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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Single molecule tracking studies of flow-aligned mesoporous silica monoliths: pore order and pore wall permeability

Park, Seok Chan January 1900 (has links)
Doctor of Philosophy / Department of Chemistry / Daniel A. Higgins / This dissertation describes single-molecule tracking (SMT) studies for the quantitative characterization of one-dimensional (1D) nanostructures in surfactant-templated mesoporous silica monoliths prepared within microfluidic channels. Single molecule diffusion of fluorescent probe molecules within the cylindrical mesopores reflects microscopic morphologies and mass-transport properties of the materials with high temporal and spatial resolution. The pore organization and materials order are initially investigated as a function of sol aging prior to loading into the microfluidic channels. Mesopores in these materials are templated by Cetyltrimethylammonium bromide (CTAB). Wide-field fluorescence videos depict 1D motion of the dyes within the individual mesopores. Orthogonal regression analysis of these motions provides a measure of the mesopore orientation. Channels filled prior to gelation of the sol produce monoliths incorporating large monodomains with highly aligned mesopores. In contrast, channels filled close to or after gelation yield monoliths with misaligned pores that are also more disordered. Two-dimensional (2D) small angle X-ray scattering (SAXS) experiments support the results obtained by SMT. These studies help to identify conditions under which highly aligned mesoporous monoliths can be obtained and also demonstrate the utility of SMT for characterization of mesopore order. The non-ionic surfactant Pluronic F127 is also utilized as the structural-directing agent. The diffusive motions of PDI dyes that are uncharged, cationic and anionic are explored by SMT and fluorescence correlation spectroscopy (FCS). The SMT studies for the uncharged dye show development of 1D diffusion along the flow direction while charged dyes exhibit predominant isotropic diffusion, with each of these behaviors becoming more prevalent as a function of aging time after filling of the microfluidic channels. SMT studies from silica-free F127 gels suggest that partitioning plays a important role in governing the diffusion behavior of the PDI dyes within the surfactant-filled mesopores. FCS results exhibit similar mean diffusion coefficients for all three dyes that suggest these dyes diffuse through similar sample regions. These studies demonstrate that the silica pore walls in the mesoporous silica monoliths remain permeable after gelation and that partitioning of solute species to different regions within the pores plays an important role in restricting the dimensionality of their diffusive motion
2

Synthèse sélective de N-hétérocycles carbonylés par multi-catalyse homogène et hétérogène / Selective synthesis of carbonylated N-heterocycles by homogeneous and heterogeneous multi-catalysis

Genelot, Marie 05 January 2011 (has links)
La synthèse tout-en-un de 4-quinolones et d'indoxyles a été réalisée par couplage de Sonogashira carbonylant suivi d'une cyclisation. Une étude en catalyse homogène a révélé que les catalyseurs présents contrôlaient la sélectivité vers l'un ou l'autre des composés. Si la première étape est pallado-catalysée, l'étape de cyclisation est catalysée par des nucléophiles organiques. Ainsi, des 4-quinolones ont été préparées par multi-catalyse {[Pd]+amine} et des indoxyles par catalyse tandem {[Pd]/phosphine}. Les systèmes catalytiques ont été hétérogénéisés par fonctionnalisation de silices mésoporeuses de type SBA. Deux stratégies ont été utilisées pour contrôler la localisation de la fonctionnalité. Différents complexes de Pd ont été intégrés dans les pores du matériau par greffage post-synthétique ou dans les murs par synthèse directe. Plusieurs amines et une phosphine ont été immobilisées par greffage post-synthétique donnant ainsi des catalyseurs nucléophiles fonctionnalisés dans leurs pores. Les activités catalytiques de ces matériaux ont été évaluées dans la synthèse de la 2-phényl-4-quinolone et du 2-benzylidène-indoxyle. La première a été préparée dans de bons rendements et le système {[Pd]@SBA+amine@SBA} est recyclable sur 3 cycles. Tous les matériaux ont montré une lixiviation du Pd mais leur utilisation permet de diminuer la contamination en Pd du produit final comparé à un complexe homogène. L'indoxyle a été obtenu avec un système semi-hétérogène {[Pd]@SBA/PPh3}, l'utilisation de la phosphine greffée conduisant à la transformation de l'indoxyle vers le 2-benzylindole. La formation d'α-céto-amides en catalyse hétérogène via double carbonylation a aussi été étudiée / The one-pot selective synthesis of 4-quinolones and indoxyls was achieved through a carbonylative Sonogashira coupling followed by cyclization. A study in homogeneous catalysis revealed that the nature of catalysts in presence controlled the selectivity toward each compounds. Whereas the first coupling step is palladium catalyzed, the cyclizations require organic nucleophilic species. Thus, 4-quinolones were obtained by one-pot multi-catalysis {[Pd]+amine} and indoxyls by one-pot tandem catalysis {[Pd]/phosphine}. The catalytic systems were heterogenized by functionalizing mesostructured SBA silicas. Two strategies were employed aiming at a control of the localization of the functionality. Different Pd complexes were integrated in the pores of the material by post-synthesis grafting or incorporated into the walls via direct synthesis. Different amines and a phosphine were immobilized by post-synthesis grafting affording hybrid materials containing amine or phosphine catalysts in their pores. Catalytic activities of those materials were evaluated in the reaction affording 2-phenyl-4-quinolone and 2-benzylidene-indoxyl. The former was obtained in good yields and the heterogeneous catalytic system {[Pd]@SBA+amine@SBA} was recyclable over 3 runs. All hybrid materials showed Pd leaching but their uses still enables to decrease the Pd contamination of the final product compared to homogeneous complexes. The indoxyle compound was obtained in a semi-heterogeneous system {[Pd]@SBA/PPh3}, the use of the grafted phosphine providing transformation of the indoxyle toward 2-benzylindole. Formation of α-keto-amids by heterogeneously catalyzed double carbonylation was also studied

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