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Die Aufgabenstellung dieser Arbeit bestand in der Entwicklung eines Schichtverbundes auf Polymerfolien mit hoher Barrierewirkung und optischer Transparenz. Dieser wurde über eine Kombination von verschiedenen Einzelschichten erzeugt, deren Abscheidung aus der Gasphase oder der Flüssigphase erfolgte. Die anorganischen Beschichtungen aus SiOx wurden mittels Combustion Chemical Vapor Deposition (CCVD) abgeschieden. Diese lieferten einen hohen Beitrag zur Barrierewirkung, welche anhand der Sauerstoff- (OTR) sowie der Wasserdampftransmissionsrate (WVTR) bewertet wurde. Zur Flexibilisierung des Schichtverbundes wurden anorganisch-organische Hybridschichten integriert, deren Erzeugung mittels Sol-Gel-Technologie (SG) erfolgte. Diese wirkten sich im Verbund positiv auf die optischen Eigenschaften des Substrates aus, welche über UV/VIS-Spektroskopie, Ellipsometrie sowie Messung des Haze-, Clarity- und Grauwertes erfasst wurden. Die Sperrwirkung der Schichten gegenüber den Testgasen konnte über eine Anpassung der Bestandteile im zugrundeliegenden Sol maßgeblich erhöht werden. Als Alternative zu den SG-Beschichtungen wurden Zwischenschichten untersucht, deren Generierung über eine Zwillingspolymerisationsreaktion (ZP) erfolgte. Die Einbringung von Epoxiden ermöglichte in Verbindung mit einem funktionalen Zwillingsmonomer eine Kombination der ZP mit einer Polyaddition. Mit den ebenso aus der Flüssigphase applizierten Beschichtungen ließ sich jedoch keine signifikante Barrierewirkung erreichen. Allerdings zeichneten sich diese Schichten durch eine hohe optische Güte aus, weshalb diese ebenfalls in Mehrlagensysteme integriert wurden. Zum Aufbau der Kombinationsschichten dienten drei bzw. fünf Einzelschichten. Ein Dreischichtsystem bestand hierbei aus zwei CCVD-Schichten (Anfangs- und Deckschicht) sowie einer Zwischenschicht. Um ein Fünfschichtsystem zu generieren wurde eines aus drei Einzelbeschichtungen um zwei weitere ergänzt, wodurch sich eine Anordnung aus abwechselnden CCVD- und SG- bzw. ZP-Schichten ergab. Sämtliche Verbundschichten sowie Einzelkomponenten des Systems wurden zudem bezüglich deren Struktur (Profilometrie, AFM und REM) sowie Schichtzusammensetzung (Festkörper-NMR, FT-IR und XPS) untersucht.

Cationic photopolymerization of multifunctional epoxides is very useful for efficient cure at room temperature and has been widely used in coatings and adhesives. Despite excellent properties of the final cured polymers, cationic photopolymerizations of epoxides have seen limited application due to slow reactions (relative to acrylates) and brittleness associated with a highly crosslinked, rigid network. To address these issues, two reaction systems were studied in this thesis: photoinitiated cationic copolymerizations of a cycloaliphatic diepoxide with epoxidized elastomers and acrylate/epoxide hybrid photopolymerizations. Oligomer/monomer structures, viscosity, compositions, and photoinitiator system were hypothesized to play important roles in controlling photopolymerizations of the epoxide-based mixtures. A fundamental understanding of the interplay between these variables for the chosen systems will provide comprehensive guidelines for the future development of photopolymerization systems comparable to the epoxide-based mixtures in this research. For diepoxide/oligomer mixtures, the observed overall enhancement in polymerization rate and ultimate conversion of the cycloaliphatic diepoxide was attributed to the activated monomer mechanism associated with hydroxyl terminal groups in the epoxidized oligomers. This enhancement increased with increasing oligomer content. The mixture viscosity influenced the initial reactivity of the diepoxide for oligomer content above 50 wt.%. Real-time consumption of internal epoxides in the oligomers was successfully determined using Raman spectroscopy. Initial reactivity and ultimate conversion of the internal epoxides decreased with increasing the diepoxide content. This trend was more pronounced for the oligomer containing low internal epoxide content. These results indicate that the reactivity of the hydroxyl groups is higher toward cationic active centers of the diepoxide than those of the internal epoxides in the oligomers. These conclusions are consistent with physical property results. The enhanced fracture toughness and impact resistance were attributed to multimodal network chain-length distribution of copolymers containing the oligomer content between 70% and 80%. For acrylate/epoxide hybrid mixtures, diacrylate oligomers significantly suppressed reactivities of cycloaliphatic mono/diepoxides, which was attributed to high mixture viscosity and highly crosslinked acrylate network. In this case, the dual photoinitiator system did not favor the epoxide reaction. Depending on the monovinyl acrylate secondary functionalities, enhanced reactivity and ultimate conversion of the diepoxide were attributed to a combined effect of a reduced viscosity and the radical-promoted cationic polymerization associated with the dual photoinitiator. The retarded and inhibited diepoxide reactivities with ether and urethane secondary groups were attributed to solvation and nucleophilicity/basicity effects, respectively. The influence of the diepoxide on the acrylate reactivity was attributed to dilution and polarity effects. In this case, high concentration of the free-radical photoinitiator is required for the dual photoinitiator system. Physical properties of hybrid polymers also varied with acrylate structures and monomer composition. Dynamic modulation methods were proposed to enhance the diepoxide reactivity and final properties in the presence of urethane acrylates.

<p>This thesis describes the structural studies of four different proteins from two organisms. Xyloglucan endotransglycosylases, XETs, are involved in plant cell wall expansion and remodeling by splitting and reconnecting xyloglucan-cellulose crosslinks. The first crystal structure of a XET enzyme has been determined to 1.8 Å. The structure provides insights into how XETs are able to bind a heavily branched xyloglucan sugar, as well as hints about the XET-transglycosylation mechanism.</p><p><i>Mycobacterium tuberculosis</i> (Mtb) is the cause of enormous human mortality each year. Despite the sequencing of the complete Mtb-genome, the biological function of a large fraction of the <i>M. tuberculosis </i>proteins is still unknown. We here report the crystal structures of three such proteins, Rv2740, Rv0216 and Rv0130. Rv2740 forms a Cystatin α+b fold with a deep active site pocket similar to a limonene-1,2-epoxide hydrolase from <i>Rhodococcus erythropolis</i>. However, in contrast to the small limonene-based substrate of the <i>Rhodococcus</i> enzyme, Rv2740 is able to degrade large fatty acid and sterol epoxides, giving suggestions for the physiological substrates of this enzyme.</p><p>The structure of <i>M. tuberculosis</i> Rv0216 exhibits a so-called double hotdog fold. Rv0216 shows similarity to a number of enzymes using thiol esters as substrates, including several <i>R</i>-enoyl hydratases and β-hydroxyacyl dehydratases. However, only parts of the hydratase / dehydratase catalytic site are conserved in Rv0216. Rv0130 in contrast, contains a highly conserved <i>R</i>-hydratase motif, housed in a dimer of two single hotdog folded molecules. This active site is situated in a long tunnel, formed by a sharp kink in the Rv0130 central helix. A number of previously predicted single / double hotdog folded proteins from <i>M. tuberculosis</i> seem to feature a similar substrate-binding tunnel, indicating that Rv0130 as well as some of these proteins, might act on long fatty enoyl chains. </p>

Ce travail aborde l'étude d'oxo radicaux anions générés par des complexes de titane à basse valence ainsi que le contrôle stéréochimique lors de la formation de liaisons carbone carbone. La première partie de ce travail traite de la synthèse de complexes chiraux du titane à partir de ligands de type salénol. Ces complexes sont ensuite mis en application dans la réaction de pinacolisation d'aldéhydes aromatiques et dans le couplage réducteurs d'imines. La réaction de l'aldéhyde avec le complexe de titane forme un radical α-oxo anion qui se dimérise et conduit à un diol. Deux atomes de carbone asymétriques sont créés. Le contrôle de la stéréochimie de la réaction constitue une partie importante du travail. Différents paramètres de la réaction sont étudiés afin d'augmenter la réactivité, la diastéréosélectivité et l'énantiosélectivité. La réactivité et la diastéréosélectivité sont parfaitement maîtrisées (> 95 % dans chaque cas). La réaction a été optimisée sur un substrat modèle, le benzaldéhyde et une énantiosélectivité égale à 84 % a pu être obtenue. Le système a ensuite été étendu au couplage réducteur d'imines pour former des diamines chirales. La seconde partie du travail consiste en l'ouverture réductrice d'époxyde par des complexes du titane. Ceci permet de créer des β-oxo radicaux anions qui sont capturés par des oléfines par réactions inter- ou intramoléculaire. Deux atomes de carbone asymétriques sont là aussi créés et le but final est de contrôler la stéréochimie de la réaction. Des hydroxy-esters sont formés après le couplage et une cyclisation intramoléculaire permet dans certains cas de synthétiser des -lactones. Dans un premier temps, il a fallu synthétiser les époxy-alcènes en plusieurs étapes. Le couplage n'a pour le moment été réalisé qu'à partir d'un complexe achiral. Abstract This work approaches the study of oxo radicals anions generated by low valent titanium complexes and their application in the asymmetric carbon carbon bond formation. The first part of this work deals with the synthesis of some chiral titanium complexes from salenol type ligands. These complexes are then tested in the pinacolisation of aromatic aldehydes and in the reducing coupling of imines. The reaction of the aldehyde with the titanium complex forms an α-oxo radical anion which dimerize and leads to a diol. Two asymmetric atoms of carbon are then created. The control of the stereochemistry of the reaction is the main part of this work. Various parameters of the reaction are studied to increase the reactivity, the diastereoselectivity and the enantioselectivity. The reactivity and the diastereoselectivity are perfectly mastered (> 95 % in every case). The reaction was optimized on a model substrate, benzaldéhyde, and enantioselectivities up to 84 % were achieved. The system was then extended to the reducing coupling of imines to form chiral diamines. The second part of the work is centered on the reducing opening of epoxide by low valent titanium complexes. This allows to create β-oxo radical anions which are captured by olefines by inter-or intramolecular reactions. Two asymmetric centers are also created and the final goal was to control the stereochemistry of the reaction. Hydroxy-esters are formed after the coupling and an intramolecular cyclization allows in certain cases to synthesize -lactones. It was first necessary to synthesize the starting epoxy-alkenes. At the present stage of the study, the coupling on the model epoxy-alkene was only tested with an achiral complex.

This thesis describes the structural studies of four different proteins from two organisms. Xyloglucan endotransglycosylases, XETs, are involved in plant cell wall expansion and remodeling by splitting and reconnecting xyloglucan-cellulose crosslinks. The first crystal structure of a XET enzyme has been determined to 1.8 Å. The structure provides insights into how XETs are able to bind a heavily branched xyloglucan sugar, as well as hints about the XET-transglycosylation mechanism. Mycobacterium tuberculosis (Mtb) is the cause of enormous human mortality each year. Despite the sequencing of the complete Mtb-genome, the biological function of a large fraction of the M. tuberculosis proteins is still unknown. We here report the crystal structures of three such proteins, Rv2740, Rv0216 and Rv0130. Rv2740 forms a Cystatin α+b fold with a deep active site pocket similar to a limonene-1,2-epoxide hydrolase from Rhodococcus erythropolis. However, in contrast to the small limonene-based substrate of the Rhodococcus enzyme, Rv2740 is able to degrade large fatty acid and sterol epoxides, giving suggestions for the physiological substrates of this enzyme. The structure of M. tuberculosis Rv0216 exhibits a so-called double hotdog fold. Rv0216 shows similarity to a number of enzymes using thiol esters as substrates, including several R-enoyl hydratases and β-hydroxyacyl dehydratases. However, only parts of the hydratase / dehydratase catalytic site are conserved in Rv0216. Rv0130 in contrast, contains a highly conserved R-hydratase motif, housed in a dimer of two single hotdog folded molecules. This active site is situated in a long tunnel, formed by a sharp kink in the Rv0130 central helix. A number of previously predicted single / double hotdog folded proteins from M. tuberculosis seem to feature a similar substrate-binding tunnel, indicating that Rv0130 as well as some of these proteins, might act on long fatty enoyl chains.

Standard chemical DNA synthesis with isotope labels requires expensive reagents; moreover, a large excess of phosphoramadites (typically 50-100 fold) must be used. We developed a process where enzymatic cyclic solid phase synthesis of DNA allows for more economic reagent use. A DNA template was immobilized on an epoxy-activated solid support. This chemistry was chosen because the formed linkage is inert to high pH conditions. High efficiency of the covalent attachment was observed when the reaction was carried out in MgCl2/CAPS buffer. It was found that Mg2+ enables the reaction to be completed over a period of 14 h, compared to 72 h under standard conditions. DNA synthesis was carried in a cyclic fashion on a support bound DNA using Klenow fragment.

Two main areas are considered in this manuscript. The first describes the synthesis of group 10 metal complexes incorporating the water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) ligand and the second deals with the preparation of Cr(salen)X catalysts for the copolymerization of CO2 and epoxides. In the first topic, the synthesis of nickel(II) and palladium(II) salicylaldiminato complexes incorporating PTA has been achieved employing two preparative routes. Upon reacting the original ethylene polymerization catalyst developed by Grubbs and coworkers (Organometallics, 1998, 17, 3149), (salicylaldiminato)Ni(Ph)PPh3, with PTA using a homogeneous methanol/toluene solvent system resulted in the formation of the PTA analogs in good yields. Alternatively, complexes of this type may be synthesized via a direct approach utilizing (TMEDA)M(CH3)2 (M = Ni, Pd), the corresponding salicylaldimine, and PTA. Polymerization reactions were attempted using the nickel-PTA complexes in a biphasic toluene/water mixture in an effort to initiate ethylene polymerization by trapping the dissociated phosphine ligand in the water layer, thereby, eliminating the need for a phosphine scavenger. Unfortunately, because of the strong binding ability of the small, donating phosphine (PTA) as compared to PPh3, dissociation did not occur at a temperature where the complexes are not subjected to decomposition. Additionally, the unexplored PTA derivative, 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), prepared by the literature procedure, was fully characterized by NMR and X-ray analysis. DAPTA is found be similar to its parent (PTA) in coordination mode and binding strength, as supported by its representative group 6 and group 10 complexes The second main topic involves the copolymerization of CO2 and epoxides (i.e., cyclohexene oxide (CHO)) for the formation of polycarbonate using Cr(salen)X (X = Br, OPh) catalysts with one equivalent of PR3 as the co-catalyst. The use of these catalysts and cocatalysts results in the most active chromium-based catalytic systems to date. The . hr-1highest activities observed are on the order of 109 mol CHO consumed . mol Cr-1 using PCy3 as the co-catalyst, and is clearly seen in the in situ monitoring of copolymer formation. An advantage of these systems involves the lack of cyclic carbonate production and high CO2 incorporation (>99%) within the polymer.

Thesis (Ph.D. (Pharmaceutical Chemistry)--North-West University, Potchefstroom Campus, 2009.