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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.
41

Titanium complexes based on aminodiol ligand for ring opening polymerization of cyclic esters

Deivasagayam, Dakshinamoorthy 06 April 2011 (has links)
Une série de complexes à base de titane porteurs de ligands aminodiols de différentes configuration (mélange de diastéréoisomère, meso, racémique ou chiral) ont été synthétisés et caractérisés par différentes techniques spectroscopiques. Ces complexes ont ensuite été utilisés comme amorceurs pour la polymérisation par ouverture de cycles de différents monomères hétérocycliques (L/rac-lactide, caprolactone, butyrolactone et triméthylène carbonate) via un mécanisme de coordination-insertion. Tous les complexes se sont révélés efficaces pour la polymérisation des lactides que ce soit en solution à 70°C ou en masse à 130°C avec un bon contrôle. Lors de la polymérisation du rac-lactide, le complexe porteur du ligand racémique a permis d‟obtenir un polylactide partiellement heterotactique, alors que tous les autres complexes n‟ont conduit qu‟à des polymères atactiques. Tous les complexes se sont également révélés très actifs pour la polymérisation de la caprolactone aussi bien en solution qu‟en masse à 70°C avec un bon contrôle. Des études cinétiques réalisées en solution ont permis de mettre en évidence un ordre cinétique unitaire en monomère. De bonnes activités ont également été obtenues pour la polymérisation de la butyrolactone et du triméthylène carbonate. De plus, le bon contrôle de ce type de la polymérisation a permis de synthétiser des copolymères à blocs du L/rac-lactide et de caprolactone. Enfin, la copolymérisation aléatoire de ces 2 monomères a permis de mettre en évidence une réactivité inversée par rapport aux réactions d'homopolymérisation. / A series of titanium isopropoxides complexes coordinated by enantiopure, racemic, meso and diastereomeric aminodiol ligands have been prepared and characterized by spectroscopic techniques. The complexes were tested as initiators for the ring opening polymerization (ROP) of cyclic esters such as L/rac-lactide, caprolactone, butyrolactone and trimethylene carbonate via coordination-insertion mechanism. In lactide polymerizations, all complexes showed significant activity both in solution at 70°C and in bulk at 130°C with a good control. The complex derived from rac-aminodiol ligand gave partially heterotactic polylactide in ROP of rac-lactide, whereas all other complexes yielded atactic polylactides. For caprolactone polymerizations, all complexes were found to be effective initiators under both solution and bulk conditions (up to 60% monomer conversion was reached within 10 min in bulk condition at 70°C), again with good control. Kinetic studies of ROP of lactides and caprolactone in solution conditions have been investigated and showed a first kinetic order in monomer. Significant activities were also observed for (ROP) of butyrolactone and trimethylene carbonate. Block copolymers of caprolactone and lactides were successfully synthesized with these catalytic systems by sequential polymerization techniques. The complexes were also tested as initiators for the production of random copolymers containing caprolactone and lactides and a reverse order of reactivity was observed between lactide and caprolactone compared to homopolymerization.
42

Oxygen plasma treatment of polycarbonate for improved adhesion of plasma deposited siloxane thin films

Muir, Benjamin Ward January 2004 (has links)
Abstract not available
43

Removal of Bisphenol A Model Compounds and Related Substances Using Octolig®

Alessio, Rachael Josephine 01 January 2012 (has links)
Bisphenol A used in the production of polycarbonate plastics and epoxy resins is ubiquitous in the environment. The raw material is released to the environment during the manufacturing process and by leaching from consumer products. Recent studies are suggesting that low-dose amounts of Bisphenol A may have adverse health effects on humans. The possibility of removing Bisphenol A from natural water sources or from solvents used to extract the material from consumer products before they enter the market has been studied. The use of model compounds and related substances (4-isopropylphenol, 4-(t-butyl) phenol, and nitrophenols) have been used to study their removal from aqueous solutions using column chromatography and Octolig®, a commercially available material with polyethylenediamine moieties covalently bonded to high-surface area silica gel. The experimental results suggest that 2-nitrophenol and 4-nitrophenol can be successfully removed while 3-nitrophenol, 4-isopropylphenol, and 4-(t-butyl) phenol did not yield a high percent removal. A look at the pKa of the compounds provides an interesting explanation of the results. It is suggested that the compounds with a pKa of approximately 8.3 or higher would require the solution to be at a high pH for anion formation. The resulting pH of the solution would simultaneously deprotonate the ethylenediamine moieties of Octolig® rendering it incapable of removing the anions by ionic interaction.
44

Estudo da formacao de cor em polimeros irradiados com feixe de eletrons

NARDI, DANIELA T. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:48:53Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:37Z (GMT). No. of bitstreams: 1 09665.pdf: 5199882 bytes, checksum: 82561843731e1ff278143adb437e1eeb (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
45

Estudo fotoluminescente de filmes de policarbonato (PC) e poli(9-vinilcarbazol) (PVK) dopados com complexo de europio / Photoluminescent study of Polycarbonate (PC) and Poly (9-vinylcarbazole) (PVK)doped films with europium complex

FORSTER, PEDRO L. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:28:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:22Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
46

Emprego dos policarbonatos makrofol-de e CR-30 em radiografia com neutrons

PEREIRA, MARCO A.S. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:48Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:33Z (GMT). No. of bitstreams: 1 11313.pdf: 4364467 bytes, checksum: 80dca67e716c2de36cf87cbbab397c48 (MD5) / Dissertacao (Mestrado) / IPEN/D / Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP
47

Estudo da formacao de cor em polimeros irradiados com feixe de eletrons

NARDI, DANIELA T. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:48:53Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:37Z (GMT). No. of bitstreams: 1 09665.pdf: 5199882 bytes, checksum: 82561843731e1ff278143adb437e1eeb (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
48

Estudo fotoluminescente de filmes de policarbonato (PC) e poli(9-vinilcarbazol) (PVK) dopados com complexo de europio / Photoluminescent study of Polycarbonate (PC) and Poly (9-vinylcarbazole) (PVK)doped films with europium complex

FORSTER, PEDRO L. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:28:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:22Z (GMT). No. of bitstreams: 0 / Polímeros dopados com complexos de terras raras são materiais vantajosos na produção de filmes para várias aplicações no campo da luminescência. Neste estudo de polímeros luminescentes obtidos a partir de polímeros como o policarbonato (PC) e o poli(9-vinilcarbazol) (PVK), os filmes dopados com o complexo diaquatris (tenoiltrifluoroacetonato) de európio (III) [Eu(tta)3(H2O)2] foram preparados e suas propriedades térmicas e luminescentes no estado sólido relatadas. O comportamento térmico foi investigado por uso de calorimetria diferencial exploratória (DSC) e análise termogravimétrica (TGA). Devido à adição de complexo terras raras [Eu(tta)3(H2O)2] na matriz de PC e PVK, foram observadas alterações no comportamento térmico, relativo à transição vítrea e estabilidade térmica. As emissões finas características do íon Eu3+ decorrentes das transições 5DO → 7FJ (J = 0-4) indicaram a incorporação de íons de Eu3+ nos polímeros. Os filmes mostraram que a intensidade de emissão luminescente aumenta com o aumento da concentração de terras raras na matriz polimérica acompanhado por uma diminuição na estabilidade térmica. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
49

Emprego dos policarbonatos makrofol-de e CR-30 em radiografia com neutrons

PEREIRA, MARCO A.S. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:48Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:33Z (GMT). No. of bitstreams: 1 11313.pdf: 4364467 bytes, checksum: 80dca67e716c2de36cf87cbbab397c48 (MD5) / Dissertacao (Mestrado) / IPEN/D / Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP
50

Carbon dioxide and vegetable oil for the synthesis of bio-based polymer precursors / Valorisation du CO2 et d'huiles végétales pour la synthèse de monomères biosourcés

Alves, Margot 17 November 2016 (has links)
Bien que thermodynamiquement et cinétiquement stable, le dioxyde de carbone est une molécule qui peut être convertie en carbonates cycliques à cinq ou six atomes respectivement au départ d’époxydes ou d’oxétanes moyennant l’utilisation d’un catalyseur approprié. Ces carbonates cycliques sont utilisés comme solvants verts, électrolytes pour les batteries au lithium ou comme intermédiaires pour la synthèse de polymères. Cependant, les performances catalytiques doivent être améliorées en particulier pour lecouplage du CO2 avec les huiles végétales époxydées ou les oxétanes. Dans ce contexte, nous avons développé un nouveau catalyseur homogène bicomposant organique composé d’un sel d’ammonium jouant le rôle de catalyseur et d’un co-catalyseur fluoré simple ou double donneur de liaison hydrogène. Dans un premier temps, l’efficacité de ces nouveaux catalyseurs a été évaluée et optimisée pour le couplage entre un époxyde terminal et le CO2 via des études cinétiques par spectroscopie FTIR ou Raman in-situ sous pression. Ces études ont démontré que l’utilisation combinée de sels d’ammonium et d’alcools fluorés induit un effet synergique permettant la fixation rapide et sélective du CO2 sur les époxydes modèles et les huiles végétales époxydées dans des conditions douces et sans solvant. L’utilisation de cette plateforme catalytique performante a ensuite été exploitée pour la synthèse d’oligocarbonates hydroxyles téléchéliques au départ d’oxétanes nettement moins réactifs que les époxydes. Ces oligocarbonates ont finalement été valorisés pour la synthèse de polyuréthanes CO2-sourcés par extension de chaines en présence de diisocyanates. En complément de ces travaux, une compréhension fine des mécanismes réactionnels a été réalisée via calculs DFT qui ont mis en évidence que l’efficacité catalytique de ces catalyseurs était liée à la stabilisation multiple des intermédiaires et états de transition par liaisons hydrogènes. A ce jour, via une étude comparative, nous avons mis en évidence que ce système catalytique bicomposant constitue un des catalyseurs organiques les plus performants pour le couplage du CO2 et d’époxydes et le seul système organique permettant la conversion d’oxétanes en synthons d’intérêt. / Although it is a thermodynamically and kinetically stable molecule, carbon dioxide can beconverted into five- and six-membered cyclic carbonates by coupling with epoxides or oxetanes, respectively, using appropriate catalysts. Cyclic carbonates are used as green solvents, electrolytes for Liion batteries or intermediates for the synthesis of polymers. However, the catalytic performance must be further enhanced in particular for the coupling of CO2 with epoxidized vegetable oils or oxetanes. In this context, we developed a new highly efficient bicomponent homogeneous organocatalyst composed of anammonium salt as the catalyst and fluorinated single or double hydrogen bond donors as co-catalysts. First,a screening of onium-based catalysts and hydrogen-bond donors was performed. Performances of thecatalysts and optimization of the reaction was realized through detailed kinetics studies using in-situ FTIR/Raman spectroscopy under pressure. We demonstrated that fluorinated alcohols showed unexpected co-catalytic activity due to synergisms between the onium salt and fluorinated co-catalysts enabling the fast and selective addition of CO2 on to model epoxides and epoxidized vegetable oils under solvent-free and mild experimental conditions. The use of this powerful dual catalyst was then extended to the first organocatalytic coupling of CO2 with less reactive oxetanes to produce hydroxyl telechelic oligocarbonates that were used asprecursor of CO2-based polyurethanes by chain-extension with a diisocyanate. In addition, a fine comprehension of the mechanisms was investigated by DFT calculations highlighting that the co-catalytic performance of the onium salt/fluorinated alcohol binary catalyst arose from the strong stabilization of the intermediates and transitions states by hydrogen-bonding. To date, through comparative studies, we evidenced that this new catalyst is one

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