Magister Scientiae - MSc / The objectives of this project were to synthesize and characterise pyridine carboxamide ligands and their palladium complexes and investigate their catalytic activity in the polymerization process of phenylactylene. / South Africa

Magister Scientiae - MSc / This study focused on the development of binuclear and multinuclear catalyst for use in vinylic monomer oligomerization and polymerization. The main objective was to develop new homogeneous catalysts systems with hopefully improved activity, selectivity and stability. / South Africa

The prediction of dynamic energy losses from stress relaxation data, using the equation ηω = - π/4.606 ( slope of relaxation curve), ……. (1) has received considerable attention recently, but for polyiso-butylene the correlation between predicted and experimental values of energy loss has been poor. This lack of agreement may have been caused by the failure of' the simple "step" distribution function of relaxation times to explain the process adequately. In this work, stress relaxation measurements with the RCA 5734 electronic transducer tube have been made in polylsobutylene at times as early as .01 second and the results show a very rapid rise in stress as t →0 rather than the constant value required by the "step" function. Another distribution function may be obtained by measuring the slopes of the log. dynamic modulus vs. log. ω , and the static modulus vs. log. time curves. For PIB the absence of data in the region near 1 second leaves a gap of nearly 2 cycles of log. time for which there are no predicted values of the distribution function and the data obtained in this research may be used to fill this gap. Simplified calculations with this function show qualitative agreement between predicted and experimental energy loss in polylsobutylene. Dynamic data for Acetate rayon show an Increase in energy loss with increased humidity, and stress relaxation experiments were performed on this material at various humidities to see if the effect was apparent. From equation (1) an increase in slope of the relaxation curve is expected to occur as the humidity is increased. No indication of this effect was found in the stress relaxation data, and in fact, the relaxation curves at higher humidity had slightly lower slopes. This would; tend to indicate that the prediction of energy loss from equation (1) is not valid in the case of Acetate rayon. Values of energy loss for Viscose rayon and Egg Albumin fiber at 65% humidity show moderate agreement with those calculated from stress relaxation experiments. / Science, Faculty of / Chemistry, Department of / Graduate

The emulsion polymerization of isoprene has been produced by using as initiating agents various compounds which are known to dissociate to a certain extent in solution into free radicals. The rate of thermal decomposition of some of the diazothio ethers employed as initiating agents have been measured by observing the rate of evolution of nitrogen from a solution of the compounds in butylphthalate. / Science, Faculty of / Chemistry, Department of / Graduate

The emulsion polymerization of isoprene by means of cumene hydroperoxide was found to yield polymers of irreproducible intrinsic viscosities. The cause was found to be in the procedure used which was that recommended for drying GR-S type rubbers. The temperature and drying period finally found to be satisfactory were 35° C. and 48 hours. The formula recommended for the production of GR-S rubber by means of cumene hydroperoxide when applied to isoprene gave a rubber with too low a molecular weight. By studying the effect of varying the concentration of each of the components, and also the temperature, conditions have been established for the production of a satisfactory polymer. / Science, Faculty of / Chemistry, Department of / Graduate

Part one of this thesis concerns the polymerizability of some α,β-unsaturated monaldehydes and also relates the synthesis of some new polyaldehydes which have not been reported in the literature. Part two concerns the polymerization of glyoxal, the simplest dialdehyde, and the structure elucidation of this new polymer.

<p>&nbsp / </p> <p align="left">The main aim of this study was to design new polyfunctional ligands based on the polypropyleneimine dendrimer&nbsp / <font face="Arial">DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 <font face="Arial">referred to as </font><b><font face="Arial,Bold">L1 </font><font face="Arial">in this work, to be used in </font></b></font></font><font face="Arial">copper mediated atom transfer radical polymerization (ATRP) of vinyl monomers. These ligands were synthesized by modifying DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 </font></font><font face="Arial">with aromatic and aliphatic substituents on the nitrogen atoms at the periphery of </font><b><font face="Arial,Bold">L1</font><font face="Arial">.</font></b></p>

Controlled radical polymerization (CRP) has emerged as a powerful method of creating polymers with tailored molecular architectures under mild reaction conditions. However, production of these polymers efficiently at an industrial scale will likely require them to be synthesized in the dispersed phase. Three types of CRP are explored, Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated Polymerization (NMP) and Catalytic Chain Transfer (CCT) to elucidate the intricacies of creating these novel polymer colloids. Compartmentalization in an ATRP dispersed phase system is explored theoretically to understand the effects of particle size and catalyst concentration on the polymerization. The results suggest that there is an optimal range of particle sizes where the rate of polymerization is greater than that in an equivalent bulk system while maintaining both a lower PDI (polydispersity index) and higher livingness. All three factors are desirable in ATRP but generally cannot be achieved simultaneously in bulk. Compartmentalization manifests itself differently in CCT dispersed phase systems, where the segregation of the CCT agents into different polymer particles leads to multimodal molecular weight distributions. Control over the particle size is notoriously difficult for nitroxide mediated polymerization, as it is challenging to decouple an increase in the particle size with an increase in target molecular weight using a two stage emulsion polymerization approach. This often leads to colloidally unstable latexes for low molecular weight, high solids conditions which are the result of superswelling. We offer several strategies to minimize this problem and create colloidally stable, high solids, n-butyl acrylate latexes by NMP with moderate to high molecular weight targets (>70 kg/mol). Using this synergy between target molecular weight and particle size, high solids (>40 wt.%), high molecular weight (<200 kg/mol) microemulsions (~20 nm) of methyl methacrylate-co-styrene were prepared. Finally, the monomer type and nucleation mechanisms also play a role in determining the particle size distribution in NMP emulsion systems. Using n-butyl methacrylate in emulsion with surfactant concentrations above the critical micelle concentration yields latexes with bimodal particle size distributions. However a surfactant-free approach allows monomodal latexes to be created. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-12-03 13:30:15.346

<p>&nbsp / </p> <p align="left">The main aim of this study was to design new polyfunctional ligands based on the polypropyleneimine dendrimer&nbsp / <font face="Arial">DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 <font face="Arial">referred to as </font><b><font face="Arial,Bold">L1 </font><font face="Arial">in this work, to be used in </font></b></font></font><font face="Arial">copper mediated atom transfer radical polymerization (ATRP) of vinyl monomers. These ligands were synthesized by modifying DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 </font></font><font face="Arial">with aromatic and aliphatic substituents on the nitrogen atoms at the periphery of </font><b><font face="Arial,Bold">L1</font><font face="Arial">.</font></b></p>

No description available.