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Title: Dynamics and structure of liquid crystal colloids
Author: Lavery, Roan
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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This thesis sets out to investigate the dynamic and structural properties of liquid crystal colloids. In themselves the fields of colloidal and liquid crystal science have been well studied, but the combination of these produces a wealth of new physics which has provoked much interest over the past few years. The research began by investigating the dynamics of dilute suspensions of colloidal particles in the isotropic phase of liquid crystal near the nematic transition. It was found that the particles exhibit an anomalously low diffusion which was explained in terms of the formation of an ordered layer of liquid crystal molecules surrounding the particles even when the bulk phase was disordered. It was also discovered around this time that due to the preparation procedure the particle could become coated with a thin layer of another type of solvent which dramatically affected the particle diffusion and this lead to an offshoot study in this area. It was found that the diffusion of these coated particles was much faster than expected because of a change to the boundary conditions at the particle surface as a solvent coating caused partial slip boundary conditions which altered the diffusion. Latterly the nature of this coating was investigated more and a hydrodynamic model employed to compare experimental results with the predictions given by the theory. It was found that these were in good agreement. The focus of investigation then changed, focusing on more concentrated systems of colloidal particles in liquid crystal solvents as these exhibited unusual structural phenomena. It was seen that a concentrated suspension of particles in liquid crystal shows a huge increase in the rigidity of the material in its nematic phase, compared with the pure liquid crystal. This is due to the creation of a honeycomb-like aggregate particle network, which increases the elastic strength of the material. The network formation was observed using microscopy and the elastic modulus was measured rheologically to be many orders of magnitude higher than the pure liquid crystal alone. The role of cooling rate from the isotropic to nematic phase was also investigated thoroughly as this has a large impact on the final structure of the material.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available