A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirement for the degree Master of Science (MSc) in Chemistry. Johannesburg, March 2017. / A series of [Pt(diimine)(Ln-O,S)]Cl complexes, where Ln-O,S represents a series of N,N dialkyl-N’-acylthiourea ligands and diimine represents (1,10-Phenanthroline; 5,6-dimethyl 1,10-phenanthroline or [3,2-d:2’,3’-f]-quinoxaline were successfully synthesised and characterised. A new crystal structure was obtained for N,N-di(2-hydroxy)-N’ benzoylthiourea which revealed an interesting herringbone crystal packing arrangement. The cytotoxicity of the series of complexes was evaluated on H1975 lung cancer cell lines at 50 µM and 5 µM. All the complexes were highly cytotoxic with cell death of 90-98% at 50 µM. However, at 5 µM there were much more variations on cell viability percentages. Although the structure–activity relationship can only be established when the IC50 (the concentration of an inhibitor where the response is reduced by half) values are determined, it is clear that the complexes containing the methyl substituents on the 5 and 6 positions of the phenanthroline moiety were the most cytotoxic with almost 98% cell death at 5 µM. The solubility of the complexes did improve by using N,N-dialkyl-N’-acylthiourea as ancillary ligands, however aqueous solubility remains a major problem. Sulphobutyl-ether-β-cyclodextrin (captisol) and low-molecular-weight surfactant micelles as drug delivery systems were considered in attempt to improve the solubility. DOSY NMR Spectroscopy revealed that there was no inclusion complex formation between the complex and capstiol, although the chemical shift trend suggested that there is at least some interaction. The low-molecular-weight surfactant micelles were considered as an alternative, which showed some promise as a drug delivery system, since the aqueous solubility improved and a colloidal suspension was obtained. / LG2018

The objective of this thesis is to investigate well-defined cross-linked particles synthesized via the reversible addition fragmentation chain transfer (RAFT) process that can be used for drug delivery. To achieve this aim, a wide range of cross-linked micelle systems have been synthesized and intensively investigated. Various biocompatible monomers were employed, including poly (ethylene glycol) methyl ether methacrylate, 2-hydroxyl ethyl acrylate, functionalized glucosamine and nucleotides containing monomers. Different cross-linked structures were used, for example, core-cross-linked, nexus-cross-linked and shell-cross-linked micelles. Diverse stimuli-responsive particles were used, such as pH-sensitive, thermo-sensitive and thiol-sensitive cross-linked systems. Evidences of the successful synthesis of all the resulting cross-linked products are given. They displayed better properties, as drug carriers, than non-cross-linked micelles. A thermo-responsive seven-arm star glycopolymer, synthesized via the RAFT process, was also investigated.

Thesis (Ph.D.)--University of Nevada, Reno, 2005. / "December 2005." Includes bibliographical references. Online version available on the World Wide Web.

Mono-dispersed supported Ni catalysts were synthesized using the water-CTAB-hexanol reverse micellar system. The core of the reverse micelles contained an aqueous solution of NiCl2. Dynamic light scattering measurements showed that microemulsions having a water-to-surfactant molar ratio, Wo, of 10 lead to reverse micelles with lowest polydispersity, longest stability, and size range of interest. At an oil-to-aqueous phase ratio of 2, the diameter of the reverse micelles was found to increase with Wo in a linear fashion. At higher values of Wo (i.e. 25-30), the polydispersity was found to increase when lowering the amount of surfactant in the system. Ultimately, O/A = 2 and Wo = 10 were chosen as optimal conditions for microemulsion preparation. The aqueous NiCl2 concentration within the micelles was varied between 0.1 and 0.001 M. DLS results showed that although the average micelle diameter was between 70-83 nm throughout the range of metal salt concentrations, the crystallite size estimate based upon the reported micelle diameter and known aqueous NiCl2 concentration ranged between 2 to 7 nm. Therefore, the Ni crystallite size was varied by changing the aqueous NiCl2 concentration due to instability issues arising when changing the value of Wo. After deposition onto an alumina mesh support, the particles were dried, calcined, and reduced to produce Ni clusters. SEM and EDS analysis was used to confirm the presence of Ni compounds after the calcination stage. By the varying the aqueous NiCl2 concentration within the micelles, .0039, .0013, and .00039 wt. % Ni catalysts were produced and characterized using SEM. Particles in the size range of 10-14 nm were noticed for the .0039 wt. % Ni catalysts after reduction, 7-11 nm for .0013 wt. % Ni, and 5-9 nm for .00039 wt. % Ni. The lower-end of these particle size ranges was comparable to the crystallite size estimates. Ethane hydrogenolysis and ethylene hydrogenation reactions were conducted over the emulsion-prepared catalysts in order to determine particle size effects on catalytic activity. Results showed that the catalytic activity, defined in terms of per unit metal surface atom (or TON, turnover number), decreases with increasing particle size for the hydrogenolysis reaction. This trend may be due to an intrinsic size effect in which smaller particles exhibit the chemical or structural properties necessary for achieving a higher reaction rate. The results for ethylene hydrogenation showed that the reaction rate did not significantly change with crystallite size, confirming that the reaction is facile or structure-insensitive.

Thèse de doctorat : Sciences Chimiques : Physico-Chimie de la Matière Condensée : Bordeaux 1 : 2008. / Titre provenant de l'écran-titre.

Thèse de doctorat : Chimie : Nancy 1 : 2009. / Titre provenant de l'écran-titre.

Thesis (Ph. D.)--University of Chicago, December 2003. / Includes bibliographical references. Also available on the Internet.

Les micelles complexes de polyions, ou « micelles PIC », formées par interaction électrostatique entre un copolymère à blocs double hydrophile neutre-ionique (DHBC) et un homopolyélectrolyte de charge opposée au DHBC possèdent des propriétés particulièrement intéressantes : solubilité des polyélectrolytes dans l'eau, stabilité des micelles, contrôle de l'association/dissociation micellaire par divers stimuli (pH, force ionique, irradiation lumineuse…). Dans cette thèse, les propriétés physico-chimiques des micelles PIC de type DHBC neutre-cationique/homopolymère anionique et DHBC neutre-anionique/homopolyélectrolyte cationique ont été étudiées en solution aqueuse en vue de leur utilisation comme agent structurant des matériaux siliciques organisés à l'échelle nanométrique. La gamme de pH de formation des micelles PIC, la concentration micellaire critique et le nombre d'agrégation des micelles ont été déterminés pour chacun des systèmes étudiés. Nous avons montré que la formation des micelles suit un mécanisme coopératif qui dépend de la taille de l'homopolymère. Par ailleurs, nous avons proposé une voie originale de formation des micelles PIC photoinduite, basée sur une modification du pH suite à l'irradiation d'une molécule photochrome. Les études concernant l'utilisation des micelles PIC comme agent structurant des matériaux nous ont permis de montrer que la morphologie (nanoparticulaire, massif) et la structure des matériaux (lamellaire, vermiculaire) peuvent être contrôlés par divers paramètres, tels que la concentration en masse du système DHBC/homopolyélectrolyte/précurseur de silice, la teneur en précurseur de silice et le rapport entre les fonctions cationique et anionique des polyélectrolytes. Le lavage des matériaux sous des conditions douces (à l'eau) permet de récupérer l'agent structurant. / Polyion complex micelles, or "PIC micelles", formed by electrostatic interaction between a neutral-ionic double hydrophilic block copolymer (DHBC) and an oppositely charged homopolyelectrolyte possess interesting properties: solubility of the polyelectrolytes in water, stability of micelles, control of the micellar association / dissociation by various stimuli (pH, ionic strength, light irradiation ...). In this thesis, the physico-chemical properties of PIC micelles of neutral-cationic DHBC/ anionic homopolymer and neutral-anionic DHBC/cationic homopolymer were studied in aqueous solution for use as structuring agents of silica-based organized nanomaterials. The pH range of PIC micelle formation, the critical micelle concentration and aggregation number of micelles were determined for each studied system. We have shown that the formation of micelles follows a cooperative mechanism which depends on the size of the homopolymer. Furthermore, we proposed an original way of photoinduced PIC micelle formation, based on a pH change after irradiation of a photochromic molecule. The studies on the PIC micelles as structuring agents of materials have shown that the morphology (nanoparticular, bulk) and the material structure (lamellar, vermicular) can be controlled by various parameters, such as the mass concentration of the DHBC / homopolyelectrolyte / silica precursor system, the content of the silica precursor and the ratio between the functions of the cationic and anionic polyelectrolytes. Finally, the template was removed by washing the hybrid materials under soft conditions in water.

The purpose of this dissertation was two-fold: 1) explore the micelle structure and microenvironment of monorhamnolipids (mRL), produced by Pseudomonas aeruginosa ATCC 9027, and their mixtures with synthetic surfactants in order to postulate possible applications of these materials in industrial products and 2) examine the effects of mRL on commercial metal oxide nanoparticle (NP) aqueous dispersion behavior to reveal the potential impact of microbial secondary metabolites on NP fate and transport in the environment. The mixing behavior of mRL with cetylpyridinium chloride (CPC) was measured using surface tensiometry. Electrostatics resulted in cooperative enhancement in mixture properties, but were not significant until α(CPC) ≥ 0.25. Steady-state and time resolved fluorescence quenching measurements in mRL micelles revealed that quenching proceeded via a combined static and dynamic mechanism. Static quenching was preferred in mRL illustrating the reactants form a globular micelle. Changing the structure of the reactants displayed changes in the degree and mechanism of quenching further supporting this aggregate model. Fluorescence measurements on mRL-Tween 20 micelles supported that a geometrically-driven shape transition occurs as mRL decreases. The corresponding decrease in probe lifetime indicated the polarity of the micelle was decreasing. Tween "sealed" the mRL micelles making them less susceptible to water penetration. The effect of mRL on metal oxide NP dispersions was evaluated on adsorption strength, NP aggregate size and stability, and zeta potential under different conditions. Silica NPs showed little adsorption of mRL and was impervious to all variables in altering the solution stable aggregate size. NP aggregate size decreased at very high mRL concentrations due to osmotic and electrosteric repulsions of mRL micelles in solution. Titania, despite expectations, indicated fairly low adsorption of mRL and displayed similar aggregate dispersion stability as that of silica. Spectroscopic investigations exposed that the commercial titania NPs were contaminated with silica altering NP surface properties. Zinc oxide (ZnO) dispersions were substantially affected by the adsorption of mRL. Without mRL, ZnO NPs were unstable independent of pH. The addition of mRL stabilized the ZnO dispersions and lowered the zeta potentials. Furthermore, mRL coating prevented the dissolution of ZnO, the major factor implicated in ZnO toxicity.

No description available.