation times approaching the nematic to isotropic transition. At lower temperatures the behaviour is seen to parallel that of the pure monomer. Finally, in chapter six, the orientational ordering of biphenyl and trans-stilbene is studied in various solvents. Both these solute molecules were found to possess a high degree of biaxiality. A simple theory is also proposed to explain the trend of (l/TNI)dTm/dx (gradient of the phase diagram at infinite dilution of solute) versus P2 for a series of diphenylpolyenes dissolved in PCH5. Reasonable agreement is found for the longer members of the series, however the shorter members show a large deviation from theory. This is rationalised in terms of the high biaxiality of the shorter members of the series.
University of Southampton
1989
Singh, Amrat Paul
(1989)
An experimental and theoretical study of binary nematogenic mixtures.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The theme that runs consistently through this thesis is concerned with the experimental and theoretical treatment of binary nematogenic mixtures. A general introduction to the liquid crystalline state of matter is given in chapter one. In chapter two we have attempted to deal with binary mixtures at both a theoretical and experimental level. The first section is concerned with developing a general theory for binary nematogenic mixtures including scalar interactions. This theory is then applied to rods and spheres and also rods and disc like molecules. Reasonable qualitative agreement between experiment and theory is found for a binary mixture of hexafluorobenzene (solute) and Phase V (solvent). In chapter three we compare the phase behaviour of rods and spheres including scalar interactions using two molecular field models. The first is based on the Humphries James and Luckhurst (HJL) theory of multicomponent mixtures. This model allows a continuum of molecular orientations. The second is a modified HJL theory in which we impose a quantization of molecular orientations. A direct comparison of the phase behaviour highlights the differences in the two models. On a slightly different note but one which is pertinent to binary nematogenic mixtures, the orientational ordering of two `quasispherical' solutes in Phase V is studied in chapter four. The `quasispherical' molecules are tetraethyltin and tetra-n-butyltin which are found to be highly ordered by the non-spherical potential of the solvent. In chapter five the molecular dynamics of a monomer (solvent) in a monomer-polymer mixture is investigated. A 5.4% w/w concentration of the polymer is seen to have dramatic effects on the spin lattice relaxation times approaching the nematic to isotropic transition. At lower temperatures the behaviour is seen to parallel that of the pure monomer. Finally, in chapter six, the orientational ordering of biphenyl and trans-stilbene is studied in various solvents. Both these solute molecules were found to possess a high degree of biaxiality. A simple theory is also proposed to explain the trend of (l/TNI)dTm/dx (gradient of the phase diagram at infinite dilution of solute) versus P2 for a series of diphenylpolyenes dissolved in PCH5. Reasonable agreement is found for the longer members of the series, however the shorter members show a large deviation from theory. This is rationalised in terms of the high biaxiality of the shorter members of the series.
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Published date: 1989
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Local EPrints ID: 461225
URI: http://eprints.soton.ac.uk/id/eprint/461225
PURE UUID: 48aca992-7f32-4d82-8179-f2ab1a3631a9
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Date deposited: 04 Jul 2022 18:40
Last modified: 04 Jul 2022 18:40
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Author:
Amrat Paul Singh
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