Segui questo link per vedere altri tipi di pubblicazioni sul tema: Silica polymerization.

Tesi sul tema "Silica polymerization"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili

Scegli il tipo di fonte:

Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Silica polymerization".

Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.

Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.

Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.

1

Yang, Minghua. "Silica supported metallocene catalysts and olefin polymerization". Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488443.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
2

Constable, Andrew N. "Functionalization of silica micro-capillaries and silica nanoparticles via polymber brushes". Akron, OH : University of Akron, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1221746490.

Testo completo
Abstract (sommario):
Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2008.
"December, 2008." Title from electronic dissertation title page (viewed 12/28/2008) Advisor, Roderic P. Quirk; Committee members, Scott Collins, Ali Dhinojwala, Li Jia, Mark D. Soucek; Department Chair, Ali Dhinojwala; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
Gli stili APA, Harvard, Vancouver, ISO e altri
3

Kaßner, Lysann, Kevin Nagel, R. E. Grützner, Marcus Korb, Tobias Rüffer, Heinrich Lang e Stefan Spange. "Polyamide 6/silica hybrid materials by a coupled polymerization reaction". Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-197628.

Testo completo
Abstract (sommario):
Polyamide 6/SiO2 hybrid materials were produced by a coupled polymerization reaction of three monomeric components namely 1,1′,1′′,1′′′-silanetetrayltetrakis-(azepan-2-one) (Si(ε-CL)4), 6-aminocaproic acid (ε-ACA) and ε-caprolactam (ε-CL) within one process. Si(ε-CL)4 together with ε-ACA has been found suitable as a precursor monomer for the silica and PA6 components. The accurate adjustment of the molar ratio of both components, as well as the combination of the overall process for producing the polyamide 6/SiO2 hybrid material with the hydrolytic ring opening polymerization of ε-caprolactam is of great importance to achieve homogeneous products with a low extractable content. Water in comparison with ε-ACA has been found unsuitable as an oxygen source to produce uniformly distributed silica. The procedure was carried out in a commercial laboratory autoclave at 8 bar initial pressure. The molecular structure and morphology of the hybrid materials have been investigated by solid state 29Si and 13C NMR spectroscopy, DSC and FTIR spectroscopy and electron microscopy measurements
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
Gli stili APA, Harvard, Vancouver, ISO e altri
4

堀内, 達郎, e Tatsuro HORIUCHI. "Effects of amide additives on polymerization of silica under acidic conditions". Elsevier, 1992. http://hdl.handle.net/2237/16357.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
5

McKittrick, Michael W. "Single-Site Olefin Polymerization Catalysts via the Molecular Design of Porous Silica". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6871.

Testo completo
Abstract (sommario):
The major goals of this work were to: develop a new methodology for the preparation of site-isolated catalytic sites on a silica surface, prepare the first truly single-site supported metallocene/CGC polymerization catalyst, and develop structure-reactivity relationships for these new systems. To synthesize these novel catalysts, the approach taken was to develop a protocol which allows for the synthesis of an aminosilica material with isolated, uniform amine sites. This patterned aminosilica was then used as a scaffold to support a constrained geometry catalyst. These functionalizations occurred at essentially a quantitative level, in stark contrast to previous literature reports. The patterned catalysts were evaluated in the polymerization of ethylene and compared to densely loaded literature materials. Overall, it was found the patterned materials were 5-10 times more active than traditional immobilized CGC catalysts. The patterned catalysts were also found to be effective catalysts for the copolymerization of norbornenes (including functionalized norbornenes) and ethylene, the first reported use of a tethered CGC for the production of ethylene-norbornene copolymers. The control materials were inactive in these polymerizations, providing further evidence that the patterning protocol allows for the synthesis of unique highly active, isolated catalytic sites. Various structural components of the immobilized CGC developed in this work were tested for their impact on catalyst synthesis and reactivity in ethylene polymerizations. The results showed the patterned materials in general behaved according to the trends seen in homogeneous CGC polymerizations. These results, while congruent with similar homogeneous CGC studies, are in direct conflict with previous work on supported CGCs reported in the literature. This discrepancy is likely the result of the difference between the isolated, possibly single-site patterned catalysts developed in the course of this work and the multi-sited catalysts prepared by traditional supporting protocols. This also further illustrates the difficulty in developing structure-reactivity relationships when ill-defined solid catalysts are used.
Gli stili APA, Harvard, Vancouver, ISO e altri
6

Liu, Yi. "Mesoporous silica/polymer nanocomposites". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31739.

Testo completo
Abstract (sommario):
Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Jacob. Karl; Committee Member: Griffin. Anselm; Committee Member: Tannenbaum. Rina; Committee Member: Thio. Yonathan S; Committee Member: Yao. Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Gli stili APA, Harvard, Vancouver, ISO e altri
7

Cheng, Xu. "The Use of Functionalized Zirconocenes as Precursors to Silica-Supported Zirconocene Olefin Polymerization Catalysts". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/30027.

Testo completo
Abstract (sommario):
Deck and coworkers previously showed that Me3Si substituents adjacent to group 4 metallocene dichlorides (M = Ti, Zr, Hf) are converted to corresponding BrMe2Si groups using BBr3, and that these BrMe2Si substituents are highly reactive to nucleophilic reagents such as water. The high reactivity of the Si-Br bonds suggested that these substituents could react with hydroxyl groups on the surface of partially dehydroxylated silica, forming covalently immobilized metallocene catalysts. This dissertation concerns the synthesis of electrophile-functionalized zirconocene dihalide complexes and the use of functionalized zirconocene dihalides as precursors to silica-supported metallocene olefin polymerization catalysts. Our first objective was to extend the metallocene "functionalization" chemistry to obtain substituents bearing more than one electrophilic bond. The reactivities of Me3Sn and Ph2MeSi substituents were explored in detail. (Me3Sn)2C5H4 combined with CpZrCl3 in toluene to afford (h5-Me3Sn-C5H4)CpZrCl2 (A). Reactions of A with electrophiles (E-X = Cl2B-Cl, I-Cl, and I-I) afforded (ï ¨5-XMe2Sn-C5H4)CpZrCl2 (and E-Me) cleanly. The reaction of A with BBr3 afforded either (ï ¨5-BrMe2Sn-C5H4)CpZrBr2 (25 ï °C, 10 min) or (ï ¨5-Br2MeSn-C5H4)CpZrBr2 (25 ï °C, 15 h). Ph2MeSi-C5H4Li combined with ZrCl4â ¢2THF to afford (h5-Ph2MeSi-C5H4)2ZrCl2 (B). The reaction of B with BCl3 led to incomplete cleavage of the Ph-Si bonds, however treatment of B with BBr3 afforded (h5-Br2MeSi-C5H4)2ZrBr2 (C) efficiently. The Sn-X bonds of the stannylated metallocenes were however relatively unreactive toward water and were excluded as candidates precursors for supported metallocene catalysts. X-ray crystal structures of (h5-ClMe2Sn-C5H4)CpZrCl2⠢½toluene, (h5-Br2MeSn-C5H4)CpZrBr2â ¢THF, B, and C were obtained. The functionalized metallocene C reacts with water to afford an oligosiloxane-supported zirconocene dibromide. Combinations of solution 1H NMR, solid state CPMAS 13C NMR, and solid state CPMAS 29Si NMR spectroscopy suggested a stereoregular structure in which the metallocene units have local Cs (meso) symmetry. Although only sparingly soluble, the oligomeric substance showed activity for homogeneous ethylene polymerization (toluene solution, MAO cocatalyst, Al:Zr = 5000, 50 ï °C) similar to Cp2ZrCl2. Supported metallocene olefin polymerization catalysts were prepared by combining a functionalized metallocene precursor (Cp2ZrBr2 bearing either BrMe2Si or Br2MeSi groups) and partially dehydroxylated silica. Ethylene polymerization activity of the resulting catalysts was examined as a function of the precursor structure (number of reactive "tethering" groups, one vs. two Si-Br bonds per tethering group) and the immobilization conditions (time, temperature, presence or absence of NEt3 promoter). The activities of the immobilized zirconocene catalysts decreased and the stabilities increased with increasing number of tethers. The immobilized catalyst prepared from (ï ¨5-Br2MeSi-C5H4)2ZrBr2, which is assumed to form two "double-tethers" to silica, was significantly more active than the catalyst prepared from [ï ¨5-1,3-(BrMe2Si)2C5H3]2ZrBr2, which is assumed to form four "single-tethers" to silica. Catalyst leaching was observed in all the immobilized zirconocene catalysts. The use of NEt3 in the immobilization reaction enabled more metallocene to be supported, but the resulting activity was lower. The dissertation also includes model studies on the immobilization reaction and the stability of the Si-O-Si bonds. The reaction of C with tBuMe2SiOH results in the formation of Si-O-Si bonds; addition of NEt3 results in further reaction to afford Si-O-Zr bonds. The reaction of Reaction of Me3Si-O-SiMe3 with MAO showed that Si-O-Si bonds can be cleaved under the conditions of our polymerization reactions.
Ph. D.
Gli stili APA, Harvard, Vancouver, ISO e altri
8

Qiao, Xiaoguang. "Synthesis of silica-polymer hybrid particles via controlled radical polymerization in aqueous dispersed media". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10332/document.

Testo completo
Abstract (sommario):
Des polymères à base de méthacrylate de poly(oxyde d'éthylène) (PEOMA) avec des chaînes pendantes PEO (Mn = 300 ou 950 g mol-1) ou des copolymères de PEOMA300 et d'acide méthacrylique (AMA) ont été synthétisés par polymérisation radicalaire contrôlée par les nitroxydes en utilisant une alkoxyamine (BlocBuilder®) comme amorceur en présence de SG1 et d'une faible quantité de styrène. Les copolymères à base de PEOMA300 et d'AMA sont thermo- et pH-sensibles. Les deux types de macroalkoxyamines ont été utilisés pour amorcer la copolymérisation en émulsion du méthacrylate de n-butyle et du styrène et former, par auto-assemblage induit par la polymérisation, des particules composées de copolymères à blocs amphiphiles, en absence ou présence de particules de silice. En absence de silice, des particules stabilisées de façon stérique ou électrostérique ont été formées. La polymérisation présente les caractéristiques d'une polymérisation contrôlée avec néanmoins la formation d'une faible proportion de chaînes mortes. L'effet du pH, de la force ionique et de la nature ou de la concentration des macroalkoxyamines sur la cinétique de polymérisation et la morphologie des particules a été étudié, et des sphères, des vésicules ou des nanofibres ont été obtenues. Les macroalkoxyamines à base de PEO s'adsorbent sur la silice via la formation de liaisons hydrogène entre les chaînes PEO et les groupes silanol. La synthèse de copolymères à blocs en surface de la silice a conduit à la formation de particules hybrides de différentes morphologies (bonhomme de neige, multipodes, framboise, coeur-écorce, têtard, mille pattes) liées à la taille de la silice, au pH et à la nature du macroamorceur
Water-soluble brush-type polymers composed of poly(ethylene)oxide methacrylate (PEOMA) units with PEO side groups of various chain lengths (Mn = 300 and 950 g mol-1) or of PEOMA300 with methacrylic acid (MAA) were synthesized by nitroxide-mediated polymerization using an alkoxyamine initiator (BlocBuilder®) and SG1 nitroxide in the presence of a low amount of styrene. The PEOMA300-MAA based copolymers showed a dual temperature/pH response. The two series of macroalkoxyamines were used in aqueous emulsion copolymerization of nbutyl methacrylate and styrene leading to the formation of particles composed of amphiphilic block copolymers through polymerization-induced self-assembly, in both the absence and presence of silica. The experiments performed in the absence of silica particles resulted in the formation of sterically or electrosterically stabilized latexes. The polymerization exhibited all the features of a controlled system with however the presence of a small proportion of dead chains. The effect of pH value, ionic strength and type and concentration of the macroalkoxyamine initiator on polymerization kinetics and latex morphologies was investigated. Depending on the reaction conditions, spherical particles, vesicles or nanofibers were successfully prepared. The PEO-based macroalkoxyamines were shown to adsorb on the silica surface via hydrogen bond interaction between PEO and the silanol groups. This enabled block copolymers to be generated in situ on the silica surface leading to hybrid particles with snowman, raspberry, daisy, core-shell, “tadpole-” and “centipede-” like morphologies depending on the silica particle size, pH value and type of macroinitiator
Gli stili APA, Harvard, Vancouver, ISO e altri
9

Fu, Anqiu. "Effect of the silica support on the reactivity and polymerization activity of organochromium complexes". Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6159.

Testo completo
Abstract (sommario):
The effect of the support in heterogeneous catalysis is very important but often poorly understood. The reaction of tetraneopentylchromium(IV) with Sylopol 952, a silica gel used industrially as a carrier for alpha-olefin polymerization catalysts, has been investigated and compared with the previously reported reaction on Aerosil 200, a fumed silica often used to model catalyst supports. Grafting, thermolysis, and metathetical exchange reactions of chromium(IV) neopentylidenes were found to be the same on either Aerosil 200 or Sylopol 952. However, reactivity of the grafted organochromium fragments towards ethylene was found to be quite different on the two supports. The research described in this thesis also explores the polymerization activity of bis(neopentyl)chromium(IV) fragments at higher ethylene pressures than were previously investigated. This result has greatly altered thinking about the nature of the active site for olefin polymerization over surface organochromium fragments. The supported bis(neopentyl)chromium(IV) is no longer believed to require thermal activation to create chromium alkylidene active sites. A possible mechanism is postulated. Propylene polymerization by the Aerosil-supported chromium alkylidene was observed as a slow pseudo-first-order reaction. The kinetics were examined at the gas-solid interface by in situ FTIR spectroscopy and the second-order rate constant compared to those previously measured for ethylene and 1-hexene.
Gli stili APA, Harvard, Vancouver, ISO e altri
10

Hicks, Jason Christopher. "Organic/inorganic hybrid amine and sulfonic acid tethered silica materials synthesis, characterization and application /". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26583.

Testo completo
Abstract (sommario):
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Jones, Christopher; Committee Member: Koros, William; Committee Member: Lyon, Andrew; Committee Member: Nair, Sankar; Committee Member: Weck, Marcus. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Gli stili APA, Harvard, Vancouver, ISO e altri
11

Nguyen, Joseph Vu. "Design, synthesis, and optimization of recoverable and recyclable silica-immobilized atom transfer radical polymerization catalysts". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6860.

Testo completo
Abstract (sommario):
Despite the growing interest in heterogeneous polymerization catalysis, the majority of the polymerization catalysts used industrially are single-use entities that are left in the polymer product. Recoverable and recyclable polymerization catalysts have not reached the industrial utility of single-use catalysts because the catalyst and product separation have not become economical. The successful development of recyclable transition metal polymerization catalysts must take a rational design approach, hence academic and industrial researchers need to further expand the fundamental science and engineering of recyclable polymerization catalysis to gain an understanding of critical parameters that allow for the design of economically viable, recoverable solid polymerization catalysts. Unfortunately, the rapid development of Atom Transfer Radical Polymerization over the past 10 years has not resulted in its wide spread industrial practice. Numerous reports regarding the immobilization of transition metal ATRP catalysts, in attempts to increase its applicability, have extended the fundamentals of recyclable polymerization catalysis. However, for industrial viability, more research is required in the area of how the catalyst complex immobilization methodology and support structure affect the catalyst polymerization performance, regeneration, and recyclability. A comprehensive rational catalyst design approach of silica-immobilized ATRP catalyst was undertaken to answer these questions and are discussed here.
Gli stili APA, Harvard, Vancouver, ISO e altri
12

Nguyen, Joseph Vu. "Design, synthesis, and optimization of recoverable and recyclable silica-immobilized atom transfer radical polymerization catalystal". Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-03072005-105351/unrestricted/nguyen%5Fjoseph%5Fv%5F200505%5Fphd.pdf.

Testo completo
Abstract (sommario):
Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005.
Jones, Christopher, Committee Chair ; Eckert, Charles, Committee Member ; Schork, Joseph, Committee Member ; Weck, Marcus, Committee Member ; Zhang, John, Committee Member. Includes bibliographical references.
Gli stili APA, Harvard, Vancouver, ISO e altri
13

Greco, Paula Palmeira. "Metalocenos suportados para a polimerização de etileno: efeito do uso de espaçadores na superfície da sílica". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/15645.

Testo completo
Abstract (sommario):
A homopolimerização de etileno foi investigada utilizando o catalisador (nBuCp)2ZrCl2 suportado em sílicas modificadas quimicamente com diferentes espaçadores. Dentre eles, foram utilizados Me3SiCl, Me2HSiCl, Ph3SiCl, polimetilhidrossiloxano (PMHS), GeCl4, SnCl4 ou PbCl2. As interações organossilano-sílica, zirconoceno-silanos suportados e zirconoceno suportadosilanos suportados foram estudadas através do método teórico ICONC. Os teores de metal foram determinados por Espectrometria de retroespalhamento Rutherford (RBS), enquanto a modificação química da superfície da sílica foi monitorado por Espectroscopia molecular no infravermelho com Transformada de Fourier (FT-IR) ou Espectroscopia molecular no infravermelho de refletância difusa (DRIFTS). As espécies zirconocenas superficiais foram investigadas por Espectroscopia de raio-X (XPS). A morfologia dos sistemas catalíticos e polímeros obtidos foram caracterizados por Microscopia eletrônica de varredura (SEM) e a distribuição de metal do sistema contendo PMHS foi estudada por Microssonda eletrônica (EPMA). Estes sistemas catalíticos produziram polietilenos com estreita polidispersidade e alta atividade catalítica utilizando metilaluminoxano como cocatalisador. Os efeitos da modificação química da sílica na performance catalítica são apresentados e discutidos.
The homopolymerization of ethylene was investigated using the catalysts of (nBuCp)2ZrCl2 supported on chemically modified silica with different spacers. The spacers used were Me3SiCl, Me2HSiCl, Ph3SiCl, polymethylhydrosiloxane (PMHS), GeCl4, SnCl4 or PbCl2. The organosilanes-silica, zirconocene-supported silanes and supported zirconocene-supported silanes interactions were studied by ICONC method. The metal contents were determined by Rutherford backscattering spectrometry (RBS), while the chemical modification of the silica surface was monitored by Fourier transform infrared spectroscopy (FT-IR) or Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The zirconocene surface species were investigated by X-ray spectroscopy (XPS). The morphology of these catalytic systems and polymers were evaluated by Scanning electron microscopy (SEM) and the metal distribution for the PMHS systems was studied by Electron microprobe analysis (EPMA). These catalytic systems produced polyethylene with a narrow molecular weight distribution and high catalyst activities using methylaluminoxane as co-catalyst. The effects of the chemical modification of the silica on the catalyst performance are presented and discussed.
Gli stili APA, Harvard, Vancouver, ISO e altri
14

Drese, Jeffrey Hayden. "The design, synthesis, and characterization of aminosilica adsorbents for CO2 capture from dilute sources". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42829.

Testo completo
Abstract (sommario):
The use of novel hyperbranched aminosilica (HAS) materials created through the ring-opening polymerization of aziridine from mesoporous silica supports was proposed for the adsorption of CO2 from dilute sources. The limits of the adsorptive performance of these adsorbents were investigated via the preparation of sets of materials with a range of aminopolymer loadings on several different silica supports with different pore space characteristics. Relationships were determined between the materials' amine loadings and the CO2 adsorption performance. Adsorbents with substantial remaining pore volume displayed universal adsorption kinetics when normalized by amine loading. However, materials with blocked pores displayed substantially slower adsorption kinetics due to hindered mass transfer. In both humid and dry conditions, the HAS adsorbent was found to have a surprisingly large CO2 capacity in light of the 250-fold reduction in CO2 partial pressure from 10% CO2 (flue gas application) to 400 ppm CO2 (air capture application). Finally, a new series of linear aminosilicas was created through the reaction of existing aminosilicas with N-protected-aziridines. Specifically, reaction of aminosilane-functionalized silicas with N-methylaziridine resulted in the linear growth of methylaminoethyl groups, effectively increasing the amine loading of the adsorbent by a stoichiometric amount of an additional amine per attached silane.
Gli stili APA, Harvard, Vancouver, ISO e altri
15

Geng, Yan. "Emulsion Polymerized Monodisperse Silica-Polymer Core-Shell Nanoparticles for Antireflective Coatings". University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1377189656.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
16

Kir, Onur [Verfasser], Wolfgang H. [Akademischer Betreuer] Binder e Guido [Akademischer Betreuer] Kickelbick. "Surface initiated polymerization of isoprene from silica nano- and glass particles via living anionic and controlled radical polymerization techniques / Onur Kir. Betreuer: Wolfgang H. Binder ; Guido Kickelbick". Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2013. http://d-nb.info/1050977734/34.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
17

Möhrke, Julia. "Kinetik der konventionellen radikalischen und der RAFT-Polymerisation an Nanopartikeloberflächen". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-87D3-9.

Testo completo
Abstract (sommario):
Diese Arbeit gibt neue Einblicke in die kinetischen und mechanistischen Aspekte der konventionellen radikalischen und der Reversible-Addition–Fragmentation-chain-Transfer- (RAFT-)Polymerisation von der Oberfläche von Silica-Nanopartikeln. Die Terminierungskinetik der oberflächeninitiierten Polymerisation von n-Butylmethacrylat (n-BMA) wurde mit Hilfe der Single-pulse–pulsed-laser-Polymerisation (SP–PLP) in Kombination mit der Elektronenspinresonanzspektroskopie (ESR-Spektroskopie) analysiert. Die Polymerisation wurde dabei durch den neu entwickelten oberflächengebundenen Photoinitiator 2,2-Dimethoxy-2-phenyl-1-(2-(2-(trimethoxysilyl)-ethyl)phenyl)-1-on (DMPTS) initiiert. Die erhaltenen Geschwindigkeitskoeffizienten der Terminierung kt, die ausschließlich der Terminierungsreaktion zwischen zwei oberflächengebundenen Radikalen zugeordnet werden konnten, waren signifikant kleiner als die Literaturwerte für das entsprechende homogene Polymerisationssystem. Erstaunlicherweise konnte außerdem keine Kettenlängenabhängigkeit von kt gefunden werden. Dies zusammen mit der Tatsache, dass bei temperaturabhängigen Untersuchungen eine Aktivierungsenergie für kt gefunden wurde, die in exzellenter Übereinstimmung mit der des Propagationsgeschwindigkeitskoeffizienten von n-BMA ist, lässt das Bild einer reaktionsdiffusionskontrollierten Terminierung oberflächengebundener Makroradikale entstehen. Die Entwicklung des oberflächengebundenen Photoinitiators DMPTS erlaubte weiterhin neue Einblicke in die Propagationskinetik – insbesondere deren Temperaturabhängigkeit betreffend – oberflächengebundener Makroradikale. Mittels der PLP von n-BMA in Kombination mit der Größenausschlusschromatographie (engl. size-exclusion chromatography, SEC) wurden Werte für den Geschwindigkeitskoeffizienten der Propagation kp und die entsprechende Aktivierungsenergie ermittelt, die exzellent mit den Daten der International Union of Pure and Applied Chemistry (IUPAC) für die Polymerisation von n-BMA in homogenem Reaktionsmedium übereinstimmen, sodass kein Einfluss der Oberflächenverankerung der Makroradikale auf die Propagationskinetik ersichtlich ist. Weiterhin wurde die Kinetik der RAFT-Polymerisation von n-Butylacrylat (BA) von Oberflächen bei –40 °C mit Hilfe verschiedener ESR-spektroskopischer Methoden für den R- und den Z-Gruppen-Ansatz unter Verwendung oberflächengebundener Trithiocarbonate als RAFT-Agenzien untersucht. Die kinetischen Analysen des R-Gruppen-Ansatzes mittels stationärer ESR-Experimente lieferten Gleichgewichtskonstanten Keq, die um eine Größenordnung kleiner sind als die Literaturwerte für entsprechende homogene Polymerisationssysteme, was darauf hindeutet, dass die Oberflächenverankerung des RAFT-Agens einen signifikanten Einfluss auf die Kinetik der RAFT-Polymerisation hat. Durch die Aufnahme zeitlicher Konzentrationsverläufe der Intermediatspezies und der propagierenden Radikale nach Einzelpulsinitiierung mittels der hochaufgelösten zeitabhängigen ESR-Spektroskopie (SP–PLP–ESR–RAFT) in Kombination mit PREDICI®-Simulationen wurden diese Ergebnisse bestätigt, da eine Abnahme des Geschwindigkeitskoeffizienten der Addition eines Makroradikals an die RAFT-Gruppe mit zunehmender Anzahl beteiligter oberflächengebundener Makromoleküle gefunden wurde. Dieser Befund ist im Einklang mit der Vorstellung, dass die Additionsreaktion bei Beteiligung verankerter Makromoleküle diffusionskontrolliert abläuft, was auf die unterdrückte Translations- und die eingeschränkte Segmentdiffusion oberflächengebundener Polymerketten zurückzuführen ist. Ein noch kleinerer Wert von Keq wurde für den Z-Gruppen-Ansatz gefunden und kann darauf zurückgeführt werden, dass die in Lösung wachsenden Ketten für die Additionsreaktion mit der RAFT-Gruppe, die sich über den gesamten Verlauf der Polymerisation in unmittelbarer Nähe zur Partikeloberfläche befindet, durch die Polymerschicht auf der Oberfläche diffundieren müssen. Die Wahrscheinlichkeit dafür, dass eine Additionsreaktion stattfindet, nimmt mit zunehmender Polymerschichtdicke ab, was durch einen kleineren Wert von Keq bei Verwendung von einem RAFT-Agens, das über die Z-Gruppe verankert war und über eine makromolekulare anstatt einer niedermolekularen R-Gruppe verfügte, gezeigt werden konnte. Die vorgestellten Ergebnisse geben einen umfangreichen Überblick über den Einfluss der Oberflächenverankerung von Komponenten, die am Prozess der radikalischen Polymerisation beteiligt sind, auf die Kinetik der oberflächeninitiierten radikalischen Polymerisation und ebnen den Weg für detaillierte, systematische Untersuchungen der Zusammenhänge zwischen der Kinetik von radikalischen Polymerisationen an Oberflächen und der molekularen Struktur der erhaltenen oberflächengebundenen Polymere.
Gli stili APA, Harvard, Vancouver, ISO e altri
18

TURNER, ROBERT HAINES. "MOLECULAR STRUCTURE OF INTERFACES FORMED WITH PLASMA POLYMERIZED SILICA-LIKE PRIMER FILMS". University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin997298644.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
19

Nitschke, Annika. "Investigation of Polymer-Filler Interactions Using Functionalized Nanoparticles". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-1363-6.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
20

Sauter, Dominique. "Développement de nouveaux supports activateurs solides pour la polymérisation des oléfines". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1249.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
21

Schmidt, Sonja. "Tuning Mesoporous Silica Structures via RAFT Polymers: From Multiblock Copolymers as new Templates to Surface Modification". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E379-C.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
22

Simerly, Thomas Max. "Immobilized Bis-Indenyl Ligands for Stable and Cost-Effective Metallocene Catalysts of Hydrogenation and Polymerization Reactions". Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etd/1473.

Testo completo
Abstract (sommario):
Reactions of catalytic hydrogenations and polymerizations are widely used in industry for manufacture of fine chemicals, pharmaceuticals, and plastics. Homogeneous catalysts for the processes that have low stability and their separation is difficult. Therefore, the development of new highly active and stable catalysts for hydrogenations and polymerizations is a necessity. The objective of this research was the development of a strategy for immobilization of heterogeneous metallocene catalysts. First, a methodology of immobilization of bis-indenyl ligands on the surface of mesoporous silica gel was designed. Four bis-indenyl ligands containing functionalized tethers of various lengths with terminal alkene groups were synthesized. All bis-indenyl ligands were immobilized on the surface of mesoporous functionalized silica gel by two methods: hydrosilylation and thiol-ene coupling of the double bond. After comparing the results, the second strategy was chosen as more efficient. The materials can be used further as intermediates for synthesis of supported metallocene catalysts.
Gli stili APA, Harvard, Vancouver, ISO e altri
23

Bui, Nhat Thi Hong. "Polyhydroxyl and Polyphosphorylcholine functionalized Silica for Hydrophilic interaction liquid Chromatography- Synthesis, characterization and application". Doctoral thesis, Umeå universitet, Kemiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-60600.

Testo completo
Abstract (sommario):
This thesis focuses on the development of new stationary phases for use in hydrophilic interaction liquid chromatography using TRIS-based and phosphorylcholine typed monomers and porous silica particles as starting substrates. In this thesis, several ways of polymerizing highly hydrophilic mono­mers onto pore surfaces of silica supports are described, based on several “grafting from” schemes. “Controlled/living” radical polymerizations including atom transfer radical polymerization (ATRP) and iniferter-mediated polymerization in conjunction with conventional free radical polymerization are demonstrated to be successful tools for grafting different hydrophilic monomers (polyhydroxyl and phosphorylcholine [meth]acrylamide/acrylates) onto the silica surfaces. Reaction solvents are proven to play an essential role to achieve efficient graft polymerization of activated silica surfaces with these amphiphilic vinylic monomers, which is difficult because of their restricted access to the activated surface in solvents that can be used because of solubility constraints. Two tentacle TRIS-based polymer grafted silica, namely TRIS-WAX – TRIS functionality bonded to silica via a C–N–C imine bond and TRIS-Amide – TRIS bonded to silica via an amide bond, prove to be useful as stationary phases for hydrophilic interaction chromatography (HILIC).The TRIS-WAX exhibits a mixed mode hydrophilic partitioning and weak anion exchange (HILIC/WAX) retention mechanism while retention by hydrophilic partitioning is the dominant mechanism on the neutral TRIS-Amide phase which lacks weak anion exchange (WAX) properties. Interestingly, both these phases have selectivities that are radically different from most commercial HILIC stationary phases. Finally, a method is demonstrated for synthesizing a stratified (graft-copolymerized) silica material based on N,N′-methylenebisacrylamide and 2-methacryloyloxyethyl phosphorylcholine (MPC) using a “controlled/living” photoiniferter-mediated polymerization from the N,N-diethyldithiocarbamate iniferter moiety immobilized silica surfaces. This polymerization method proves to be successful for graft-blockcopolymerization of different highly hydrophilic monomers onto the activated surfaces of porous silica. In this way, silica surfaces are grafted with a cross-linked amide-based hydrogel, on top of which a tentacle zwitterionic phosphorylcholine-typed layer is synthesized. The resulted material proves to be useful for HILIC separations and possesses different selectivity for the tested organic acids compared to that of commercial ZIC-cHILIC stationary phase.
Gli stili APA, Harvard, Vancouver, ISO e altri
24

Hubert, Céline. "Ingénierie de particules et assemblages à l’échelle colloïdale". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0185/document.

Testo completo
Abstract (sommario):
La synthèse et l’assemblage de particules colloïdales de morphologie et de fonctionnalité originale permet d’envisager la fabrication de matériaux aux propriétés électromagnétiques innovantes. Au cours de ce travail, nous nous sommes intéressés à la synthèse de colloïdes hybrides silice/polystyrène par un processus de polymérisation en émulsion du styrène ensemencé par des germes de silice préalablement fonctionnalisés en surface par des groupements méthacrylate. Ces particules hybrides, composées d’une particule centrale de silice entourée d’un nombre contrôlé de nodules de polystyrène, ont été utilisées comme moules afin de synthétiser des nanocages d’or de morphologie contrôlée. Ces nanocages d’or ont été caractérisées structuralement et optiquement. Nous nous sommes également intéressés à l’assemblage des particules hybrides silice/polystyrène via la génération d’interactions entre les nodules de polystyrène grâce au contrôle de qualité du solvant pour le polystyrène. Les particules présentant un nodule de polystyrène s’assemblent en petits clusters alors que celles présentant deux nodules de polystyrène forment des chaînes
The synthesis and the assembly of colloidal particles with original morphology and functionality should allow the fabrication of next-generation materials. This study deals with the synthesis of hybrid silica/polystyrene particles by an emulsion polymerization of styrenes eeded by surface functionalized silica particles. These particles, made by a silica coredecorated by a controlled number of polystyrene nodules, has been used as templates for thesynthesis of goldnanocages morphologically controlled. Theses gold nanocages has been characterized structurally and optically. We have also investigated the self-assembly of hybrid silica/polystyrene particles by generating interaction between polystyrene nodules due to the control of the solvent quality for polystyrene. Particles with one polystyrene nodule self assemble in little clusters and particle with two nodules in chains
Gli stili APA, Harvard, Vancouver, ISO e altri
25

Junges, Fernando. "Novel catalyst systems based on Ni(II), Ti(IV), and Cr(III) complexes for oligo-and polymerization of ethylene". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2005. http://hdl.handle.net/10183/6358.

Testo completo
Abstract (sommario):
Le complexe de Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) a été caractérisé après impregnation sur silice (S1) et a silices modifié avec MAO (4,0, 8,0 et 23,0 wt.% Al/SiO2 appelé S2, S3 et S4, respectivement). Le traitement de ces composés greffé avec MAO produit des catalyseurs actifs pour la polymérisation de l'éthylène. Un haute activité catalytique a été obtenue en utilisant le système supporté 1/S3 (196 kg de PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min et pression atmosphérique d'éthylène). Les effets des conditions de la polymérisation ont été testés avec le catalyseur greffé S2 et la meilleure activité catalytique a été obtenue avec le solvant hexane, MAO comme cocatalyseur, la proportion molaire Al/Ni de 1000 et à la température de 30°C (285 kg de PE/mol[Ni].h.atm). Quand la réaction a été conduite selon la méthodologie in situ, l'activité a pratiquement doublé et les polymères ont montré des propriétés semblables. Les polymères produits par les catalyseurs supportés ont montré l'absence de température de fusion, resultats senblables à seux obtenus avec les systèms homogène par analyse DSC. En revanche, le polymères obtenus avec les système greffé presentent selon les courbes GPC une (MwD) polydispersité qui varie de 1,7 à 7,0. Un mélange de polyéthylène lineaire et ramifié (BPE/LPE) préparé utilisant les complexes Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)- acenaphthenediimine) et {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5- mesitylpyrazol-1-yl)) greffés in situ sur silice modifiée avec MAO (4,0 wt. -% Al/SiO2, S2). Les réactions de polymérisation ont été exécutées dans le toluène à deux températures différentes (0 et 30°C), variant la fraction molaires du nickel (xNi), et utilisan MAO comme cocatalyseur externe. A toutes les températures, les activités montrent une tendence de variation linéaire avec xNi et indiquent l´absence d´effet synerque entre les espéces de nickel et du titane. Des activités les plus elèvees ont été trouvées à 0°C. Les températures de fusion pour les mélanges de polyéthylène produits à 0 °C diminuent alors que xNi augmente l'indiquant une bonne compatibilité entre les phases du polyéthylène obtenues avec les deux catalyseurs. La température de fusion des mélanges de polyéthylène dépendre de l'ordre selon lequel les catalyseurs ont été greffés sur la silice modifiée avec MAO. L'immobilisation initiale de 1 sur le support (2/1/S2) produit des polymères avec une temperature de fusion (Tm) inférieure à celle des polymère obtenus lorsque le titane a etè greffé inicialment 1/2/S2. L´observation des polyèthylènes obtenus avec les deux systèms (2/1/S2 et 1/2/S2) par microscopie electronique à balayage (SEM) a montré la formation de polymére sphérique montrant que la morphologie sphérique du support à été reproduite. Sont décrits la synthèse, la caractérisation et les propriètès catalytique pour l'oligomerization de l'éthylène de quatre composés organometalliques du CrIII possèdante les ligands (([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine]chromiun(III)chloride (3a), [bis[2- (3,5-dimethyl-l-pyrazolyl)ethyl] benzylamine]chromiun(III)chloride (3b), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). Concernent l'oligomerization, exception faite du composè 3a, tous les complexe du chrome se sont montré actif après activation avec MAO et les FR obtenues ont une effet differencie à celles atteintes avec CrCl3(thf)3. La coordination d´un ligand tridentatè sur le centre metallique ne provoque pas de changements considérables sur la formation des C4 et C6, mais la montantè de C8 est diminuèe et celles des C10 et +C12 ont ètè augmentèes. Les polymères produits par le catalyseur 3a à 3 et 20 atm d'éthylène possèdent, selon les analyses par DSC la températures de fusion de 133,8 et 136ºC respectivement. Ceci indique que dans les deux cas la production de polyèthylène de haut densité. Effectivement le masse molar moyenne, obtenus par GPC, est de 46647 g/mol avec Mw/Mn = 2,4 (3 atm). Le système 3c/MAO a montré des valeurs de FR, activité et sélectivité à α-olefins differents selon la pression d´éthylène utilisèe. Se qui montré une grand sensibilitè à la concentration d´éthylène solubilisè.
The complex of Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) has been characterized after impregnation on silica (S1) and MAO-modified silicas (4.0, 8.0 and 23.0 wts.% Al/SiO2 called S2, S3 and S4, respectively). The treatment of these heterogeneous systems with MAO produces some active catalysts for the polymerization of the ethylene. A high catalytic activity has been gotten while using the system supported 1/S3 (196 kg of PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min and atmospheric pressure of ethylene). The effects of polymerization conditions have been tested with the catalyst supported in S2 and the best catalytic activity has been gotten with solvent hexane, MAO as cocatalyst, molar ratio Al/Ni of 1000 and to the temperature of 30°C (285 kg of PE/mol[Ni].h.atm). When the reaction has been driven according to the in situ methodology, the activity practically doubled and polymers showed some similar properties. Polymers products by the supported catalysts showed the absence of melting fusion, results similar to those gotten with the homogeneous systems by DSC analysis. But then, polymers gotten with the transplanted system present according to the GPC’s curves the polydispersity (MwD) varies between 1.7 and 7.0. A polyethylene blend (BPE/LPE) was prepared using the complex Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine) and {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5-mesitylpyrazol-1-yl)) supported in situ on MAO-modified silica (4.0 wts. -% Al/SiO2, S2). Reactions of polymerization of ethylene have been executed in the toluene in two different temperatures (0 and 30°C), varying the molars fraction of nickel (xNi), and using MAO as external cocatalyst. To all temperatures, the activities show a linear variation tendency with xNi and indicate the absence of the effect synergic between the species of nickel and the titanium. The maximum of activity have been found at 0°C. The melting temperature for the blends of polyethylene produced at 0 °C decrease whereas xNi increases indicating a good compatibility between phases of the polyethylene gotten with the two catalysts. The melting temperature for the blends of polyethylene showed be depend on the order according to which catalysts have been supported on the MAO-modified silica. The initial immobilization of 1 on the support (2/1/S2) product of polymers with a melting temperature (Tm) lower to the one of the polymer gotten when the titanium has been supported inicially (1/2/S2). The observation of polyethylenes gotten with the two systems (2/1/S2 and 1/2/S2) by scanning electron microscopy (SEM) showed the spherical polymer formation showing that the spherical morphology of the support to been reproduced. Are described the synthesis, the characterization and the catalytic properties for the oligomerization of the ethylene of four organometallics compounds of CrIII with ligands ([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine] chromium (III) chloride (3a), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]benzylamine] chromium (III) chloride (3b), [bis[2-(3,5-dimethyl-lpyrazolyl) ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). In relation of the oligomerization, at exception made of the compounds 3a, all complex of the chromium showed be active after activation with MAO and the TOF gotten have one effect differentiated to those formed with CrCl3(thf)3. The coordination of a tridentate ligand on the metallic center doesn't provoke any considerable changes on the formation of the C4 and C6, but the amount of C8 are decrease and the C10 and C12+ have increased. The Polymers produced by the catalyst 3a to 3 and 20 bar of ethylene have, according to analyses by DSC, the temperatures of fusion of 133,8 and 136ºC respectively. It indicates that in the two cases the production of high density polyethylene. The molar mass, gotten by GPC, is 46647 g/mols with MwD = 2,4 (3 bar). The system 3c/MAO showed values of TOF, activity and selectivity to different α-olefins according to the pressure of ethylene uses. Himself that shown a big sensibility to the concentration of ethylene solubilized.
Gli stili APA, Harvard, Vancouver, ISO e altri
26

Yammine, Elham. "Synthèse de nanoparticules de latex de polystyrène à patchs magnétiques". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0397.

Testo completo
Abstract (sommario):
Les particules à patchs magnétiques ont pris une importance toute particulière dans l’étude des assemblages vers de nouvelles structures colloïdales. L’état de l’art nous a montré que la majorité des systèmes synthétisés et étudiés concerne des particules à un seul patch magnétique limitant ainsi les possibilités de structures accessibles par assemblage. Notre objectif s’est donc centré sur l’obtention de nanoparticules sphériques de polystyrène (PS) porteuses de plusieurs nanoparticules superparamagnétiques à leur périphérie. La voie multi-étapes retenue a consisté à préparer par polymérisation en émulsion ensemencée des particules Janus magnétiques (MJPs) présentant un nodule de PS qui a ensuite été rendu « collant » dans un mélange de bon/mauvais solvant pour fusionner avec celui d’un nombre limité de particules similaires. Pour servir de patchs magnétiques d’environ 100 nm, nous avons préparé des supraparticules colloïdales de nanoparticules d’oxyde de fer superparamagnétiques par un procédé incluant des étapes d’évaporation d’une phase émulsifiée, de consolidation par la silice et de resserrement de la distribution de taille par purification. Les paramètres optimaux de la polymérisation en émulsion ensemencée (composition du mélange de tensioactifs, nature et taux de greffage de l’agent de couplage) et de l’assemblage (nature et fraction du bon solvant, concentration particulaire, température et durée d’incubation) ont été préalablement déterminés avec des nanoparticules-modèles de silice présentant un diamètre et un état de surface similaires. L’application de ces conditions aux MJPs s’est avérée plus compliquée que prévue notamment en raison de la faible quantité de supraparticules disponible et cela a notamment conduit à définir de nouvelles conditions de polymérisation en émulsion ensemencée. Finalement, des lots de nanoparticules de latex à deux ou trois patchs magnétiques ont été obtenus, mais nécessiteront des étapes de purification avant d’envisager des études d’assemblage sous champ magnétique
Magnetic patchy particles are of great interest for assembly into novel colloidal structures. The state of the art showed us that the vast majority of synthesized and studied systems concerns particles with a single magnetic patch, thus limiting the structures accessible by particles assembly. Therefore, the main goal of the present study was to develop spherical polystyrene (PS) nanoparticles with two or many superparamagnetic nanoparticles on their surface. Our multistep process involved first the fabrication of Magnetic Janus particles (MJPs) by seeded-growth emulsion polymerization and subsequent incubation in suitable mixtures of good and bad solvents to make their polystyrene lobe “sticky”. MJPs are then ready to coalesce into self-assembled structures with small aggregation numbers. In order to obtain magnetic patches with a size range of 100 nm, we prepared colloidal supraparticles highly loaded with superparamagnetic iron oxide nanoparticles through a multistep procedure, including evaporation-induced emulsion, silica coating and purification, leading to a narrowing of the size distribution. The optimal parameters of the seeded-growth emulsion polymerization (surfactant mixture composition, coupling agent type, surface grafting density) and of the assembly (solvent quality, good solvent content, particle concentration, temperature and incubation time) were previously determined with silica nanoparticles as models with similar particle diameter as well as surface chemistry. We demonstrated that under the same conditions MJPs synthesis became trickier, mainly because of the small amount of available supraparticules. This led us to implement new seeded-growth emulsion polymerization conditions. Finally, batches of latex nanoparticles with two or three magnetic patches were obtained, but required further purification steps before investigating their assembly behavior under magnetic field
Gli stili APA, Harvard, Vancouver, ISO e altri
27

Louis, Chakkalakal Golda [Verfasser]. "Homopolymer and Block Copolymer Composites Based on Silica Nanoparticles Coated with Polymeric Single or Double Shells Synthesized by Atom Transfer Radical Polymerization / Golda Louis Chakkalakal". Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1026043026/34.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
28

Rotzoll, Robert [Verfasser], Philipp [Akademischer Betreuer] Vana e Konrad [Akademischer Betreuer] Samwer. "Tailored Silica Polymer Composites and ABA Type Copolymers: Polymerization Kinetics, Structural Design, and Mechanical Properties / Robert Rotzoll. Gutachter: Philipp Vana ; Konrad Samwer. Betreuer: Philipp Vana". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2011. http://d-nb.info/1043992995/34.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
29

Zhou, Xu. "Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51669.

Testo completo
Abstract (sommario):
Nanoporous organic polymers, including hypercrosslinked polymers (HCPs), covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), and conjugated microporous polymers (CMPs) etc., are considered good candidates for potential gas storage and gas separation applications. Porosities and surface areas of a series of semirigid alternating copolymers, which contained tert-butyl carboxylate-functionalized stilbene or tert-butyl carboxylate-functionalized styrene, and maleic anhydride or tert-butyl carboxylate-functionalized phenyl maleimide, were investigated using nitrogen sorption/desorption isotherms at 77 K and molecular simulations. These alternating copolymers were found to have Brunauer-Emmett-Teller (BET) surface areas in the range of 20-40 m2/g. Surface areas of these alternating copolymers increased as the steric crowding of the polymer backbone increased, which was the result of introducing extra phenyl rings and/or N-phenyl substituent maleimide units. Surface areas were found to increase as the persistence length increased. A series of HCPs containing functionalized stilbene and N-substituted phenyl maleimide were synthesized via free radical suspension polymerization. The incorporation of these functionalized, chain stiffening, Tg enhancing comonomers raised the Tgs of precursor polymers before they were crosslinked. Surface areas of these HCPs, obtained from nitrogen adsorption/desorption isotherms at 77 K, were up to 1058 m2/g. However, the surface areas of these HCPs were systematically lower than the controls. The high rigidity of the polymer backbone, which was the result of incorporating Tg enhancing comonomer, likely affected the chain mobility of the precursor polymer, decreased the efficiency of post-crosslinking reactions, and thus resulted in lower surface areas. Amine-functionalized styrene/stilbene polymers were prepared via free radical polymerization or post-modification. Amine-containing silica-based sorbents were prepared using the impregnation method. Sorption of CO2 by these materials was tested using TGA and compared with control samples. Both high amine content and certain levels of surface area were found to be important for a sorbent to achieve high CO2 uptake. Highest CO2 uptake (12 wt%) under our testing condition in these materials was achieved by an amine-containing silica sorbent.
Ph. D.
Gli stili APA, Harvard, Vancouver, ISO e altri
30

Ptacek, Saija Maria. "Funktionalisierte Alkylmethacrylat-Blockcopolymere als Template zur Darstellung geordneter Silica-Strukturen". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26524.

Testo completo
Abstract (sommario):
Die vorliegende Arbeit befasst sich mit der Synthese von Alkylmethacrylat-Blockcopolymeren, der Charakterisierung ihrer chemischen Struktur und ihres Mikrophasenseparationsverhaltens sowohl im Festkörper als auch in dünnen Filmen. Grundlegendes Ziel war die Einführung funktioneller Gruppen in ein Alkylmethacrylat-Blockcopolymersystem. Eine erste Einschätzung der Effektivität von funktionalisierten Diblockcopolymeren als Template für die Darstellung geordneter Silica-Strukturen über Sol-Gel-Reaktionen von Alkoxysilanen wurde angestrebt. Es wurde das Diblockcopolymersystem Poly(pentylmetacrylat-b-methylmethacrylat) PPMA-b-PMMA untersucht. Dieses wurde nach dem Mechanismus der anionischen Polymerisation dargestellt, um eine größtmögliche Kontrolle über Molmassen, Zusammensetzungen und Polydispersitäten ausüben zu können. Als vielseitig modifizierbare und stabile funktionelle Gruppe wurde die Allylfunktion ausgewählt. Diese konnte durch Endcapping mit Allylbromid an das Kettenende der Diblockcopolymere angebunden werden. An den Kettenanfang konnte die Allylfunktion durch Initiierung mittels Allyllithium gebunden werden. Durch Kombination von funktionellem Initiator und funktionellem Endcapping wurden bifunktionelle Diblockcopolymere erzeugt. Multifunktionalisierte Blockcopolymerproben wurden ebenfalls durch anionische Polymerisation erhalten. Durch sequenzielle Polymerisation von PMA, Allylmethacrylat und schließlich MMA wurden Triblockcopolymere dargestellt. Zwei weitere Typen von multifunktionalisierten Diblockcopolymeren, in denen die funktionellen Gruppen nahezu statistisch verteilt über einen der beiden Blöcke vorliegen, wurden durch statistische Copolymerisation erhalten. Alle Klassen von mono-, di- und multiallylfunktionalisierten Blockcopolymeren konnten durch Hydroborierung mit 9-BBN und anschließende Oxidation in mono-, di- und multihydroxylfunktionalisierte Blockcopolymere überführt werden. Die polymeranaloge Umsetzung der Hydroxylfunktion in eine Triethoxysilylfunktionon konnte modellhaft an einem hydroxylfunktionalisierten PMMA durchgeführt werden. Das Mikrophasenseparationsverhalten der Blockcopolymere wurde durch eine Kombination von analytischen Methoden wie SAXS, T-SAXS, GISAXS, TEM und AFM untersucht. Der Einfluss von Anzahl und Position der funktionellen Gruppen auf die Phasenseparation wurde geprüft. Die dargestellten Blockcopolymere zeigen ein Mikrophasenseparationsverhalten, das weitgehend mit den bereits vorliegenden Ergebnissen übereinstimmt. Trotz des geringen Wechselwirkungsparamters von χPMA,MMA = 0,065 tritt Phasenseparation auf, der Übergang von nichtgeordneter zu geordneter Phase (ODT) kann an ausgewählten Proben verfolgt werden. Die Bulkmorphologien werden nicht durch die Anwesenheit von ein oder zwei funktionellen Gruppen der Allyl- oder Hydroxylfunktion beeinflusst. Sind deutlich mehr als zwei funktionelle Gruppen entlang der Blockcopolymerkette vorhanden, kann das Mikrophasenseparationsverhalten nicht mehr direkt mit dem der nichtfunktionalisierten Diblockcopolymere verglichen werden. Blockcopolymere mit funktionellen Gruppen, die statistisch verteilt über einen der Alkylmethacrylatblöcke vorliegen, verhalten sich prinzipiell wie Diblockcopolymere. Die Phasenseparation ist schlechter ausgeprägt als in reinen Diblockcopolymeren, teilweise kann keine Phasenseparation festgestellt werden. Zum Teil kann dies auf vergrößerte Polydispersitäten und nachträgliche partielle Vernetzungsreaktionen zurückgeführt werden. Durch den Einbau von deutlich mehr als zwei funktionellen Gruppen entlang der Kette wird eine Verstärkung der Tendenz zur Phasenseparation erreicht, wenn der effektive Wechselwirkungsparameter zwischen den Blöcken größer wird als im nichtfunktionalisierten Diblockcopolymeren. Sehr polare Gruppen wie Hydroxylfunktionen beeinflussen Mikrophasenseparationsverhalten und Morphologieausbildung der Alkylmethacrylat-Diblockcopolymere stärker als wenig polare Allylfunktionen. In Triblockcopolymeren mit einem multiallyl- bzw. multihydroxylfunktionalisierten Mittelblock strebt das System einem dreiphasigen Zustand entgegen. Die experimentellen Befunde zum Phasenseparationsverhalten wurden mit theoretischen Phasendiagrammen verglichen, die für nichtfunktionalisierte Diblockcopolymere und Triblockcopolymere mit einem multiallyl- oder multihydroxylfunktionalisierten Mittelblock durch Mean-Field-Kalkulation auf Basis der RPA simuliert wurden. Das experimentell ermittelte Phasenseparationsverhalten der dargestellten Proben erfolgt im Einklang mit der berechneten Spinodalbedingung. Zum besseren Verständnis des Phasenseparationsverhaltens wurde das dynamische Relaxationsverhalten des Systems betrachtet. Zu diesem Zweck wurden Untersuchungen mittels dielektrischer Breitbandspektroskopie durchgeführt. Es wurde gezeigt, dass lokale Beweglichkeiten in den untersuchten Blockcopolymeren gehemmt und kooperative Bewegungen der α-Relaxationsprozesse im PPMA-Block langsamer bzw. bei höheren Temperaturen und im glasartigen PMMA-Block schneller bzw. bei niedrigeren Temperaturen als in den jeweiligen Homopolymeren erfolgen. Nach Untersuchung der Festkörpermorphologie wurden nicht-, mono-, di- und multifunktionalisierte Blockcopolymere hinsichtlich ihrer Morphologieausbildung in dünnen Filmen untersucht. Prinzipiell finden sich in dünnen Filmen dieselben Morphologien wie in Bulk. Durch die eingeschränkte Geometrie der Filme kommt es in dicken Filmen zur Ausbildung von Strukturen, die parallel zur Siliciumwaferoberfläche ausgerichtet vorliegen, während in sehr dünnen Filmen mit Schichtdicken kleiner als die entsprechenden Bulkdomänenabstände stehende Strukturen erzwungen werden. Für zylindrische Morphologien ist der Einfluss der Filmdicke auf die Orientierung der Strukturen deutlicher als für symmetrische lamellare Morphologien. Im Hinblick auf eine spätere Anwendung von nanostrukturierten Diblockcopolymeren wurden im Rahmen des Projektes verschiedene Ansätze verfolgt, für die nicht-, mono- und difunktionalisierte Diblockcopolymerproben der vorliegenden Arbeit von Projektpartnern eingesetzt wurden. Besonders wichtig war in diesem Zusammenhang die Anwendung von Blockcopolymeren als Template zur Erzeugung geordneter Silica-Strukturen. An der Universität von Modena und Reggio Emilia wurde eine Dissertation zum Thema organisch-anorganischer Hybridmaterialien durch den Sol-Gel-Prozess angefertigt. Die in der genannten Arbeit entwickelten Methoden wurden für die vorliegende Arbeit übernommen und für multifunktionalisierte Blockcopolymersysteme weiterführend selbst untersucht. Erste Untersuchungen zur Einschätzung der Templateigenschaften von Alkylmethacrylat-Blockcopolymeren in Silica-Sol-Gel-Reaktionen wurden an einigen multihydroxylfunktionalisierten Di- und Triblockcopolymeren durchgeführt. Die ersten vorliegenden Ergebnisse geben Grund zur Annahme, dass multihydroxylfunktionalisierte Blockcopolymere in der Lage sind, die Ausbildung von Silica-Partikeln bei in-situ durchgeführten Sol-Gel-Reaktionen mit SiO2-Precursoren in eine Richtung zu lenken, eine chemische Anbindung von organischer und anorganischer Phase zu erzwingen und die Form der ausgebildeten Silica-Nanostrukturen durch die vorgegebene Diblockcopolymermorphologie zu beeinflussen. Tatsächlich ist es gelungen, Silica in geordneter Weise in die Zylindermorphologie von PPMA-b-PMMA-Diblockcopolymeren einzubinden. Versuche, die organische Matrix durch Lösungsmittel oder Pyrolyse zu entfernen und die verbleibenden Silica-Strukturen hinsichtlich Ihrer Form und Porosität zu charakterisieren, werden zukünftig zum Verständnis des Bildungsprozesses in einer bevorzugten Phase oder an deren Grenzfläche beitragen. Die Steuerung der Silica-Partikelform kann nur dann tatsächlich gezielt erfolgen, wenn Phasenverhalten und Morphologiebildung für das Composit-System mit Silica-Precursor und verschiedenen Zwischenstufen mit jeweils unterschiedlichen Wechselwirkungen zu den Blockcopolymerphasen sowohl aus theoretischer Sicht verstanden als auch experimentell über eine größere Bandbreite nachgewiesen wurden. Das in dieser Arbeit entwickelte Blockcopolymersystem ließe sich in Bezug auf seine chemische Struktur sehr leicht auf vielfältige Weise erweitern. Für multifunktionalisierte Blockcopolymere bietet sich eine große Bandbreite von Variationen hinsichtlich Zusammensetzung, Molmasse und Verteilung von funktionellen Gruppen über beliebige Positionen entlang der Polymerkette sowohl innerhalb der drei für die vorliegende Arbeit gewählten Klassen von Di- und Triblockstrukturen als auch außerhalb dieser an. Es wurde gezeigt, dass eingebaute Allylfunktionen in der Lage sind, Vernetzungsreaktionen einzugehen, die u. U. steuerbar sind und zu definierten Nanogelstrukturen umgesetzt werden könnten. Kohlenstoffdoppelbindungen bieten Angriffspunkte für eine Vielzahl von polymeranalogen Umsetzungen, so dass aus allylfunktionalisierten Blockcopolymeren ein Pool von unterschiedlich funktionalisierten Blockcopolymeren darstellbar ist. Die Resultate der vorliegenden Arbeit zeigen, dass eine Anbindung funktioneller Gruppen an das Alkylmethacrylat-Blockcopolymer unter den gewählten Bedingungen mit guter Kontrolle über Anzahl und Position der Gruppen entlang der Kette grundsätzlich möglich ist. Der Einfluss der erzeugten funktionellen Gruppen auf das Mikrophasenseparationsverhalten des Blockcopolymersystems wurde eingeschätzt und wird in künftigen Arbeiten zum Verständnis der Strukturbildung in organisch/anorganischen Hybridmaterialien beitragen
The present study deals with the synthesis of alkyl methacrylate block copolymers, the characterization of their chemical structure and the microphase separation behavior in bulk and thin films. The main objective of this work was the attachment of functional groups to an alkyl methacrylate diblock copolymer system. A first evaluation of the ability of functionalized block copolymer structures to act as a templating material regarding silica formation in sol-gel synthesis of alkoxysilanes was aspired. The diblock copolymer system of poly(pentyl metacrylate-b-methyl methacrylate) (PPMA-b-PMMA) was chosen. It was synthesized following the mechanism of anionic polymerization to achieve effective control over molar mass, composition and polydispersity. The allyl functionality was chosen for a versatilely modifiable and stable functional group and attached to the terminal chain end by endcapping the living polymer chain ends with allyl bromide. The head of the chain was functionalized by initiation with allyl lithium. By combining functional initiation and endcapping, bifunctional diblock copolymers were synthesized. Furthermore multifunctionalized block copolymers were produced by anionic polymerization. By sequential anionic polymerization of PMA, allyl methacrylate and finally MMA, triblock copolymers were obtained. Two more classes of multifunctionalized block copolymers with functional groups randomly distributed in one of the two blocks were synthesized by random copolymerization. All types of mono-, di- and multiallylfunctionalized block copolymers were transformed into mono-, di- and multihydroxylfunctionalized block copolymers by hydroboration and subsequent oxidation. The polymer-analogue reaction of hydroxyl groups to triethoxysilane functions was carried out exemplarily for hydroxy terminated PMMA. The microphase separation behavior of the block copolymers was investigated by a combination of methods such as SAXS, T-SAXS, GISAXS, TEM and AFM. The influence of number and position of functional groups along the chain was examined. The block copolymers synthesized show a microphase separation behavior in accordance to previous results. Despite the low value of the Flory-Huggins interaction parameter χPMA,MMA = 0,065 phase separation occurred and the transition from the ordered to the disordered state (ODT) was followed for selected samples. Bulk morphologies are not influenced by the presence of one or two allyl or hydroxyl groups. In case of considerably more than two functional groups attached to the block copolymer chain the microphase separation behavior of nonfunctionalized and functionalized block copolymers cannot be compared directly. Block copolymers having functional groups randomly distributed along the chain of one of the two methacrylic blocks generally show the typical behavior of diblock copolymers. Their phase separation becomes less pronounced than in pure diblock copolymers, sometimes cannot be detected. To some extent this observation may be referred to increased polydispersities and partial crosslinking. If considerably more than two groups were attached to the block copolymer chain, the tendency towards phase separation increased in case of an increasing value of the effective interaction parameter compared to nonfunctionalized diblock copolymers. Microphase separation behavior and morphology formation are more affected by highly polar groups such as the hydroxyl function than by less polar groups like the allyl function. In triblock copolymers with a middle block of successive allyl or hydroxyl functions the systems tends to form a three phase system which offers much more possibilities regarding the formation of ordered structures. Experimental results of phase separation were compared to theoretical phase diagrams, which were calculated by a Mean Field approach for nonfunctionalized diblock and triblock copolymers with multiallyl- or multihydroxylfunctionalized middle block based on RPA. The experimental results are in good accordance with the simulated spinodal condition. To increase the understanding of microphase separation processes, the dynamic relaxation behavior of the system was investigated. Therefore samples were examined by broadband dielectric spectroscopy. It was shown that local movements of the block copolymer system were decelerated in general, cooperative dynamics of the α processes were slowed down for the fluent PPMA block while they were accelerated for the glassy PMMA block. After bulk morphology investigation thin films of non-, mono-, di- and multifunctionalized block copolymers were prepared. Generally thin films develope the same morphologies as in the bulk state. Due to the confined geometry of a thin film thick films tend to form structures oriented parallel to the wafer surface, while in thin films with thicknesses lower than the respective bulk domain spacing standing structures are constraint. For cylindrical morphologies the impact of film thickness is more obvious than in symmetric lamellar structures. With respect to a possible application of nanostructured diblock copolymers different approaches were taken by project partners using non-, mono- and difunctionalized block copolymers of the present study. Remarkable in this context was the application of block copolymers as template for the creation of ordered silica structures. A doctoral dissertation on organic/inorganic hybrid materials by sol-gel process was prepared in Modena. Methods developed in this thesis were adopted to the present study and further investigated on multifunctionalized block copolymer systems. First investigations aiming at the evaluation of the templating abilities of alkyl methacrylate block copolymers in silica sol-gel reactions were carried out with multihydroxyfunctionalized di- and triblock copolymers. Preliminary results give reason to the expectation of multihydroxyfunctionalized di- and triblock copolymers being able to direct the formation of silica nanoparticles in sol-gel reactions carried out in situ with silica precursors, enforcing the chemical bonding between organic and inorganic phases and influencing the shape of silica nanostructures by the default block copolymer nanostructure. Indeed silica was incorporated successfully into the cylindrical structure of PPMA-b-PMMA diblock copolymers. Future experiments on removing the organic matrix by solvent or pyrolysis to investigate shape and porosity of the remaining silica structures will increase the understanding of the silica formation process inside a preferential phase or at the interface of the block copolymers. Nevertheless, the silica particle shape can be taylored deliberately only if phase separation behavior and morphology evolution in the composite system containing silica precursor and several derivatives thereof with nonuniform interactions towards block copolymer phases are well understood from the theoretical point of view as well as experimental proof needs to be given over a broader range. The block copolymer system developed in the present study easily can be extended manifoldly regarding the chemical structure of the polymer. In the case of multifunctionalized block copolymers a tremendous variety of different products can be obtained by modulation of composition, molar mass and especially distribution of functional groups to any position along the polymer chain far beyond the limits of the three classes of multifunctionalized di- and triblockstructures chosen for this thesis. It was shown that allyl functions incorporated inherently are able to undergo crosslinking reactions, which may be controlled similarly to network formations by inorganic crosslinkers and may result in defined nanogel structures. Furthermore carbon doublebonds are open to attacks for various polymer-analogue reactions hence offering the possibility of creating a pool of differently functionalized block copolymers from a single sample of allylfunctionalized block copolymer. The results of the present study basically prove a feasibility of the binding of functional groups to alkyl methacrylate block copolymer chains with high control over number and position of functional groups along the polymeric chain. The impact of functional groups on the microphase separation behavior of the block copolymer system was evaluated and will increase the understanding of structure formation in organic/inorganic hybrid materials of future work
Gli stili APA, Harvard, Vancouver, ISO e altri
31

Long, Wei. "Designing immobilized catalysts for chemical transformations: new platforms to tune the accessibility of active sites". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/49017.

Testo completo
Abstract (sommario):
Chemical catalysts are divided into two traditional categories: homogeneous and heterogeneous catalysts. Although homogeneous (molecular) catalysts tend to have high activity and selectivity, their wide application is hampered by the difficulties in catalyst separation. In contrast, the vast majority of industrial scale catalysts are heterogeneous catalysts based on solid materials. Immobilized catalysts, combining the advantages of homogeneous and heterogeneous catalysts, have developed into an important field in catalysis research. This dissertation presents synthesis, characterization and evaluation of several novel immobilized catalysts. In the first part, MNP supported aluminum isoproxide was developed for ROP of Є-caprolactone to achieve facile magnetic separation of catalysts from polymerization system and reduce toxic metal residues in the poly(caprolactone) product. Chapter 3 presents a silica coated MNP supported DMAP catalyst that was synthesized and displayed good activity and regio-selectivity in epoxide ring opening reactions. In Chapter 4, hybrid sulfonic acid catalysts based on polymer brush materials have been developed. The unique polymer brush architecture permits high catalyst loadings as well as easy accessibility of the active sites to be achieved in this catalytic system. In Chapter 5, aminopolymer-silica composite supported Pd catalysts with good activity and selectivity were developed for the selective hydrogenation of alkynes. In this case, the aminopolymer composite works as a stabilizer for palladium nanoparticles, as well as a modifier to tune the catalyst selectivity. All in all, the general theme of the thesis is developing new immobilized catalysts with improved activity/selectivity as well as easy separation via rational catalyst design.
Gli stili APA, Harvard, Vancouver, ISO e altri
32

Mariot, David. "Nouveau procédé de modification de silice pour le renforcement d'élastomères silicones". Thesis, Montpellier, Ecole nationale supérieure de chimie, 2011. http://www.theses.fr/2011ENCM0013.

Testo completo
Abstract (sommario):
L'objectif de ces travaux était de mettre au point une nouvelle voie de modification de la silice comme renfort d'élastomères silicones. La polymérisation par ouverture de cyclosiloxanes anionique (POCA) amorcée directement à partir de la silice dispersée en phase aqueuse a été réalisée. Les caractéristiques des silices utilisées dans cette étude ainsi que leur comportement en dispersion aqueuse ont tout d'abord été étudiés. La silice affiche des groupements silanolates à la surface de la silice pour des pH supérieurs au point de charge nulle. A pH 7, ces groupements silanolates en surface sont capables d'amorcer une polymérisation des cyclosiloxanes, et pas en suspension aqueuse. L'influence du contre-ion et de sa concentration sur le greffage obtenu s'est avérée primordiale, en complément des propriétés adsorbantes de la silice via les liaisons siloxanes. Les silices obtenues par ce nouveau procédé ont fait l'objet d'analyses poussées par thermogravimétrie, fragmentation-CPG, 29Si RMN simple impulsion et pyrolyse CPG-SM dans le but de décrire précisément la conformation du greffage. Le procédé a été transféré à plus grande échelle pour permettre la production d'importantes quantités de silice qui ont ensuite été incorporées dans une matrice silicone. Des limites de densités de greffage au-delà et en deçà desquelles la silice est mal dispersée dans le matériau ont été mises en évidence par traitement d'image. Les propriétés des élastomères ont été évaluées à partir de tests de dureté, de traction uniaxiale, de traction cyclique et de résistance à la déchirure dans le but d'étudier l'influence du greffage (conformation et groupements vinylés) sur le renforcement
This work deals with a new way of modifying silica surface in a view to reinforce silicone elastomers. The surface-initiated ring-opening-polymerization (Si-ROP) of cyclosiloxanes was performed directly from the surface of silica dispersed in water. The characteristics of silica used in this study and their behavior in aqueous dispersion were first studied. For pH higher than the Point of Zero Charge, silica presents silanolate groups at its surface that are able to initiate the ROP of cyclosiloxanes from the surface, and not in aqueous suspension. The influence of the counter-cation and its concentration proved to be essential, in addition to silica's adsorbing properties. Modified silicas obtained by this new process were deeply analyzed by thermogravimetric analyses (TGA), fragmentation-GC, simple impulsion 29Si RMN and pyrolysis GC-MS in order to describe precisely the grafting conformation. The polymerization process was then scaled up to produce higher quantities of modified silica, which were incorporated in a model silicone formulation. Highest and lowest grafting densities tended to poor silica dispersions, as shown by image treatment. Hardness tests, uniaxial tensile and cyclic tests and tear resistance tests were performed in order to evaluate the influence of the grafting (conformation and vinylated groups) on silicone elastomers properties
Gli stili APA, Harvard, Vancouver, ISO e altri
33

Cuoq, Fabrice. "Fonctionnalisation d’un nouveau matériau pour le traitement de l’eau potable par floculation lestée". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4337.

Testo completo
Abstract (sommario):
Le but de ce projet a été d'améliorer un procédé de clarification développé par VEOLIA Environnement : l'Actiflo®. L'Actfilo® est basé sur l'ajout de microsable lors de l'étape de floculation afin d'augmenter les vitesses de décantation. Toutefois, une importante quantité de polymère est continuellement ajoutée au procédé, et des résiduels de ce dernier peuvent être rencontrés dans les eaux décantées. Notre travail a été de fonctionnaliser (i.e. greffer) le microsable avec un polymère floculant afin de pouvoir recycler en continu le matériau hybride par hydrocyclonage. La fonctionnalisation par « Grafting Onto » a consisté à greffer un polymère floculant commercial sur le microsable alors que la fonctionnalisation par « Grafting From » a consisté à faire croître un polymère floculant depuis la surface. Les capacités floculantes des microsables ont été testées en essais classiques de coagulation/floculation. Les microsables fonctionnalisés avec un polymère cationique par « Grafting From » ont démontré leur supériorité en conduisant à un abattement en Carbone Organique Dissous (COD) de 25% contre un abattement de 15 % pour le procédé classique ou pour les microsables fonctionnalisés par « Grafting Onto ». Une turbidité légèrement supérieure est toutefois toujours obtenue avec les sables fonctionnalisés par rapport à l'ajout de polymère libre (+ 0,5 NTU). Enfin, des procédés de régénération permettant de réutiliser les microsables ayant servi en coagulation/floculation ont été mis en place, le plus efficace d'entre eux étant un traitement à base d'Acide Oxalique. Ce traitement a permis de régénérer les propriétés floculantes du sable sur deux cycles
The purpose of this project was to improve a clarification process developed by VEOLIA Environment: The Actiflo®. The Actfilo® is based on adding microsand in the flocculation stage in order to increase the speed of sedimentation. However, a significant amount of polymeric flocculant is continuously added to the process, and residuals can be found in the decanted water. Our work was to graft a polymeric flocculant onto microsand in order to recycle the full hybrid material through hydrocycloning. Functionalization by "Grafting Onto" was based on grafting a commercial polymer onto microsand whereas “Grafting From” was based on surface-initiated polymerization. Flocculation properties of functionalized microsands were then tested in conventional coagulation/flocculation tests where the effectiveness of the two grafting methods was compared. Cationic functionalized sands, obtained by “Grafting From”, exhibit the best properties as a decrease of Dissolved Organic Carbon of 25% was reached whereas a decrease of 15% was reached by adding free polymer or adding sands from the “Grafting Onto” method. However final turbidity value was always slightly lower for the flocculation that occured when free polymer was added (- 0,5 NTU). Finally, regeneration processes to recycle the functionalized sands were established. The most effective of them being a treatment with Oxalic Acid. This treatment allowed us to regenerate flocculating properties of functionalized sands twice
Gli stili APA, Harvard, Vancouver, ISO e altri
34

Persson, Per. "Strategies for cellulose fiber modification". Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3730.

Testo completo
Abstract (sommario):

This thesis describes strategies for and examples ofcellulose fiber modification.The ability of an engineered biocatalyst, acellulose-binding module fused to theCandida antarcticalipase B, to catalyze ring-openingpolymerization of e-caprolactone in close proximity tocellulose fiber surfaces was explored. The water content in thesystem was found to regulate the polymer molecular weight,whereas the temperature primarily influenced the reaction rate.The hydrophobicity of the cellulose sample increased as aresult of the presence of surface-deposited polyester.

A two-step enzymatic method was also investigated. Here,Candida antarctica lipase B catalyzed the acylation ofxyloglucan oligosaccharides.The modified carbohydrates werethen incorporated into longer xyloglucan molecules through theaction of a xyloglucan endotransglycosylase. The modifiedxyloglucan chains were finally deposited on a cellulosesubstrate.

The action ofCandida antarcticalipase B was further investigated inthe copolymerization of e-caprolactone and D,L-lactide.Copolymerizations with different e-caprolactone-to-D,L-lactideratios were carried out. Initially, the polymerization wasslowed by the presence of D,L-lactide. During this stage,D,L-lactide was consumed more rapidly than ε-caprolactoneand the incorporation occurred dimer-wise with regard to thelactic acid units.

Morphological studies on wood fibers were conducted using asol-gel mineralization method. The replicas produced werestudied, without additional sample preparation, by electronmicroscopy and nitrogen adsorption. Information concerning thestructure and accessibility of the porous fiber wall wasobtained. Studies of never-dried kraft pulp casts revealedmicro-cavities and cellulose fibrils with mean widths of 4.7(±2) and 3.6 (±1) nm, respectively.

Finally, cationic catalysis by simple carboxylic acids wasstudied. L-Lactic acid was shown to catalyze the ring-openingpolymerization of ε-caprolactone in bulk at 120 °C.The reaction was initiated with methylß-D-glucopyranoside, sucrose or raffinose, which resultedin carbohydrate-functionalized polyesters. The regioselectivityof the acylation was well in agreement with the correspondinglipase-catalyzed reaction. The polymerization was alsoinitiated with a hexahydroxy-functional compound, whichresulted in a dendrimer-like star polymer. The L-lactic acidwas readily recycled, which made consecutive reactions usingthe same catalyst possible.

Keywords:Candida antarcticalipase B, cationic catalysis,cellulose-binding module, dendrimer, enzymatic polymerization,fiber modification, silica-cast replica, sol-gelmineralization, organocatalysis, xyloglucanendotransglycosylase

Gli stili APA, Harvard, Vancouver, ISO e altri
35

Freitas, Alan John Duarte de. "Preparação e estudo de reatividade de sistemas catalíticos, a base de zirconocenos, frente à reação de homo- e copolimerização de eteno". Universidade Federal de Alagoas, 2007. http://repositorio.ufal.br/handle/riufal/1060.

Testo completo
Abstract (sommario):
Catalytic systems based on zirconoces which are able to polymerize ethene have been studied. Structural modifications on the basic catalytic precursor, diphenylmethylidene(η5- cyclopentadienyl)(η5-9-fluorenyl) zirconium dichloride (5a) have been carried out. The catalytic precursors 5a and bis(para-fluorophenyl)methylidene(η5-cyclopentadienyl)(η5-9- fluorenyl)zirconium dichloride (5b) were synthesized, as well the pre-ligand (1- cyclopentadienyl)(9-fluorenyl)[1,1-bis(para-methoxyphenyl)]methane (3c). Complex Ph2C(Cp)(Flu)ZrCl2 was supported on silica by two different techniques. i) directly on silica, grafting, and ii) on silica modified with MAO. Catalytic tests on homopolymerization of ethene and copolymerization of ethene/1- hexene reactions, using the catalytic precursor 5a, were carried out either on homogeneous and heterogeneous media. The polymers obtained were characterized and their properties were correlated with the reaction polymerization conditions. Three different reactors, under different reaction conditions, were employed to carried out polymerization reactions. Several analytical techniques were employed to characterize the pre-ligands, catalytic precursors, polymers, and supports obtained.
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Neste trabalho foram estudados sistemas catalíticos, a base de metalocenos de zircônio, capazes de promover reações de polimerização de eteno. Foram realizadas de modificação estrutural do precursor catalítico base, difenilmetilideno(η5-ciclopentadienil)(η5- 9-fluorenil)zircônio (5a). Os precursores catalíticos metalocênicos 5a e dicloreto de bis(parafluorofenil) metilideno(η5-ciclopentadienil)(η5-9-fluorenil)zircônio (5b) foram sintetizados, como também o pré-ligante (1-ciclopentadienil)(9-fluorenil)[1,1-bis(para-metoxifenil)] metano (3c). O complexo Ph2C(Cp)(Flu)ZrCl2 (5a) foi suportado em sílica através de duas técnicas: i) diretamente em sílica, grafting e ii) em sílica modificada por metilaluminoxano (MAO). Foram realizados testes catalíticos empregando-se o precursor catalítico 5a, tanto em meio homogêneo, quanto heterogêneo, frente a reações de homopolimerização de eteno e copolimerização de eteno/1-hexeno. Os polímeros obtidos foram caracterizados e suas propriedades foram correlacionadas com as condições da reação de polimerização. As reações de polimerização foram realizadas em três diferentes reatores, sob diferentes condições reação. Várias técnicas analíticas foram empregadas para caracterização dos pré-ligantes, precursores catalíticos, polímeros e suportes obtidos.
Gli stili APA, Harvard, Vancouver, ISO e altri
36

Desert, Anthony. "Colloïdes hybrides silice/polystyrène de morphologie contrôlée". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00949569.

Testo completo
Abstract (sommario):
Les molécules colloïdales peuvent être décrites comme des agrégats robustes de particules sphériques prenant la forme de certaines molécules simples. La préparation de suspensions de molécules colloïdales est étudiée afin d'obtenir de hauts rendements en morphologie et des distributions étroites en taille des objets, conditions indispensables pour envisager de futures applications comme leur assemblage et l'élaboration de matériaux. La stratégie repose sur l'introduction de germes de silice fonctionnalisés dans une polymérisation en émulsion du styrène, menant à la nucléation-croissance d'un nombre restreint de nodules sphériques de latex ancrés à la surface de la silice.Les travaux proposent une optimisation des voies de préparation (i) des germes de silice par voie sol-gel et (ii) des particules de latex de PS par polymérisation en émulsion. Les structures des clusters silice/PS sont caractérisées par cryo-tomographie électronique et leur formation fait l'objet de discussions notamment en s'appuyant sur des modèles géométriques connus et en proposant un nouveau modèle de croissance des nodules. Enfin, une étude préliminaire est menée afin de recouvrir ces clusters d'une couche d'oxyde (SiO2 et TiO2).
Gli stili APA, Harvard, Vancouver, ISO e altri
37

Bonnevide, Marine. "Nanocomposites élastomère-nanoparticules de silice greffées : de la synthèse aux mécanismes de dispersion". Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0354.

Testo completo
Abstract (sommario):
L’ajout de charges nanométriques dans une matrice polymère permet d’améliorer les propriétés d’usage des matériaux. L’optimisation du renforcement des nanocomposites est liée à l’état de dispersion des charges dans la matrice ainsi qu’aux interactions charge/charge et charge/polymère. Dans l’industrie du pneu, ces paramètres ont fait l’objet de nombreuses recherches dans le but de maîtriser le renforcement de matrices élastomères par des particules de silice. Ainsi à l’échelle industrielle, on utilise des agents de couplage, comme le bis(triéthoxysilyl)propyl tétrasulfide ou des polymères fonctionnels qui permettent d’améliorer la dispersion des particules de silice dans des élastomères. Cependant il est difficile de moduler certains paramètres susceptibles d’influencer l’état de dispersion et les interactions, comme la densité de greffage, la nature et la longueur des chaînes de polymère greffées à la surface des particules. Afin de remédier à ces limites nous proposons, dans ce travail de thèse, de synthétiser des nanoparticules de silices greffées de polyisoprène, polybutadiène et copolymère poly(butadiène-co-styrène) par la méthode de « grafting from » associée à une polymérisation contrôlée par les nitroxydes. Pour cela une alcoxyamine est greffée sur la surface en deux étapes en maintenant la stabilité colloïdale des particules. Après l’optimisation des conditions de greffage et la polymérisation des monomères à partir de l’alcoxyamine greffée, les nanoparticules greffées ainsi obtenues sont caractérisées et leur état de dispersion est étudié en solution et dans des matrices de masses molaires et de compositions différentes après l’élaboration de nanocomposites
The addition of nanometric fillers into a polymer matrix significantly improves its use properties. Optimization of nanocomposite reinforcement is related to the filler dispersion state in the matrix as well as to the filler/filler and filler/matrix interactions. In the tire industry, numerous studies have been devoted to these parameters in order to understand and control the reinforcement of elastomeric matrices such as Styrene Butadiene Rubber by silica nanoparticles. On an industrial scale, functional polymer or coupling agents such as bis(triethoxysilyl)propyl tetrasulfide are used to improve the dispersion of silica particles in elastomers and strengthen the matrix. However, it is difficult to control the grafting density and to modulate some parameters that may influence the dispersion state and interactions e.g. the nature and molar mass of the polymer chains covalently attached to the surface. To address these limitations, in this project we propose to synthesize silica nanoparticles grafted with polyisoprene, polybutadiene and statistical poly(butadiene-co-styrene) chains using the “grafting from” method associated to nitroxide mediated polymerization. In this aim, an alkoxyamine is grafted onto the nanoparticle surface in two steps by keeping the colloidal stability of the particles. After optimizing grafting parameters and polymerize the different monomers, the obtained grafted nanoparticles are characterized in terms of molar mass, microstructure, grafting density and gyration radius of the grafted chains. Their dispersion state is evaluated in solution as well as in matrices of various molecular weight and composition after the elaboration of nanocomposites
Gli stili APA, Harvard, Vancouver, ISO e altri
38

Huang, Chun. "An optical emission study on DC plasma polymerization /". free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418031.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
39

Tsuchihara, Kenji. "Polymerization and Polymer Properties of Silicon- and Fluorine-Containing Acetylenes". Kyoto University, 1992. http://hdl.handle.net/2433/168754.

Testo completo
Abstract (sommario):
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第5109号
工博第1230号
新制||工||868(附属図書館)
UT51-92-J156
京都大学大学院工学研究科高分子化学専攻
(主査)教授 東村 敏延, 教授 今西 幸男, 教授 山岡 仁史
学位規則第4条第1項該当
Gli stili APA, Harvard, Vancouver, ISO e altri
40

Wu, Lei Verfasser], Alexander [Akademischer Betreuer] Böker e Andrij Z. [Akademischer Betreuer] [Pich. "Surface-initiated controlled radical polymerizations from silica nanoparticles / Lei Wu ; Alexander Böker, Andrij Pich". Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130590585/34.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
41

Wu, Lei [Verfasser], Alexander Akademischer Betreuer] Böker e Andrij Z. [Akademischer Betreuer] [Pich. "Surface-initiated controlled radical polymerizations from silica nanoparticles / Lei Wu ; Alexander Böker, Andrij Pich". Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130590585/34.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
42

LEPETIT, POURCELOT CHRISTINE. "Mise au point de nouveaux catalyseurs de dimerisation du propylene a base de complexes supportes du nickel : controle de la stabilite et de la selectivite par effet de ligands : influence electronique sterique et mecanistique". Paris 6, 1987. http://www.theses.fr/1987PA066489.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
43

De, Camargo Chaparro Thaissa. "Synthesis of nanocomposites with anisotropic properties by controlled radical emulsion polymerization Lorena". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1045/document.

Testo completo
Abstract (sommario):
L'objectif de ce travail de thèse est de préparer des latex nanocomposites à base d’argile, la Laponite RD, en émulsion aqueuse, à l'aide de la polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT). Les plaquettes de Laponite ont été choisies comme charge inorganique surtout pour leur anisotropie de forme, ce qui pourrait permettre l’elaboration de films nanostructurés, mais aussi pour leurs propriétés thermiques et mécaniques, leur pureté chimique élevée et la distribution uniforme en taille des plaquettes. Des polymères hydrophiles (macroRAFT) à base de polyéthylène glycol (PEG), d’acide acrylique (AA) ou de méthacrylate de N,N- diméthylaminoéthyle (DMAEMA) et comportant des unités hydrophobes d’acrylate de n-butyle (ABu) (dans certains cas) et un groupe trithiocarbonate terminal, ont été tout d'abord synthétisés. Ensuite, l'interaction entre les macroRAFTs et l’argile a été étudiée à travers le tracé des isothermes d'adsorption. En agissant comme des agents de couplage et des stabilisants, ces macroRAFTs ont eté utilisés dans la copolymérisation en émulsion du (méth)acrylate de méthyle et de l’ABu en mode semi-continu en presence d’argile. Des particules de latex hybrides de différentes morphologies ont été obtenues et les morphologies ont été reliées à la nature et à la concentration de l’agent macroRAFT, au pH de la dispersion macroRAFT/Laponite, à la température de transition vitreuse du copolymère final (fonction de la composition du mélange de monomères hydrophobes) et aux conditions de polymérisation. Les analyses par cryo-MET indiquent des plaquettes de Laponite décorées par des particules de polymère (plusieurs particules de latex en surface des plaquettes d'argile), des particules ‘haltère’, janus, ‘carapace’ (particules de latex décorées en surface par les plaquettes de Laponite) ou encore des particules multi-encapsulées (plusieurs plaquettes encapsulées dans chaque particule de latex). Les propriétés mécaniques des films de polymère/Laponite ont été étudiées par spectrométrie mécanique dynamique et corrélées à la morphologie des particules et à la microstructure des films
The aim of this work is to prepare Laponite RD-based nanocomposite latexes by aqueous emulsion polymerization, using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Laponite platelets were selected as the inorganic filler due, especially, to their anisotropic shape, which allows the production of nanostructured films, but also for their thermal and mechanical properties, their high chemical purity and the uniform dispersity of the platelets. Hydrophilic polymers (macroRAFT) composed of poly(ethylene glycol) (PEG), acrylic acid (AA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) and comprising hydrophobic n-butyl acrylate (BA) units (in some cases) and trithiocarbonate terminal group were initially synthesized. Then, the interaction between the macroRAFTs and the clay was studied through the plot of adsorption isotherms. By acting as coupling agents and stabilizers, the macroRAFT agents were used in the emulsion copolymerization of methyl (meth)acrylate and BA by semi-continuous process in the presence of the clay. Hybrid latex particles with different morphologies were obtained and the results were associated to the nature and concentration of the RAFT (co)polymers, to the pH of the macroRAFT/Laponite dispersion, the glass transition temperature of the final copolymer (function of the composition of the hydrophobic monomers mixture) and to the polymerization conditions. The cryo-TEM images indicate the formation of polymerdecorated Laponite platelets (several latex particles located at the surface of the platelets), dumbbell-like, janus, Laponite-decorated (armored) latex particles, and multiple encapsulated particles (several platelets inside each latex particle). The mechanical properties of polymer/Laponite films were studied by dynamic mechanical analysis and correlated with the particles morphology and the films microstructure
Este trabalho de tese tem como objetivo a preparação de látices nanocompósitos à base da argila Laponita RD em emulsão aquosa, via polimerização radicalar controlada por transferência de cadeia via adição-fragmentação reversível (RAFT). A Laponita foi escolhida como carga inorgânica devido principalmente à forma anisotrópica de suas lamelas, o que permite a elaboração de filmes nanoestruturados, mas também por suas propriedades térmicas e mecânicas, por sua alta pureza química e pela distribuição uniforme, em termos de tamanho, de suas partículas. Inicialmente, polímeros hidrofílicos (macroRAFT) à base de poli(etileno glicol) (PEG), de ácido acrílico (AA) ou de metacrilato de N,N-dimetilaminoetila (DMAEMA) que contêm unidades hidrofóbicas de acrilato de nbutila (ABu) (em alguns casos) e um grupo tritiocarbonílico terminal foram sintetizados. Em seguida, a interação entre os macroagentes de controle (macroRAFTs) e a argila foi estudada através de isotermas de adsorção. Atuando como agentes de acoplamento e estabilizantes, esses macroRAFTs foram então utilizados na copolimerização em emulsão do (met)acrilato de metila e do ABu em processo semicontínuo na presença da argila Laponita. Partículas de látex híbrido de diferentes morfologias foram obtidas e os resultados foram correlacionados à natureza e à concentração dos macroRAFTs, ao pH da dispersão macroRAFT/Laponita, à temperatura de transição vítrea do copolímero final (função da composição da mistura de monômeros hidrofóbicos) e às condições de polimerização. As análises de cryo-TEM indicam a formação de lamelas de Laponita decoradas com partículas de polímero (várias partículas de látex localizadas na superfície das lamelas), de partículas do tipo dumbbell, janus, blindadas (partículas de látex decoradas com lamelas de argila em sua superfície) ou ainda de partículas multiencapsuladas (diversas lamelas encapsuladas dentro de uma única partícula de látex). As propriedades mecânicas dos filmes de polímero/Laponita foram estudadas por análise dinâmico-mecânica e correlacionadas à morfologia das partículas e à microestrutura dos filmes
Gli stili APA, Harvard, Vancouver, ISO e altri
44

Kowatz, Thomas. "Mechanisms of silicate polymerisation, carbohydrate epimerisation and metalloprotease inhibition". Thesis, St Andrews, 2009. http://hdl.handle.net/10023/771.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
45

Sacristán, Benito Marta. "Soybean oil based copolymers containing silicon, boron or phosphorus: polymerization, characterization and fire retardance properties". Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/9040.

Testo completo
Abstract (sommario):
Introducción y antecedentes
El concepto de desarrollo sostenible surgió como idea principal tras la reunión de la comisión Brundtland en 1987. Esta reunión fue organizada por Naciones Unidas con el fin de tratar el deterioro del medio ambiente, originado por el desarrollo descontrolado de la humanidad. El desarrollo sostenible fue definido como un avance social y económico que asegure una vida sana y productiva al ser humano, pero que no comprometa las posibilidades de desarrollo de las generaciones venideras. Entre las conclusiones alcanzadas, se resaltó la necesitad de disponer de una mayor variedad de fuentes de energía. La filosofía de esta cumbre fue recogida en Agenda 21, un documento que pretendía servir como guía general de actuación para alcanzar un desarrollo sostenible a todos los niveles. Respecto a las ciencias, Agenda 21 subrayaba la necesidad de emplear todo el conocimiento científico en la consecución de los objetivos del desarrollo sostenible. En este sentido, la Environmental Protection Agency acuñó en 1998 un término, Green Chemistry, que reunía estas ideas y las aplicaba a la química a través de 12 principios que debían ser cumplidos en el camino hacia una química sostenible. Entre estos principios, el uso de fuentes renovables para la obtención de materias primas ha adquirido gran relevancia debido a las previsiones de agotamiento de una de las fuentes de energía y materias primas más importantes: el petróleo. Los aceites vegetales se incluyen entre estas fuentes renovables de materias primas, siendo actualmente una de las fuentes renovables más utilizadas por la industria química. Los aceites vegetales están básicamente compuestos por triglicéridos, que son moléculas formadas por glicerol y tres ácidos grasos. En general los ácidos grasos pueden ser completamente saturados o contener varios dobles enlaces que en algunos casos pueden encontrarse conjugados, pero también existen ácidos grasos que contienen grupos hidroxilo o epóxido. Cada aceite vegetal posee una distribución característica de ácidos grasos que determina sus propiedades físicas y químicas. En lo que respecta a la química de los polímeros, los aceites vegetales constituyen una atractiva materia prima debido a la amplia gama de transformaciones químicas que pueden llevarse a cabo para sintetizar monómeros de diversa naturaleza. La epoxidación de los dobles enlaces internos es la transformación más común, ya que permite, a través de la apertura del anillo oxiránico con diferentes reactivos, la introducción de una gran variedad de grupos funcionales. Los dobles enlaces internos pueden polimerizarse directamente en condiciones térmicas, con iniciadores de radicales o por polimerización catiónica.
Introducction
The sustainable development concept came out of the United Nations Commision on Environment and Development in 1987 (Bruntland Commission) and it is defined as "the development that meets the needs of the present without compromising the ability of future generations to meet their own needs". From this point, both the society and the industry have considered what a sustainable development really means and the best ways to start to achieve it from their own standpoints.
The principles of the United Nations Conference on environment and Development (UNCED) held in June 1992 in Rio de Janeiro, and Agenda 21, were formulated with the aim of preparing the world for the challenges of the 21st century. In this context, during the early 1990s the US Environmental Protection Agency (EPA) coined the phrase Green Chemistry "To promote innovative chemical technologies that reduce or eliminate the use of generation of hazardous substances in the design, manufacture and use of chemical products". The main challenges of Green Chemistry and Engineeiring can be summarized as:
· utilizing renewable instead of scarce resources.
· avoiding toxic/dangerous chemicals in safer processes to obtain safer products.
· minimizing energy use.
· minimizing waste and resource use, re-using products, recovering and recycling materials. So making processes globally more efficient.

Plant oils are one of the most widely applied renewable raw materials in the chemical industry for non-fuel applications. Vegetable oils are triglycerides (tri-esters of glycerol with long-chain fatty acids) with varying composition of fatty acids depending on the plant they are extracted from. Depending on the composition of plant oils, their Chemicals and physical properties are different.Vegetable oils are very used in polymer chemistry. Triglycerides have different reactive points through which we can obtain polymers from plant oils.There are two main approaches:The first one is the chemical modification of the triglycerides obtaining a large number of polymerizable monomers like expoxides or alcohols. The second approach is the direct polymerization of the carbon-carbon doubles bonds of plant oils through a free radical or a cationic mechanism.The free radical polymerization of double bonds has received less attention than cationic mechanism which has been very studied by Larock's group.In both cases thermosetting polymers with comparable properties to those of industrial can be obtained. Because of increasing use of synthetic polymeric materials during the lasts decades and the large fraction of the fire load in homes, it is necessary the use of fire retardants to reduce combustibility of the polymers, and smoke or toxic fume production. To get these requirements, the development of effective flame retardant materials is a key factor. To reduce the flammability, flame retardants can act in the gas phase or in condensed phase. In the gas phase fire retardants act as scavengers of the highly reactive radical species that propagate the combustion. In the condensed-phase fire retardants interfere in the thermal degradation processes modifying the reaction pathways and promoting the formation of char instead of volatile degradation products. Finally some flame retardants can act in both phases.
Objectives
The main objective of this Thesis was to develop new fire retardant biobased thermosets from vegetable oils as renewable resources. To achieve this goal it was carried out the cationic copolymerization of soybean oil, styrene and divinylbenzene with different silicon-or boron-or phosphorus containing comonomers.
Gli stili APA, Harvard, Vancouver, ISO e altri
46

Kaßner, Lysann. "Stickstoffhaltige Monomere zur Herstellung von Hybridmaterialien". Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171321.

Testo completo
Abstract (sommario):
In der vorliegenden Arbeit wurden stickstoffhaltige Monomere ausgehend von aromatischen Aminen oder Lactamen durch Umsetzung mit Chlorsilanen synthetisiert. Die so erhaltenen Derivate wurden mit Hilfe spektroskopischer und thermischer Analysenmethoden umfassend charakterisiert. Auf Basis der stickstoffhaltigen Monomere wurden über unterschiedliche Synthesestrategien organisch-anorganische, nanostrukturierte Hybridmaterialien hergestellt. Durch die thermisch induzierte Zwillingspolymerisation der Monomere 2,2‘-Spirobi[3,4-dihydro-1H-1,3,2-benzodiazasilin] und 1,1’,4,4‘-Tetrahydro-2,2‘-spirobi[benzo[d][1,3,2]-oxazasilin] gelang es, Hybridmaterialien bestehend aus Polyanilin-Formaldehyd-Harzen und Polysilazanen bzw. Siliciumdioxid unter Variation der Reaktionstemperatur herzustellen. Die Untersuchung der entstandenen Materialien erfolgte mittels spektroskopischer Methoden. Die Lactam-Monomere wurden durch die Zugabe von Aminocarbonsäuren zu Polyamid 6/SiO2- bzw. Polysiloxan-Kompositen umgesetzt. Hier stand die Ermittlung der molekularen Struktur, wie auch die Bestimmung des thermischen Verhaltens und der Homogenität der Materialien im Vordergrund. Es konnte gezeigt werden, dass die Synthese der thermoplastischen Kompositmaterialien auch in vergrößertem Maßstab reproduzierbar ist und die Produkte zudem zu Folien extrudierbar sind
In the present work nitrogen-containing monomers have been synthesized by reactions of silicon tetrachloride with amines or lactames and were characterized by different spectroscopic and thermal analysis methods. The twin monomers 2,2‘-spirobi[3,4-dihydro-1H-1,3,2-benzodiazasiline] and 1,1’,4,4‘-tetrahydro-2,2‘-spirobi[benzo[d][1,3,2]¬oxazasiline] can be converted to hybrid materials containing polyaniline-formaldehyde resins and polysilazane or SiO2 by thermal induced twin polymerization under variation of the reaction temperature. The obtained nano composites were investigated by spectroscopic methods and electron microscopy. The lactam containing monomers were polymerized to polyamide 6/SiO2-composites by addition of aminocarbonic acids and -caprolactam. The analysis of the molecular structure as well as the investigation of the thermal behavior and the homogeneity of materials was emphasized. It could be shown, that the synthesis can be performed reproducible. Furthermore, it is possible to extrude the thermoplastic composite materials to films
Gli stili APA, Harvard, Vancouver, ISO e altri
47

Weißhuhn, J., T. Mark, M. Martin, P. Müller, A. Seifert e S. Spange. "Ternary organic–inorganic nanostructured hybrid materials by simultaneous twin polymerization". Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-220068.

Testo completo
Abstract (sommario):
The acid and base catalyzed simultaneous twin polymerization (STP) of various 2,2′-disubstituted 4H-1,3,2-benzodioxasiline derivatives 2a–d with 2,2′-spirobi[4H-1,3,2-benzodioxasiline] (1) are presented in this paper. The products are nanostructured ternary organic–inorganic hybrid materials consisting of a cross-linked organic polymer, silica and a disubstituted polysiloxane. It can be demonstrated whether and in which extent the copolymerization of the two inorganic fragments of 1 and 2 takes place among the STP and how the molar ratio of the two components determines the structure formation of the resulting hybrid material. Steric and electronic effects of the substituents at the silicon center of 2 on the molecular structure formation and the morphology of the resulting hybrid material were investigated by means of solid state CP MAS 29Si and 13C NMR spectroscopy as well as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The mechanical properties (hardness and Young's modulus) of the hybrid materials were analyzed by means of nanoindentation measurements
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
Gli stili APA, Harvard, Vancouver, ISO e altri
48

Kitschke, Philipp. "Experimental and theoretical studies on germanium-containing precursors for twin polymerization". Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-205443.

Testo completo
Abstract (sommario):
Im Fokus dieser Arbeit standen zwei Ziele. Zum einem war es Forschungsgegenstand, dass Konzept der Zwillingspolymerisation auf germaniumhaltige, molekulare Vorstufen wie zum Beispiel Germylene, spirozyklische Germaniumverbindungen und molekulare Germanate zu erweitern und somit organisch-anorganische Komposite beziehungsweise Hybridmaterialien darzustellen. Dazu wurden neuartige Germaniumalkoxide auf der Basis von Benzylalkoholaten, Salicylalkoholaten sowie Benzylthiolaten synthetisiert, charakterisiert und auf ihre Fähigkeit Komposite beziehungsweise Hybridmaterialien über den Prozess der Zwillingspolymerisation zu erhalten studiert. Ein zweites Ziel dieser Arbeit war es, Beziehungen zwischen der Struktur und der Reaktivität dieser molekularen Vorstufen sowie deren Einfluss auf die Eigenschaften der erhaltenen Polymerisationsprodukte zu identifizieren und systematisch zu untersuchen. Hierfür wurden zum einen verschiedene Substituenten, welche unterschiedliche elektronische sowie sterische Eigenschaften aufweisen, an den aromatischen Einheiten der molekularen Vorstufen eingeführt. Die Effekte der Substituenten auf den Prozess der Zwillingspolymerisation und auf die Eigenschaften der Komposite beziehungsweise Hybridmaterialien wurden für die Verbindungsklasse der Germanium(II)salicylalkoholate, der molekularen Germanate sowie der spiro-zyklischen Siliziumsalicylalkoholate untersucht. Spirozyklische Siliziumsalicylalkoholate, wie zum Beispiel 4H,4’H-2,2‘-Spirobi[benzo[d][1,3,2]dioxasilin], wurden im Rahmen dieser Arbeit mit einbezogen, da sie aufgrund ihres nahezu idealen Zwillingspolymerisationsprozesses geeignete Modelverbindungen für Reaktivitätsstudien darstellen. Zudem wurde der Einfluss der Substituenten auf die Charakteristika der aus den Kompositen beziehungsweise Hybridmaterialien erhaltenen Folgeprodukte (poröse Kohlenstoffmaterialien und oxydische Materialien) studiert. Des Weiteren wurde eine Serie von spirozyklischen Germaniumthiolaten, welche isostrukturell zu 4H,4’H-2,2‘-Spirobi[benzo[d][1,3,2]dioxasilin] sind, synthetisiert, um systematisch den Einfluss der Chalkogenide, Sauerstoff und Schwefel, in benzylständiger sowie phenylständiger Position auf deren Reaktionsvermögen im Polymerisationsprozess zu untersuchen. Die experimentellen Ergebnisse zu den Struktur-Reaktivitätsbeziehungsstudien wurden, soweit es jeweils durchführbar war, mittels quantenchemische Rechnungen validiert und die daraus gezogenen Schlüsse in die Diskussion zur Interpretation der experimentellen Ergebnisse mit einbezogen.
Gli stili APA, Harvard, Vancouver, ISO e altri
49

Silva, Rafael Caetano Jardim Pinto da. "Síntese e caracterização de nanocompósitos do tipo polímero/silicatos lamelares com propriedades anisotrópicas via polimerização RAFT em emulsão". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-01022016-143552/.

Testo completo
Abstract (sommario):
Nos últimos anos, a incorporação de partículas inorgânicas em uma matriz polimérica com a finalidade de se obter sistemas híbridos orgânico/inorgânico utilizando diferentes técnicas de polimerização tem recebido grande atenção. Neste sentido, preservar e controlar as propriedades físico-químicas das partículas inorgânicas torna-se essencial para manter a integridade destas em nanoescala, bem como para obtenção de dispersões uniformes, magnificando os efeitos de reforço e demais ganhos de propriedades desejadas para a matriz polimérica. Quando se utiliza partículas inorgânicas anisotrópicas tais como a montmorilonita, silicato lamelar mais utilizado para obtenção de nanocompósitos do tipo polímero/silicato lamelar, este controle apresenta-se como um problema particularmente desafiador. Nesse contexto, a polimerização radicalar controlada (PRC) vem se destacando como uma importante via para atingir os objetivos mencionados acima, encontrando-se na literatura diversas estratégias de síntese em meio a solventes orgânicos na qual a efetiva nanoencapsulação de partículas inorgânicas dá-se por meio do crescimento de cadeias poliméricas na superfície destas estruturas inorgânicas. Entretanto, poucos trabalhos são encontrados envolvendo rota de obtenção semelhante em meio aquoso, tais como suspensão, emulsão e miniemulsão, processos estes que possuem grande interesse industrial, ambiental e viabilidade real de ampliação de escala quanto à produção.Desta forma, o objetivo deste projeto de pesquisa concentra-se na síntese e na caracterização de nanocompósitos do tipo polímero/silicato lamelar via polimerização radicalar controlada em emulsão. As polimerizações radicalares controladas de estireno em emulsão, via mecanismo de transferência reversível de cadeia por adição-fragmentação (RAFT), foram conduzidas na presença de argila montmorilonita (MMT) e mediadas por dois macroagentes de transferência de cadeia com grupo funcional tri-tioéster, sendo o primeiro constituído de cadeia polimérica não iônica de monoetil éter de poli(etilenoglicol) (MPEG-CPP) e outro derivado do MPEG-CPP contendo adicionalmente um bloco ionizável de poli(ácido metacrílico) incorporado à cadeia polimérica (MPEG-b-PMAA-CPP). Foram avaliados inicialmente os parâmetros de adsorção dos macroagentes MPEG-CPP e MPEG-b-PMAA-CPP na superfície da MMT bem como a influência das variáveis do processo de polimerização na adsorção dos macroagentes na MMT e na estabilidade coloidal dos complexos macroagente RAFT / MMT formados. Posteriormente foram avaliados os efeitos do pH, das concentrações dos macroagente RAFT e de MMT, bem como do tipo de iniciador na cinética de polimerização em emulsão \"ab-initio\" de estireno, conduzidas na ausência de surfatantes. As técnicas utilizadas nos estudos de adsorção e para a caracterização das argilas, dos látices híbridos e dos materiais nanocompósitos incluem: espectroscopia de UV-vis, espalhamento dinâmico de luz (DLS), espalhamento eletroforético de luz (ELS), cromatografia de permeação em gel (GPC), análise termogravimétrica (TGA), calorimetria diferencial de varredura (DSC) e microscopia eletrônica de transmissão (TEM).
In recent years, the incorporation of inorganic particles in a polymer matrix in order to obtain hybrid organic/inorganic systems using different polymerization techniques have received great attention. In this sense, preserve and manage the physical and chemical properties of inorganic particles is essential to maintain its integrity at the nanoscale, as well as to obtain uniform dispersions of them, magnifying the effects of reinforcement and other desired properties into the polymer matrix. When using anisotropic inorganic nanoobjects such as montmorillonite, the most used layered silicate to obtain polymer / layered silicate nanocomposites, this control is presented as a particularly challenging problem. In this context, the controlled radical polymerization (CRP) has been highlighted as an important way to achieve the goals mentioned above, several strategies of organic solvent-borne synthesis can be found in literature in which the effective nanoencapsulation of inorganic particles is given by through the growth of polymer chains on the surface of these inorganic structures. However, few works are found involving obtaining similar route in water-borne, such as suspension, emulsion, miniemulsion, these procedures have great interest in industrial, environmental and actual feasibility of expanding scale in manufacture. Thus, the objective of this research project focuses on the synthesis and characterization of nanocomposite-type polymer / layered silicate via controlled radical polymerization in emulsion media. The controlled radical polymerizations in emulsion, via transfer mechanism for the reversible addition-fragmentation chain (RAFT) have been conducted in the presence of montmorillonite clay (MMT) and mediated by two macroRAFT agents with functional tri-thioesters groups, being the first one constituted by a nonionic poly(ethylene glycol) methyl ether polymeric chain (MPEG-CPP) and the second on being MPEG-CPP derived but containing additionally an ionizable block of poly(methacrylic acid) inserted to its polymeric chain. The parameters of adsorption of MPEG-CPP and MPEG-b-PMAA-CPP agent on the surface of MMT as well as the influence of the polymerization process variables on the adsorption of PEO-RAFT in MMT and colloidal stability of the complex formed macroRAFT agents / MMT were firstly evaluated. Subsequently, the influence of pH, macroRAFT agents and MMT concentrations as well as the type of initiator on the kinetics of RAFT emulsion polymerization were equally evaluated. The techniques used the for adsorption studies and characterization of clays, latexes of hybrid materials and nanocomposites include: UV-vis spectroscopy, dynamic light scattering (DLS), electrophoretic light scattering (ELS), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), dynamic scanning calorimetry (DSC) and transmission electron microscopy (TEM).
Gli stili APA, Harvard, Vancouver, ISO e altri
50

Eroglu, Damla. "Electrochemical Synthesis Of Poly(methylsilyne), And The Effect Of Silicon-based Preceramic Polymers On The Properties Of Polypropylene Based Composites". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609878/index.pdf.

Testo completo
Abstract (sommario):
In the first part of this dissertation, poly(methylsilyne) was produced both in small and large-scales. In the small-scale, the aim was to synthesize the polymer by electrochemical polymerization of methyltrichlorosilane at a constant potential of -6 V supplied by batteries, using sodium dodecyl sulfate (SDS) as the supporting electrolyte. The polymer was characterized by 1H-NMR, FTIR, UV-Visible Spectroscopy and GPC in addition to its distinctive yellow color. The yellow color and the 1H-NMR, FTIR, UV-Visible and GPC results proved that poly(methylsilyne) was produced successfully in small-scale. In the second part of the synthesis, the objective was to scale-up the electrochemical synthesis of poly(methylsilyne) while investigating the effects of the parameters like the electrode, solvent and supporting electrolyte types, monomer/solvent ratio and reaction time on the synthesis. Although successful results were obtained in large-scale synthesis with acetonitrile and SDS, the problems with the reproducibility of the synthesis were solved using a system containing 1.2-dimethoxyethane (DME) and tetrabutylammonium perchlorate (TBAP). In the second part of the dissertation, the aim was to prepare polypropylene/silicon-based preceramic polymer blends and to characterize them in terms of flammability, thermal and mechanical properties and morphologies. In order to investigate the effect of the silicon-based preceramic polymers, two different polymers were used: poly(methylsilyne) (PMSy) and allylhydridopolycarbosilane (SMP-10) where the latter was a commercially available silicon carbide precursor. Triphenylphosphate (TPP) and a metal complex were also used in polypropylene based composites to gain a synergy with the silicon containing polymers. The polymer composites were prepared using a twin-screw extruder and molded in an injection molding machine. As a result of the flammability tests, it was seen that in order to achieve a significant decrease in the flammability of polypropylene, at least 20 wt% additive was needed. Furthermore, it was observed that the most significant improvement in flame retardancy was obtained in PP/10SMP/5TPP/5M sample containing 10 wt% SMP-10, 5 wt% TPP and 5 wt% metal complex with a limiting oxygen index (LOI) value of 23.5%. This was explained by the synergy obtained by SMP-10, TPP and the metal complex. With the addition of these silicon containing polymers, thermal properties of the composites increased to a great extent. For the mechanical properties, it was seen that impact strength of the composites significantly increased with the addition of SMP-10, PMSy and TPP.
Gli stili APA, Harvard, Vancouver, ISO e altri
Offriamo sconti su tutti i piani premium per gli autori le cui opere sono incluse in raccolte letterarie tematiche. Contattaci per ottenere un codice promozionale unico!

Vai alla bibliografia