Global ETD Search

1	CONTROLLED MODIFICATION OF SILOXANE OR HYDROCARBON INTERFACES USING ORGANOSILANES Zhang, Jianfeng January 2015 (has links) Surfaces/interfaces are considered as one of the key factors that determine performance, and ultimately the application, of materials. In many cases, surface/interface modifications are required for desired properties, such as adhesion and wettability. Organosilanes have been widely used to alter surface/interfacial properties for many materials including metals, glass, and polymers, etc. However, controllable processes for surface/interfacial modification are desired. This thesis aims to explore controllable paths for surface/interfacial modifications on siloxane or hydrocarbon-based materials using organosilanes. Further understanding about the methodologies for quantification of functional groups located at surfaces/interfaces is also within the scope of this thesis. In this thesis, a comprehensive study of PDMS surface modification using thioalkylsilane coupling agents is described. An equilibrium silanization allowed the introduction of thiols on silicone elastomer surfaces under control and without damaging the surface. Two different titration methods for testing thiols in solution were developed and improved for quantification of thiol groups located at air-solid interfaces. The thiol-functionalized silicone could be further modified with maleic anhydride and/or with a variety of polymers and surfactants in a single step or two steps. A long term, stable hydrophilic surface was obtained after these modifications. In this thesis, the modification of hydrocarbon-based materials is also described. A method based on the Piers-Rubinsztajn reaction was used to convert lignin into value-added chemicals, including monomeric/oligomeric aromatics and lignin composites. For the hard wood lignin, reduction of the ether bonds and silylation with hydrosilanes led to nearly complete fragmentation. The monomeric/oligomeric aromatics decomposed from hard wood lignin are easy to process as demonstrated by their excellent solubility in various solvents. Alternatively, softwood, which does not have an ideal structure for fragmentation, is effectively employed as “green filler” in silicones for lignin-based elastomer/foams. The partial (interfacial) reduction of hydrosilanes at lignin interfaces results in covalent linkage sbetween lignin and siloxane network, improving the interfacial miscibility. The softwood lignin, thus plays dual roles as a crosslinking and reinforcing agent. Formulations were readily developed to prepare silicone foams/elastomers by controlling processing parameters and methods. Lignin-based silicone elastomers could be obtained with additional solvent and casting in an open mold; lignin-based silicone foams could be molded in a volume-confined mold after extrusion. / Thesis / Doctor of Philosophy (PhD) interfacial modification organosilane
2	Creation of crosslinkable interphases in polymer blends by means of novel coupling agents / Erzeugung von vernetzbaren Grenzschichten in Polymerblends durch Einsatz neuartiger Kopplungsagenzien Sadhu, Veera Bhadraiah 14 August 2004 (has links) (PDF) The goal of the work is to study possibilities for the modification of interface in immiscible polymer blends, which determine to a large degree of the blend properties. For this purpose novel coupling agents (named SCA) containing 2-oxazoline, 2-oxazinone, and hydrosilane reactive sites have been prepared. In blends of amino- functional and carboxylic acid terminated polymers the oxazoline and oxazinone units of the SCA react selectively with one of the polymers and, therefore, the SCA should locate at the interface. The remaining hydrosilane sites can now be used for further modification, e.g. for crosslinking. In the thesis we discussed the effect of the SCA on the morphology and thermal and rheological properties of blends based on carboxylic acid terminated polystyrene (PS) and amino-terminated polyamide 12 (PA) or poly(methyl methacrylate) (PMMA). The morphology of the blends and the location of the SCA strongly depends on the processing conditions. The crosslinkability of the interface could be proven by changes in the solubility behavior of the blends. Kopplungsagenzien Modification von Grenzschichten Polymerblends coupling agents interfacial modification polymer blends ddc:540 rvk:VE 8007 Dünne Schicht Polymer-Blend Vernetzung
3	Creation of crosslinkable interphases in polymer blends by means of novel coupling agents Sadhu, Veera Bhadraiah 24 June 2004 (has links) The goal of the work is to study possibilities for the modification of interface in immiscible polymer blends, which determine to a large degree of the blend properties. For this purpose novel coupling agents (named SCA) containing 2-oxazoline, 2-oxazinone, and hydrosilane reactive sites have been prepared. In blends of amino- functional and carboxylic acid terminated polymers the oxazoline and oxazinone units of the SCA react selectively with one of the polymers and, therefore, the SCA should locate at the interface. The remaining hydrosilane sites can now be used for further modification, e.g. for crosslinking. In the thesis we discussed the effect of the SCA on the morphology and thermal and rheological properties of blends based on carboxylic acid terminated polystyrene (PS) and amino-terminated polyamide 12 (PA) or poly(methyl methacrylate) (PMMA). The morphology of the blends and the location of the SCA strongly depends on the processing conditions. The crosslinkability of the interface could be proven by changes in the solubility behavior of the blends. info:eu-repo/classification/ddc/540 ddc:540
4	Modification électrochimique de l'interface liquide - liquide avec de la silice mésoporeuse / Electrochemical modification of the liquid - liquid interface with mesoporous silica Poltorak, Lukasz 25 September 2015 (has links) Ce travail combine l'électrochimie à l'interface liquide - liquide avec le procédé sol - gel pour la modification interfaciale avec de la silice mésoporeuse. Dans la première partie de ce travail, l’interface liquide – liquide macroscopique a été utilisée pour séparer la solution aqueuse de l'espèce de précurseur de silice hydrolysées (tétraéthoxysilane (TEOS)) de l'agent tensioactif cationique (cethyltrimethylammonium (CTA+) qui a agi comme un template et a été dissous dans le dichloroéthane. Le dépôt de matériau de silice a été déclenchée par le transfert du CTA+ à partir de la phase organique vers la phase aqueuse. CTA+ qui a transféré à la phase aqueuse a catalysé la réaction de condensation de la silice sur l’interface liquide – liquide. Le dépôt de silice à des interfaces liquide – liquide miniaturisées était la deuxième partie de ce travail. Les dépôts stables sur le côté de l'interface ont été synthétisés in situ par voie électrochimique. La stabilité mécanique des dépôts de silice permis un traitement thermique de la silice. Basé sur les techniques d’imagerie (par exemple SEM) il a été constaté que les dépôts forment des hémisphères pour des temps plus long. La réaction interfaciale a également été suivie in situ par spectroscopie Raman confocale. Caractéristiques moléculaires de l'interface ont été modifiées de manière spectaculaire une fois les espèces CTA+ ont été transférés à la phase aqueuse. Les interfaces liquide – liquide miniaturisés et modifiés ont également été évaluée avec le transfert voltampérométrique / This work combines the electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) with the Sol – Gel process of silica leading to an interfacial modification with mesoporous silica using soft template. In the first part of this work the macroscopic liquid – liquid interface was employed to separate the aqueous solution of the hydrolyzed silica precursor species (tetraethoxysilane (TEOS)) from the cationic surfactant (cethyltrimethylammonium (CTA+)) dissolved in the dichloroethane. The silica material deposition was controlled by the electrochemical CTA+ transfer from the organic to the aqueous phase. Template transferred to the aqueous phase catalyzed the condensation reaction and self-assembly resulting in silica deposition at the interface. Silica deposition at the miniaturized ITIES (membranes supporting array of micrometer in diameter pores were used in this regard) was the second part of this work. Silica interfacial synthesis performed in situ resulted in stable deposits growing on the aqueous side of the interface. Mechanical stability of the supported silica deposits allowed further processing – silica material was cured. Based on imaginary techniques (e.g. SEM) it was found that deposits forms hemispheres for longer experimental time scales. Interfacial reaction was also followed with in situ confocal Raman spectroscopy. Molecular characteristics of the interface were changed dramatically once CTA+ species were transferred to the aqueous phase. Array of microITIES modified with silica was also assessed by ion transfer voltammetry Tetraethoxysilane Interface liquide – liquide Ities Silice mésoporeuse Procédé Sol – Gel Cetyltrimethylammonium Tetraethylammonium Tetramethylammonium Tetrabuthylammonium Voltammétrie cyclique Spectroscopie Raman confocale Tamis moléculaire Modification interfaciale Dépôt de silice Voltammétrie de transfert d’ions 4-Octylbenzenesulfonate Miniaturisation MicroITIES Μities Membrane à base de silicium mésoporeux Tetraethoxysilane Liquid – liquid interface Ities Mesoporous silica Sol – Gel process Soft template Cetyltrimethylammonium Worm like structures Tetraethylammonium Tetramethylammonium Tetrabuthylammonium PAMAM dendrimers Cyclic voltammetry Confocal Raman spectroscopy Molecular sieving Interfacial modification Silica deposition Ion transfer voltammetry 4-Octylbenzenesulfonate Miniaturization MicroITIES Μities Mesoporous silicon wafers 541.37 660.297

1

Page generated in 0.1564 seconds