Epoxides are very useful key intermediates in the construction of synthetically challenging molecules. Owing to their strategic importance in organic synthesis, novel polymer-supported iminium salts were investigated for the catalytic oxidation of unfunctionalised alkenes. A solid-phase methodology was initiated and then developed for the evaluation of several heterogeneous catalysts. In an initial approach, immobilised iminium salts were prepared by condensation of 2-(bromoethyl)benzaldehyde with commercially available aminomethyl resins. These materials were shown to be able to successfully catalyse the epoxidation of 1-phenylcyclohexene. The epoxidation reactions were performed in a triphasic system using Oxone® as the oxidising agent and 25 mol% of the catalyst. For all the resin type employed, namely NovaSyn TG, NovaGel, ArgoGel or PEGA, complete conversion of the alkenes to their respective epoxides was obtained.

Bacterial infection and colonisation of polymeric biomaterials represents a major problem that is on the rise within the health care industry. Bacterial attachment and biofilm formation on medical polymers is often the cause of addition discomfort, pain and in the worse case scenario sepsis and even mortality. This, in combination to the overuse of antibiotics and evolution of resistant bacterial stains, means there is a need for a more intelligent approach in the prevention of biofilm formation and bacterial infection. In this work, the antimicrobial properties of metals (in particular silver and zinc) was utilized and incorporated into polymeric biomaterial to render them antimicrobial. Several methods of functionalising polymers with antimicrobial metals were assessed. The materials developed throughout this work were designed to respond to changes in environmental as a result of infection. These changes include differences in pH and temperature all of which are altered in response to infection. This smart design allows for the reduction of unnecessary release of antimicrobial, and will reduce the likelihood of toxicity and resistance. Polymer modifications in this research include modifications made during polymer synthesis, i.e. reaction with additional antimicrobial monomer. In this case, pH responsive zinc containing crosslinker molecule was designed to crosslink into any polymeric material. Post synthesis modifications were also investigated, and include the ‘grafting to’ and ‘grafting from’ of polymers which could then be functionalised with antimicrobial metals. This work demonstrated methods to modify non-woven polypropylene. A system, for the ‘grafting from’ approach to give a pH responsive release of antimicrobial metals from a polymer brush was investigated. Secondly a ‘grafting to’ approach to give a temperature responsive release of metals was investigated. Finally, several zinc compounds were synthesised and assessed for there ability to graft via plasma assisted grafting. The results presented in this work demonstrate novel ways of incorporating antimicrobial metal functionality into polymeric biomaterials and their antimicrobial efficacy.

Biomedical research has shown that one-dimensional nanostructures present many potential advantages as delivery vehicles for drugs and biologics. These elongated structures have high aspect ratios that enable increased drug loading capacities and have been shown to have longer in vivo circulation times than other spherical nanoparticles. The increasing interest in these one-dimensional structures has necessitated the developments of fabrication methods for the precise control of the final morphology. A simple, cost effective means of producing nanotubes and nanorods is known as solution template wetting. While this technique has been used to fabricate many different types of elongated nanostructures, the parameters governing the final morphology remain ambiguous. The objectives of this research are to investigate these critical parameters, and furthermore to develop an understanding of the physical mechanism of nanostructure formation. The effects of the infiltration technique, dipping time, polymer molecular weight and template pore size on the morphology of the resulting nanostructure have been evaluated. Key results have established that the infiltration technique is a critical parameter that can enable the formation of stable nanotubes at very low polymer concentrations. Additionally, a tube to rod transition occurs as the infiltration time is increased over 18 hr. An investigation of the rheological properties of high and low molecular weight solutions also indicates that the capillary flow and infiltration of polymer occurs differently. Finally, the pore size was also shown to affect the ability to form hollow, stable structures, and that relatively large pore sizes are necessary for nanotube formation. The culmination of these results is an understanding of the physical layering mechanism of structure formation, and the tube to rod transition can thus be predicted by researchers investigating the use of elongated nanostructures for biomedical applications.

by Jiang Suhong. / "2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / 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.

Gypsum has been used almost exclusively as the mould material for casting sanitary-ware due to its high versatility, strength and homogenous pore distribution. However gypsum moulds have a number of disadvantages including deterioration on contact with water, deformation, long set times and short mould lives such that a large number of moulds are required for a commercial manufacturing processes. These drawbacks have led to attempts to find a new synthetic material to create moulds with similar properties to gypsum with respect to fine homogeneous pores, but with increased durability. Porous PMMA was developed in 1971 for the purpose of moulding ceramics. The basic approach to making the materials has remained unchanged since its commercial introduction with few academic studies undertaken on the formulations. This thesis describes an investigation into porous PMMA from an academic perspective studying the mechanism of formation of the materials and the role of the components in polymerisation. In particular: the surfactant type and level, monomer type, water to monomer ratio and bead size have been probed to assess their effect on the porosity and mechanical strength. A particular importance has been placed on the commercial viability of formulations because gypsum is a relatively inexpensive material and, due to its versatility and ease of manufacture, is still used throughout the ceramics industry. To increase cost competitiveness through spreading the higher cost of the raw materials and capital investment, the mechanical strength of porous PMMA materials has to be significantly greater to increase the number of casting cycles from each mould. In addition, to achieve competitive advantage in the marketplace, a deep understanding of the formulation was undertaken. This should allow for tailoring of the mould properties allowing for specialised moulds for different applications. In addition, this focused approach facilitates cost-savings allowing for the minimum input of raw materials. The thesis is a comprehensive body of work which looks individually at the components assessing their effect on the properties of the final material. In addition, the formation mechanism of the materials has been explored by breaking down the polymerisation into key stages. Highlighted is the excessive use of surfactant in a commercial formulation and the influence of plasticisation of the ligaments by the surfactant and excess monomer. The theory behind the polymerisation process, which generates the ligaments and traps the polymer beads in an immobile matrix, is developed; forming a comprehensive understanding of the formation of porous PMMA materials and factors influencing their development and final properties.

No description available.

Thermoplastic elastomer is one of the priority polymeric compound identified for promotion and further development, given the growing demand for a number of commercial industries such as automobile, construction, footwear, healthcare, medical and food packaging sectors. In this study polypropylene (PP)/ethylene propylene diene monomer (EPDM) based thermoplastic elastomers are preferred for improving their properties as it can serve as a good replacement for PP or EPDM material, bridging the gap between thermoset and thermoplastic materials. This study focuses to develop PP/EPDM which can resist changes or improve properties when exposed to E-beam radiation, as E-beam also offers sustainable sterilization at low cost. The PP/EPDM blends with mixing ratios of 80/20, 50/50 and 20/80 were melt blended with the process parameters optimized using Design of experiments (DOE). The effect of E-beam on mechanical properties, thermal stability, crystallization and dynamic mechanical properties over the dose of 0 to 100 kGy were studied. The blends with high EPDM content (20PP/80EPDM) showed improvement in tensile strength up to 36% (at 40kGy and 60kGy) and resistant to impact strength up to 100 kGy, at the expense of elongation at break. On the other hand, the blends with high PP content (80 PP/20 EPDM and 50 PP/50 EPDM) showed detrimental effects on mechanical properties at all radiation dose studied and found to be not compatible for E-beam sterilization. Further, ethylene vinyl acetate (EVA) was incorporated to PP/EPDM blends at 10EVA/40EPDM/50PP, 20EVA/30 EPDM/50PP, 30EVA/20 EPDM/50PP and 40EVA/10 EPDM/50PP ratios. The gel content analysis showed that the efficiency of crosslinking decreased with increase in EVA loading. However, the presence of EVA in ternary blend especially facilitated the induction of sufficient crosslinks leading to improvement in tensile strength (up to 29% at 60 kGy), impact strength (up to 15% at 80 kGy) and retention of stiffness and thermal properties under radiation at the expense of elongation at break. In order to develop antibacterial ternary blends, silver nanoparticles (AgNP) were added by varying the loading from 0.3wt% to 1wt%. The Ag-ternary blends showed enhancement in impact properties (up to 9%) at the expense of decrement in tensile properties due to the agglomeration of AgNP. When, exposed to E-beam radiation, the mechanical and thermal properties exhibited similar trend of increment and decrement across radiation dose similar to the blends without AgNP. While, 1% Ag blend composites showed bacteriostatic effect on Staphylococcus aureuson, no significant reduction of Pseudomonas aeruginosa bacteria was observed. All the blends, before and after sterilization showed no significant toxicity on HaCaT cells investigated using in vitro analysis. Thus, the blends showed an instinct that their application could be extended to manufacturing of healthcare products and food packaging sector, as they are biocompatible and can withstand E-beam sterilization as demanded by the respective application. Among all the blends ternary blends studied (that exhibited biocompatibility even after radiation), 20EVA/30EPDM/50PP without AgNP showed the highest tensile strength of 18.41 MPa and impact strength of 43.64 J/m. Only a slight increase in tensile and impact properties was witnessed upon addition of 20% EVA to PP/EPDM blend in comparison to the binary blend (50PP/50EPDM blend). However, unlike the binary blend (whose properties decreased upon radiation), the ternary blend (20EVA/30EPDM/50PP) showed improvement in tensile strength up to 29% at 60kGy and up to 15% increase in impact strength at 80kGy.

$\sp2$H-NMR is a powerful spectroscopic technique for investigating dynamics in solids. to extend the range of motional rates that can be quantitatively investigated, a new approach for measuring the quadrupolar spin-lattice relaxation time $T\sb{1Q}$ was developed. This uses a Broadband Jeener-Broekaert (BBJB) sequence with echo-detection, which avoids the frequency-discriminated excitation profile and spectral baseline distortion intrinsic to the conventional Jeener-Broekaert (JB) experiment. By combining the BBJB experiment with an Inversion-Recovery sequence with Quadrupole-Echo detection (IRQE), two independent longitudinal relaxation times, $T\sb{1Q}$ and $T\sb{1Z}$, can be measured. Spectral densities of motion $J\sb1(\omega\sb{o}$) and $J\sb2(2\omega\sb{o}$) are extracted from these relaxation times. The new approach was demonstrated on a nematic liquid crystal binary mixture of 4-methyl-4$\sp\prime$-cyanobiphenyl-d$\sb{11}$ (1CB) and 4-n-pentyl-4$\sp\prime$-cyanobiphenyl-d$\sb6$ (5CB). Measurements on mixtures containing 10 and 25 mol% 1CB revealed that rotational motion can be described by the third rate model and the correlation times and activation energies of 1CB and 5CB are concentration independent. In hexamethylbenzene, it was demonstrated that the orientation dependence of spectral densities provides geometric and kinetic information. This technique works well for motions which are in the fast regime ($k\ge10\sp7 s\sp{-1}$) and contribute to relaxation. at ambient temperature, the experimental data were fit by a simulation which included simultaneous threefold and sixfold rotations, with geometric distortions of the electric field gradient tensors of the methyl group. The best-fit jump rates for threefold methyl rotation was $k\sb3 = 5.0\times10\sp{11} s\sp{-1}$ and sixfold aromatic rotation was $k\sb6 = 3.85\times10\sp8 s\sp{-1}$, with out-of-plane and in-plane distortions of 2.5$\sp\circ$ and 1.2$\sp\circ$ respectively. Relaxation times of the bisphenol-A polycarbonate (BPA-PC) and its monomer (BPA) were measured between 250K to 400K. The data were fit to several dynamic models. Simple threefold methyl rotation accounts for the spectral density anisotropies of BPA but not those of the polymer BPA-PC. Inclusion of a semilogarithmic distribution of jump rates, $k\sb3$, improved the agreement qualitatively but not quantitatively. Modulation of threefold methyl jumps by libration of the $C\sb{3V}$ axis was treated with the Stochastic Liouville formalism. Best agreement is found if the two motions are correlated. Activation energies for methyl group rotation are 19.2 $\pm$ 2.0 kJ/mol and 13.0 $\pm$ 0.8 kJ/mol in monomer and polymer respectively.

Polyamide-11 (PA11) is a polymer of the Nylon family whose monomer is obtained from the castor bean, a renewable resource. It is widely used in offshore oil and gas production as a non-rigid flexible pipe liner, allowing for oil and gas transport from the wellhead to floating platforms for processing. The degradation of PA11 over time may lead to the pipe's failure, with possibly catastrophic results which include loss of life. Until now, the characterization of the degredative process has been limited to laboratory studies of the effects of water and temperature on the rate and degree of hydrolysis. In this dissertation, a more exact model than those proposed in the literature thus far is defined and used to quantify the effects of temperature on the rate and degree of PA11 hydrolysis. This is performed using accelerated aging experiments in the lab which are evaluated by a primary means of molecular weight determination, size exclusion chromatography---multiple angle laser light scattering (SEC-MALLS). The effects of methanol and ethanol, used in the industry to control solid hydrate formation, are then characterized with respect to concentration and temperature, a topic which has not yet been addressed in the literature. Also novel to this work is the discovery of the effects of acetic acid, valeric acid, and 3-cyclopropionic acid on the rate and degree of PA11 hydrolysis. While these acids are present in the offshore oil and gas environment, acetic acid is the most common, and has been identified as a serious factor affecting degradation. The effects of acetic acid on rate and degree of hydrolysis are incorporated into the temperature dependence described above, and adapted to a model well suited for characterizing the degradation of PA11 in the changing temperature environments found in the field. By characterizing coupons removed from PA11 pipes in oil production fields in various parts of the world, the model is tested and used to predict aging of PA11 pipe. The model is shown to be effective at predicting degredation for times greater than ten years, which has never before been described. The effects of annealing coupled with decline in molecular weight on PA11 mechanical properties in accelerated aging experiments versus aging in the field environment is discussed. These contributions to understand and predict the aging of PA11 flexible pipes are central to increasing the safety of offshore oil and gas production, a topic that today is vastly important.

Carbon-13 NMR spectroscopy was used to investigate the microstructures of poly(vinyl acetate) prepared by solution polymerization in benzene. A series of aromatic compounds was synthesized in order to model the structures formed via chain transfer to solvent. The peaks near 126.5 and 128.5 ppm in the spectra of the polymer samples were assigned to a 1-phenyl-(2n + 1)-multi-acetoxyalkane (where n = 1, 2, 3, etc.) microstructure. The concentration of that structure obtained from NMR spectra was correlated with the concentration calculated from reported kinetic data.;Chain transfer to benzene was shown to occur by addition of the macroradical to benzene, followed by rearomatization involving loss of a hydrogen atom. No evidence was obtained for a transfer mechanism involving hydrogen abstraction from benzene, and the copolymerization of benzene with vinyl acetate also was shown to be absent. The transfer mechanism actually established accounts for the unexpectedly large transfer constant of benzene in vinyl acetate polymerization. General mechanisms are proposed for the solution polymerization of vinyl acetate in aromatic solvents.