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Structure and phase transitions of some crystalline and liquid crystalline aromatic polyestersHanna, Simon January 1988 (has links)
No description available.
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Statistical mechanics of nematic polymersWang, Xin-Jiu January 1991 (has links)
In this work I model the liquid crystal polymers as worms and explore the Spheroidal approach to examine their statistical mechanics. Several models are presented in this work to describe main chain-, side chain-polymers, polymer networks and gels in their nematic state. In the case of main chain nematic polymers, the worm flexibility, favouring disorder, and the nematic potential, tending to align segments to be parallel to each other, compete to determine the properties of polymers. I predict the temperature dependence of order parameter and phase transition behaviour for different lengths of the polymers, and the dimensions as well. Subsequently, I examine the critical features of the nematic polymer when an electrical field is applied. Side chain polymers with semi-flexible backbone and stiff nematogenic pendants form interesting nematic phases, largely as a consequence of competition between backbone entropy and pendant order. I classify them into three categories: NI, NII, and NIII phase, according to volume fractions, temperature, nematic coupling constants, and stiffness. In these phases the backbone and pendants have orders different in magnitude and/or in sign in order to achieve a stable state. Phase diagrams are given. In addition, I predict unusual properties such as anomalous temperature variation of optical anisotropy and molecular conformational changes. Crosslinks confine polymer chains in a network so that their strands have a shape different from their natural ones. Such constraints shift phase transition temperature. The other effect is that crosslinks give the system rubber elasticity. Combining rubber elasticity with liquid crystal features, networks exhibit unusual phenomena, such as discontinuous stress-strain relations, spontaneous shape changes, non-linear stress-optical laws and deviations from classical behaviour of conventional elastomers. It is proposed that residual nematic interaction is responsible for deviations found in classical elastomers. The nematic networks swollen by isotropic solvent form nematic gels. At low temperatures a nematic gel coexists with excess solvent, at high temperatures the coexisting gel is isotropic. In addition, coexistence is predicted between nematic and isotropic gels. There is an associated triple point. There are possible elastic problems associated with different phases coexisting in one gel sample. Main chain nematic polymers have been modelled either as homogeneous worms, or as jointed rods by others. In reality the polymers are composed of the mesogens linked by semi-flexible spacers. One must expect that the spacers have an order differing from the mesogens. The consecutive mesogens are not decoupled and the spacers are able to talk to each other via the mesogens in between. The model presented takes account of molecular parameters, such as length of the mesogen and spacer, and their interactions. The nematic order of the two components, the nematic-isotropic transition, and dimensions of the polymers are addressed. Finally, I examine both worm and jointed rod models, to see when each is applicable. Accordingly an elastically jointed rod model is presented. Hairpins, found naturally in the worm problem, also exist for jointed systems but their scaling is quite different. Comparisons of these results with experiments are accordingly made and are found to be satisfactory.
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The investigation of novel charge transfer systemsBatty, Simon V. January 1991 (has links)
In this project a number of synthetic procedures were investigated with a view to preparing a new type of charge transfer polymer system having a structure based on that of side chain liquid crystal polymers, in that the hoped for polymer was composed of charge transfer acceptors connected to a polymer backbone via a flexible alkyl spacer linkage. As part of this work new charge transfer complexes were prepared some of which have shown possible novel properties, such as, co-operative magnetic effects and film forming capabilities. Finally, in order to characterise materials prepared, a Faraday magnetic susceptibility balance and instrumentation for measuring electrical conductivity has been built.
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Hyperbranched polysiloxysilanes-liquid crystalline core-shell structures : preparation and propertiesCarpentier, Alice Ursula January 1999 (has links)
No description available.
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Characterisation, processing and mechanical modelling of a thermotropic main-chain liquid crystalline polymerDimitriades, Klisthenis January 1997 (has links)
No description available.
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Investigation of the mechanical and structural properties of cellulose tricarbanilate/polymethylacrylate blendsCameron, Juliet Dallas January 2000 (has links)
No description available.
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Liquid crystal polymers containing crown ether ligandsRodenhouse, Randall Alan January 1991 (has links)
No description available.
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The viscoelastic properties of nematic monodomains containing liquid crystal polymersGu, Dongfeng January 1994 (has links)
No description available.
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Model compounds for liquid crystal polymers containing rod-like and disk-like mesogensPugh, Coleen Renee January 1991 (has links)
No description available.
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Molecular engineering of liquid crystal polymers by living polymerizationLee, Myongsoo January 1992 (has links)
No description available.
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