<p>The interaction of boronic acid with diols is reversible and pH-dependent. Boronate groups are able to form complex with 1,2- diol or 1,3-diols at pH values above 9. Therefore, the unique property of boronic esters was employed to exploit controllable self-assembly by three independent mechanisms, each of which is independent of the other two. The three interaction mechanisms are 1) electrostatic attraction between positive polymers and negative surfaces. 2) Polyethylene glycol (PEG)—phenolic polymer complex formation, which is one type of hydrogen bonding. 3) Phenylboronate (PBA) binding to polyols.</p> <p>To exploit these interactions, families of water-soluble and bifunctional copolymers containing pairs of non-interacting groups were prepared and characterized. Characterization includes structure, molecular weight, composition, etc. These bifunctional polymers can specifically interact with two other types of polymers/surfaces. Therefore, it provides a possibility to prepare complex assemblies by using multiple polymer/polymer interactions in one step.</p> <p>The utility of multiple, independent interactions was demonstrated by formation of self-assembled multilayer thin films on both silicon wafers and polystyrene latex particles. Moreover, the formation of well-defined nanoparticle aggregates with three different sizes of polystyrene latex particles was studied to extend the application of controllable self-assembly by multiple interactions. The assembly structures of multilayers and latex aggregates were controllable by adjusting the pH and addition of competitive small molecules.</p> <p>In addition to the study of multilayer self-assembly, a new approach for controllable deposition of latex nanoparticles on surfaces was also exploited. Regenerated cellulose films were chemically modified to fabricate the cellulose films bearing surface phenylboronic acid groups (cellulose-PBA). The poly(glycerol monomethacrylate)- stabilized polystyrene (PGMA-PS) latex particles were used to have reversible, pH-dependent adsorption onto the cellulose-PBA by the interaction of boronic acids and diols. Specific adsorption of PGMA-PS onto cellulose-PBA was observed at pH 10.5, whereas the latex particles were removed at pH 4.</p> / Doctor of Engineering (DEng)

The present work describes the design and synthesis of a series of dimers [(η5 - ring)MCl]2(μ2 -Cl)2, (where (η5 -ring)MCl = (η5 -Me4C5R)Rh(III)Cl or (η5 -Me4C5R)Ir(III)Cl). Iridium and rhodium dimeric complexes were synthesized via a microwave reaction and directly compared through single-crystal X-ray crystallography. Finally, the dimeric complexes were evaluated as potential oxidation catalysts. The modified HCp*R (R = isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, nheptyl, n-octyl, phenyl, benzyl, phenethyl, cyclohexyl, and cyclopentyl) type ligands were synthesized by reaction of 2,3,4,5-tetramethylcyclopent-2-en-1-one with the respective Grignard reagent (RMgX), followed by elimination of water under acidic conditions to produce the tetramethyl(alkyl or aryl)cyclopentadienes in moderate to excellent yields (39 - 98%). Reaction of the HCp*R ligands with [M(COD)](μ2 -Cl)2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) gave the dimeric complexes [Cp*RMCl]2(μ2 -Cl)2 in yields ranging from 16 - 96%. The dimers were characterized by nuclear magnetic resonance (NMR)spectroscopy, single-crystal X-ray diffraction (XRD) (supplemented by powder XRD), high-resolution mass spectrometry (HRMS), and elemental analysis. Complexes studied by XRD were analyzed to understand the bond lengths and bond angles throughout each complex. The dimeric complexes synthesized, will facilitate a complete study on how the R group influences catalytic activity. / Master of Science

Os não-carbeno complexos pentacoordenados do tipo [RuCl2(PPh3)2(amina)], sendo as aminas pirrolidina, azocano e dietilamina, foram sintetizados e caracterizados por análise elementar, espectroscopia de absorção na região do infravermelho, espectroscopia de absorção na região do ultravioleta e visível, espectroscopia de ressonância magnética nuclear de fósforo-31 e espectroscopia de ressonância paramagnética eletrônica. Estudos da teoria do funcional da densidade dos complexos foram realizados para buscar melhor interpretação dos resultados experimentais obtidos. O complexo [RuCl2(PPh3)2(pirrolidina)] exibiu uma geometria do tipo pirâmide de base quadrada em solução, com a amina na posição apical e as trifenilfosfinasestão trans-posicionada. Os complexos [RuCl2(PPh3)2(azocano)] e [RuCl2(PPh3)2(dietilamina)] exibiram geometria do tipo bipirâmide trigonal na qual as duas trifenilfosfinas estão trans-posicionadas no eixo axial. O complexo [RuCl2(PPh3)2(pirrolidina)] exibiu boa atividade catalítica nas polimerizações de norborneno e norbornadieno, tanto em atmosfera de argônio quanto em ar a 25 °C, como observado com os complexos similares [RuCl2(PPh3)2(peridroazepina)] e [RuCl2(PPh3)2(piperidina)]. Os complexos [RuCl2(PPh3)2(azocano)] e [RuCl2(PPh3)2(dietilamina)] obtiveram baixo rendimento de polimerização mesmo a 40 °C. Acredita-se que a geometria do tipo pirâmide de base quadrada seja a ativa para formação da espécie metal-carbeno com o etil diazoacetato no período de indução e favorável para iniciar a reação de polimerização via metátese por abertura de anel. A geometria do tipo bipirâmide trigonal pode dificultar o período de indução. Os estudos teóricos corroboraram com essa discussão. Os polinorbornenos, polinorbornadienos e seus copolímeros obtidos com os três complexos ativos foram caracterizados por espectroscopia de ressonância magnética nuclear de carbono-13, calorimetria exploratória diferencial, análise dinâmico-mecânica, termogravimetria e microscopia eletrônica de varredura. O complexo [RuCl2(PPh3)2(peridroazepina)] foi eficiente na metátese cruzada entre lignina metacrilada e o 10-undecen-1-ol para modificar a lignina Protobind 2400, e a lignina modificada foi solúvel em diversos solventes. O complexo [RuCl2(PPh3)2(peridroazepina)] também foi utilizado na autometátese da olefina terminal do 10-undecen-1-ol para obtenção de um diol que foi usado como segmento flexível e extensor de cadeia em reações de poliuretanas com óleo de mamona ou poli(&epsilon;-caprolactona) diol. Esse diol, quando utilizado em pequenas quantidades (10% em massa) nas poliuretanas derivadas do óleo de mamona, foi capaz de prover características adesivas a um material inicialmente rígido. Os resultados das reações de poliuretanas derivadas da poli(&epsilon;-caprolactona) diol não apresentaram resultados satisfatórios. / Non-carbene five-coordinate [RuCl2(PPh3)2(amina)] complexes, with pyrrolidine, azocane and diethylamine, were synthesized and characterized by elemental analysis, infrared absorption spectroscopy, ultraviolet-visible absorption spectroscopy, phosphorus-31 nuclear magnetic resonance and electron paramagnetic resonance. Density functional theory studies of the complexes were performed to complete and improve the experimental studies. [RuCl2(PPh3)2(pyrrolidine)] presented a square pyramidal geometry in solution, with the amine in the apical position and trans-positioned phosphines. [RuCl2(PPh3)2(azocane)] and [RuCl2(PPh3)2(diethyl amine)] exhibited a trigonal bipyramidal geometry in solution, with two phosphine molecules trans-positioned in the axial axis. [RuCl2(PPh3)2(pyrrolidine)] presented activity for ring opening metathesis polymerization of norbornene and norbornadiene under either air or inert atmosphere of argon at 25 °C, as observed with the parent complexes with perhydroazepine and piperidine. The latter three complexes presented square pyramidal geometries and high yields of polynorbornene and polynorbornadiene, different from the trigonal bipyramidal geometry of the complexes with azocane and diethylamine, which showed lower yields for polymerization even at 40 °C. This suggests that the cyclic amines in the apical position of the square pyramidal geometry provoke less steric hindrance, which provides prompt reactivity for ring opening metathesis polymerization. The bipyramidal geometry can hinder the induction period. Theoretical studies corroborate this discussion. The polynorbornenes, polynorbornadienes, and their copolymers obtained with the three active complexes were characterized by carbon-13 nuclear magnetic resonance, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetry analysis, and scanning electron microscopy. [RuCl2(PPh3)2(perhydroazepine)] was efficient to perform cross metathesis between the methacrylate lignin and 10-undecen-1-ol to modify the Protobind 2400 lignin, and the modified lignin was soluble in several solvents. Self-metathesis of the terminal olefin in 10-undecen-1-ol was conducted in the presence of [RuCl2(PPh3)2(perhydroazepine)] and ethyl diazoacetate to form a bioderived diol. The diol was utilized as soft segment and chain extender in polyurethane reactions with castor oil or poly(&epsilon;-caprolactone) diol. At only 10 wt% of the diol, an adhesive characteristic was observed in the castor oil-based polyurethane. The results from poly(&epsilon;-caprolactone) diol-based polyurethane were not satisfactory.

Os não-carbeno complexos pentacoordenados do tipo [RuCl2(PPh3)2(amina)], sendo as aminas pirrolidina, azocano e dietilamina, foram sintetizados e caracterizados por análise elementar, espectroscopia de absorção na região do infravermelho, espectroscopia de absorção na região do ultravioleta e visível, espectroscopia de ressonância magnética nuclear de fósforo-31 e espectroscopia de ressonância paramagnética eletrônica. Estudos da teoria do funcional da densidade dos complexos foram realizados para buscar melhor interpretação dos resultados experimentais obtidos. O complexo [RuCl2(PPh3)2(pirrolidina)] exibiu uma geometria do tipo pirâmide de base quadrada em solução, com a amina na posição apical e as trifenilfosfinasestão trans-posicionada. Os complexos [RuCl2(PPh3)2(azocano)] e [RuCl2(PPh3)2(dietilamina)] exibiram geometria do tipo bipirâmide trigonal na qual as duas trifenilfosfinas estão trans-posicionadas no eixo axial. O complexo [RuCl2(PPh3)2(pirrolidina)] exibiu boa atividade catalítica nas polimerizações de norborneno e norbornadieno, tanto em atmosfera de argônio quanto em ar a 25 °C, como observado com os complexos similares [RuCl2(PPh3)2(peridroazepina)] e [RuCl2(PPh3)2(piperidina)]. Os complexos [RuCl2(PPh3)2(azocano)] e [RuCl2(PPh3)2(dietilamina)] obtiveram baixo rendimento de polimerização mesmo a 40 °C. Acredita-se que a geometria do tipo pirâmide de base quadrada seja a ativa para formação da espécie metal-carbeno com o etil diazoacetato no período de indução e favorável para iniciar a reação de polimerização via metátese por abertura de anel. A geometria do tipo bipirâmide trigonal pode dificultar o período de indução. Os estudos teóricos corroboraram com essa discussão. Os polinorbornenos, polinorbornadienos e seus copolímeros obtidos com os três complexos ativos foram caracterizados por espectroscopia de ressonância magnética nuclear de carbono-13, calorimetria exploratória diferencial, análise dinâmico-mecânica, termogravimetria e microscopia eletrônica de varredura. O complexo [RuCl2(PPh3)2(peridroazepina)] foi eficiente na metátese cruzada entre lignina metacrilada e o 10-undecen-1-ol para modificar a lignina Protobind 2400, e a lignina modificada foi solúvel em diversos solventes. O complexo [RuCl2(PPh3)2(peridroazepina)] também foi utilizado na autometátese da olefina terminal do 10-undecen-1-ol para obtenção de um diol que foi usado como segmento flexível e extensor de cadeia em reações de poliuretanas com óleo de mamona ou poli(&epsilon;-caprolactona) diol. Esse diol, quando utilizado em pequenas quantidades (10% em massa) nas poliuretanas derivadas do óleo de mamona, foi capaz de prover características adesivas a um material inicialmente rígido. Os resultados das reações de poliuretanas derivadas da poli(&epsilon;-caprolactona) diol não apresentaram resultados satisfatórios. / Non-carbene five-coordinate [RuCl2(PPh3)2(amina)] complexes, with pyrrolidine, azocane and diethylamine, were synthesized and characterized by elemental analysis, infrared absorption spectroscopy, ultraviolet-visible absorption spectroscopy, phosphorus-31 nuclear magnetic resonance and electron paramagnetic resonance. Density functional theory studies of the complexes were performed to complete and improve the experimental studies. [RuCl2(PPh3)2(pyrrolidine)] presented a square pyramidal geometry in solution, with the amine in the apical position and trans-positioned phosphines. [RuCl2(PPh3)2(azocane)] and [RuCl2(PPh3)2(diethyl amine)] exhibited a trigonal bipyramidal geometry in solution, with two phosphine molecules trans-positioned in the axial axis. [RuCl2(PPh3)2(pyrrolidine)] presented activity for ring opening metathesis polymerization of norbornene and norbornadiene under either air or inert atmosphere of argon at 25 °C, as observed with the parent complexes with perhydroazepine and piperidine. The latter three complexes presented square pyramidal geometries and high yields of polynorbornene and polynorbornadiene, different from the trigonal bipyramidal geometry of the complexes with azocane and diethylamine, which showed lower yields for polymerization even at 40 °C. This suggests that the cyclic amines in the apical position of the square pyramidal geometry provoke less steric hindrance, which provides prompt reactivity for ring opening metathesis polymerization. The bipyramidal geometry can hinder the induction period. Theoretical studies corroborate this discussion. The polynorbornenes, polynorbornadienes, and their copolymers obtained with the three active complexes were characterized by carbon-13 nuclear magnetic resonance, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetry analysis, and scanning electron microscopy. [RuCl2(PPh3)2(perhydroazepine)] was efficient to perform cross metathesis between the methacrylate lignin and 10-undecen-1-ol to modify the Protobind 2400 lignin, and the modified lignin was soluble in several solvents. Self-metathesis of the terminal olefin in 10-undecen-1-ol was conducted in the presence of [RuCl2(PPh3)2(perhydroazepine)] and ethyl diazoacetate to form a bioderived diol. The diol was utilized as soft segment and chain extender in polyurethane reactions with castor oil or poly(&epsilon;-caprolactone) diol. At only 10 wt% of the diol, an adhesive characteristic was observed in the castor oil-based polyurethane. The results from poly(&epsilon;-caprolactone) diol-based polyurethane were not satisfactory.

Le mycothiazole-4,19-diol, découvert en 2006, est une molécule naturelle isolée de l'éponge marine cacospongia mycofijiensis, dont il n'existe à ce jour aucune synthèse. La structure originale, combinée à la faible abondance naturelle et à une activité biologique potentielle du mycothiazole-4,19-diol font de cette molécule une cible synthétique attractive pour le chimiste organicien et constitue l'objectif de ces travaux de thèse. Le principal enjeu de cette synthèse est la construction du motif diol-1,2 allylique. Au total, quatre déconnections ont été étudiées. Pour chacune d'entre elles, plusieurs approches ont été effectuées afin de construire de manière efficace et élégante le mycothiazole-4,19-diol. Une étude sur l'utilisation du palladium en synthèse organique a également été effectuée au cours cette thèse. Parmi les nombreux systèmes catalytiques dans lesquels ce métal intervient, nous nous sommes intéressés à l'oxydation aérobique des alcools en leurs dérivés carbonylés. Nous avons élaboré un nouveau système permettant l'oxydation sélective des alcools allyliques. Les résultats obtenus sur la haute chimiosélectivité intramoléculaire font de cette méthode un outil puissant et efficace et a été mis à profit dans le cadre des approches du mycothiazole-4,19-diol. Une étude supplémentaire réalisée sur l'utilisation du palladium en réactions séquentielles a également été menée avec l'élaboration d'un processus oxydation aérobique-formation de liaison C-C par couplage de Heck. L'originalité de la méthodologie développée est que le catalyseur intervient dans deux réactions totalement différentes permettant ainsi la synthèse rapide de molécules relativement complexes à partir de substrats simples.

[pt] A reconstrução da temperatura da superfície do mar (TSM) através de proxies geoquímicos orgânicos tem sido um tema central das pesquisas paleoclimáticas nos últimos anos. Determinações da variabilidade da paleotemperatura no Atlântico Sul são de grande interesse dado o papel da TSM no transporte de calor global, mas este tema ainda requer estudos mais aprofundados. O sistema de ressurgência de Cabo Frio (SRCF) representa uma área de estudo particularmente interessante por ser um sistema de ressurgência de contorno oeste sujeito a vários processos oceanográficos peculiares. Este projeto tem como objetivo a utilização de proxies geoquímicos orgânicos como indicadores de paleotemperatura, tais como: o índice de insaturação das alquenonas (U37K), o índice dos tetraéteres (TEX86H) e o índice dos diois de cadeira longa (LDI) registrados em sedimentos da margem continental sudeste brasileira. Também foram testados os índices de metilação e de ciclização dos tetraéteres ramificados (MBT e CBT) como indicadores da temperatura média anual do ar (TMAA) e do pH do solo. O presente trabalho possui dois focos: (i) investigar a aplicabilidade dos índices U37K, TEX86H e MBT/CBT considerando as condições ambientais locais e regionais observadas na região da Bacia de Campos utilizando 53 amostras de sedimento superficiais; (ii) aplicar uma abordagem multiproxy (U37K, TEX86H e LDI) para reconstruir a paleotemperatura durante o período do Holoceno a partir de dois testemunhos sedimentares localizados nas plataformas adjacentes a Cabo Frio e Rio de Janeiro. Os resultados revelam que U37K e TEX86H são proxies de temperatura adequados para estudos paleoclimáticos em escala regional na margem continental do sudeste brasileiro. Exceções na forma de desvios negativos entre a TSM média anual reconstruída e observada (World Ocean Atlas 2013) foram observados na porção sul da região estudada e ressaltam que, em escala local, os efeitos da ressurgência devem ser levados em consideração ao aplicar esses proxies na mesma região. Em relação aos índices MBT/CBT, os resultados se encaixam na faixa superior do pH do solo e na faixa inferior da TMAA encontrados na bacia de drenagem adjacente para a maioria das amostras. No entanto, a distribuição dos GDGTs ramificados apontam para a existência de diferentes fontes e efeitos pós deposicionais, e.g. degradação seletiva e produção in situ, que comprometem a aplicabilidade desses proxies nos sedimentos marinhos na Bacia de Campos. Ao aplicar os proxies U37K, TEX86H e LDI na reconstrução da temperatura para os últimos 14,5 kyr no testemunho do Rio de Janeiro e 7,1 kyr no testemunho de Cabo Frio, as variações observadas estão em acordo com diversos dados paleoclimáticos pré-existentes para a mesma região e período. Na plataforma do Rio de Janeiro, uma fase distinta antes de 7,5 cal kyr BP coincide com o período em que o nível do mar se encontrava baixo e passou a aumentar gradualmente. Na plataforma de Cabo Frio, a transição entre o Holoceno médio e o tardio é bem marcada pelo aumento na TSM-U37K e da TSMLDI provavelmente relacionados a uma atividade mais intensa da Corrente do Brasil (BC) sobre a plataforma, enquanto a temp-TEX86H apresentou uma tendência oposta de resfriamento que pode ser um resultado da ressurgência das Águas Centrais do Atlântico Sul em subsuperfície. Uma diminuição na temperatura reconstruída após cerca de 2,0 cal kyr BP pode ser explicada pelo estabelecimento do SRCF às condições modernas. Diferenças entre o Rio de Janeiro e Cabo Frio provavelmente estão relacionadas às instabilidades locais da CB próximo à região do SRCF. De forma geral, para o período investigado em ambos os testemunhos, a TSM-LDI mostrou-se mais quente, a TSM-TEX86H obteve uma clara tendência a temperaturas mais frias de subsuperfície e a TSM-U37K foi a mais afetada pela variação no nível do mar e pelo fluxo da CB. As diferenças entre os proxies forneceram informações valiosas sobre as mudanças paleoceanográficas locais durante o Holoceno, contribuindo para os estudos paleoclimáticos na margem sudeste do Brasil. / [en] The reconstruction of past sea surface temperature (SST) using organic geochemical proxies has been a central theme of paleoclimatic research in recent years. Paleotemperature variability determinations in the South Atlantic are of great interest given the SST role in the global heat transport, but still requires further studies. The Cabo Frio Upwelling System (CFUS) is a particularly interesting study area for being a western boundary upwelling system subject to several peculiar oceanographic processes. This thesis aims at using organic geochemical proxies as indicators of paleotemperature, namely: the alkenoneunsaturation index (U37K), the tetraether index (TEX86 H ) and the long-chain diols index (LDI) as registered in sediments in the south-eastern Brazilian continental margin. The methylation of branched tetraether index (MBT’) and the cyclization of branched tetraether index (CBT) were also tested as potential indicators of continental mean annual air temperature (MAAT) and soil pH. There are two focuses: (i) to investigate the applicability of U37K, TEX86H and MBT’/CBT proxies under local and regional environmental conditions in the Campos Basin region using 53 surface sediments; (ii) to use a multiproxy approach (U37K, TEX86H and LDI) to reconstruct the paleotemperature during the Holocene period from two sediment cores located in the shelves adjacent to Cabo Frio and Rio de Janeiro. The results reveal that U37K and TEX86H are suitable temperature proxies for paleoclimate studies in regional scale in the SE Brazilian continental margin. Exceptions in the form of strong negative biases between reconstructed and observed mean annual SST (World Ocean Atlas 2013) were observed in the southern portion of the Campos Basin and highlight that, on a local scale, the effects of upwelling must be taken in consideration when applying these proxies to the same region. Regarding the MBT/CBT proxies, the results for most of the marine sediments agree with the upper range of soil pH and lower range of MAAT found in the adjacent drainage basin. However, the spatial distribution of the branched GDGTs points to the existence of different sources and post-depositional effects, e.g. selective degradation and in situ production, that compromise the applicability of these proxies to the marine sediments in the Campos Basin, especially more offshore. When applying the U37K, TEX86H and LDI proxies to reconstruct the SST for the past 14.5 kyr in the Rio de Janeiro core and 7.1 kyr in the Cabo Frio core, the variations observed agreed with several pre-existing paleoclimatic data for the same region and period. In the Rio de Janeiro shelf, a distinct phase before 7.5 cal kyr BP coincides with the period when the sea level was low and gradually increased. In the Cabo Frio shelf, the transition between mid- and late Holocene is well marked by a warming in SST-U37K and SST-LDI, probably related to a more intense Brazil Current (BC) activity over the shelf, whereas temp-TEX86H showed an opposite cooling trend that may be a result of the subsurface upwelling of the cold South Atlantic Central Waters. A decrease in reconstructed temperatures after ca 2.5 kyr BP may be related to the establishment of the CFUS to modern conditions. Differences between Rio de Janeiro and Cabo Frio can be explained by the local instabilities of the BC near de CFUS region. Overall, for the entire covered period in both sediment cores, SST-LDI was warmer, SST-TEX86H was clearly biase towards colder subsurface temperatures and SST-U37K was the most affected by the sea level variation and BC flow. The differences between the proxies signal provided valuable information about the local paleoceanographic changes during the Holocene period, contributing to the paleoclimatology studies in the southeastern Brazilian margin. / [de] Die Rekonstruktion Oberflächenwassertemperaturen in der Vergangenheit mit organisch geochemischen Proxies ist in den vergangenen Jahren ein wichtiges Thema der Palaoklimaforschung gewesen. Die Rekonstruktion von Palaotemperaturvariabilitat im Südatlantik ist hierbei in Anbetracht der wichtigen Rolle der Ozeane im globalen Wärmetransport von zentraler Bedeutung, erfordert jedoch noch weiterführende Untersuchungen. Das Auftriebssystem von Cabo Frio ist in diesem Zusammenhang wegen seiner speziellen Lage auf der westlichen Seite eines Ozeanbeckens und der damit zusammenhangenden besonderen ozeanographischen Prozesse ein interessantes Arbeitsgebiet. Diese Arbeit hat zum Ziel, die organisch-geochemischen Proxies U37K (Alkenon-UntersattigungsIndex), TEX86H (Tetraether-Index an sogenannten GDGTs, Glycerol Dialkyl Glycerol Teteraether) und LDI (Langkettige-Diole-Index) aufgezeichnet in Sedimenten des sudostlichen brasilianischen Kontinentalrands zu verwenden. Zudem wurden die Indices MBT und CBT, die die Methylierung bzw. Zyklisierung verzweigter GDGTs quantifizieren, als Proxies fur die Jahresmitteltemperatur an Land und fur den pHWert der Boden getestet. Der Fokus der Arbeit liegt hierbei einerseits darauf i) die Anwendbarkeit der Proxies U37K, TEX86H , MBT/CBT im unter den lokalen und regionalen Umwelteinflussen des Campos Bessens auf Grundlage von 53 Oberflachensedimentproben zu uberprufen und ii) eine sogenannte multi-proxy Rekonstruktion der Palaoumweltbedingungen anhand der U37K, TEX86H und LDI Proxies an zwei Sedimentkernen vom Schelf vor Cabo Frio und Rio de Janeiro zu erstellen. Es zeigt sich, dass sich sowohl U37K als auch TEX86H fur regionale Palaoumweltstudien am sudostlichen brasilianischen Kontinentalrand eignen. Ausnahmen in Form von starken negativen Abweichungen zwischen rekonstruierter und instrumentell beobachteter (World Ocean Atlas 2013) Oberflachenwassertemperatur treten im sudlichen Teil des Campos Beckens auf und zeigen, dass sehr lokal die Auswirkungen von Auftrieb bei der einer regionalen Anwendung dieser Proxies berucksichtigt werden mussen. Die Ergebnisse der MBT/CBT Proxies an marinen Sedimenten stimmen mit den Gegebenheiten an Land weitgehend uberein, wobei die pH-Rekonstruktionen im oberen Bereich der Beobachtungen im angrenzenden Einzugsgebiet liegen, wahrend die Rekonstruktion der Jahresmitteltemperatur an Land zu den niedrigeren Werten der Beobachtungen neigen. Die raumliche Verteilung der verzweigten GDGTs in deutet zudem auf unterschiedliche Quellen sowie diagenetische Effekte wie selektiven Abbau und in-situ Produktion von verzweigten GDGTs hin, die die Anwendbarkeit der MBT/CBT Proxies an marinen Sedimenten des Campos Beckens, insbesondere in den kustenfernen Regionen, einschranken. Die Rekonstruktion der Palao-Oberflachenwassertemperaturen mithilfe von U37K, TEX86H und LDI fur die letzten 14.5 kyr vor Rio de Janeiro und fur die letzten 7.1 kyr vor Cabo Frio ergab eine Variabilitat, die mit Ergebnissen aus mehreren vorherigen palaoklimatischen Studien fur die Region ubereinstimmt. Auf dem Schelf vor Rio de Janeiro kann eine Phase vor 7.5 kyr deutlich vom Rest der Zeitreihe unterschieden werden, wahrend derer der Meeresspiegel niedriger war und allmahlich anstieg. Auf dem Schelf vor Cabo Frio ist der ubergang vom mittleren ins spate Holozan von deutlichen Anstiegen der U37K - und LDI-basierten Temperaturrekonstruktionen gepragt, die wahrscheinlich mit der Intensivierung des Brasilstroms auf dem Schelf in Verbindung stehen. Im Gegensatz dazu verzeichnet die TEX86H -basierte Temperaturrekonstruktion eine deutliche Abkuhlung, die das Ergebnis von verstarktem Auftrieb von kaltem sudatlantischem Zentralwasser sein kann. Eine Abnahme der rekonstruierten Temperaturen nach 2.5 kyr vor heute deutet auf die Etablierung moderner Bedingungen im Cabo Frio Auftriebssystem hin. Unterschiede zwischen den Temperaturrekonstruktionen fur die Regionen Cabo Frio und Rio de Janeiro konnen mit lokaler Instabilitat des Brasil-Stroms im Bereich des Cabo Frio Auftriebssystems zusammenhangen. Insgesamt sind über die gesamte Untersuchungsperiode die Temperaturrekonstruktionen auf Grundlage von LDI am warmsten, die auf TEX86H basierenden von kalteren Temperaturen in etwas groberen Wassertiefen beeinflusst und diejenigen auf Grundlage von U37K am starksten von Meeresspiegelanderungen und Variabilitat im Brasil-Strom betroffen. Diese Unterschiede zwischen den einzelnen Proxies liefern wertvolle Informationen uber die lokalen palaozeanographischen Veranderungen wahrend des Holozans und somit einen Beitrag zum Verstandnis des Palaoklimas am sudostlichen brasilianischen Kontinentalrand.

The use of enzymes as catalysts for chemical transformations has emerged as a “greener” alternative to traditional organic synthesis. An issue to solve though, is that enzymes are designed by nature to catalyze reactions in a living cell and therefore, in many cases, do not meet the requirements of a suitable biocatalyst. By mimicking Darwinian evolution these problems can be addressed in vitro by different types of directed evolution strategies. α-Hydroxy aldehydes and α-hydroxy ketones are important building blocks in the synthesis of natural products, fine chemicals and pharmaceuticals. In this thesis, two alcohol dehydrogenases, FucO and ADH-A, have been studied. Their potentials to serve as useful biocatalysts for the production of these classes of molecules have been investigated, and shown to be good. FucO for its strict regiospecificity towards primary alcohols and that it strongly prefers the S-enantiomer of diol substrates. ADH-A for its regiospecificity towards secondary alcohols, its enantioselectivity and that is has the ability to use a wide variety of bulky substrates. The kinetic mechanisms of these enzymes were investigated using pre-steady state kinetics, product inhibition, kinetic isotope effects and solvent viscosity effects, and in both cases, the rate limiting steps were pin-pointed to conformational changes occurring at the enzyme-nucleotide complex state. These characterizations provide an important foundation for further studies on these two enzymes.   FucO is specialized for activity with small aliphatic substrates but is virtually inactive with aryl-substituted compounds. By the use of iterative saturation mutagenesis, FucO was re-engineered and several enzyme variants active with S-3-phenylpropane-1,2-diol and phenylacetaldehyde were obtained. It was shown that these variants capability to act on larger substrates are mainly due to an enlargement of the active site cavity. Furthermore, several amino acids which are important for catalysis and specificity were identified. Phe254 interacts with aryl-substituted substrates through π-π stacking and may be essential for activity with these larger substrates. One mutation caused a loss in the interactions made between the enzyme and the nucleotide and thereby enhanced the turnover number for the preferred substrate

Ce travail de thèse a porté sur la synthèse et la caractérisation de dispersions aqueuses de polyuréthane. Les matières premières envisagées pour la synthèse ont tout d'abord été caractérisées et un procédé de fabrication adapté a été mis en place. Des dispersions de polyuréthane commerciales et leurs polymères ont aussi été caractérisés, afin d'établir une référence en terme de propriétés physico-chimiques (taille de particules, viscosité, température de transition vitreuse, énergie de surface). Les dispersions aqueuses de polyuréthane ont ensuite été synthétisées. Différents paramètres ont été analysés, tels que la nature du diisocyanate, le rapport NCO/OH, la nature du (ou des) diol(s) et leurs poids moléculaire, la proportion d'agent émulsifiant et son degré de neutralisation. Toutes ces dispersions ainsi que leurs polymères ont enfin été caractérisés afin de mettre en évidence des relations structures-propriétés.

The desirable properties of polyurethanes (PUs) such as mechanical flexibility associated with chemical versatility make these polymers attractive in the development of biomedical devices. In this study, various segmented polyurethanes were synthesized through polymerization reactions between polycaprolactone (PCL) diol or triol and excess hexamethylene diisocyanate (HDI) with varying NCO/OH ratios and the effect of composition on the properties of the resultant polyurethane films were examined. Initially, isocyanate terminated prepolymers were synthesized through one-shot polymerization, and then these prepolymers were cured by introducing crosslinkages into the structure and thus PUs were obtained. In order to enhance biocompatibility and hydrophilicity of the resulting polymers, heparin was added into the prepolymer before the curing process. The influence of excess HDI as a crosslinker on the degree of H-bond formation between hard-hard segments or hard-soft segments was examined by using Fourier transform infrared-Attenuated total reflectance spectroscopy (FTIR-ATR). Also the effects of HDI content on the chemical, physical and mechanical properties of the polyurethanes were examined with differential scanning calorimetry (DSC), X-Ray diffraction spectroscopy (XRD), dynamic mechanical analyzer (DMA), mechanical tester and goniometer. FTIR- ATR, DSC and DMA analyses showed that use of triol resulted in better network formation and homogenous distribution of hard segments within soft segment matrix. Incorporation of heparin into the polymer matrix produced more hydrophilic films (water contact angle reduced from 80 to 60). Polyurethanes from PCL and HDI in the absence of any solvent, initiator, catalyst or chain extender were successfully synthesized and this kind of synthesis enhanced biocompatibility and increased the potential of polymers for use in biomedical applications.

No description available.