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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Polymerization Of 2,4,6 Trichlorophenol By Microwave Initiation

Okyay, Ozden 01 December 2006 (has links) (PDF)
Polymerization reaction is carried out by the reaction of 2,4,6 trichlorophenol with sodium hydroxide, in the presence of small amount of water by microwave initiation. Synthesis of polymers were successfully performed under microwave enegy. The use of microwave energy was due to advantages of shorter processing time. The main focus of attention was the 90 to 600 watt microwave energy. Polymerizations were performed with different time intervals by keeping the microwave energy and water content constant / or with different energy levels by keeping the time interval and water content constant / or by varying the amount of water by keeping the time and energy level constant.Beside poly(dichlorophenylene oxide), conducting polymer, ion-radical polymer, crosslinked polymer were also be successfully synthesized and characterized. Characterizations of the products were performed by FTIR, 1H-NMR, 13C-NMR, DSC, TGA and elemental analysis. Molecular weight distribution was measured by PL-GPC 220 Polymer Laboratories Instrument. Conductivity measurements were performed by four probe technique.
2

The Effect Of Potassium Hydroxide On The Polymerization Of Trichlorophenol, Pyrrole And Thiophene By Microwave Initiation

Unsal Gungor, Elif Mufide 01 June 2008 (has links) (PDF)
The synthesis of black conducting polymer (CP) and/or crosslinked polymers (CLP) and/or radical ion polymer (RIP) and/or white polymers (WP) and/or orange polymer (OP) were achieved by using KOH with TCP, pyrrole and thiophene via microwave energy in a very short time interval. Polymerizations were carried out by constant microwave energy with different time intervals varying from 1 to 25 min / or at constant time intervals with variation of microwave energy from 90 to 900 watt / or varying the water content from 0, 0.5 to 5 ml at constant time intervals and microwave energy, or at constant time interval, water content, microwave energy with variation of amount of KOH 0.03 mol to 6x10-4 mol. The effects of heating time, microwave energy, water content and amount of KOH on the percent conversion and the polymer synthesis were also investigated.White, orange polymers and radical ion polymers were characterized by FTIR (Fourier Transform Infrared), 1H-NMR (Proton Nuclear Magnetic Resonance), 13C-NMR (Carbon-13 Nuclear Magnetic Resonance), TGA/ FTIR (Thermal Gravimetric Analysis / Fourier Transform Infrared), DSC (Differential Scanning Calorimeter), SEM (Scanning Electron Microscope), ESR (Electron Spin Resonance), GPC (Gel Permeation Chromatography), UV-Vis (UV-Visible Spectroscopy) and Light Scattering. Conducting and crosslinked polymers were characterized by FTIR, TGA/ FTIR, DSC, SEM, ESR, XRD (Powder Diffraction X-Ray) and conductivity.
3

Microwave Initiated Polymerization Of Trihalophenyleneoxide And Aniline

Levent, Fulya 01 February 2011 (has links) (PDF)
The aim of the study is to synthesize poly(dibromophenyleneoxide) and polyaniline separately applying different microwave energies (90-900 watt), water amounts (1-5 ml) and time intervals (2-10 min) and investigate the effects of these parameters on the percent conversion of the polymers. The synthesis of poly(dibromophenyleneoxide) (P), radical ion polymer (RIP) and crosslinked polymer (CLP) were achieved by using tribromophenol (TBP) and Ca(OH)2 via microwave energy in a very short time interval. P and RIP were characterized by ATR-FTIR, 1H-NMR, 13C-NMR, TGA-FTIR, ESR, GPC, UV-VIS, DLS and SEM. Crosslinked polymers were characterized by ATR-FTIR and TGA-FTIR and polyaniline was characterized by ATR-FTIR.
4

Influence of Crosslink Density on Swelling and Conformation of Surface-Constrained Poly(N-Isopropylacrylamide) Hydrogels

Cates, Ryan S 31 March 2010 (has links)
A stimuli-responsive microgel is a three-dimensional polymer network that is able to absorb and expel a solvent (commonly water). These materials are unique in the fact that their sponge-like behavior can be actuated by environmental cues, like temperature, ion concentration, pH, and light. Because of the dynamic properties of these materials they have found applications in drug-delivery systems, micro-assays, selective filtration, artificial muscle, and non-fouling surfaces. The most well-known stimuli-responsive polymer is Poly(N-isopropylacrylamide) or PNIPAAm and it experiences a switchable swelling or deswelling over a critical temperature ( Tc=~32°C). Below the critical temperature, the gel begins mixing with the surrounding solvent and swells; above this temperature, the opposite is true. The unconstrained hydrogel will continue to swell in all directions until equilibrium is established between its propensity for mixing with the surrounding solvent and the elastic restoring forces of the gel matrix. The strength of the elastic restoring forces is dependent on the interconnectedness of the polymer network and is therefore a function of crosslink density. An increase in crosslink density results in a decreased swelling and vice versa. If the hydrogel is mechanically constrained to a surface, it can experience various wrinkling and buckling conformations upon swelling, as the stresses associated with its confinement are relieved. These conformation characteristics are a strong function of geometry (aspect ratio) and extent of swelling (i.e. crosslink density). In order to capitalize on the utility of this material, it is imperative that its volume transition is well characterized and understood. Toward this end, pNIPAAm gels have been created with 1x10-7 to 2x10-³ mol/cm³ crosslink density and characterized. This was done by first examining its bulk, unattached swelling ability and then by evaluating its microscale properties as a surfaceconfined monolithe. The latter was achieved through the use of confocal microscopy and copolymerization with a fluorescent monomer. This method allows for a detail analysis of the deformations experienced (bulk-structural bending and surface undulating) and will ultimately lend itself to the correlation between crosslink density and the onset of mechanical phenomena.
5

Thermally crosslinked polyimide hollow fiber membranes for natural gas purification

Chen, Chien-Chiang 05 October 2011 (has links)
Robust industrially relevant membranes for CO₂ removal from aggressive natural gas feed streams were developed and characterized. Asymmetric hollow fiber membranes with defect-free selective skin layers on an optimized porous support substructure were successfully spun and subsequently stabilized by covalent crosslinking within the economical membrane formation process. Thermal treatment conditions, which promote sufficient crosslinking without introducing defects or undesired substructure resistance, were identified. It was found that crosslinking improves membrane efficiency and plasticization resistance as well as mechanical strength of fibers. The capability to maintain attractive separation performance under realistic operating conditions and durability against deleterious impurities suggests that the crosslinked fibers have great potential for use in diverse aggressive applications, even beyond the CO₂/CH₄ example explored in this work.
6

Microwave-assisted Simultaneous Novel Synthesis Of Poly(dibromophenylene Oxide)s, Poly(diiodophenylene Oxide)s (p), Conducting(cp) And/or Crosslinked (clp) And/or Radical Ion Polymers (rip)

Celik, Guler (bayrakli) 01 March 2007 (has links) (PDF)
Microwave-assisted novel synthesis of poly(dibromophenylene oxide) or poly(diiodophenylene oxide) (P), conducting polymer (CP) and/or crosslinked polymer (CLP) and/or radical ion polymer (RIP) were achieved simultaneously from lithium, sodium or potassium 2,4,6-bromophenolate or sodium 2,4,6-iodophenolate in a very short time interval. Polymerizations were carried out by constant microwave energy with different time intervals varying from 1 to 20 min / or at constant time intervals with variation of microwave energy from 70 to 900 watt / or varying the water content from 0.5 to 5 ml at constant time intervals and microwave energy. Poly(dihalophenylene oxide) and radical ion polymers were characterized by FTIR (Fourier Transform Infrared), 1H-NMR (Proton Nuclear Magnetic Resonance), 13C-NMR (Carbon-13 Nuclear Magnetic Resonance), TGA/ FTIR (Thermal Gravimetric Analysis / Fourier Transform Infrared), DSC (Differential Scanning Calorimeter), SEM (Scanning Electron Microscope), ESR (Electron Spin Resonance), GPC (Gel Permeation Chromatography), UV-Vis (UV-Visible Spectroscopy), Light Scattering and Elemental Analysis. Conducting and crosslinked polymers were characterized by FTIR, TGA/ FTIR, DSC, SEM, ESR, XRD (Powder Diffraction X-Ray) and Elemental Analysis. The effects of heating time, microwave energy and water content on the percent conversion and the polymer synthesis were also investigated.
7

Phase behaviour of random copolymers and crosslinked homopolymer blends / Phasenverhalten zufälliger Kopolymere und vernetzter Homopolymermischungen

Wald, Christian 08 November 2005 (has links)
No description available.
8

Heterogeneous epoxy-amine networks from the dispersion of cross-linked polymer microparticles / Réseaux époxy-amine hétérogènes à partir de dispersions de microparticules polymères réticulées

Michon, Marie-Laure 14 February 2014 (has links)
Lors de cette étude, il a été étudié l'influence de l'ajout de microparticules de polymère réticulé (CPM) dans des formulations d'époxy-amine, sur la cinétique, la morphologie et les propriétés thermo-mécaniques des réseaux finaux obtenus. Tout d'abord, un protocole simple, robuste et bien contrôlé a été développé afin d’ obtenir une large gamme de taille de CPM, de Tg et de fonctionnalité amine. Ce protocole de polymérisation par précipitation, basé sur les phénomènes de séparation de phases, a également été appliqué à différentes compositions chimiques et différents monomères époxy hydrosolubles, ceci montrant les grandes possibilités de cette méthode. Une bonne interface entre les CPMs et la matrice a été recherchée en synthétisant les CPMs en excès de groupes amines. La quantification de ces groupes amines réactifs sur les CPMS était d'un grand intérêt et a donc été étudiée en profondeur. Le titrage des amines de surface a été réalisé en mettant au point un nouveau protocole qui a permis la quantification des amines primaires et secondaires sur les CPMs. Il a ensuite été mis en évidence que, bien que ces microparticules réticulées ne soient pas poreuses, des fonctions amines sont disponibles au cœur des particules et peuvent réagir avec d'autres molécules qui sont capables de diffuser dans la CPM. Il a été montré que lorsque les CPM ont été dispersées dans des mélanges d'époxy- amine, la diffusion des monomères dans le cœur de la CPM s'est produite mais différemment selon le procédé de dispersion. En effet, en utilisant le tétrahydrofurane comme solvant pour aider à la dispersion, la diffusion de la DGEBA est amplifiée et modifie les propriétés thermo-mécaniques du réseau final en modifiant le rapport stœchiométrique de la matrice. Le même phénomène a été observé mais moins amplifié lorsque les microparticules sont uniquement dispersées mécaniquement. En dispersant les CPMs dans l'amine qui est l'agent réticulant, on observe l'absorption complète de l'amine au coeur des CPMs, conduisant ainsi à la désorption de celle-ci dans une deuxième étape, permettant de créer le réseau. Ainsi, un comportement très complexe des CPM a été mis en évidence en présence des monomères et/ou solvant : le gonflement et les phénomènes de diffusion qui dépendent d'un certain nombre de paramètres tels que la température, la densité de réticulation des CPM, les paramètres de solubilité, etc. L'intensité du phénomène de diffusion conduit à une variété de comportements lorsque les CPMs sont ajoutées dans une formulation d'époxy-amine tels que: (a) une légère diminution du temps de gélification et l'augmentation de la conversion, (b) la modification de la température de transition vitreuse de la matrice. / Throughout this work, the influence of the addition of cross-linked polymer microparticles (CPMs) in epoxy-amine formulations on the kinetics, morphology and thermo-mechanical properties of the final networks have been investigated. First, an easy, robust and well-controlled protocol was developed to obtain a large range of CPM size, Tg and amine functionality. This protocol based on reaction induced phase separation via precipitation polymerization was also applied to different chemistries and water soluble epoxy pre-polymers showing the large possibilities of this method. The capacity of obtaining a good compatibility between the CPMs and the matrix was ensure by synthesizing the CPMs in excess of amino groups. The study of the remaining reactive amino groups on the CPMS was of great interest and therefore deeply investigated. The titration of the surface amine was performed by developing a new protocol that enabled the quantification of primary and secondary amines on CPMs. It was then highlighted that even though these cross-linked microparticles were not porous, amino groups are available into the core and can react with other molecules that are able to diffuse into the CPM core. It was shown that when CPMs were dispersed into epoxy-amine blends, the diffusion of monomers into the CPM core occurred but differently depending on the dispersion process. Indeed, using tetrahydrofuran as solvent to help for the dispersion increased the diffusion of DGEBA into the CPM core and changed the thermo-mechanical properties of the final network by modifying the stoichiometric ratio of the matrix. Same phenomenon was observed but less amplified when CPMs were mechanically dispersed in DGEBA. Regarding the dispersion of CPMs in the amine cross-linker, IPD, its complete absorption could be observed into the CPMs, leading then to the desorption of IPD to create the network. Thus, a very complex behavior of CPMs was highlighted in presence of monomers or/and solvent: swelling and diffusion phenomena that are dependent on a number of parameters such as temperature, CPM cross-link density, solubility parameters, etc. The intensity of those phenomena leads to a variety of behaviors when CPMs are added into an epoxy-amine formulation: (a) slight decrease of gel times and increase of conversion, (b) modification of glass transition temperature of the matrix.

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