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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

Functional and complex topological applications of plasma polymerized ultrathin films

Anderson, Kyle D. 07 May 2012 (has links)
This study is focused on the fabrication of plasma polymerized ultrathin films and the elucidation of their unique properties with an emphasis on the solvent-less, dry polymerization process to introduce post-deposition functionality, robustness, and shape preservation. Two major classes of materials are the subject of this study: biological monomers, specifically the amino acids tyrosine and histidine and synthetic organic and inorganic monomers including acrylonitrile, 2-hydroxyethyl methacrylate, N-isopropylacrylamide, titanium isopropoxide and ferrocene. The unique chemical and physical properties of highly cross-linked ultrathin plasma polymerized amino acid and synthetic polymer films are demonstrated along with their functional response and robustness on both planar and complex surface structures. The work emphasizes the facile ability of plasma polymerization to create unique, tailored ultrathin coatings. Chemical functionality retention (OH, NH₂) of the tyrosine and histidine amino acids is demonstrated by the subsequent mineralization of gold or titania nanoparticles on the plasma polymerized ultrathin films using a wet chemical approach. Inorganic nanoparticle mineralization is further investigated as a method to modify the optical properties of composite nanocoatings. Plasma co-polymerization of tyrosine and synthetic monomers is used to create nanocomposite coatings with unique surface functionalities, responsive behavior, optical characteristics and a high level of integration between monomers. The fabrication of novel plasma polymerized Janus microspheres, micropatterned substrates and free-standing films also demonstrate numerous plasma polymerized materials which exhibit unique structural properties. Overall, facile plasma polymerization of novel, functional ultrathin films and complex topological coatings having potential biocompatible and optical applications is established.
2

Copolymérisation plasma : étude des mécanismes de croissance et de la structuration des couches minces copolymères / Plasma copolymerization : study of the growth mechanisms and structuration of thin copolymer layers

Chahine, Claudine 24 January 2013 (has links)
Le travail présenté dans ce mémoire consiste à élaborer en une seule étape une couche mince organique ayant les propriétés chimiques et/ou morphologiques souhaitées. Cette démarche vise à copolymériser par voie plasma (PECVD) deux monomères antagonistes (apolaire et polaire) afin de contrôler la répartition et la taille des nodules de l’un des polymères dispersé dans l’autre phase et d’obtenir ainsi une structuration chimique et/ou morphologique. Pour ce faire, six précurseurs ont été sélectionnés de façon à couvrir une large gamme de polarité: l’alcool allylique (AA), l’acide acrylique (AAc), l’aniline (ANi), le diéthylèneglycol diméthyl éther (DEGDME), le 1H,1H,2H-perfluoro-1-décène (HDFD) et le 2-(diméthylamino) éthyle méthacrylate (DMAEMA).La première partie de ce travail est centrée sur l’étude des mécanismes de croissance des différents homopolymères par voie plasma pulsé. Les cinétiques de dépôt, les structures chimiques et les morphologies sont plus spécifiquement détaillées pour deux monomères, les HDFD et DMAEMA en fonction des paramètres du procédé plasma, la polymérisation plasma de ces deux précurseurs étant pour la première fois décrite. La caractérisation des couches minces obtenues repose sur la spectroscopie Infrarouge à Transformée de Fourier (FTIR), la spectroscopie de photoélectrons X (XPS) et la microscopie à force atomique (AFM). Cette étude a montré le rôle catalytique des groupements fluorés induisant des vitesses de dépôt plus conséquentes. Même si la croissance est prépondérante durant le temps de décharge, le dépôt est non négligeable pendant la post-décharge. La structure chimique des polymères plasma est fortement dépendante des paramètres de la décharge et notamment la puissance et le temps de décharge. La spectroscopie FTIR s’est révélée comme un outil performant pour l’évaluation de la rétention de la structure chimique de l’entité monomère initiale dans le polymère plasma. Ces homopolymères présentent une morphologie homogène sans rugosité.Dans la deuxième partie, nous abordons la copolymérisation plasma pulsé. Les différents copolymères synthétisés sont p-AA-co-HDFD, p-AAc-co-HDFD, p-ANi-co-HDFD, p-DEGDME-co-HDFD, p-DMAEMA-co-HDFD, p-DMAEMA-co-ANi. La plupart sont issus de comonomères hydrophiles et hydrophobes à l’exception d’un synthétisé à partir de deux précurseurs polaires. Les cinétiques de dépôt, les propriétés chimiques et morphologiques sont discutées en fonction des paramètres plasma tels que la puissance injectée mais aussi des proportions relatives des différents comonomères. Les différentes analyses chimiques entreprises montrent plutôt la formation d’un mélange d’homopolymères ou d’un copolymère à bloc plutôt que la croissance d’un nouveau matériau. Cette hypothèse est étayée par la mise en évidence d’une structuration morphologique correspondant à la présence d’îlots à la surface. / The work presented in this thesis consists to elaborate only in one step a thin organic layer having the required chemical and/or morphological properties. This approach aims to plasma copolymerize (PECVD) two antagonistic monomers (nonpolar and polar) in order of controlling the repartition and the size of nodules of one of the polymers dispersed in the other phase and thus, of inducting a chemical and/or morphological structuring. For this, six precursors have been selected to cover a large range of polarity: allyl alcohol (AA), acrylic acid (AAc), aniline (ANi), the diethylene glycol dimethyl ether (DEGDME), the 1H,1H,2H-perfluor-1-decene (HDFD) and 2-(dimethylamino)ethyl methacrylate (DMAEMA).The first part of this work is centered on studying the growth mechanism of different homo-polymers through pulsed plasma. The kinetics of deposition, the chemical structures and morphologies are more specifically detailed for two monomers, HDFD and DMAEMA in function of plasma parameters, the plasma polymerization of these two precursors being described for the first time. The thin layers were characterized through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). This study showed the catalytic role of fluorine groups inducing more consequent deposit rates. Even if the growth is significant during the plasma on-time, the deposit is not negligible during the plasma off-time. The chemical structure of plasma polymers is highly dependent on the discharge parameters and mainly the power and the pulse period. The FTIR spectroscopy was shown to be a relevant tool for evaluating the chemical structure’s retention of the initial monomer entity in the plasma polymer. These homopolymers present a homogenous morphology without roughness.In the second part, the pulsed plasma copolymerization is described. The different synthesized copolymers are p-AA-co-HDFD, p-AAc-co-HDFD, p-ANi-co-HDFD, p-DEGDME-co-HDFD, p-DMAEMA-co-HDFD, p-DMAEMA-co-ANi. The majorities are issued from hydrophilic and hydrophobic co-monomers excepted for one synthesized from two polar precursors. The kinetics of deposits, the chemical and morphological properties were discussed in function to plasma parameters such as the injected power as well as the relative proportions of different co-monomers. The different chemical analyses showed the formation of a mixture of homopolymers or of a block copolymer rather than the growth of a new material. This hypothesis is unsubstantiated by evidencing a morphological structuring corresponding to the presence of spherical nanostructure at the surface.
3

Charakterisierung und Modifizierung poröser Cellulosepartikel für die flüssige Hochleistungs-Chromatographie und ihr Einsatz zur Untersuchung von Protein-Wechselwirkungen

Wieland, Christoph 01 March 2010 (has links)
Perlcellulose stellt ein interessantes Material für den Einsatz in der wässrigen Größenausschlusschromatgraphie (SEC) dar. Sie ist aufgrund ihrer guten Modifizierbarkeit zudem ein perfektes Ausgangsmaterial für Protein-Aggregationsuntersuchungen. Ein Protein von besonderem praktischem Interesse ist Insulin. Dessen Fehlfaltung und Aggregation verursacht eine Reihe von schwerwiegenden Problemen (z.B. in Drug-Delivery-Systemen). Hierbei erfolgt eine Umwandlung von alpha-Helix- in beta-Faltblatt-Strukturen wobei sich unlösliche Fibrillen bilden. Deren Rückfaltung mit Hilfe fluorierter Alkohole sowie mit fluorierten Nanopartikeln wurde in der Literatur beschrieben. Der Ansatzpunkt dieser Arbeit war es zu untersuchen, ob Fluor auf Oberflächen mit hohem Anteil von Hydroxygruppen eine Rückfaltung von Proteinen wie Insulin bewirken kann. Das Ziel war es, schaltbare stationäre Phasen zu erhalten, mit denen sowohl eine Rückfaltung als auch die Trennung von Proteinen durchgeführt werden können. Zunächst erfolgte die Charakterisierung geeigneter Perlcellulosen, wobei erstmals eine Kombination der „klassischen“ Porosimetrie (Hg-Intrusion, N2-Sorption) mit SAXS und Inverser SEC zur Untersuchung der Porenstruktur von Cellulose angewandt wurde. Es konnte die reversible Schrumpfung der Poren während der Trockungsprozesse beschrieben werden. Die Immobilisierung von Fluor auf der Oberfläche von Cellulosepartikeln erfolgte u.a. durch Pfropfung von fluorierten Acrylaten mittels Cer(IV)-Redoxinitiierung. Es gelang eine homopolymerfreie Pfropfung, wobei es zu keiner Veränderung der Porenstruktur kam. Die Kontrolle der Proteinadsorption auf der modifizierten Oberfläche mittels chemischer Stimuli konnte beschrieben werden. Aggregationsuntersuchungen mittels SEC, DLS und SAXS ergaben, dass fluormodifizierte Perlcellulose keine Verzögerung der Insulinaggregation bewirkt. Jedoch zeigte sich, dass unmodifizierte Perlcellulose eine signifikante Verzögerung der Aggregation bewirken kann. / Porous bead cellulose is an interesting material for the application in aqueous size exclusion chromatography (SEC). Its good modifiability makes it furthermore to a perfect starting material for protein aggregation studies. A protein with huge practical importance is insulin. Misfolding and aggregation of insulin creates serious problems e.g. in drug delivery systems. Thereby it undergoes a change from alpha-helix to beta-sheet structure and forms insoluble fibrils. A back-folding with (toxic) fluorinated alcohols and fluorinated nanoparticles was already shown in literature. The approach for this work was that fluorine (CF3-) on a surface with high hydroxyl-content can induce the back folding of proteins like insulin. The purpose was to get stationary phases that can induce back folding and separation of proteins on a single column. At first a characterization of suitable cellulose beads with focus on different porosimetry methods was done. For the first time a combination of “classical” porosimetry methods (Hg-Intrusion; N2-Sorption) with SAXS and inverse SEC was applied for porous cellulose particles. A reversible shrinking of pores during drying process was shown. Immobilization of fluorine on the surface of cellulose beads was done by grafting of fluorinated acrylates via cer(IV)-redox-initiation and by polymer analogous reaction with fluorinated iodo alkanes. Homopolymer free graft-copolymerization was achieved, whereas no effect on pore structure was observed. The control of protein adsorption on surface by chemical stimuli was shown. Aggregation studies using SEC, DLS and SAXS showed that fluoro-modified cellulose beads do not delay insulin-aggregation due to strong adsorption effects. Though a significant aggregation delay for insulin with unmodified cellulose beads was discovered.
4

Přímá syntéza vysokomolekulárních polymerů kyseliny mléčné / Direct Synthesis of High-Molecular Polymers of Lactic Acid

Mikulík, David January 2016 (has links)
This master thesis deals with the direct synthesis of polymers from lactic acid. The theoretical part focuses on both natural and synthetic ways of production the lactic acid monomer, their advantages and properties. Furthermore, the theoretical part focuses on the synthesis of poly(lactic acid) (PLA) from lactide, and direct polycondensation from lactic acid discussing about influences of catalysts, co-catalysts as well as chain extenders. The experimental part focuses on the synthesis of PLA polymers and co-polymers wherein investigates suitable catalysts, reaction medium for azeotropic dehydration and co-catalyst influence on products. Thermal and analytical analysis of PLA polymers are mentioned at the end of the experimental part.

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