by Chow Kim-fung. / Bibliography: leaves 112-114 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985

Thesis (M.Phil.)--Chinese University of Hong Kong. / Includes bibliographies.

No description available.

No description available.

Graduation date: 1994

Recently, there has been an expanding interest in the packaging industry concerning thermoplastic film laminations. These types of materials provide a packaging material that can be tailored to the consumers' needs. An understanding of the bonding mechanisms between plastics might prove useful in the improvement or development of film lamination. Infrared spectrometry has been used to study the structures of plastics in the 3.0 - 100 micron region. It was decided that a study of infrared spectrometry in the 1.0 - 3.5 region could provide a tool for studying bonding mechanisms between thermoplastic material. The results of the qualitative study of the structural groups of nine polymers showed that the spectral identification in the 1.0 - 3.5 micron region was possible. These results could provide a means of determining the groups involved in bonding mechanisms. Beer's law has normally been applied to the quantitative analysis of homogeneous gaseous and liquid mixtures. A study shewed that Beer's law was applicable, with limited quantitative accuracy, to solid thermoplastic mixtures. The results indicate that a base-line analysis technique, based on Beer's law can be used to determine concentration gradients. A study of such concentration gradients across the interface of a lamination could indicate the types of bending mechanisms. All samples were analyzed in the form of films with a Beckman DK-2 ratio recording spectrophotometer. An improved method for the preparation of film samples was developed. Thermoplastic resins were pressed between 10 mil Mylar and Teflon FEP films on a Carver laboratory press. / Master of Science

Mechanistic aspects of phosphorylation, dephosphorylation, pyrophosphorylation and depyrophosphorylation reactions that mimic phosphorylases, dephosphorylases, pyrophosphorylases and depyrophosphorylases have been studied in the biologically important middle pH region. The different systems monitored are; (a) the reactions between [{CoN4(OH)(OH2)}]2+ and [HPO4]- for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [HPO4]2- ratios. (b) the reactions between [{CoN4PO4] and [O2NC6H4O]- (abbreviated as NP-) for 1:1, 2:1 and 3:1 [{CoN4PO4] to [O2NC6H4O]- ratios. (c) the reactions between [{CoN4(OH)(OH2)}]2+ and [O2NC6H4PO4]2- (abbreviated as NPP2-) for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [O2NC6H4PO4]2- ratios. (d) the reactions between [{CoN4(OH)(OH2)}]2+ and [H2P2O7]2- for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [H2P2O7]2- ratios. (e) the reactions between [{CoN4P2O7}]- and [O2NC6H4O]- for 1:1, 2:1 and 3:1 [{CoN4P2O7}]- to [O2NC6H4O]- ratios. Significant phosphorylation was noted for systems containing 1:1 molar ratio [{CoN4PO4] and [O2NC6H4O]-. Enhanced phosphorylation was depicted for system containing 1:1 molar ratio of [{CoN4(OH)}2PO4]+ and [O2NC6H4O]-. Pyrophosphorylation was noted for reactions of 1:1 molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. The rate of pyrophosphorylation was substantially reduced for systems that were 2:1 in molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. No appreciable pyrophosphorylation was noted for systems, which has a 3:1 molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. Specific mechanistic features and the possible roles metal ions play in phosphorylase, dephosphorylase and pyrophosphorylase are highlighted from results of UV-Visible spectroscopy, 31P {1H} NMR spectroscopy and Surface Enhanced Raman Scattering (SERS) studies / Chemistry / D.Phil. (Chemistry)

Different optical and calorimetric techniques were utilized to gain a better understanding of aggregated macromolecules. This research looked at two different macromolecules: poly(9,9'-dioctylfluorene), a conjugated polymer that forms aggregates in organic solvents; and bovine insulin, which forms amyloid fibrils. Conjugated polymers are of increasing interest due to their thermal stability and ease of solution processing for use in devices. A member of the polyfluorene family, poly(9,9'-dioctylfluorene) (PFO), has been studied due to its blue-emitting spectral properties. However, PFO has been found to form aggregates in solution, which is detected by the presence of a red-shifted absorption peak. This peak is caused when a section of the backbone planarizes forming the [beta]-phase. The [beta]-phase can be removed from the solution upon heating and will not return until the solution is cooled, making it a non-equilibrium process. The dissolution and reformation of the -phase were monitored using absorption spectroscopy and differential scanning calorimetry. Atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) were able to probe the aggregates in films. It is important to understand polymer properties in solution in order to understand film morphology. Amyloid fibrils contribute to over 20 different neurodegenerative diseases, in which cures have yet to be found. The fibrils form when a soluble protein misfolds and self-assembles to form insoluble protein aggregates, and the cause of the fibril formation in vivo has still yet to be determined. Spectroscopy studies have been made possible with the use of fluorescent dyes: thioflavin T (ThT), BTA-2, and Congo red (CR). These dyes bind to amyloid fibrils and exhibit changes in their spectral properties. However, the exact mechanism for the binding of these dyes has only recently been studied. Through the use of calorimetry, the forces involved with binding of ThT and CR to amyloid fibrils can be determined. Absorption and fluorescence spectroscopy techniques were employed to study the spectral properties of these dyes. Polarized NSOM was used to determine the ThT or BTA-2's orientation with an individual fibril. Understanding how these dyes bind to fibrils will enable researchers to use spectroscopy to study the early stages of fibril formation. / text

Mechanistic aspects of phosphorylation, dephosphorylation, pyrophosphorylation and depyrophosphorylation reactions that mimic phosphorylases, dephosphorylases, pyrophosphorylases and depyrophosphorylases have been studied in the biologically important middle pH region. The different systems monitored are; (a) the reactions between [{CoN4(OH)(OH2)}]2+ and [HPO4]- for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [HPO4]2- ratios. (b) the reactions between [{CoN4PO4] and [O2NC6H4O]- (abbreviated as NP-) for 1:1, 2:1 and 3:1 [{CoN4PO4] to [O2NC6H4O]- ratios. (c) the reactions between [{CoN4(OH)(OH2)}]2+ and [O2NC6H4PO4]2- (abbreviated as NPP2-) for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [O2NC6H4PO4]2- ratios. (d) the reactions between [{CoN4(OH)(OH2)}]2+ and [H2P2O7]2- for 1:1, 2:1 and 3:1 [{CoN4(OH)(OH2)}]2+ to [H2P2O7]2- ratios. (e) the reactions between [{CoN4P2O7}]- and [O2NC6H4O]- for 1:1, 2:1 and 3:1 [{CoN4P2O7}]- to [O2NC6H4O]- ratios. Significant phosphorylation was noted for systems containing 1:1 molar ratio [{CoN4PO4] and [O2NC6H4O]-. Enhanced phosphorylation was depicted for system containing 1:1 molar ratio of [{CoN4(OH)}2PO4]+ and [O2NC6H4O]-. Pyrophosphorylation was noted for reactions of 1:1 molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. The rate of pyrophosphorylation was substantially reduced for systems that were 2:1 in molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. No appreciable pyrophosphorylation was noted for systems, which has a 3:1 molar ratio of [{CoN4P2O7}]- and [O2NC6H4O]-. Specific mechanistic features and the possible roles metal ions play in phosphorylase, dephosphorylase and pyrophosphorylase are highlighted from results of UV-Visible spectroscopy, 31P {1H} NMR spectroscopy and Surface Enhanced Raman Scattering (SERS) studies / Chemistry / D.Phil. (Chemistry)

Polypyrrole is an electrochemically synthesized conductive polymer that has physical properties which impede efforts to develop structure-properties relationships. The extent of conjugation, as limited by the presence of structural disorders in the polymer, is important in determining its inherent conductivity. The extent of conjugation in thin electrochemically generated films of polypyrrole and poly-N-methylpyrrole has been examined with resonance Raman spectroscopy. The Raman experiment was performed within the electrochemical cell and does not suffer from exposure to the contaminants encountered when transfer techniques are employed. Electrochemically reduced films of polypyrrole exhibited intense resonance Raman spectra of the carbon-carbon stretching frequencies. The position of these bands is a function of the number of double bonds in conjugation. The conjugation length within the polymer chain was found to be between 3 and 4 rings for PP and slightly less in PNMP (2-3 rings). This is the first reported determination of the conjugation length in PP and PNMP. This data confirms the idea that PNMP is less conductive than PP due to reduced planarity within the chain, thus less conjugation. Reduced films of PP and PNMP yielded intense luminescence that disappeared upon oxidation. The luminescence is a broad featureless band that consumes the weakly enhanced Raman of PNMP. The intensity of the luminescence increased as the reduction potential increased and the highest intensities occurred at potentials far cathodic of the E₀ for the film. The explanation for this is still obscure but may involve either further reduction of highly luminescent segments or a decrease in the amount of quenching by solvent or counter-ion interactions with the luminescer. / Ph. D.