Poly(dimethylsiloxane) (PDMS) and similar polymers have proved to be of widespread interest for use in microfluidic and similar microanalytical devices. Surface modification of PDMS is required to extend the range of applications for devices made of this polymer, however. Here we report on the grafting of perfluorooctyltriethoxysilane via hydrolysis onto an oxidized PDMS substrate in order to form a fluorinated microchannel. Such a fluorinated device could be used for separating fluorous tagged proteins or peptides, similar to that which has been recently demonstrated in a capillary electrophoresis system, or in an open tubular capillary column. The modified polymer is characterized using chemical force titrations, contact angle measurements and X-ray photoelectron spectroscopy (XPS). We also report on a novel means of performing electroosmotic measurements on this material to determine the surface zeta potential. As might be expected, contact angle and chemical force titration measurements indicate the fluorinated surface to be highly hydrophobic. XPS indicates that fluorocarbon groups segregate to the surface of the polymer over a period of days following the initial surface modification, presumably driven by a lower surface free energy. One of the most interesting results is the zeta potential measurements, which show that significant surface charge can be maintained across a wide range of pH on this modified polymer, sufficient to promote electroosmotic flow in a microfluidic chip. Matrix-assisted time of flight mass spectrometry (MALDI-TOF MS) measurements show that a fluorous-tagged peptide will selectively adsorb on the fluorinated PDMS in aqueous solution, demonstrating that the fluorinated polymer could be used in devices designed forenrichment or enhanced detection of fluorous-labeled proteins and peptides. However, the non-specific adsorption of other proteins may interfere with the test results. The adsorption of four different proteins (cytochrome-C, carbonic anhydrase, insulin and ubiquitin) onto the unmodified, oxidized and fluorinated PDMS surfaces respectively was studied here with MALDI-TOF MS measurements. The results showed us that when rinsed in water/methanol solutions of high methanol concentration, cytochrome-C strongly adheres to the fluorinated surface. Carbonic anhydrase shows the opposite trend. Retention of ubiquitin on the surface shows relatively little sensitivity to either the nature of the substrate or the solution composition. Finally, the results using insulin demonstrated that this protein adheres relatively strongly to the oxidized PDMS surface as compared to the fluorinated or unmodified PDMS and showed a relative independence on the composition of the washing solution. The influence of the hydrophilicity of the protein, the surface and solvents, stability and size of proteins are discussed in the context of these observations. / Thesis (Master, Chemistry) -- Queen's University, 2008-05-12 16:49:23.672

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Halle, Wittenberg, University, Diss., 2004.

The objective of the experiments was to compare qualitatively the monosaccharides in the hydrolysis products of the extracellular polysaccharides of several yeasts and yeast-like fungi. Specifically, the study was aimed at finding similarities and differences that might be useful in suggesting and supporting taxonomic relationships. Gas chromatography and paper chromatography were used as methods of analyses in an effort to find out what method is sufficient at the qualitative level for distinguishing some genera of yeasts and yeast-like fungi; and what method would be best at the quantitative level for distinguishing amongst some species of the same genus. From the analytical results it was found that paper chromatography using the solvents ethyl acetate: pyridine: water, (8:2:2) was sufficient for qualitative determination of the monosaccharides in the extracellular polysaccharide hydrolysis products. However, indications were that quantitative analyses by gas chromatography, using the trimethylsilyl derivatives of the monosaccharides would have been successful in distinguishing among species of the same genus. Two groups were formed on the bases of the qualitative results. Group I contained two subgroups. Subgroup I encompassed those yeasts and yeast-like fungi with the monosaccharides galactose, glucose, mannose, xylose present in the hydrolysis products of their extracellular polysaccharides. Included in this Subgroup I are: Cryptococcus laurentii, Tremella mesenterica, Bullera alba, Sporobolomyces odorus, Sporobolomyces singularis, and Rhodotorula glutinis. Subgroup II is Ustilago hordei only, with the monosaccharides galactose, glucose, mannose, and lacking xylose. Group II contains Taphrina populina only, with glucose and mannose present and both galactose and xylose absent. The two groups formed support some of the taxonomic relationships that have already been suggested. The Tremella - Cryptococcus taxonomic relationship that had previously been postulated on the basis of similarities in extracellular polysaccharide hydrolysis products, morphology, carbon assimilation patterns, enzymatic xylosylation reaction, and starch formation was supported. Secondly, the Cryptococcus-Bullera relationship that had been suggested on the basis of inositol assimilation, lack of pseudomycelium, and similarities in starch synthesis, was supported by the qualitative analysis of the monosaccharides present in the extracellular polysaccharide hydrolysis products. The monosaccharides found in both Cryptococcus laurentii and Bullera alba extracellular polysaccharides were the same qualitatively. Duality amongst species of Sporobolomyces might be supported with further work using quantitative gas chromatographic analyses. This duality had been postulated on account of the duality shown in antigenic analyses and percent G+C base analyses of DNA. Taphrina populina can be distinguished from Rhodotorula glutinis and Cryptococcus laurentii. Cryptococcus laurentii produces starch and assimilates inositol: Rhodotorula glutinis assimilates inositol but does not produce starch; and Taphrina populina produces starch but does not assimilate inositol. Two monosaccharides present in the extracellular polysaccharide hydrolysis products of both Cryptococcus laurentii and Rhodotorula glutinis are galactose and xylose whereas Taphrina populina lacks these two monosaccharides. Results obtained from the qualitative analyses of the extracellular polysaccharides produced by fungi may be important taxonomically. This is because the qualitative information may be used when deciding on Perfect-Imperfect fungal relationships. However, this information should be considered along with data from other fields such as morphology, cytology, and genetics before hypothesizing on a taxonomic relationship. / Science, Faculty of / Botany, Department of / Graduate

La compréhension du comportement des actinides dans l’environnement est un enjeu important et très complexe en raison des nombreux phénomènes intervenant dans les processus chimiques. Parmi eux, nous pouvons citer la complexation, notamment via les fonctions carboxylates issues des substances humiques présentes dans les sols. En milieu aqueux, les actinides au degré d’oxydation IV sont très sensibles à l’hydrolyse impactant alors leur mobilité. Au cours de ce travail de thèse, nous avons étudié la réactivité de ces actinides(IV) (Th, U et Np) en présence de ligands organiques de type carboxylate aromatique, afin d’enrichir nos connaissances sur les entités formées. Plus de quarante nouveaux composés à base d’actinides(IV) et d’acides polycarboxyliques ont été synthétisés. Leurs structures cristallographiques ont été déterminées par DRX sur monocristal et leurs descriptions sont rapportées. Le contrôle de l’hydrolyse de ces métaux au sein de nos composés a été effectué par une variation de l’acidité en milieu aqueux ou par ajout contrôlé de quantités d’eau dans des solvants organiques. Certains des composés présentés sont construits autour d’assemblages polynucléaires possédant entre 2 et 38 centres métalliques. Pour ces derniers ({U38} et {Np38}), une nouvelle voie de synthèse a été investiguée. Au cours de l’étude de ces différents composés, nous avons mis en évidence les analogies ou les différences existant entre ces actinides, et avons enrichis notamment nos connaissances sur la cristallochimie du neptunium(IV). Enfin, nous avons montré la capacité de ligands N- et O- donneurs à complexer simultanément l’uranium(IV) avec d’autres métaux di- (Mn) ou trivalent (Ln). / Understanding the behavior of actinides in the environment is an important and very complex issue due to phenomena involved in chemical processes. Among them, one can mention the complexation, via carboxylate functions from the humic substances present in the soils. In an aqueous medium, actinides at the oxidation state IV are very sensitive to the hydrolysis process impacting their mobility. This thesis focuses the reactivity of these actinides (IV) (Th, U and Np) in the presence of organic ligands with aromatic carboxylate functions, in order to improve our knowledge about entities formed and linked to such organic linkers.More than forty new compounds based on actinides (IV) and polycarboxylic acids have been synthesized. Their crystallographic structures were determined by single crystal XRD and their descriptions are reported. The control of the hydrolysis of these metals within our compounds has been managed by varying the acidity in aqueous medium or by addition of controlled amount of water in organic solvents. Some of the compounds presented are built from polynuclear moieties having from 2 to 38 metal centers. For the latter ({U38} and {Np38}), a new synthetic pathway was investigated. During the study of these different compounds, we have demonstrated the analogies or the differences existing between these actinides, and have improved our knowledge on the crystallochemistry of neptunium (IV). Finally, we proved the ability of N- and O-donor ligands to simultaneously complex the uranium (IV) with other di- (Mn) or trivalent (Ln) metals.

No description available.

No description available.

Ce travail de thèse décrit la synthèse de copolymères diblocs amphiphiles par polymérisation radicalaire contrôlée par transfert d'iode en mode inverse (RITP). Dans un premier temps, des homopolymères à base de monomères activés (styrène, acrylate de méthyle, méthacrylate de méthyle), non activés (acétate de vinyle) et fonctionnels (chlorométhylstyrène, acrylate de tert-butyle), ont été synthétisés par RITP. Des aspects tels que le contrôle des masses molaires ainsi que la fonctionnalité en iode du bout de chaîne ont été examinés. Afin de démontrer la compatibilité de la RITP avec d'autres techniques de polymérisation contrôlée/vivante (non radicalaires), le copolymère amphiphile non-ionique poly(styrène)-b-poly(2-méthyl-2-oxazoline) (PS-b-P(MOx)) a été élaboré par la voie toute iode en procédé « one-pot » en combinant de manière consécutive la RITP du styrène avec la polymérisation cationique par ouverture de cycle (CROP) de la 2-méthyl-2-oxazoline. Par ailleurs, des copolymères cationiques poly(styrène)-b-poly(chlorométhylstyrène) quaternisé avec la triéthylamine (PS-b-PCMS+) et anioniques poly(styrène)-b-poly(acide acrylique) (PS-b-PAA-) ont été synthétisés par RITP du styrène suivie de l'ITP du bloc hydrophile. Tous ces copolymères amphiphiles ont été obtenus à partir de polystyrène iodé (PS-I) de faibles masses molaires, allant de 1000 à 3000 g.mol-1, jouant le rôle de macro-amorceurs (CROP) ou de macro-agents de transfert (ITP). L'étude de l'auto-organisation en phase aqueuse de ces copolymères amphiphiles a révélé la formation de micelles pour des concentrations supérieures à la concentration d'agrégation critique (CAC) dont la valeur a été déterminée par diffusion dynamique de la lumière (DDL) et spectroscopie de fluorescence. Enfin, des résultats très prometteurs ont été obtenus dans l'utilisation d'un copolymère cationique amphiphile PS-b-PCMS+ comme agents structurants de matériaux siliciques mésoporeux nanostructurés élaborés par procédé sol-gel en milieu basique. La synthèse de ces copolymères amphiphiles ainsi que leur caractérisation physico-chimique ont mis en exergue que la RITP permet de couvrir la synthèse de différentes catégories de copolymères amphiphiles, tout en étant une technique simple à mettre en œuvre, peu couteuse et robuste. / This manuscript describes the synthesis of amphiphilic diblock copolymers by reverse iodine transfer polymerization (RITP). Firstly, homopolymers derived from activated (styrene, methyl acrylate, methyl methacrylate), non-activated (vinyl acetate) and functional monomers (chloromethylstyrene, tert-butyl acrylate) synthesized by RITP, were studied. Aspects including molecular weight control as well as iodine chain-end functionality were investigated. In order to highlight the compatibility of RITP with other living/controlled (non-radical) polymerization techniques, a poly(styrene)-b-poly(2-methyl-2-oxazoline) (PS-b-P(MOx)) non-ionic copolymer was conceived through an ‘all-iodine', ‘one-pot' process by combining successively RITP of styrene with cationic ring-opening polymerization (CROP) of 2-methyl-2-oxazoline. Besides, poly(styrene)-b-poly(chloromethylstyrene) quaternized with triethylamine (PS-b-PCMS+) cationic copolymers and poly(styrene)-b-poly(acrylic acid) (PS-b-PAA-) anionic copolymers were elaborated by RITP of styrene, followed by ITP of the hydrophilic moiety. All these amphiphilic copolymers were obtained from iodine-bearing chain-end poly(styrene) (PS-I) of low molecular weights, in the range of values of 1000 to 3000 g.mol-1, playing the role of macro-initiators (CROP) or macro-transfer agents (ITP). Studies of the self-assembly of these amphiphilic copolymers in aqueous phases revealed the formation of micelles for concentrations superior to the critical aggregation concentration (CAC). The latter value was determined by dynamic light scattering (DLS) and fluorescence spectroscopy. Moreover, highly-promising results were obtained in the use of PS-b-PCMS+ cationic copolymers as structuring agents meant for the elaboration of nanostructured, mesoporous silica-based materials through the sol-gel process in basic medium. Both the synthesis of the amphiphilic copolymers and their physico-chemical characterizations have evidenced that RITP fosters the synthesis of different categories of amphiphilic copolymers, while being a simple, cheap and robust technique.

Résumé : Le poly(acide lactique) ou PLA est une famille de polyester thermoplastique linéaire qui a connu un essor commercial important durant la dernière décennie. L'enthousiasme pour le PLA vient de sa nature biosourcée, de ses bonnes propriétés mécaniques comme un module élastique élevé et de la possibilité de le biodégrader. Toutefois, certaines carences comme une faible résistance thermique et une faible élasticité à l’état fondu limitent son champ d’application. Fait à noter, le monomère d’acide lactique possède deux stéréo-isomères (L et D). Il est possible de polymériser les isomères L ou D pour former respectivement le PLLA ou le PDLA mais de façon surprenante, le mélange de PLLA et de PDLA permet la formation d’une structure cristalline distincte appelée le stéréocomplexe. Cette forme cristalline a un point de fusion 50[degré]C plus élevé par rapport aux formes cristallines du PLLA ou de PDLA d’où un premier intérêt pour augmenter la résistance thermique du matériau. Dans ce travail, l’usage de petites quantités (0-5 % massique) de PDLA comme additif dans une phase majeure de PLLA sera analysé. L’effet du stéréocomplexe formé à haute température sur la nucléation du PLLA et sur les propriétés rhéologiques du mélange sera plus particulièrement étudié. La présente thèse comprend une revue de littérature sur la cristallisation des PLA suivie de quatre parties expérimentales, conclusions et recommandations. La revue de littérature a pour objectif de réinterpréter l’ensemble des données disponibles sur la cristallisation du PLA afin d’en tirer des conclusions claires. La première partie expérimentale porte sur la cinétique de formation du stéréocomplexe à l'état fondu. Il a été constaté que la formation du stéréocomplexe est lente aux températures usuelles de mise en forme du PLLA ( 180[degré]C). De plus, la coexistence d’une morphologie baptisée dans ce travail « structure en réseau » et d’une morphologie sphérulitique a été révélée pour la première fois. Il a été démontré que la structure de réseau a une température de fusion moins élevée que la structure sphérulitique. Dans la seconde partie du travail, la cinétique de stéréocomplexation a été améliorée significativement pour adapter celle-ci aux cycles de refroidissement courts typiques des méthodes de mise en forme à l’état fondu. Ceci a été réalisé en ajoutant des agents nucléants qui initient la cristallisation à plus haute température et des agents plastifiants qui viennent augmenter la mobilité des polymères. Cette stratégie a permis de réduire le temps de cristallisation d’un ordre de grandeur. Dans un troisième temps, l'effet du stéréocomplexe sur les propriétés rhéologiques d’un mélange PDLA/PLLA a été investigué. En raison de son point de fusion élevé, le stéréocomplexe peut être préservé dans une matrice PLLA fondue et ainsi changer significativement les propriétés rhéologiques. La présence du stéréocomplexe a mené à une augmentation significative de la viscosité et de l'élasticité du PLA expliqué par la formation de points de « réticulation physique » dans la matrice amorphe. Enfin, dans la dernière partie expérimentale, le stéréocomplexe a été utilisé pour améliorer le comportement en moussage du PLA. Des expériences de visualisation et de moussage en mode discontinu ont montré que la présence de stéréocomplexe augmente la densité de nucléation de bulles et améliore significativement la morphologie de la mousse finale grâce à un effet de nucléation et à l’augmentation de l’élasticité du fluide. La revue de littérature et les trois premières parties expérimentales sont présentées sous forme d’articles scientifiques. La dernière partie expérimentale est à titre prospectif pour la suite du projet et ne sera pas soumise pour publication. // Abstract : Poly(lactic acid), or PLA, is a family of linear thermoplastic polyesters that has experienced strong market growth over the past decade. The enthusiasm for PLA originates from its bio-based nature, its good properties and its biodegradability. However, some of PLA deficiencies such as low thermal resistance and low melt elasticity have limited the development of this polymer. It is noteworthy that the lactic acid monomer has two stereo-isomers (L and D) that can be polymerized respectively into PLLA and PDLA but surprisingly, blending of PLLA and PDLA can lead to the formation of a “stereocomplex” which has a distinct crystalline structure from that of the homopolymers. This crystalline form has a melting point 50 oC greater than the crystalline PDLA or PLLA forms, thus it has by itself an interest in terms of heat resistance. In this work, the use of small amounts of PDLA (0-5%) in a matrix of PLLA will be explored. Particular emphasis will be on the nucleating ability of the stereocomplex (formed at high temperature) on PLLA crystallization and on its effect on the blends rheological properties. The current thesis comprises a literature review on PLA crystallization followed by four experimental sections. The objective of the literature review was to reinterpret the large body of data available on PLA in order to draw clear conclusions on PLA crystallization. The first experimental part of the work focused on the kinetics and conditions of stereocomplex formation in the melt state. It was found that stereocomplex formation is slow in the melt processing temperature range of PLLA (180 oC). Co-existence of a so-called “network structure” with a spherulitic structure was revealed for the first time. It was shown that the network structure has a lower melting point than the spherulitic one. In the second part of the work, stereocomplexation kinetics was improved significantly to match it with the fast cooling cycles typical of melt processing techniques. This was achieved by adding nucleating agents that initiated crystallization at higher temperatures and plasticizers that enabled more polymer fluidity. This strategy enabled an order of magnitude decrease in crystallization time. The third part of the work was the investigation of rheological properties upon formation of the stereocomplex structure in 0-5% PDLA in PLLA blends. Due to its higher melting point, the stereocomplex can be preserved in molten PLLA and alter significantly the blend melt rheology. Stereocomplex formation was monitored through rheological measurements and compared to classical calorimetry data. The presence of the stereocomplex lead to a significant increase in viscosity and in melt elasticity explained through the presence of physical crosslink points in the amorphous matrix. Finally, in the last experimental part of the work, the stereocomplex was employed to enhance PLA foaming behavior. Foaming visualization experiments as well as batch foaming tests showed that the presence of the stereocomplex can increase bubble nucleation density and led to a finer and more uniform foam morphology due to its nucleating effect and to the increased melt elasticity. The literature review and the three first experimental sections are presented in Peer-reviewed journal format. The last experimental section is meant as an exploratory and prospective part for the project and will not be submitted for publication.

No description available.