Blends of Poly(ethylene Terephthalate) with Bisphenol-A-Polycarbonate The objective of the study was to determine the extent to which bisphenol-Apolycarbonate (PC) influences the rheology, processing behaviour and subsequent crystallinity and mechanical properties of poly(ethylene terephthalate) (PETP) in the 'compatible' region, when the polycarbonate is the minor blend component. Also, further characterisation of this blend system, in terms of miscibility and micro- structure development was required. After careful drying in a desiccant-type hopper drier melt-phase, blending was carried out using a twin-screw extruder with a purpose-designed screw configuration. Blends were made up at three levels (PETP/PC); 85/15,80/20 and 75/25 using three different molecular weights of PC, and virgid-materials were also included in the study. The extrudates were then dried and injection moulding was carried out under various conditions, which were chosen to modify the degree of order in the crystallisable phase. The effects of PC on the shear-flow behaviour of the blends was examined, and in general the PETP/PC 80/20 blends demonstrated lower shear viscosities than expected from additivity. Otherwise the shear flow behaviour was generally consistent with blend composition. Thermal analysis and crystallisation behaviour of the blends were investigated to determine the effects of PC on the crystallisability of the blend and the PETP T. Solid state isothermal crystallisation behaviour was studied using a modified thermal analysis technique. Crystallisation of the PETP portion of the blend was shown to be impeded by PC. A specific and rapid technique has been developed to determine depth-dependent orientation distributions Three dimensional analyses of birefringence were obtained for moulded plaques of various PETP/PC blends. The orientation distribution was in accordance with the flow pattern during processing and was noticeably planar in nature. However, the level of orientation in the mouldings investigated was very low. Thermal analysis and microscopy techniques indicate there is no evidence for miscibility in the blends. The effect of PC molecular weight and content on mechanical properties of the blend was investigated. Generally, the PETP/PC blends exhibited improved toughness, in terms of total energy absorbed, and the properties were influenced further by the degree of crystallinity. It has been shown that mechanical properties of the blend deteriorate rapidly when samples are stored for extended periods in water at 70'C. Due to the PET? portion in the blends crystallising, and hydrolysis, the samples pass into the brittle mode. The addition of PC to PETP was found to modify the thermoelastic behaviour. Addition of PC permits thermoelastic processing of PETP/PC blends over a wider temperature range than would be suitable for PETR Also, the addition of PC appears to accelerate the onset of strain-induced crystallisation in the PETP.

<p> Colloidally prepared nanocrystals of transparent conducting oxide (TCO) semiconductors have emerged in the past decade as an exciting new class of plasmonic materials. In recent years, there has been tremendous progress in developing synthetic methods for the growth of these nanocrystals, basic characterization of their properties, and their successful integration into optoelectronic and electrochemical devices. However, many fundamental questions remain about the physics of localized surface plasmon resonance (LSPR) in these materials, and how their optoelectronic properties derive from their underlying structural properties. In particular, the influence of the concentration and distribution of dopant ions and compensating defects on the optoelectronic properties of TCO nanocrystals has seen little investigation. </p><p> Indium tin oxide (ITO) is the most widely studied and commercially deployed TCO. Herein we investigate the role of the distribution of tin dopants on the optoelectronic properties of colloidally prepared ITO nanocrystals. Owing to a high free electron density, ITO nanocrystals display strong LSPR absorption in the near infrared. Depending on the particular organic ligands used, they are soluble in various solvents and can readily be integrated into densely packed nanocrystal films with high conductivities. Using a combination of spectroscopic techniques, modeling and simulation of the optical properties of the nanocrystals using the Drude model, and transport measurements, it is demonstrated herein that the radial distribution of tin dopants has a strong effect on the optoelectronic properties of ITO nanocrystals. </p><p> ITO nanocrystals were synthesized in both surface-segregated and uniformly distributed dopant profiles. Temperature dependent measurements of optical absorbance were first combined with Drude modeling to extract the internal electrical properties of the ITO nanocrystals, demonstrating that they are well-behaved degenerately doped semiconductors displaying finite conductivity at low temperature and room temperature conductivity reduced by one order of magnitude from that of high-quality thin film ITO. </p><p> Synchrotron based x-ray photoelectron spectroscopy (XPS) was then employed to perform detailed depth profiling of the elemental composition of ITO nanocrystals, confirming the degree of dopant surface-segregation. Based on free carrier concentrations extracted from Drude fitting of LSPR absorbance, an inverse correlation was found between surface segregation of tin and overall dopant activation. Furthermore, radial distribution of dopants was found to significantly affect the lineshape and quality factor of the LSPR absorbance. ITO nanocrystals with highly surface segregated dopants displayed symmetric LSPRs with high quality factors, while uniformly doped ITO nanocrystals displayed asymmetric LSPRs with reduced quality factors. These effects are attributed to damping of the plasmon by Coulombic scattering off ionized dopant impurities. </p><p> Finally, the distribution of dopants is also found to influence the conductivity of ITO nanocrystal films. Films made from nanocrystals with a high degree of surface segregation demonstrated one order of magnitude higher conductivity than those based on uniformly doped crystals. However, no evidence was found for differences in the surface electronic structure from one type of crystal to the other based on XPS and the exact mechanism for this difference is still not understood. </p><p> Several future studies to further illuminate the influence of dopant distribution on ITO nanocrystals are suggested. Using synchrotron radiation, detailed photoelectron spectroscopy on clean ITO nanocrystal surfaces, single-nanoparticle optical measurements, and hard x-ray structural studies will all be instructive in elucidating the interaction between oscillating free electrons and defect scattering centers when a plasmon is excited. In addition, measurements of temperature and surface treatment-dependent conductivity with carefully controlled atmosphere and surface chemistry will be needed in order to better understand the transport properties of ITO nanocrystal films. Each of these studies will enable better fundamental knowledge of the plasmonic properties of nanostructures and improve the development of nanocrystal based plasmonic devices.</p>

This thesis includes a theoretical and experimental analysis of electrophoresis of colloidal particles in non-Newtonian polymeric fluids with shear-rate dependent viscosities. A model is derived that predicts field dependent electrophoretic mobility in shear-thinning Carreau uids. The latter effect is experimentally investigated for submicron particles in solutions of linear polyacrylamide using capillary electrophoresis. The mobilitiies of the particles studied in these solutions did not depend on field strength, yet the mobilities were consistently an order of magnitude greater than in water and glycerol solutions with similar bulk viscosities. The increase in particle mobility could be attributed to several mechanisms, however it is consistent with the depletion of polymer apparent viscosity of the fluid as it migrates by electrophoresis is the same as experienced by the particle in Brownian diffusion. A comparison of particle mobility in both glycerol and polyacrylamide solutions to diffusion coefficients of the particles measured by dynamic light scattering supports this conclusion.

The objective of the research was to assess the effects of tannins in ruminant nutrition and the ameliorating effects of polymers.  It also aimed to investigate and propose an improved method for determining concentrations of condensed tannins using the Butanol/HCl assay (Porter et al., 1986). The study has found tannins to suppress microbial growth, carbohydrate degradation and fermentation of mixed rumen microbes and of fungus.

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A semiconductor based gas sensor was developed by integrating a gas sensitive polymer with a floating-gate metal-oxide-semiconductor (FGMOS). The integration of the gas sensitive polymer with a semiconductor device enables the design of a large sensor array in a single chip for electronic sensing application. A new FGMOS structure was designed to reduce the number of post-processing steps during electrochemical polymer deposition. In this new design, the top metal layer of a standard CMOS process was used as an extended sensor pad which was connected to the floating gate. A sensor chip was designed using a standard 0.35 µm CMOS process. A polymer film was selectively deposited on the top metal layer (sensor pad) of a FGMOS using two post processing steps. The sensor response was measured by exposing the sensor in different concentration of water and methanol vapor. A short pulse measurement technique was introduced to measure the sensor response which was not affected by the measurement parameters.