Thesis (Ph. D.)--Memorial University of Newfoundland, 1997. / Blbliography: leaves 205-216.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaf 50). Also available on the Internet.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 77-84. Also available online.

Electrospinning is a technique, which can be used to produce nanofibrous materials by introducing electrostatic fields into the polymer solution. Due to their intrinsic properties, such as small fiber diameter, small pore size and large surface area, nanofibres are suitable for use in a variety of applications including wound dressing, filtration, composites and tissue engineering. The study demonstrates the successful and optimised production of Poly(ethylene oxide) (PEO) and chitosan nanofibres by electrospinning. The biocidal effects of chitosan, chitosan-silver nanofibres and silver nanoparticles were successfully investigated. To set up a functional electrospinning apparatus, the PEO solution parameters (concentration, molecular weight, solvent, and addition of polyelectrolyte) and applied potential voltage on the structural morphology and diameter of PEO nanofibres were studied. At lower PEO concentrations, the fibres had morphology with a large variation in fibre diameter, whereas at the higher concentrations, the nanofibres exhibited ordinary morphology with uniform but larger fibre diameters. Higher molecular weight showed larger average diameters when compared to that obtained with the same polymer but of a lower molecular weight. The addition of polyelectrolyte to the polymer solution had an influence on the structural morphology of the PEO. Flow simulation studies of an electrically charged polymer solution showed that an increase in the flow rate was associated with an increase in poly(allylamine hydrochloride) (PAH) concentration for the low molecular weight polymer, the shape and size of the Taylor cone increasing with an increase in PAH concentration for the low molecular weight polymer. During optimization of the PEO nanofibres, based on statistical modelling and using the Box and Behnken factorial design, the interaction effect between PAH concentration and the tip-to-collector distance played the most significant role in obtaining uniform diameter of nanofibres, followed by the interaction between the tip-to-collector distance and the applied voltage and lastly by the applied voltage. The production and optimization of chitosan nanofibres indicated that the interactions between electric field strength and the ratio of trifluoroacetic acid (TFA) and dichloromethane (DCM), TFA/DCM solvents as well as between electric field strength and chitosan concentration had the most significant effect, followed by the concentration of chitosan in terms of producing nanofibres with uniform diameters. Chitosan and chitosan-silver nanofibres could be successfully electrospun by controlling the solution properties, such as surface tension and electrical conductivity with the silver nanoparticles in the chitosan solutions affecting the electrospinnability. The silver nanoparticles in the chitosan solution modified the morphological characteristics of the electrospun nanofibres, while the conductivity and the surface tension were elevated. The fibre diameter of the chitosan and chitosan-silver nanoparticles decreased with an increase in the silver content. The electrospun chitosan nanofibres had a smooth surface and round shape as compared to the silver-chitosan nanofibres with a distorted morphology. The chitosan and chitosan-silver nanofibres as well as the silver nanoparticles exhibited antimicrobial or inhibition activity against S. aureus than against E. coli. S. aureus bacterial culture showed good cell adhesion and spreading inwards into the chitosan nanofibrous membrane. The chitosan-silver nanofibres exhibited a greater minimum inhibitory concentration (MIC), followed by silver nanoparticles and then chitosan nanofibres; suggesting a synergistic effect between the chitosan and silver nanoparticles.

No description available.

<p> This thesis is an experimental study of the effects of injecting dilute polymer solutions into a turbulent boundary layer developed on a flat plate submerged in water.</p> <p> A flat plate having a plexiglass surface together with a separate leading edge piece were specially designed for observing the boundary layer phenomena. Aqueous polymer solutions were introduced into the boundary layer through a slit situated in the leading edge piece. Hot-film anemometer technique was employed in the measurements of velocity profiles, turbulence intensities and lateral correlation coefficients at several locations on the plate. The investigation was carried out for two Reynolds Numbers, based on the length of the plate, of 2.4 x 10^5 and 6.4 x 10^5. The variation in the drag force with respect to the polymer concentrations and the injection rates was assessed based on the velocity profile data. It was found that the momentum diffusivity was smaller than for pure water, and that the presence of the polymer molecules seemed to promote a more uniform distribution of the sizes of the turbulence eddies.</p> / Thesis / Master of Engineering (MEngr)

No description available.

Peng Shufu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

A number of high performance fibres (aramid, PBZT and PBO) spun from liquid crystal polymer solutions were examined in this work. In particular, a thorough investigation of the mechanical response of these fibres under tensile and compressive deformations was carried out. The major experimental tool employed was the technique of Laser Raman Spectroscopy. It was found that stress-induced changes of these fibres at molecular level are proportional to the macroscopic deformation applied. This correlation is unique for the fibres. A method for converting spectroscopic data to predicted stress-strain curves in tension and compression was proposed. An estimation of their compressive strength was derived and an understanding of the nature of their compressive failure was discussed. The adhesion of these fibres to epoxy resin was also investigated by monitoring in situ the interfacial stresses developed along the interface/interphaseo f model single fibre composite coupons. The strength of the interfacial bond was measured. The effect of various parameters such as fibre modulus, fibre diameter and fibre nature upon the interfacial strength of the various systems was evaluated. The mechanisms of stress transfer along with the nature of interfacial damage was examined accurately. It was found that the major parameter controlling the above mechanisms was interfacial yielding in shear. A numerical appoximation (using Finite Element Analysis) was employed in order to evaluate the experimental results. Finally, general conclusions concerning the performance of these fibres were drawn.

This thesis describes a novel microfluidic platform to control the macromolecular concentrations and their applications in constructing the phase diagram of polymer aqueous solutions and in the high-throughput screening of protein crystallization conditions at the nanoliter scale. The microfluidic platform was fabricated using the soft-lithography method and based on poly(dimethylsiloxane) (PDMS) material, which is widely used in microfluidic device. PDMS is gas and water permeable elastomer. By exploiting the permeability of the gas and water in PDMS, we developed the degassed-PDMS nanoliter liquid dispensing system, the controlled microevaporation method in constructing the phase diagram of polymer aqueous solution, and the screening platform of protein crystallization conditions. / This thesis describes two types of degassed-PDMS nanoliter liquid dispensing system. One is dispensing without the microvalve, in which various liquids are dispensed through the degassed PDMS microchannel. It involves two steps: in the first step, the PDMS microchannel patch (or the entire microchip) is placed in a vacuum chamber for a certain time; in the second step, the target liquid is deposited at the inlet of the PDMS channel and dispensed into the PDMS microchamber. The other method is dispensing with the aid of PDMS microvalve. This method combines the valve control and degassed PDMS pumping source, which provides more control over on the liquid dispensing, such as isolating, mixing, etc. / Zhou, Xuechang. / Adviser: Bo Zheng. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 53-56). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.