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Rate constants for chemical reactions in various aqueous and micro- heterogeneous systems have been measured and analysed. A large part of the thesis is concerned with interpreting kinetic trends in two water-in-oil microemulsions. Kinetic data for inorganic reactions involving low-spin iron (II) di-imine oorplexes and for reactions involving the organic substrates, 2,4-dinitrochlorobenzene, crystal violet and malachite green in microemulsions have been collected and used to identify different structural zones in these solvent systems. The kinetic data are interpreted in terms of a model in which reaction occurs at an interfuse. Reactions involving cis-bis(pyridine)tetracarbonylmolybdenum (0) in oil- in-water, water-in-oil microemulsions and organic solvent mixtures have been studied. Aquation reactions of iron (II) hexadentate Schiff base have been used to identify microheterogeneous phases in water-rich '2-butoxyethanol + water' mixtures. Solvent effects on initial and transition states are discussed for reactions of iron (II) glyoxal bis-N methylamine with hydroxide ions in 'methanol + water' mixtures and reactions of iron(II) 1,10-phenan- throline with hydroxide ions in 'isopropanol + water' mixtures. Transfer chemical potentials for single ions, in 'acetone + water' mixtures, have been estimated, using solubility data for salts in conjunction with the assumption that transfer chemical potentials for tetraphenylboronate and tetraphenylarsonium ions are equal. Effects of added salt on the neutral hydrolysis of phenyldichloro- acetate in aqueous solutions are examined in terms of solvent cosphere interactions between ions. The temperature dependence of rate constants for reactions of iron (II) 4-methyl, 1,10-phenanthroline have been examined. The results are discussed in terms of isobaric, isothermal and isochoric activation parameters. The meaning of the term 'isochoric' is clarified in this context.

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The interest in microemulsions as transdermal delivery systems have been motivated by their large surface area for mass transfer, their high solubilization capacity of hydrophobic actives, and their ability to improve skin penetration. Lecithins (mixtures of phospholipids similar to those find in the skin) have been proposed as ideal surfactants in microemulsions due to their skin compatibility. Unfortunately, their incorporation into microemulsions used to require toxic medium-chain alcohols or viscous polymeric co-surfactants. Recently, microemulsion-base “green solvents” were formulated with lecithin and linker molecules. The main objective of this dissertation was to test this concept of linker-based lecithin microemulsions in transdermal delivery. In the first part of this study, linker-based lecithin formulations were developed using soybean lecithin as main surfactant, sorbitol monooleate as lipophilic linker, and caprylic acid/sodium caprylate as hydrophilic linkers. These additives, at the suggested concentration, are safe for cosmetic and pharmaceutical applications. The low toxicity of these formulations was confirmed in cultured human skin tissues. The solubilization and permeation of a common anaesthetic, lidocaine, was evaluated. The concept of “skin” permeability was introduced to account for the differences in solvent-skin partition when comparing different delivery systems. The linker-based lecithin microemulsion produced a substantial absorption of lidocaine into the skin, when compared to a conventional pentanol-lecithin microemulsion. The second part of this study takes advantage of the lidocaine adsorbed in the skin with the linker-based lecithin microemulsion as reservoir for in situ skin patches. The in situ patches were able to release 90% of the lidocaine over 24 hours, which is comparable to the release profile obtained from conventional polymer or gel-based patches. In the third part of this work, the role of surfactant droplets on the transport of lidocaine was studied. A mass balance model that accounted for mass transfer and partition coefficients was introduced. The parameters generated from the model confirm that in most cases the transport through the skin limits the overall penetration of lidocaine. Besides the conventional diffusion mechanism, the results suggest that surfactant droplets, carrying lidocaine, also penetrate into the skin and contribute to the accumulation of the lidocaine in the skin.

The interest in microemulsions as transdermal delivery systems have been motivated by their large surface area for mass transfer, their high solubilization capacity of hydrophobic actives, and their ability to improve skin penetration. Lecithins (mixtures of phospholipids similar to those find in the skin) have been proposed as ideal surfactants in microemulsions due to their skin compatibility. Unfortunately, their incorporation into microemulsions used to require toxic medium-chain alcohols or viscous polymeric co-surfactants. Recently, microemulsion-base “green solvents” were formulated with lecithin and linker molecules. The main objective of this dissertation was to test this concept of linker-based lecithin microemulsions in transdermal delivery. In the first part of this study, linker-based lecithin formulations were developed using soybean lecithin as main surfactant, sorbitol monooleate as lipophilic linker, and caprylic acid/sodium caprylate as hydrophilic linkers. These additives, at the suggested concentration, are safe for cosmetic and pharmaceutical applications. The low toxicity of these formulations was confirmed in cultured human skin tissues. The solubilization and permeation of a common anaesthetic, lidocaine, was evaluated. The concept of “skin” permeability was introduced to account for the differences in solvent-skin partition when comparing different delivery systems. The linker-based lecithin microemulsion produced a substantial absorption of lidocaine into the skin, when compared to a conventional pentanol-lecithin microemulsion. The second part of this study takes advantage of the lidocaine adsorbed in the skin with the linker-based lecithin microemulsion as reservoir for in situ skin patches. The in situ patches were able to release 90% of the lidocaine over 24 hours, which is comparable to the release profile obtained from conventional polymer or gel-based patches. In the third part of this work, the role of surfactant droplets on the transport of lidocaine was studied. A mass balance model that accounted for mass transfer and partition coefficients was introduced. The parameters generated from the model confirm that in most cases the transport through the skin limits the overall penetration of lidocaine. Besides the conventional diffusion mechanism, the results suggest that surfactant droplets, carrying lidocaine, also penetrate into the skin and contribute to the accumulation of the lidocaine in the skin.

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.

Microemulsions are nanostructured dispersions that have unique properties, which make them attractive for applications such as biomaterials, drug delivery, and nanoparticle synthesis. The behaviour of hydrocarbon microemulsions and their applications have been extensively studied, however, there have been very few studies in the preparation or the polymerization of silicone microemulsions. Silicone microemulsions offer a unique template by which to create novel nanoporous silicone elastomers and/or hydrogels. The prevalent use of silicones in biomaterials, coatings, and personal care (to name a few) make the development of silicone-based microemulsions of particular interest. The aim of thesis research was to polymerize silicone microemulsions and to understand the factors that contribute to retaining initial template morphology in the polymeric product. Chapter Two of this thesis focuses on the preparation of silicone microemulsions containing a non-polymerizable and polymerizable trisiloxane surfactant, respectively. Formulations were prepared and characterized by electrical conductivity to determine the microemulsion structure type. Formulations located in the bicontinuous region of the phase diagram were polymerized, producing transparent silicone elastomers. The focus of Chapter Three was to determine the tolerance of silicone microemulsions to selected chemistry that is relevant to silicone polymers. Previous work done in the field of polymerizing silicone microemulsions has been based on radical polymerization processes. There are no reports that examine the polymerization of a silicone microemulsion by room temperature vulcanization (RTV), a common process for creating silicone elastomers. We aimed to better understand the effects of RTV cure on morphology retention from the liquid to polymeric product to determine if this type of chemistry could be used in the formation of nanoporous silicone elastomers either on its own or in conjunction with a radical polymerization process. In order to understand the effects of an RTV process on polymer structure, we examined the effect of the variable components (necessary for the RTV cure) on the silicone microemulsion template. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used as tools to characterize materials prior to and after cure. Silicone microemulsions that were cured using the RTV process produced nanoporous polymeric elastomers, however, the initial bicontinuous microemulsion template was not retained. RTV cured microemulsions retained the bicontinuous structure if the RTV cure was preceded by a photopolymerization reaction to “lock-in” surfactant monomers at the oil/water interface. Chapter Four explores the use of silicone microemulsions as a reaction vehicle in the formation of nano-TiO2 particles. The focus of this chapter was the exploitation of microemulsion droplets and bicontinuous structures that were designed to retard TiO2 particle formation in situ. Titanium isopropoxide (TTIP) was incorporated into silicone microemulsions containing varying amounts of water. Interactions between TTIP and the trisiloxane polyether surfactant result in the formation of a compound containing a Ti4+, coordinated to silicone surfactant molecules via a polyether linkage. Titania forms in situ as water is titrated into the surfactant/oil mixture, resulting in the formation of a microemulsion. The formation of TiO2 was monitored by UV-Vis spectroscopy and the TiO2 particles were characterized using transmission electron microscopy. / Thesis / Doctor of Philosophy (PhD) / This thesis is about the chemical modification and polymerization of nanostructured liquids in the form of silicone microemulsions to create nanoporous silicone elastomers (nano is one billionth, 10-9, so 1 nanometer = 1 billionth of meter). Despite the highly prevalent commercial use of silicones and the utility of silicone elastomers, little is known about the polymerization of silicone microemulsions to create nanoporous materials. The first goal of this thesis was to polymerize silicone microemulsions, using methods that have been previously used in the polymerization of hydrocarbon microemulsions. Silicone microemulsions were successfully polymerized using a reactive surfactant and rigidification of the oil phase was achieved using common silicone crosslinking chemistry. The second goal was to understand how the type of chemistry affects changes in structure upon transition from liquid microemulsion to solid polymer. Nanostructuring was retained in polymerized microemulsions both with and without oil phase polymerization. Finally, the third goal was to exploit silicone microemulsion domains to control titanium dioxide particle formation. Particle formation was slowed as a result of domain constricted particle growth.

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La membrane échangeuse de protons est un élément essentiel des piles à combustible. Elle permet le transfert des protons d’une électrode à l’autre pour produire de l’électricité. La conduction protonique des membranes actuelles est optimale vers 80°C et très sensible à l’eau. La conception de nouvelles membranes permettant le fonctionnement des piles à combustible à température ambiante et moins sensibles à l’eau est nécessaire. La solution proposée pendant ma thèse est de concevoir des microémulsions solidifiées conductrices de protons. Les microémulsions sont des mélanges liquides nanostructurés d’eau, d’huile et de tensioactifs à l’équilibre thermodynamique. Des microémulsions bicontinues, constituée de canaux d’eau et d’huile séparés par une monocouche de tensioactifs, formulées avec des tensioactifs conducteurs protoniques devraient avoir des propriétés intéressantes de conduction protonique. Il est ensuite nécessaire de solidifier les microémulsions obtenues pour pouvoir les utiliser comme membrane échangeuse de protons. Dans ce travail, la voie explorée consiste à utiliser une huile solide à température ambiante pour résoudre ce problème. Deux systèmes, contenant une huile solide à température ambiante et des tensioactifs conducteurs protoniques, ont été étudiés. Des microémulsions bicontinues sont ainsi préparées au-dessus du point de fusion de l’huile. Il s’agit ensuite de maîtriser comment un simple refroidissement permet d’obtenir des microémulsions solidifiées, matériaux solides avec la même structure que le liquide de départ. Cette étude a permis de mettre en évidence l’influence de la cristallisation sur la structure du matériau obtenu. / Proton-exchange membrane is an important part of fuel cells. It allows protons to move from one electrode to the other while producing energy. Proton conduction in current membranes is optimum at 80°C and very sensitive to water. It is therefore necessary to build new proton-exchange membranes to design fuel cells that are effective at ambient temperature and less water-sensitive.During my PhD, we intend to prepare solidified microemulsions as proton-exchange membranes. Microemulsions are nanostructured liquids composed of water, oil and surfactants at thermodynamic equilibrium. Bicontinuous microemulsions, made of water and oil channels separated by surfactants, obtained using proton conducting surfactants should have interesting proton conductivity. It is then necessary to solidify the obtained liquid to be able to use them as proton-exchange membrane. In this study, we use oil that is solid at room temperature to overcome this trouble. Two systems, with an oil solid at room temperature and proton-conducting surfactants, were studied. Bicontinuous microemulsions are prepared above the melting point of the oil. The point is then to understand how cooling down the liquid microemulsion allow to prepare a solidified microemulsion which is a solid with the same nanostructure as the initial liquid. This study highlights the influence of crystallization on nanostructure during cooling.