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Title: Statistical mechanics of photo-elastomers
Author: Corbett, D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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Liquid Crystalline Elastomers (LCE) are unusual materials. As suggested by their name they inhabit the grey area between liquids and solids. They have many remarkable properties. This dissertation is concerned with the equilibrium statistical mechanics of dye doped LCE films. We propose a free energy to describe the destabilising effects of illumination on the underlying nematic order and combine this with the phantom chain model for the elastic free energy of elastomeric films in order to calculate the equilibrium mechanical response. We consider thin polydomain films, and describe the effects of illuminating them with both polarised and unpolarised light. In both cases we predict that the mechanical response is a non-monotonic function of the incident intensity, which should allow a rich set of deformation modes when thicker samples are illuminated. The underlying mechanisms leading to the mechanical response are the optically induced reorientation of the nematic ordering direction and the associated changes in the order parameters. We investigate these changes in some detail and in chapter 4 we predict the results of Nuclear Magnetic Resonance (NMR) experiments designed to detect them. In chapter 5 we consider the stress generated by films which are rigidly clamped, in this case mechanical relaxation is not possible. Director reorientation and order parameter reduction are still important in determining the stress response. We predict that the stress is a non-monotonic function of the incident intensity, in much the same way as the mechanical response. In the same chapter we also consider the mechanical response of a doped cholesteric film when illuminated with unpolarised light. We predict that the deformation in this case can be extremely large.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available