To see the other types of publications on this topic, follow the link: Particle polymerization.
Dissertations / Theses on the topic 'Particle polymerization'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Particle polymerization.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Leswin, Joost Sieger Kaspar. "Particle Formation in RAFT-mediated Emulsion Polymerization." University of Sydney, 2007. http://hdl.handle.net/2123/2176.
Full textAbstract:
Doctor of Philosophy(PhD)Particle formation in RAFT-mediated emulsion polymerization has been studied using reaction calorimetry. By measuring the heat flow during controlled feed ab-initio emulsion polymerization in the presence of amphipathic RAFT agents, particle formation by self-assembly of these species could be observed. Two different monomer systems, i.e. styrene and n-butyl acrylate, and various degrees of hydrophobicity of the initial macro-RAFT agents have been studied and compared. The different macro-RAFT agents were synthesized by first forming a hydrophilic block of poly(acrylic acid) that would later on act as the electrosteric stabilizing group for the particles. Subsequently, different lengths of hydrophobic blocks were grown at the reactive end of the poly(acrylic acid) hydrophilic block via the RAFT-mediated controlled radical polymerization, either comprised of n-butyl acrylate or styrene. Two processes govern particle formation: adsorption of macro-RAFT agents onto growing particles and formation of new particles by initiation of micellar aggregates or by homogeneous nucleation. Competition between these processes could be observed when monomers with a relatively high (n-butyl acrylate) or low (styrene) propagation rate coefficient were used. A model describing particle formation has been developed and the results of model calculations are compared with experimental observations. Preliminary modeling results based on a set of reasonable physico-chemical parameters already showed good agreement with the experimental results. Most parameters used have been verified experimentally. The development of the molecular weight distribution of the macro-RAFT agents has been analyzed by different techniques. Quantification of the particle formation process by analytical techniques was difficult, but qualitative insights into the fundamental steps governing the nucleation process have been obtained. The amount of macro-RAFT agents initially involved in particle formation could be determined from the increase of molecular weight. The particle size distribution has been measured by capillary hydrodynamic fractionation, transmission electron microscopy and dynamic light scattering. From the data obtained from these particle-sizing techniques, the number of particles during the reaction could be monitored, leading to an accurate estimate for the particle formation time. Upon implementation of the experimental data obtained for the surface active macro-RAFT systems, the model demonstrated to be very sensitive towards the “headgroup” area of the macro-RAFT species. Three nucleation cases based on the initial surface activity of the macro-RAFT species in the aqueous phase are proposed to explain the deviations from the assumptions of the nucleation model. Even though the macro-RAFT species have a narrow molecular weight distribution, they are nevertheless made up of a distribution of block lengths of polystyrene upon a distribution of block lengths of poly(acrylic acid). The resulting differences in initial surface activity are the most probable reason for the observed differences between model calculations and experimental results for the nucleation time and particle size distribution of the final latex product. With the procedure described above, latexes have been synthesized without using conventional surfactants and the mechanisms involved in the particle formation for these systems have been elucidated. The results of this work enable production of latex systems with well defined molecular mass distributions and narrow particle size distributions. Furthermore, the technique based on the application of amphipathic RAFT agents is promising for the production of complex polymeric materials in emulsion polymerization on a technical scale.
2
Gilmore, Cheryl Matthews. "Particle nucleation and growth in a polymerically stabilized emulsion polymerization system." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/11707.
Full text
3
Brunier, Barthélémy. "Modeling of Pickering Emulsion Polymerization." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10320/document.
Full textAbstract:
L’objectif du présent projet est de développer une méthodologie pour la modélisation fondamentale de procédés de polymérisation en émulsion sans tensioactif stabilisés par des particules inorganiques, dénommées "polymérisation en émulsion Pickering". La modélisation des systèmes de polymérisation en émulsion nécessite la modélisation de la distribution de taille des particules (PSD), qui est une propriété importante d'utilisation finale du latex. Cette PSD comprend des sous-modèles dédiés à la nucléation des particules, le transfert de masse entre les différentes phases (monomère, radicaux, stabilisant) et la coagulation des particules. Ces modèles devraient de préférence être validés expérimentalement de manière individuelle. La première partie principale du travail est consacrée à l'étude expérimentale. Cette partie peut être divisée en trois parties. La première partie décrit l'adsorption de particules inorganiques sur le polymère sans réaction. Une adsorption multicouche a été observée et l’isotherme B.E.T. a été capable de décrire cette adsorption. L'adsorption se révèle être plus importante pour une force ionique plus élevée. La dynamique d'adsorption semple être rapide et par conséquent le partage peut être considéré à l'équilibre pendant la polymérisation. La deuxième partie concerne l'étude de différents paramètres de réaction sur le nombre de particules et la vitesse de réaction dans des polymérisations ab initio. L'effet du mélange, de la concentration initiale des monomères et de la concentration de l'initiateur a été étudié. L'optimisation de ces conditions a été utile pour la partie de modélisation. La dernière partie décrit les différences entre plusieurs Laponite® à travers la polymérisation en émulsion ab initio du styrène.La deuxième partie principale du manuscrit a porté sur la modélisation de la polymérisation en émulsion Pickering. Le modèle de bilan de population et le nombre moyen de radicaux par particule ont été calculés en fonction de l'effet des particules organiques. La croissance des particules de polymère a été optimisée en ajustant les modèles d'entrée et de désorption des radicaux décrits dans la littérature aux données expérimentales. Aucune modification n'a été nécessaire, ce qui nous a permis de conclure que l'argile n'avait aucune influence sur l'échange radical. Cependant, la stabilisation joue un rôle important dans la production de particules de polymère. Le modèle de nucléation coagulante a été capable de décrire le taux de nucléation et de prédire le nombre total de particulesThe aim of the present project is to develop a methodology for fundamental modeling of surfactant-free emulsion polymerization processes stabilized by inorganic particles, referred to as “Pickering emulsion polymerization”. Modeling emulsion polymerization systems requires modeling the particle size distribution (PSD), which is an important end-use property of the latex. This PSD includes submodels dedicated to particle nucleation, mass transfer between the different phases (monomer, radicals, stabilizer), and particle coagulation. These models should preferably be individually identified and validated experimentally. The first main part of the work is dedicated to the experimental study. This part can be divided in three parts. The first part describes the adsorption of inorganic particles on polymer without reaction. Multilayer adsorption was observed and B.E.T. isotherm was able to describe this adsorption. The adsorption was found to be enhanced at higher ionic strength. The adsorption dynamics were found fast and therefore clay partitioning can be considered at equilibrium during polymerization. The second part concerned the investigation of different reaction parameters on the particles number and reaction rate in ab initio polymerizations. The effect of mixing, initial monomer concentration and initiator concentration were considered. Optimization of these conditions was useful for the modeling part. The last part described the differences between several LaponiteR_ grades through the ab initio emulsion polymerization of styrene. The second main part of the manuscript focused on the modeling of the Pickering emulsion polymerization. The population balance model and average number of radicals balance were adapted regarding the effect of inxi organic particles. The growth of the polymer particles was optimized by fitting the models of radicals’ entry and desorption described available in literature to the experimental data. No modification was needed, which allowed us to conclude that the clay had no influence on radical exchange. However, LaponiteR_ stabilization played an important role in polymer particles production. Coagulative nucleation model was able to describe the nucleation rate and predict the total number of particles
4
Roßner, Christian. "High-Precision Particle Arrangement in Gold‒Polymer-Nanocomposites using RAFT Polymerization." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://hdl.handle.net/11858/00-1735-0000-002B-7CAD-0.
Full text
5
Rodrigues, Jeffrey Collin. "Comparison of shear stability of mini and macroemulsion latexes with respect to particle size and number distribution." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/9136.
Full text
6
Godin, Alexandra [Verfasser]. "Particle formation and multiphase morphologies in catalytic aqueous ethylene polymerization / Alexandra Godin, geb. Tchernook." Konstanz : Bibliothek der Universität Konstanz, 2017. http://d-nb.info/113819610X/34.
Full text
7
Downey, Jeffrey S. "Precipitation polymerization of divinylbenzene to monodisperse microspheres : an investigation of the particle formation mechanism /." *McMaster only, 2000.
Find full text
8
Virtanen, Otto L. J. [Verfasser], Walter [Akademischer Betreuer] Richtering, and Sebastian [Akademischer Betreuer] Seiffert. "Insight into precipitation polymerization of N-isopropylacrylamide : reaction mechanism, particle formation and particle structure / Otto L. J. Virtanen ; Walter Richtering, Sebastian Seiffert." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130792501/34.
Full text
9
Rawlston, Jonathan A. "Multiscale modeling of free-radical polymerization kinetics." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33933.
Full textAbstract:
Polymer chain microstructure, including characteristics such as molecular weight and branch length, can impact the end-use properties of the polymer. The assumptions contained in deterministic models prevent examination of the structure of individual polymer chains, so removal of these assumptions is necessary to gain insight into molecular-level mechanisms that determine chain microstructure. The work presented here uses a combination of stochastic and deterministic models to examine two significant mechanistic issues in free radical polymerization. The zero-one assumption concerning the number of radicals is often made for miniemulsion polymerization using oil-soluble initiators because of accelerated termination due to radical confinement. Although most of the initiator is present inside the particles, opposing viewpoints exist as to whether the locus of radical generation is the particle phase or the aqueous phase. A well-mixed kinetic Monte Carlo (KMC) model is used to simulate the molecular weight distribution and the results are compared to estimated molecular weights for several chain-stopping events, with the finding that the dominant nucleation mechanism varies with reaction temperature and particle size. Intramolecular chain transfer to polymer, or backbiting, is often assumed to produce only short-chain branches. Using a lattice KMC model, a cumulative distribution function (CDF) is obtained for branch lengths produced by backbiting. Implementation of the CDF in both a rate-equation model and the well-mixed KMC model shows that, for the butyl acrylate solution polymerization system used for comparison, backbiting is responsible for most of the branches, including long-chain branches, even though overlap of the polymer coils in the solution is predicted, a condition which would normally be expected to lead to significant intermolecular chain transfer to polymer. The well-mixed KMC model provides a more thorough analysis of chain microstructure while the rate-equation model is more computationally efficient.
10
Rajabi-Hamane, Mehdi [Verfasser]. "Modeling, Validation and Time Optimal Control of Particle Size Distribution in Emulsion Polymerization / Mehdi Rajabi-Hamane." Aachen : Shaker, 2007. http://d-nb.info/1166511340/34.
Full text
11
Nazaran, Pantea. "Nucleation in emulsion polymerization : steps towards a non-micellar nucleation theory." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/1752/.
Full textAbstract:
For more than 70 years, understanding of the mechanism of particle nucleation in emulsion polymerization has been one of the most challenging issues in heterophase polymerization research.
Within this work a comprehensive experimental study of particle nucleation in emulsion polymerization of styrene at 70 °C and variety of conditions has been performed. To follow the onset of nucleation, on-line conductivity measurements were applied. This technique is highly sensitive to the mobility of conducting species and hence, it can be employed to follow aggregation processes leading to particle formation. On the other hand, by recording the optical transmission (turbidity) of the reaction mixture particle growth was followed. Complementary to the on-line investigations, off-line characterizations of the particle morphology and the molecular weight have been performed. The aim was to achieve a better insight in the processes taking place after starting the reaction via particle nucleation until formation of colloidally stable latex particles.
With this experimental protocol the initial period of styrene emulsion polymerization in the absence as well as in the presence of various surfactants (concentrations above and below the critical micellization concentration) and also in the presence of seed particles has been investigated. Ionic and non-ionic initiators (hydrophilic and hydrophobic types) have been applied to start the polymerizations.
Following the above algorithm, experimental evidence has been obtained showing the possibility of performing surfactant-free emulsion polymerization of styrene with oil-soluble initiators. The duration of the pre-nucleation period (that is the time between starting the polymerization and nucleation) can be precisely adjusted with the initiator hydrophobicity, the equilibration time of styrene in water, and the surfactant concentration. Spontaneous emulsification of monomer in water, as soon as both phases are brought into contact, is a key factor to explain the experimental results. The equilibration time of monomer in water as well as the type and concentration of other materials in water (surfactants, seed particles, etc.) control the formation rate and the size of the emulsified droplets and thus, have a strong influence on the particle nucleation and the particle morphology.
One of the main tasks was to investigate the effect of surfactant molecules and especially micelles on the nucleation mechanism. Experimental results revealed that in the presence of emulsifier micelles the conductivity pattern does not change essentially. This means that the presence of emulsifiers does not change the mechanism of particle formation qualitatively. However, surfactants assist in the nucleation process as they lower the activation free energy of particle formation. Contrary, seed particles influence particle nucleation, substantially. In the presence of seed particles above a critical volume fraction the formation of new particles can be suppressed. However, micelles and seed particles as absorbers exhibit a common behavior under conditions where monomer equilibration is not allowed.
Results prove that the nucleation mechanism comprises the initiation of water soluble oligomers in the aqueous phase followed by their aggregation. The process is heterogeneous in nature due to the presence of monomer droplets.Polymere dominieren unsere Welt. Die natürlich vorkommenden Polymeren, wie Proteine, Polynukleotide, und Polysaccharide, sind nötig um das Leben zu erhalten. Ebenso wichtig sind die kommerziell erhältlichen Makromoleküle. Beides sind Bausteine, um Materialien zu konstruieren, welche man in beiden Welten finden kann- der natürlichen und der „Mensch-gemachten“ Welt. Unter den verschiedenen Polymerisationsmethoden hat sich die Emulsions-polymerisation zu einem weit verbreiteten Prozess entwickelt. Die Emulsionspolymerisation ist ein einzigartiger Polymerisationsprozess, bei dem ein Monomer oder ein Gemisch von Monomeren in einem wässrigen Medium polymerisiert wird. Dabei entsteht eine Dispersion von Polymeren, welche auch als Latex bezeichnet wird. Derzeit werden mehrere Millionen Tonnen von synthetischen Latices mit Hilfe der Emulsionspolymerisation hergestellt. Diese finden zum Beispiel Verwendung als synthetische Gummi, Latexschaum, Latexfarben, Papierbeschichtungen und Klebstoffen. Außerdem findet man sie auch bei Spezialanwendungen, wie Diagnosetests, Pharmakotherapien und chromatographischen Trennmethoden. Trotz der Vielzahl von industriellen Anwendungen, sollten all jenen, die sich mit Emulsionspolymerisation beschäftigen, den wissenschaftlichen und technologischen Herausforderungen, die sich stellen, bewusst sein. Die wichtigsten Fragen beim Umgang mit der Emulsionspolymerisation beinhalten das Verständnis des Prozesses der Partikelbildung und des Partikelwachstums. Die vorliegende Dissertation beschäftigt sich mit der Frage der Keimbildungs-etappe in Emulsionspolymerisationen. Die Untersuchungen wurden mit Hilfe eines on-line Leitfähigkeitsmessverfahren sowie einigen off-line analytischen Experimenten durchgeführt. Basierend auf den klaren experimentellen Daten, wurde ein besserer Einblick in die tatsächlichen Zustände des Polymerisationssystems, von der Zeit der neu geboren Kerne bis zu endgültig stabilisierten Teilchen, gewonnen.
12
Chabrol, Virginie. "Functionalized latex particles as substrates for metal mediated radical polymerization." Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-01012004.
Full textAbstract:
Le sujet de cette thèse consiste à incorporer une couronne de polymère hydrophile à la surface de particules de latex par amorçage et croissance en utilisant la polymérisation radicalaire contrôlée par transfert d'atome induite par les métaux. Les particules de latex, obtenues par, polymérisation radicalaire en émulsion ont été fonctionnalisées avec un " inimère ", monomère comportant une fonction halogénée capable de jouer le rôle d'amorceur dans l'étape de greffage. Cette étape de greffage a ensuite été effectuée en présence de CuBr2, PMDETA et d'un métal à valence zéro tel que le cuivre, àtempérature ambiante à partir de latex non post-purifiés (présence de tensio-actif et d'amorceur résiduels et à taux de solide élevés). Au cours du processus, l(incorporation de l'inimère et de la couronne hydrophile a été vérifée par ToF-SIMS (time-of-light secondary ion mass spectrometry), par FTIR et par l'étude des propriétés colloïdales des latex greffés.
13
Druma, Calin. "A particle in cell formulation for extrusion of fluoropolymers." Ohio : Ohio University, 2003. http://www.ohiolink.edu/etd/view.cgi?ohiou1178048890.
Full text
14
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.
Full textAbstract:
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 macroamorceurWater-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
15
Roßner, Christian [Verfasser], Philipp [Akademischer Betreuer] [Gutachter] Vana, and Alec [Gutachter] Wodtke. "High-Precision Particle Arrangement in Gold‒Polymer-Nanocomposites using RAFT Polymerization / Christian Roßner ; Gutachter: Philipp Vana, Alec Wodtke ; Betreuer: Philipp Vana." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/114064193X/34.
Full text
16
Khan, Ikram Ullah. "Microfluidic-assisted synthesis and release properties of multi-domain polymer microparticles drug carriers." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF042/document.
Full textAbstract:
Les caractéristiques et les propriétés de libération de microparticules chargées de médicament dépendent de la nature des matériaux employés, des propriétés physicochimiques des microparticules, du choix de la méthode de production, et enfin des propriétés des molécules encapsulées. A l'inverse de la plupart des méthodes conventionnelles, les méthodes microfluidiques présentent l’avantage de bien mieux contrôler la génération de gouttelettes, leur taille et leur distribution de tailles. Ainsi des dispositifs microfluidiques à base de capillaires ont été développés pour obtenir des microbilles de polymère mais également des microparticules de type janus, coeur-écorce ou troyenne, toutes monodisperses en taille et chargées de médicament(s). Ces particules ont été produites à partir de solutions de monomère qui furent polymérisées par irradiations UV de telle sorte à garder intacte l'activité des molécules chargées. Ces dispositifs peuvent être assemblés dans un court laps de temps et un simple changement dans leur conception permet d’obtenir des morphologies de particules très différentes. Ces particules ont été développées dans le but de résoudre les problèmes rencontrés dans l’administration orale de médicaments. Par exemple les microbilles peuvent être utilisées pour délivrer des anti-inflammatoires non stéroïdiens de manière continue tandis que les particules Janus peuvent libérer, simultanément et sur le même site, deux principes actifs possédant des propriétés complètement différentes (solubilité, compatibilité) également de manière prolongée. Quant aux particules coeur-écorce, elles ont été conçues pour cibler la région du côlon de l'intestin humain, et y libérer simultanément deux médicaments. Les particules troyennes furent synthétisées à l’aide d’un procédé microfluidique semi-continu qui a permis une manipulation plus sécurisée des nanoparticules vectrices ainsi que la libération continue d’un médicament dans un liquide gastrique simulé. Chaque système a été entièrement caractérisé pour assurer l’invariance entre lots et la reproductibilité. En général, la libération des ingrédients actifs a pu être facilement contrôlée/ajustée par le réglage des paramètres opératoires et de matériaux tels que les débits des différentes phases, la nature et la concentration du médicament, des (co)monomères, des agents tensioactif et de réticulation, le pH du milieu de libération. Ces différents paramètres influencent les propriétés des microparticules telles que leur morphologie, forme, taille et densité de réticulation du réseau polymèreCharacteristics and release properties of drug loaded microparticles depend upon material used and choice of production method. Conversely to most of the conventional ones, microfluidic methods give an edge by improving the control over droplet generation, size and size distribution. Capillary-based microfluidic devices were successfully used to obtain monodisperse drug(s) loaded microbeads, janus, core-shell and trojan particles using UV initiated free radical polymerization while keeping activity of active loaded molecules. These devices can be assembled in a short period of time and a slight change in design gives completely different microparticles morphologies. These particles were developed with the aim to address different issues experienced in oral drug delivery. For instance microbeads can be used to deliver NASIDs in a sustained release manner while janus particles can release two APIs with completely different properties (solubility, compatibility) also in a sustained release manner. Core-shell particles were designed to target colonic region of human intestine for dual drug delivery. Trojan particles were synthesized in a new semi-continuous microfluidic process, thus improving nanoparticles safety handling and release in simulated gastric fluid. Each system was fully characterized to insure batch to batch consistency and reproducibility. In general, the release of active ingredients was controlled by tuning the operating and material parameters like phases flow rates, nature and concentration of drug, (co)monomers, surfactant and crosslinker, pH of release media with the result of different particle morphologies, sizes and shapes or matrix crosslinking density
17
Hunt, Paul Edward. "Protective colloids : understanding nucleation and grafting." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/protective-colloids-understanding-nucleation-and-grafting(a5f5c8c9-acc7-492b-bf81-3cf327af98cf).html.
Full textAbstract:
Alkali-soluble resins (ASRs) were prepared by (i) solution and (ii) emulsion polymerization. All ASRs were synthesized with number-average molar masses < 20,000 g mol-1 and all had 15 wt% methacrylic acid 5 wt% styrene, the remaining 80 wt% was composed of either methyl methacrylate or a combination of methyl methacrylate and ethyl acrylate. All emulsion ASRs were made to 20% solids, with volume-average particle diameters (dv) in the region 30 – 50 nm, with a glass transition temperature of 80 – 120 °C. Emulsion polymerization was the preferred route for ASR synthesis, to allow further studies on their dissolution behaviour. Before their use as colloidal stabilizers, the dissolution behaviour of the ASRs needed to beinvestigated e.g. effect of temperature, molar mass, and composition. Particle size and absorbance measurements were taken during dissolution of ASRs to achieve 100%neutralization and these were shown to have two stages, an apparent particle swelling (whichwas rapid), and a slower, decrease in particle size as water-soluble polymeric material wasdiffusing out of the ASR particles. From this, further interpretation allowed for calculating the diffusion coefficient of the ASR polymer using the Stokes-Einstein equation. Time-domain nuclear magnetic resonance (TD-NMR) was employed to enhance understanding of what is occurring in the ASR particles, and in the aqueous, continuous phase. The final aspect of this project was to use the ASRs prepared as colloidal stabilizers in emulsion polymerizations of butyl acrylate (BA) and butyl methacrylate (BMA) using varying levels and also the effect of adding additional surfactant. The results show that the effect of ASR molar mass, the concentration of stabilizer, and also the impact of the EA-containing ASR greatly influence stability, whereby lower ASR molar mass, higher levels of stabilizer and including EA greatly benefit colloidal stability in PBA latexes. In PBMA latexes, a similar trend was also observed, but, the presence of ethyl acrylate (EA) in the ASR backbone has a detrimental effect on the colloidal stability, caused by the inability of grafting to occur between the ASR and PBMA.
18
Clarke, Stephen Armour. "Modeling & optimisation of coarse multi-vesiculated particles." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20242.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Multi-vesiculated particles (MVP) are synthetic insoluble polymeric particles containing a multitude of vesicles (micro-voids). The particles are generally produced and used as a suspension in an aqueous fluid and are therefore readily incorporated in latex paints as opacifiers. The coarse or suede MVP have a large volume-mean diameter (VMD) generally in the range of 35-60μm, the large VMD makes them suitable for textured effect paints. The general principle behind the MVP technology is as the particles dry, the vesicles drain of liquid and fill with air. The large refractive index difference between the polymer shell and air result in the scattering of incident light which give the MVP their white opaque appearance making them suitable as an opacifier for the partial replacement of TiO2 in coating systems. Whilst the coarse MVP have been successfully commercialized, insufficient understanding of the influence of the MVP system parameters on the final MVP product characteristics coupled with the MVP’s sensitivity towards the unsaturated polyester resin (UPR) resulted in a product with significant quality variation. On the other hand these uncertainties provided the opportunity to model and optimise the MVP system through developing a better understanding of the influence of the MVP system parameters on the MVP product characteristics, developing a model to mathematically describe these relationships and to optimise the MVP system to achieve the product specifications whilst simultaneously minimising the variation observed in the product characteristics. The primary MVP characteristics for this study were the particle size distribution (quantified by the volume-mean diameter (VMD)) and the reactor buildup.1 The approach taken was to analyse the system determining all possible system factors that may affect it, and then to reduce the total number of system factors by selecting those which have a significant influence on the characteristics of interest. A model was then developed to mathematically describe the relationship between these significant factors and the characteristics of interest. This was done utilising a set of statistical methods known as design of experiments (DoE). A screening DoE was conducted on the identified system factors reducing them to a subset of factors which had a significant effect on the VMD & buildup. The UPR was characterised by its acid value and viscosity and in combination with the identified significant factors a response surface model (RSM) was developed for the chosen design space, mathematically describing their relationship with the MVP characteristics. Utilising a DoE method known as robust parameter design (specifically propagation of error) an optimised MVP system was numerically determined which brought the MVP product within specification and simultaneously reduced the MVP’s sensitivity to the UPR. The validation of the response surface model indicated that the average error in the VMD prediction was 2.16μm (5.16%) which compared well to the 1.96μm standard deviation of replication batches. The high Pred-R2 value of 0.839 and the low validation error indicates that the model is well suited for predicting the VMD characteristic of the MVP system. The application of propagation of error to the model during optimisation resulted in a MVP process and formulation which brought the VMD response from the standard’s average of 44.56μm to the optimised system’s average of 47.84μm which was significantly closer to the desired optimal of 47.5μm. The most notable value added to the system by the propagation of error technique was the reduction in the variation around the mean of the VMD, due to the UPR, by over 30%1 from the standard to optimised MVP system. In addition to the statistical model, dimensional analysis, (specifically Buckingham-Π method) was applied to the MVP system to develop a semi-empirical dimensionless model for the VMD. The model parameters were regressed from the experimental data obtained from the DoE and the model was compared to several models sited in literature. The dimensionless model was not ideal for predicting the VMD as indicated by the R2 value of 0.59 and the high average error of 21.25%. However it described the VMD better than any of the models cited in literature, many of which had negative R2 values and were therefore not suitable for modelling the MVP system.
AFRIKAANSE OPSOMMING: Sintetiese polimeer partikels wat veeltallige lugblasies huisves en omhul, staan beter bekend as MVP (verkort vanaf die Engelse benaming, "multi-vesiculated particles"). Tipies word hierdie partikels berei en gestabiliseer in 'n waterige suspensie wat dit mengbaar maak met konvensionele emulsie sisteme en dit dus in staat stel om te funksioneer as 'n dekmiddel in verf. Deur die volume gemiddelde deursnee (VGD) te manipuleer tot tussen 35 en 60μm, word die growwe partikels geskik vir gebruik in tekstuur verwe, soos byvoorbeeld afwerkings met 'n handskoenleer (suède) tipe tekstuur. Die dekvermoë van MVP ontstaan soos die partikels droog en die water in die polimeer partikel vervang word met lug. As gevolg van die groot verskil in brekingsindeks tussen die polimeer huls en die lugblasies, word lig verstrooi in alle rigtings wat daartoe lei dat die partikels wit vertoon. Dus kan die produk gebruik word om anorganiese pigmente soos TiO2 gedeeltelik te vervang in verf. Alhoewel growwe MVP al suksesvol gekommersialiseer is, bestaan daar nog net 'n beperkte kennis oor die invloed van sisteem veranderlikes op die karakteristieke eienskappe van die finale produk. Dit volg onder andere uit waarnemings dat die kwaliteit van die growwe MVP baie maklik beïnvloed word deur onbekende variasies in die reaktiewe poliëster hars wat gebruik word om die partikels te maak. Dit het egter die geleentheid geskep om die veranderlikes deeglik te modeleer en te optimiseer om sodoende 'n beter begrip te kry van hoe eienskappe geaffekteer word. 'n Wetenskaplike model is opgestel om verwantskappe te illustreer en om die sisteem te optimiseer sodat daar aan produk spesifikasies voldoen word, terwyl produk variasies minimaal bly. Die oorheersende doel in hierdie studie was om te fokus op partikelgrootte en verspreiding (bepaal met behulp van die VGD) as primêre karakteristieke eienskap, asook die graad van aanpaksel op die reaktorwand gedurende produksie. Vanuit eerste beginsel is alle moontlike veranderlikes geanaliseer, waarna die hoeveelheid verminder is na slegs dié wat die karakteristieke eienskap die meeste beïnvloed. Deur gebruik te maak van eksperimentele ontwerp is die wetenskaplike model ontwikkel wat die effek van hierdie eienskappe statisties omsluit. 'n Afskerms eksperimentele ontwerp is uitgevoer om onbeduidende veranderlikes te elimineer van dié wat meer betekenisvol is. Die hars is gekaraktiseer met 'n getal wat gebruik word om die aantal suur groepe per molekuul aan te dui, asook die hars se viskositeit. Hierdie twee eienskappe, tesame met ander belangrike eienskappe is gebruik om 'n karakteristieke oppervlakte model te ontwikkel wat hul invloed op die VGD van die partikels en reaktor aanpakking beskryf. Deur gebruik te maak van 'n robuuste ontwerp, beter beskryf as 'n fout verspreidingsmodel, is die MVP sisteem numeries geoptimiseer. Dit het tot gevolg dat die MVP binne spesifikasie bly en die VGD se sensitiwiteit vir variasie in die hars verminder het. Geldigheidstoetse op die oppervlakte model het aangetoon dat die gemiddelde fout in VGD 2.16μm (5.16%) was. Dit is stem goed ooreen met die 1.96μm standaard afwyking tussen herhaalde lopies. Hoë Pred-R2 waardes (0.839) en lae geldigheidsfout waardes het getoon dat die voorgestelde model die VGD eienskappe uiters goed beskryf. Toepassing van die fout verspreidingsmodel gedurende optimisering het tot gevolg dat die VGD vanaf die standaard gemiddelde van 44.56μm verskuif het na die geoptimiseerde gemiddelde van 47.84μm. Dit is aansienlik nader aan die verlangde optimum waarde van 47.5μm. Die grootste waarde wat toegevoeg is na afloop van hierdie studie, is dat die afwyking rondom die gemiddelde VGD, toegeskryf aan die eienskappe van die hars, verminder het met oor die 30%1 (vanaf die standaard tot die optimiseerde sisteem). Verdere dimensionele analise van die sisteem deur spesifiek gebruik te maak van die Buckingham-Π metode het gelei tot die ontwikkeling van 'n semi-empiriese dimensielose VGD model. Regressie op eksperimentele data verkry uit die eksperimentele ontwerp is vergelyk met verskeie modelle beskryf in ander literatuur bronne. Hierdie dimensionele model was nie ideaal om die VGD te beskryf nie, aangesien die R2 waarde 0.59 was en die gemiddelde fout van 21.25% relatief hoog was. Nietemin, hierdie model beskryf die VGD beter as enige ander model voorgestel in die literatuur. In talle gevalle is negatiewe R2 waardes verkry, wat hierdie literatuur modelle geheel en al ongeskik maak vir toepassing in die MVP sisteem.
19
Silva, Wandeklébio Kennedy da. "Monitoramento em linha e em tempo real do diâmetro médio das partículas e dos teores de não voláteis e monômero durante a polimerização em emulsão usando espectroscopia NIR." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-14082009-171518/.
Full textAbstract:
A técnica de polimerização em emulsão tem sido usada cada vez mais na indústria de tintas, resinas, plásticos, entre outros. Esse crescimento se deve as razões ambientais (uma vez que se utiliza água como fase contínua desta reação), também a versatilidade e a capacidade de produzir látex com diferentes propriedades para diferentes aplicações. Polímeros em emulsão são produtos por processo, isto é, suas propriedades são definidas durante a polimerização. Por isso, é importante o adequado monitoramento da reação de modo a permitir o controle das propriedades desejadas. A técnica de espectroscopia na região do infravermelho próximo (NIR), combinada com o uso de fibras óticas, é muito promissora para o monitoramento multivariável, em linha e em tempo real do processo de polimerização. O objetivo deste trabalho foi o de estudar o uso de espectroscopia NIR para o monitoramento em linha e em tempo real das concentrações de monômero e de não- voláteis (conhecido também como teor de sólidos) e da evolução do tamanho médio das partículas de látex (Dp) durante a reação de polimerização em emulsão de metacrilato de metila (MMA), em escala de laboratório e processo semi-batelada. Os modelos de calibração para estas variáveis foram obtidos experimentalmente empregando o método de regressão por mínimos quadrados parciais, PLS. Os resultados obtidos confirmaram algumas regiões espectrais do NIR indicadas em literatura como sendo adequadas na predição de monômero e Dp e revelaram -1 comportamentos espectrais ainda não explicados na região entre 10.475 e 13.000 cm , relacionados às variações no tamanho das partículas. Os resultados mostram também que é possível monitorar em linha e em tempo real a evolução do Dp e dos teores de monômero (MMA) e de não voláteis, simultaneamente em um único instrumento, utilizando modelos de calibração com bandas espectrais e pré-tratamentos distintos.Emulsion polymerization is a largely and increasingly used technique in industrial production of paints, resins, plastics among others. This increase is due to environmental reasons (since water, rather than organic solvents is used as dispersing medium), as well as to the versatility and capacity of producing products with different properties for different applications. Emulsion polymers are products by process, i.e., the properties are mainly defined during the polymerization process. Thus, the adequate process monitoring is important for achieving the target properties. The NIR spectroscopy combined with optical fibers is a promising technique for the task of multivariable, real-time, in-line monitoring of polymerization processes. The aim of this work is the study of use of NIR spectroscopy for in-line, real time monitoring of the monomer and solids content, as well as the evolution of average size of the polymer particles (Dp), during semi-batch emulsion polymerization of methyl methacrylate in laboratory reactor. The calibration models for each of the monitored variables were obtained by applying the partial least squares regression method (PLS). The results confirmed that some NIR spectral ranges recommended in the literature are appropriate for the prediction of monomer content and Dp, and that there are spectral -1 . The results behaviors not yet explained in the region between 10475 and 13000cm also show that the in-line, the changes in Dp, monomer and polymer content can be simultaneously monitored in-line and in real time by NIR spectroscopy by using calibration models based on adequate spectral regions and distinct data pretreatments.
20
Kozempel, Steffen. "Emulgatorfreie Emulsionspolymerisation : Monomerlösungszustand und Teilchenbildung." Phd thesis, Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2005/610/.
Full textAbstract:
Polymere sind zweifelsohne der Werkstoff in unserer Zeit. Ein bedeutender Anteil der heute industriell produzierten Polymere wird durch Emulsionspolymerisation hergestellt. Obwohl die Emulsionspolymerisation breite Anwendung findet, sind die involvierten Mechanismen von Teilchenbildung und -wachstum noch heute Gegenstand heftiger Kontroversen.Ein Spezialfall der Emulsionspolymerisation ist die emulgatorfreie Emulsionspolymerisation. Hierbei handelt es sich um ein scheinbar einfacheres System der Emulsionspolymerisation, weil diese Methode ohne Zusatz von Emulgatoren auskommt.
Die Teilchenbildung ist ein fundamentaler Vorgang im Verlauf der Emulsionspolymerisation, da sie zur Ausbildung der polymeren Latexphase führt. Detaillierte Kenntnisse zum Mechanismus der Nukleierung ermöglichen eine bessere Kontrolle des Reaktionsverlaufes und damit der Eigenschaften des Endproduktes der Emulsionspolymerisation, dem Polymer-Latex.
Wie bereits vorangegangene Arbeiten auf dem Gebiet der emulgatorfreien Emulsionspolymerisation von Styrol sowie Methylmethacrylat und Vinylacetat zeigen konnten, verläuft die Teilchenbildung in diesen Systemen über den Mechanismus der aggregativen Nukleierung. Im Zusammenhang mit den Ergebnissen der genannten Arbeiten tauchte dabei immer wieder ein interessanter Effekt im Bereich der Partikelnukleierung auf. Dieses als JUMBO-Effekt bezeichnete Phänomen zeigte sich reproduzierbar in einem Anstieg der Transmission im Bereich der Teilchenbildung von emulgatorfreien Emulsionspolymerisationen von Styrol, MMA und VAc. Nach der Initiierung der Polymerisation in einer wässrigen Monomerlösung durch Kaliumperoxodisulfat steigt die Durchlässigkeit bei 546 nm auf über 100 % an. Für diese „Abnahme der optischen Dichte“ wurden verschiedene Erklärungsmöglichkeiten vorgeschlagen, jedoch blieb ein Nachweis der Ursache für den JUMBO-Effekt bisher aus. Dieser Mangel an Aufklärung eines offenbar grundlegenden Phänomens in der emulgatorfreien Emulsionspolymerisation bildet den „Nukleus“ für die vorlie¬gende Arbeit.
Durch die vorliegende Dissertation konnte das Verständnis für Phänomene der Teilchenbildung in der emulgatorfreien Emulsionspolymerisation von Styrol mit KPS erweitert werden. In diesem Rahmen wurde das Online-Monitoring des Polymerisationsvorganges verbessert und um verschiedene Methoden erweitert:
Zur simultanen Erfassung von Trübungsdaten bei verschiedenen Wellenlängen konnte ein modernes Spektrometer in Kombination mit einer Lichtleitersonde in die Reaktionsapparatur integriert werden.
Es wurde ein verbesserter Algorithmus zur Datenbearbeitung für die Partikelgrößenbestimmung mittels faseroptischer dynamischer Lichtstreuung entwickelt.
Es wurden Online-Partikelgrößenanalysen mittels statischer Vielwinkellichtstreuung bei Polymerisationen direkt in entsprechenden Lichtstreuküvetten durchgeführt.
Diese zur Beschreibung des untersuchten Systems eingeführten Methoden sowie ein zeitlich vollständiges Monitoring des gesamten Polymerisationsverlaufes, beginnend mit der Zugabe von Monomer zu Wasser, führten zu neuen Erkenntnissen zur emulgatorfreien Emulsionspolymerisation.
Es wurden große Monomeraggregate, die sog. Nanotröpfchen, in wässriger Lösung (emulgatorfrei) nachgewiesen. Diese Aggregate bilden sich spontan und treten verstärkt in entgastem Wasser auf.
Die Existenz von Nanotröpfchen in Verbindung mit Trübungs- und gaschromatografischen Messungen lässt auf eine molekular gelöste „Wirkkonzentration“ von Styrol in Wasser schließen, die bedeutend geringer ist als die absolute Sättigungskonzentration.
Es konnten Hinweise auf eine Reaktion höherer Ordnung im System Wasser/Styrol/KPS gefunden werden.
Es konnte gezeigt werden, dass eine präzise Einstellung der Nukleierungsdauer über die Zeit der Equilibrierung von Wasser mit Styrol möglich ist.
Der JUMBO-Effekt, dem in dieser Arbeit ein besonderes Interesse galt, konnte in gewisser Weise entmystifiziert werden. Es konnte gezeigt werden, dass die Durchlässigkeit der Reaktionsmischung bereits beim Lösen von Styrol in Wasser durch Bildung von Styrolaggregaten abnimmt. Der darauf folgende kurzzeitige Transmissionsanstieg im Zusammenhang mit der Nukleierung erreicht dabei nicht mehr 100 % des Referenzwertes von reinem Wasser. Alle experimentellen Daten sprechen für die Nanotröpfchen als Ursache des JUMBO-Effekts.
Wie die Ergebnisse dieser Arbeit zeigen, ist selbst das relativ „einfache“ System der emulgatorfreien Emulsionspolymerisation komplizierter als angenommen. Die Existenz von großen Styrolaggregaten in wässriger Lösung erfordert eine neue Betrachtungsweise des Reaktionssystems, in die auch der Lösungszustand des Monomers mit einbezogen werden muss.
Polymers are doubtless the material of today. Large amounts of industrially produced polymers are made via emulsion polymerization. Although emulsion polymerization is widely used commercially, the mechanisms of particle formation and -growth involved are still intensely controversial.
A special case of the emulsion polymerization is the emulsifier-free emulsion polymerization. This apparently easier procedure is performed without addition of emulsifier.
Particle formation is a fundamental event in the progression of emulsion polymerization because it leads to the formation of a polymeric latex phase. Explicit knowledge concerning the mechanism of nucleation facilitates better control of the reaction process and therefore of the properties of the final polymeric latex product.
Other contributions in emulsifier-free emulsion polymerization of styrene could already proof that particle formation in the present system proceeds via aggregative nucleation. In the context of the results of these contributions, an interesting effect was always detected in the time range of particle nucleation. This so-called “JUMBO-effect” appeared highly reproducible as an increase of transmittance during nucleation period in the emulsifier-free emulsion polymerization of styrene. After initiation of the polymerization in an aqueous monomer solution with potassiumperoxodisulfate the transmittance at 546 nm increases to more than 100 %. For this “decrease in optical density” various possible explanations have been suggested, but a proof for any of them is still to be found. This lack of insight into an apparently fundamental phenomenon in emulsifier-free emulsion polymerization arises as the “nucleus” of the present thesis.
Within this work the understanding of the phenomena of particle formation in emulsifier-free emulsion polymerization of styrene with potassiumperoxodisulfate could be enhanced. In this frame the online monitoring of the polymerization process could be improved and expanded to several methods:
For the simultaneous recording of UV-spectra respectively turbidity data at various wavelengths a modern spectrometer in combination with a fibre optical probe could be integrated into the reaction vessel.
An improved algorithm for data treatment of particle size determination via fibre optical dynamic light scattering was developed.
We implemented online particle size determinations via multi angle laser light scattering directly in light scattering cuvettes.
These newly introduced methods, in combination with temporally complete monitoring of the whole polymerization progression, starting with the addition of monomer to water, lead to novel insight into emulsifier-free emulsion polymerization of styrene:
Big monomer aggregates, so called “nano droplets”, could be detected in an aqueous solution of styrene. These aggregates form spontaneously and appear especially in degassed water. Polymerisation as the origin of the nano droplets can be excluded.
In context with turbidity and gas chromatographic measurements, the existence of nano droplets leads us to conclude that there is a molecularly dissolved “effective” concentration of styrene in water which is much lower than the absolute concentration reported in the literature.
We could find some hints for a higher reaction order in the system water/styrene/potassiumpersulfate. The induced decomposition of the peroxodisulfate ion in the presence of styrene and ethylbenzene shows an additional reaction of the initiator with aromatic compounds besides the thermolytical cleavage.
Furthermore it could be shown that it is possible to precisely adjust the duration of nucleation with the solubilisation time of styrene in water. This kind of control can be useful for other applications.
The JUMBO-effect, which was a major topic of this thesis, could be partly de-mystified. It could be shown that the turbidity of the reaction mixture already increases during the dissolution process of styrene due to the formation of aggregates. The turbidity decrease which is depicted by the JUMBO-effect in the time range of nucleation never reaches 100 % of the reference water. An interference of the used measuring wavelength with the domain size of density fluctuations according to the theory of spinodal decomposition could not be verified. The experimental data suggest rather the nano droplets as origin of the JUMBO-effect.
The results of the present thesis show clearly that the relatively “simple” system of the emulsifier-free emulsion polymerisation (water/styrene/potassiumpersulfate) is more complex than expected. The existence of big styrene aggregates in aqueous solution requires a new approach of the reaction system, which also includes the solution state of the monomer.
21
Sun, Wen. "A study of interacting stochastic networks : large scale, long time behavior and fluctuations, with applications in communication networks and protein polymerization." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS075.
Full textAbstract:
Ce document est consacré aux analyses de grands réseaux stochastiques utilisés pour étudier des réseaux de communication et ainsi que certains phénomènes biologiques. La première partie se compose de trois modèles pour évaluer l’efficacité des algorithmes de duplication et de placement dans les grands systèmes distribués. Au chapitre 2, la dynamique du système est décrite l’aide de la mesure empirique associée à un processus de transient multidimensionnel. Une étude détaillée de ces processus est effectuée sur plusieurs échelles de temps rapides. Des principes de moyenne stochastique avec plusieurs échelles de temps sont étudiées. Aux chapitres 3 et 4, les interactions considérées peuvent avoir des tailles de saut illimitées et se produire dans un ensemble aléatoire fini de nœuds. Le processus de la mesure empirique associé n’ayant pas d’équations d’évolution simples, nous développons une analyse de champ moyen spécifique pour étudier ces systèmes. Le comportement en temps long des processus de diffusions non linéaires correspondants est aussi analysé. La deuxième partie présente deux modèles pour étudier la variabilité dans les modèles de polymérisation. Dans le chapitre 5, nous étudions les processus de polymérisation et de fragmentation avec l’hypothèse d’un noyau critique pour la taille des polymères. Notre résultat montre que ces modèles semblent donner une explication raisonnable de la transition de phase courte du phénomène de polymérisation, et surtout de la grande variabilité de l’instant de transition, qui ont été observés dans de nombreuses expériences. Au chapitre 6, nous proposons un théorème de limite centrale fonctionnelle dans le modèle de Becker-DöringThis PhD document is devoted to the analyses of large stochastic networks used to study mathematical models in communication networks and in biology. The first part consists of the analysis of three models used to evaluate the efficiency of duplication and placement algorithms in large distributed systems. These models are represented by large stochastic networks under different scaling regimes assumptions. In Chapter 2, the dynamic of the system can be described with the empirical measure associated to a multi-dimensional transient Markov process. We provide a detailed study of these processes on several fast time scales. Stochastic averaging principles with multiple time scales are investigated in particular. In Chapter 3 and Chapter 4, the interactions have unbounded jump sizes and occur within a limited random set of nodes. We develop a convenient mean field analysis in despite that the associated empirical measures do not have autonomous evolution equations. We also study the long time behavior of the corresponding limiting nonlinear jump diffusions. The second part analyzes two models used to study the variability in the polymerization phenomena occurring in a biological context. In Chapter 5, we investigate the polymerization and fragmentation processes with an assumption of critical nucleus size. A scaling analysis of these stochastic models show that the sharp phase transition and, especially the large variance, observed in the experiments can be explained by these models. In Chapter 6, we provide a functional central limit theorem in the classical (infinite dimensional) stochastic Becker-Döring model
22
Storms, William Kenneth. "Polymeric Amphiphilic Nanoparticles Via Intramolecular Chain Collapse Using 1-Functionalized Vinylbenzocyclobutenes." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1436548338.
Full text
23
Youssef, Itab. "Polymérisation en émulsion et en miniémulsion. Influence de la combinaison de stabilisants moléculaires et macromoléculaires et suivi en situ par spectroscopie Raman." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0191/document.
Full textAbstract:
Cette thèse a pour objet la comparaison des procèdes de polymérisation en émulsion et en miniémulsion. L'influence de la combinaison de stabilisants moléculaires et macromoléculaires sur la cinétique réactionnelle et la distribution de tailles de particules sont les critères pertinents dans notre étude. Un stabilisant polymère, le poly (alcool vinylique-co-acétate de vinyle) (PVA), a été synthétisé avec différents taux d'hydrolyse par saponification directe du polyacétate de vinyle. Le taux d'hydrolyse de ce copolymère a été caractérisé par la Résonance Magnétique Nucléaire du proton (RMN 1H). Puis, nous avons étudié l'influence de la composition d'un mélange stabilisant [copolymères poly (alcool vinylique-co-acétate de vinyle) (PVA)/laurylsulfate de sodium (SDS)] et en particulier le taux d'hydrolyse du PVA. La présence de complexe (PVA/SDS) influence légèrement la cinétique de polymérisation. Par contre la capacité des complexes à stabiliser les particules de latex final dépend du taux d'hydrolyse du PVA, plus ce dernier est faible, plus l'agrégation est importante. Enfin, nous avons suivi en ligne par spectroscopie Raman des polymérisations en émulsion et en miniémulsion du styrène. Une exploitation du spectre a été réalisée et a permis d'attribuer les différents pics aux vibrations de certaines liaisons. La consommation du monomère et l'apparition du polymère a pu être suivi tout au long de la polymérisationThe aim of this work is to compare processes of emulsion and miniemulsion polymerization. The influence of the combination of molecular and macromolecular stabilizers on the reaction kinetics and particle size distribution are relevant factors in our study. A stabilizer polymer, poly (vinyl alcohol-co-vinyl acetate) (PVA), was synthesized with different degrees of hydrolysis by a direct saponification of polyvinyl acetate. The degree of hydrolysis of this copolymer was characterized by Nuclear Magnetic Resonance (1H NMR). Then, we studied the influence of the composition of a mixture stabilizer [poly (vinyl alcohol-co-vinyl acetate) (PVA)/sodium lauryl sulfate (SDS)], and particulary the degree of hydrolysis of PVA. The presence of complex (PVA/SDS) influences slightly the kinetic of polymerization. The ability of the complexes to stabilize the particles of latex depends on the degree of hydrolysis of PVA, the lower it is, the more the aggregation is important. Finally, we followed in situ emulsion and miniemulsion polymerizations of styrene by Raman spectroscopy. The exploitation of the spectrum allowed us to assign the different peaks to vibrations of certain bands. The consumption of the monomer and the appearance of the polymer could be followed throughout the polymerization
24
Garnier, Jérôme. "Elaboration de latex nanostructurés à base de poly(chlorure de vinylidène) par polymérisation en émulsion." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2012. http://www.theses.fr/2012ENCM0011.
Full textAbstract:
Les emballages alimentaires et pharmaceutiques doivent de nos jours répondre à de nombreux critères : ils doivent non seulement préserver le produit emballé, mais également être inoffensifs, économes en énergie et jetables. Les polymères barrières ont permis de répondre à ces besoins, en offrant des alternatives à des matériaux plus demandeurs en énergie et plus lourds tels que le verre ou les métaux, tout en conservant une faible perméabilité à l’eau et/ou à l’oxygène. Parmi la grande variété de polymères barrières existants, les copolymères du poly(chlorure de vinylidène) (PVDC) offrent une protection plus complète aux contaminants extérieurs, grâce à leurs faibles perméabilités à l’eau et à l’oxygène. Cependant, les films de PVDC sont sujets à des processus de dégradation ayant lieu lors du thermoformage ou sous exposition aux rayonnements UV. Ces effets sont encore plus prononcés dans le cas de films obtenus à partir de latex, dû à des quantités plus importantes d’additifs qui accentueraient les phénomènes de dégradation du polymère. Par conséquent, la synthèse de latex à base de PVDC pour des applications en tant que films barrières aux stabilités thermique et UV améliorées revêt un grand intérêt. Des latex composites à base de PVDC ont tout d’abord été synthétisés en présence de latex semences à fonctionnalité époxy en vue d’améliorer la stabilité thermique du polymère. En effet, les groupements époxy jouent le rôle de stabilisants thermiques en piégeant le chlorure d’hydrogène, dégagé lors du thermoformage et présentant un effet catalytique indirect sur le processus de dégradation du polymère. Dans une première étape, des latex semences à fonctionnalité époxy ont été synthétisés par copolymérisation en émulsion du methacrylate de glycidyle (GMA) et du methacrylate de butyle (BMA). Lors d’une seconde étape, la copolymérisation en émulsion ensemencée du chlorure de vinylidene et de l’acrylate de méthyle a été effectuée en présence des semences de poly(GMA-co-BMA). Des analyses thermogravimétriques effectuées sur les échantillons composites ont mis en évidence le rôle de stabilisant thermique joué par les fonctions époxy. La seconde partie du projet concerne la synthèse de latex hybrides à base d’oxyde de cérium (CeO2) afin d’améliorer la résistance du PVDC aux rayonnements UV. Les nanoparticules d’oxyde de cérium sont en effet attrayantes en tant que stabilisants UV en raison de leur haute absorption des rayonnements UV et d'une faible activité photocatalytique. Cependant, étant donné l’incompatibilité intrinsèque entre les phases inorganique et organique, la synthèse de latex hybrides requiert souvent une étape préliminaire de modification de surface des particules minérales. Le greffage d’alcoxysilanes a d’abord été entrepris sur des particules d’oxyde de cérium afin d’encourager la réaction de polymérisation à leur surface. Des observations par cryo-Microscopie Electronique à Transmission (cryo-MET) effectuées sur les latex hybrides obtenus par cette stratégie ont montré que le greffage d’alcoxysilanes ne permettait pas d’améliorer efficacement la compatibilité entre les phases inorganique et polymère. Enfin, des macro-agents RAFT amphiphatiques ont été employés comme agents comptabilisant réactifs afin de promouvoir la réaction de polymérisation à la surface de l’oxyde de cérium. Des oligomères RAFT ont été obtenus par des réactions de co- ou terpolymérisation en présence d’un agent de contrôle RAFT. Après caractérisation de l’adsorption des macro-agents RAFT à la surface de l’oxyde de cérium, les particules modifiées ont été utilisées dans des réactions de polymérisation en émulsion. Les observations des latex hybrides par cryo-MET ont confirmé l’efficacité de la méthode pour l’obtention de structures hybrides. Cette stratégie semble ainsi la plus prometteuse pour la synthèse de latex hybrides CeO2/PVDC pour des applications en tant que films barrières présentant une stabilité UV amélioréeFood and pharmaceutical packages should nowadays fulfill a wide range of requirements : not only should they preserve the packed products from external polluting agents, but they must also be innocuous, more energy-efficient and disposable. Barrier polymers have enabled to meet these criteria, by offering alternatives to more energy-consuming and heavier materials like glass or metals, while maintaining a low permeability to water and/or oxygen. Among the large variety of barrier polymers, poly(vinylidene chloride) (PVDC) copolymers provide a more complete protection to external contaminants, due to their extremely low permeabilities towards water and oxygen. Nonetheless, PVDC films still suffer from limitations as far as their thermal and UV stabilities are concerned. This effect is even more pronounced in the case of films obtained from latexes, due to the presence of higher amounts of additives that could take part in the polymer degradation. Therefore, the synthesis of PVDC-based latexes for use as waterborne barrier films with improved thermal and UV stabilities are of great importance. PVDC-based composite latexes were first synthesized from epoxy-functionalized seed latexes in order to enhance the polymer thermal stability. Given that hydrogen chloride displays an indirect catalytic effect on the polymer degradation, epoxy groups were indeed expected to act as thermal stabilizers by scavenging the HCl released by the polymer under thermal stress. In a first step, epoxy-functionalized seed latexes were synthesized via the emulsion copolymerization of glycidyl methacrylate (GMA) and butyl methacrylate (BMA). In a second step, the seeded emulsion copolymerization of vinylidene chloride and methyl acrylate was carried out in the presence of poly(GMA-co-BMA) seed latexes. Thermogravimetric analyses carried out on the resulting composite samples evidenced the thermal stabilization provided by epoxy groups. The second part of the project focused on the synthesis of cerium oxide-based hybrid latexes so as to improve the stability of PVDC to UV radiation. Cerium oxide (CeO2) nanoparticles are indeed very attractive as UV-stabilizers due to their high absorption of radiation in the UV range and a low photocatalytic activity. However, due to the intrinsic incompatibility between inorganic and polymer phases, the synthesis of inorganic-organic hybrid latexes often requires a preliminary step of modification of the mineral particles surface. The grafting of alkoxysilanes onto nanoceria was first attempted in order to promote the polymerization reaction at the surface of the inorganic particles. Cryo-Transmission Electron Microscopy (cryo-TEM) observations of hybrid latexes obtained via this route showed that this strategy was unsuccessful at improving the compatibility between the inorganic and polymer phases. Amphiphatic macro-RAFT agents were finally considered as reactive compatibilizing agents to direct the polymerization towards the cerium oxide surface. RAFT oligomers were first obtained by co- or terpolymerization reactions in the presence of a RAFT controlling agent. After characterizing the adsorption of amphiphatic macro-RAFT agents at the surface of nanoceria, surface-modified cerium oxide particles were then engaged in reactions of emulsion polymerization reactions. In most cases, cryo-TEM observations carried out on the resulting latexes confirmed the efficiency of the amphiphatic macro-RAFT agent route for the synthesis of hybrid structures. Therefore this route appeared so far to be the most promising for the synthesis of CeO2/PVDC hybrid latexes for use as waterborne barrier films with improved UV-stability
25
Chern, Chorng-Shyan. "Polymerization in non-uniform latex particles." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/12170.
Full text
26
Michal, Lukáš. "Zlepšení sedimentační stability MR kapalin použitím bentonitových jílů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443152.
Full textAbstract:
The diploma thesis is focused on the issue of sedimentation stability of magnetorheological fluids, whis represents one of the most important characteristics determining the reliability of these fluids. Higher sedimentation stability can by achieved in several ways. Methods that are further examined in the thesis include particle polymerization and the addition of clay mineral additives. Both achieve positive results by schowing increased sedimentation stability. However, in the case of additives, the effect is much higher. In particular, the CLAYTONE 40 additive achieves a lower particle sedimentation rate while maintaining the same viscosity as the commercial LORD-122ED. The results provide significant knowledge in the field and can bring magnetorheological fluids closer to wider commercial use.
27
Costamagna, Federica. "Colloidal stability, intracellular fate and toxicology of drug nanocarriers - Application to polymerized micelles and organometallic nanogels Nanotoxicology at the particle/micelle frontier: influence of core-polymerization on the intracellular distribution, cytotoxicity and genotoxicity of polydiacetylene micelles." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS128.
Full textAbstract:
Une compréhension approfondie de la stabilité colloïdale est nécessaire pour concevoir des nanoparticules pour la vectorisation de molécules actives. En particulier, prévoir le comportement in vivo des particules (désagrégation ou agrégation) est fondamental pour prédire l’efficacité et la toxicité des nanoformulations. Les objectifs de cette thèse concernaient (1) l’amélioration de la stabilité colloïdale en conditions physiologiques et (2) l’étude in vitro du comportement biologique de deux types de nanovecteurs : nanogels à base de chitosane-fer et micelles de polydiacétylèneA thorough understanding of the colloidal stability is important to design nanoparticles for drug delivery purposes. In particular, anticipating the in vivo particles disassembly or aggregation is fundamental in order to predict efficacy and toxicity of the nanoformulations. The objectives of this thesis concerned (1) the improvement of the colloidal stability in physiological conditions and (2) the in vitro investigation of the biological behavior of two types of drug nanocarriers: chitosan-iron based nanogels and polydiacetylene micelles
28
Etmimi, Hussein Mohamed. "Hydrophobic core/shell particles via miniemulsion polymerization." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019/539.
Full text
29
Neqal, Mehdi. "Smart polymeric materials by ring-opening metathesis polymerization." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0658/document.
Full textAbstract:
Ce travail de thèse consiste à combattre le développement microbien des réservoirs de carburant aéronautiques dont le métabolisme entraine la production d’acides organiques susceptibles de corroder les parois métalliques des réservoirs. Des substances biocides sont habituellement utilisées pour éliminer les populations microbiennes. Ces substances peuvent être des composés organiques ou bien de manière plus courante du chrome (VI) sous forme de revêtement à la surface des parois afin de créer une couche passive et d’empêcher la corrosion chimique. Cependant, le chrome appartient à la catégorie des substances cancérogènes, mutagènes et reprotoxiques et se trouve maintenant soumis à restriction par la réglementation européenne Registration, Evaluation and Authorization of Chemicals (REACh). Pour remplacer les systèmes en place, le choix s’est porté sur la préparation de particules polymères pH-sensibles capables de libérer une molécule biocide en présence de microorganismes. De telles particules sont obtenues par copolymérisation par métathèse de cyclo-oléfines (ROMP) de norbornène avec un macromonomère linéaire de polyglycidol α-norbornenyl. Ce dernier permet d’une part la stabilisation des particules et d’autre part la multifonctionnalisation de l’objet par des molécules de biocide. Celles-ci sont introduites sur la chaîne de polyglycidol via un lien imine pH-sensible par substitution des fonctions hydroxyle par des entités dodécylamine. La libération du biocide à un pH inférieur à 7 a été validée ainsi que les capacités de ces particules à lutter contre des microorganismes tel que Hormoconis resinae souche identifiée comme se développant dans les réservoirs d’avions. Dans une dernière étape, les particules fonctionnalisées dodécylamine ont été incorporées dans un revêtement usuel en aéronautique et la capacité des particules à ne pas altérer la résistance du revêtement de base à des conditions de corrosion extrêmes a permis de vérifier leur applicabilité dans ce domaineThe aim of this Thesis work was to address the issue of microbial contamination inside fuel tanks. Microorganisms induce the chemical corrosion of airplane tank walls due to their production of organic acids. Biocide compounds are typically used to inhibit these microorganisms, either in the form of organic small molecules, or most commonly as chromium-based coatings on the walls to hinder chemical corrosion. Organic biocides need to be replenished regularly, while chromium is a particularly dangerous compound targeted by the European Registration, Evaluation and Authorization of Chemicals (REACh) legislation due to its carcinogenic nature. A replacement approach selected for this project was the development of a smart system of multifunctional polymeric particles synthesized by dispersion ROMP, which can deliver a biocide following an acidic trigger due to the presence of microorganisms. The polymerization utilized a linear α-norbornenyl-polyglycidol macromonomer as a reactive surfactant. The hydroxyl-rich polyglycidol backbone of the macromonomer was beneficial for the conjugation of dodecylamine through a pH-sensitive imine bond and permitted the preparation of highly functionalized bioactive particles. A proof of concept for the pH sensitivity of the system was provided and the antifungal efficacy of the biocide-functionalized macromonomer and particles was verified. The particles were also integrated in a coating formulation to simulate their application on tank walls. The qualities of the original coating were preserved even after prolonged exposure to corrosive conditions, making this system viable for its foreseen application
30
Marinangelo, Giovane. "Copolimerização em emulsão de estireno e acrilato de butila com alto teor de sólidos: estudo experimental e modelagem matemática do processo em reator semicontínuo." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-19012011-112636/.
Full textAbstract:
Neste trabalho estudou-se a copolimerização em emulsão de estireno e acrilato de butila em processo semicontínuo onde o produto final é um látex com alto teor de sólidos. Foi dado enfoque à distribuição de tamanhos de partículas do látex e seus efeitos no produto. Foi realizada uma série de experimentos de copolimerização em emulsão em um reator de vidro, empregando receitas com teores de sólidos de até 64% em massa. Durante os experimentos, amostras eram retiradas periodicamente do reator visando analisar o teor de polímeros (conversão dos monômeros) por gravimetria, a concentração de monômero residual por cromatografia gasosa headspace, o diâmetro médio das partículas por espectroscopia de espalhamento dinâmico de luz e a distribuição de tamanhos de partículas por microscopia eletrônica de transmissão. A viscosidade do látex final era obtida em viscosímetro Brookfield. Aplicando estratégias para renucleação de novas partículas no decorrer do processo, foram obtidos látices com distribuição bimodal de tamanhos de partículas e com viscosidades reduzidas. Aplicou-se um modelo matemático para descrever o processo, incluindo a evolução no tempo da distribuição de tamanhos de partículas, calculada a partir de equações de balanço populacional para as partículas e para os radicais dentro das partículas. Para a solução das equações empregou-se discretização por método de classes e a técnica de pivô fixo. O modelo tem apenas dois parâmetros ajustáveis, referentes às eficiências de captura de radicais por micelas e por partículas. Estes parâmetros foram ajustados para os dados experimentais de um ensaio, e usados, sem reajuste, para outros ensaios em condições diferentes. Os resultados do modelo mostraram boa adequação aos resultados experimentais.The aim of this work was the study of the high solid contents emulsion copolymerization of styrene and butyl acrylate in semi-batch process. In this context the particle size distribution and its effects on the product viscosity was studied. Copolymerization reactions were carried out in a glass reactor, and recipes with solid contents up to 64 wt.% were used. During each run, samples are periodically taken from the reactor, and analysis are performed to measure the polymer content (monomer conversion) by gravimetry, the concentrations of the residual monomers by head-space gas chromatography, the average particle size by dynamic light scattering, and the particle size distribution by transmission electronic microscopy. The viscosity of the final emulsion is also measured using a Brookfield viscosimeter. By applying operating strategies to nucleate new particles along the process, latexes with bimodal particle size distributions and low viscosities were obtained. A mathematical model was employed for simulating the polymerization process, including the evolution of the particle size distribution along the process, calculated from population balance equations for the particles and the radicals inside the particles. The numerical solution was obtained using the discretized population balance equations by the method of classes and the fixed pivot technique. The model has only two adjustable parameters, the efficiencies for radical capture by micelles and by particles. These two parameters were fitted to the experimental data of one run and used, without further readjustment, for other runs under different conditions. The model results presented satisfactory agreement with the experimental data.
31
Girard, Nathalie Renee Claude. "Oil-in-water microemulsions and their polymerization." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369502.
Full text
32
Kim, Hong-Youl. "PMMA bone cement reinforced by plasma treated particles /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841158.
Full text
33
Limé, Fredrik. "Synthesis and modification of monodisperse polymer particles for chromatography." Doctoral thesis, Umeå universitet, Kemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1948.
Full textAbstract:
Liquid chromatography is an analytical technique that is constantly facing new challenges in the separation of small molecules and large biomacromolecules. Recently the development of ultra high pressure liquid chromatography has increased the demand on sturdy particles as stationary phase. At the same time the particle size has decreased to sub-2 µm and packed into shorter analytical columns. This thesis deals with the development of new ways of preparing particulate polymer materials using divinylbenzene (DVB) as crosslinker. It includes a novel procedure for synthesizing monodisperse polymer particles by photoinitiated precipitation polymerization. A 150 W short arc xenon lamp was used to initiate the polymerizations. The synthesized particles are monodisperse and have an average particle size ranging from 1.5 to 4 μm depending on reaction conditions and have subsequently been used as grafting templates. The surface of DVB particles contains residual vinyl groups that serve as anchoring points for further functionalization via a variety of grafting schemes. Copolymerization with incorporation of 2,3-epoxypropyl methacrylate yielded pendant oxirane groups on the particle surface. Atom transfer radical polymerization (ATRP) was used to graft methacrylates from the surface resulting in a core-shell type material. A “grafting to” scheme was used to attach pre-made sulfopropyl methacrylate telomers onto particles containing oxirane rings.Populärvetenskaplig sammanfattning på svenska: Vätskekromatografi är en analytisk kemisk teknik som ständigt står inför nya utmaningar när det gäller att separera allt från små organiska föreningar till stora makro¬molekyler. Denna avhandling beskriver tillverkning av polymera partiklar med exceptionellt jämn storleksfördelning och ytmodifiering av dessa, för användning som stationärfas i kromatografi¬kolonner. Polymeriserings¬tekniken som används är utfällnings¬polymerisering där lösningen UV-bestrålas av en 150 W xenonlampa. Monomeren (byggstenen) löses tillsammans med en intiator i ett lösningsmedel och efterhand som polymeriseringen fortskrider faller polymerpartiklarna ut. Polymerpartiklarna är gjorda av monomeren divinylbensen som fungerar som en tvärbindare, dvs att den länkar ihop flera kedjor till ett hårt litet nystan. Partiklarna växte till en storlek på 1,5 till 4 µm under två till fyra dygn. Efter tillverkningen är partiklarnas yta täckta av vinylgrupper som kan användas för att fästa funktionella polymerkedjor. Genom att tillföra monomeren 2,3-epoxipropyl¬metakrylat i polymeriseringen kunde man desutom få en partikelyta som innehöll epoxigrupper. Epoxigrupperna användes för att fästa positivt laddade polymerkedjor av bestämd längd. Materialet packades i en kromatografikolonn och användes för att separera en testlösning bestående av fyra proteiner. Partiklarna användes även som bas för ymppolymerisering där den vinyltäckta ytan fått reagera med vätebromid. Detta gör att partiklarna blir stora makroinitiatorer som kan användas för att på ett kontrollerat sätt låta polymerkedjor växa från ytan. I en undersökning ympades 2,3-epoxypropylmetakrylat från ytan på partiklarna och resultatet blev ett tjockt ytskikt. Epoxigrupperna kunde sedan hydrolyseras till dioler vilket gjorde partiklarna mer hydrofila.
34
Dorresteijn, Robert [Verfasser]. "Particles with tunable functionality by a nonaqueous emulsion polymerization approach / Robert Dorresteijn." Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1073303241/34.
Full text
35
Yu, Zhou. "Surface Polymerization, Interface Structure, and Low Temperature Consolidation of Nano Ceramic Particles." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin971379308.
Full text
36
Hernandez, Garcia Hugo Fernando. "Multiscale simulation of heterophase polymerization : application to the synthesis of multicomponent colloidal polymer particles." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/2503/.
Full textAbstract:
Heterophase polymerization is a technique widely used for the synthesis of high performance polymeric materials with applications including paints, inks, adhesives, synthetic rubber, biomedical applications and many others. Due to the heterogeneous nature of the process, many different relevant length and time scales can be identified. Each of these scales has a direct influence on the kinetics of polymerization and on the physicochemical and performance properties of the final product. Therefore, from the point of view of product and process design and optimization, the understanding of each of these relevant scales and their integration into one single model is a very promising route for reducing the time-to-market in the development of new products, for increasing the productivity and profitability of existing processes, and for designing products with improved performance or cost/performance ratio.
The process considered is the synthesis of structured or composite polymer particles by multi-stage seeded emulsion polymerization. This type of process is used for the preparation of high performance materials where a synergistic behavior of two or more different types of polymers is obtained. Some examples include the synthesis of core-shell or multilayered particles for improved impact strength materials and for high resistance coatings and adhesives. The kinetics of the most relevant events taking place in an emulsion polymerization process has been investigated using suitable numerical simulation techniques at their corresponding time and length scales. These methods, which include Molecular Dynamics (MD) simulation, Brownian Dynamics (BD) simulation and kinetic Monte Carlo (kMC) simulation, have been found to be very powerful and highly useful for gaining a deeper insight and achieving a better understanding and a more accurate description of all phenomena involved in emulsion polymerization processes, and can be potentially extended to investigate any type of heterogeneous process. The novel approach of using these kinetic-based numerical simulation methods can be regarded as a complement to the traditional thermodynamic-based macroscopic description of emulsion polymerization. The particular events investigated include molecular diffusion, diffusion-controlled polymerization reactions, particle formation, absorption/desorption of radicals and monomer, and the colloidal aggregation of polymer particles.
Using BD simulation it was possible to precisely determine the kinetics of absorption/desorption of molecular species by polymer particles, and to simulate the colloidal aggregation of polymer particles. For diluted systems, a very good agreement between BD simulation and the classical theory developed by Smoluchowski was obtained. However, for concentrated systems, significant deviations from the ideal behavior predicted by Smoluchowski were evidenced. BD simulation was found to be a very valuable tool for the investigation of emulsion polymerization processes especially when the spatial and geometrical complexity of the system cannot be neglected, as is the case of concentrated dispersions, non-spherical particles, structured polymer particles, particles with non-uniform monomer concentration, and so on. In addition, BD simulation was used to describe non-equilibrium monomer swelling kinetics, which is not possible using the traditional thermodynamic approach because it is only valid for systems at equilibrium.
The description of diffusion-controlled polymerization reactions was successfully achieved using a new stochastic algorithm for the kMC simulation of imperfectly mixed systems (SSA-IM). In contrast to the traditional stochastic simulation algorithm (SSA) and the deterministic rate of reaction equations, instead of assuming perfect mixing in the whole reactor, the new SSA-IM determines the volume perfectly mixed between two consecutive reactions as a function of the diffusion coefficient of the reacting species. Using this approach it was possible to describe, using a single set of kinetic parameters, typical mass transfer limitations effects during a free radical batch polymerization such as the cage effect, the gel effect and the glass effect.
Using multiscale integration it was possible to investigate the formation of secondary particles during the seeded emulsion polymerization of vinyl acetate over a polystyrene seed. Three different cases of radical generation were considered: generation of radicals by thermal decomposition of water-soluble initiating compounds, generation of radicals by a redox reaction at the surface of the particles, and generation of radicals by thermal decomposition of surface-active initiators "inisurfs" attached to the surface of the particles. The simulation results demonstrated the satisfactory reduction in secondary particles formation achieved when the locus of radical generation is controlled close to the particles surface.Eine der industriell am meisten verwendeten Methoden zur Herstellung von Hochleistungspolymeren ist die Heterophasenpolymerisation. Industriell von besonderer Bedeutung ist die sogenannte Saatemulsionspolymerisation bei der kleine Saatteilchen durch die sequentielle Zugabe von weiteren Monomeren gezielt modifiziert werden, um Kompositpolymerteilchen mit den gewünschten mechanischen und chemischen Gebrauchseigenschaften herzustellen. Ein häufig auftretendes Problem während dieser Art der Heterophasenpolymerisation ist die Bildung von neuen, kleinen Teilchen im Polymerisationsverlauf. Diese sogenannte sekundäre Teilchenbildung muss vermieden werden, da sie die Herstellung der gewünschten Teilchen mit den angestrebten Eigenschaften verhindert. Ein spezieller Fall der Saatemulsionspolymerisation ist die Kombination von Vinylacetat als Monomer, das auf Saatteilchen aus Polystyrol polymerisieren soll. Die Unterdrückung der Teilchenneubildung ist in diesem Beispiel besonders schwierig, da Vinylacetat eine sehr hohe Wasserlöslichkeit besitzt. In der vorliegenden Arbeit wurden zur Lösung der Aufgabenstellung verschiedene numerische Simulierungsalgorithmen verwendet, die entsprechend den charakteristischen Längen- und Zeitskalen der im Verlauf der Polymerisation ablaufenden Prozesse ausgewählt wurden, um die passenden Bedingungen für die Unterdrückung der sekundären Teilchenbildung zu finden. Die verwendeten numerischen Methoden umfassen Molekulare Dynamik Simulationen, die benutzt werden, um molekulare Bewegungen zu berechnen; Brownsche Dynamik Simulationen, die benutzt werden, um die zufälligen Bewegungen der kolloidalen Teilchen und der molekularen Spezies zu beschreiben, und kinetische Monte Carlo Simulationen, die das zufällige Auftreten von individuellen physikalischen oder chemischen Ereignissen modellieren. Durch die Kombination dieser Methoden ist es möglich, alle für die Beschreibung der Polymerisation relevanten Phänomene zu berücksichtigen. Damit können nicht nur die Reaktionsgeschwindigkeit und die Produktivität des Prozesses simuliert werden sondern auch Aussagen bezüglich der physikalischen und chemischen Eigenschaften des Produktes sowie den Applikationseigenschaften getroffen werden. In dieser Arbeit wurden zum ersten Mal Modelle für die unterschiedlichen Längen- und Zeitskalen bei Heterophasenpolymerisationen entwickelt und erfolgreich zur Modellierung des Prozesses angewendet. Die Ergebnisse führten zu bedeutenden Verbesserungen der Theorie von Emulsionspolymerisationen insbesondere für die Beschreibung des Massenaustausches zwischen den Phasen (bspw. Radikaleintritt in und Radikalaustritt aus die Polymerteilchen), der Bildung von neuen Teilchen, und der Polymerisationskinetik unter den heterogenen Reaktionsbedingungen mit uneinheitlicher Durchmischung.
37
WU, DAN. "LIQUID-CORE CAPSULES VIA INTERFACIAL POLYMERIZATION AND ALTERNATING COPOLYMERIZATION." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179427662.
Full text
38
Huang, Yun. "Synthesis of Novel Polymer-brush-afforded Hybrid Particles for Well-organized Assemblies." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189679.
Full text
39
Sutrisno, Joko. "Surface polymerization of iron particles for magnetorheological elastomers (MRes) and their potential application as sensors." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453614.
Full text
40
Abboud, Mohammed K. [Verfasser]. "Video Microscopy Studies on Growth Kinetics of Single Catalyst Particles During Olefin Polymerization / Mohammed K Abboud." Aachen : Shaker, 2005. http://d-nb.info/1186577401/34.
Full text
41
Anderson, Kyle D. "Functional and complex topological applications of plasma polymerized ultrathin films." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/48969.
Full textAbstract:
This study is focused on the fabrication of plasma polymerized ultrathin films and the elucidation of their unique properties with an emphasis on the solvent-less, dry polymerization process to introduce post-deposition functionality, robustness, and shape preservation. Two major classes of materials are the subject of this study: biological monomers, specifically the amino acids tyrosine and histidine and synthetic organic and inorganic monomers including acrylonitrile, 2-hydroxyethyl methacrylate, N-isopropylacrylamide, titanium isopropoxide and ferrocene. The unique chemical and physical properties of highly cross-linked ultrathin plasma polymerized amino acid and synthetic polymer films are demonstrated along with their functional response and robustness on both planar and complex surface structures. The work emphasizes the facile ability of plasma polymerization to create unique, tailored ultrathin coatings. Chemical functionality retention (OH, NH₂) of the tyrosine and histidine amino acids is demonstrated by the subsequent mineralization of gold or titania nanoparticles on the plasma polymerized ultrathin films using a wet chemical approach. Inorganic nanoparticle mineralization is further investigated as a method to modify the optical properties of composite nanocoatings. Plasma co-polymerization of tyrosine and synthetic monomers is used to create nanocomposite coatings with unique surface functionalities, responsive behavior, optical characteristics and a high level of integration between monomers. The fabrication of novel plasma polymerized Janus microspheres, micropatterned substrates and free-standing films also demonstrate numerous plasma polymerized materials which exhibit unique structural properties. Overall, facile plasma polymerization of novel, functional ultrathin films and complex topological coatings having potential biocompatible and optical applications is established.
42
Kir, Onur [Verfasser], Wolfgang H. [Akademischer Betreuer] Binder, and 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.
Full text
43
Mathlouthi, Chourouk. "Étude des propriétés thermodynamiques et dynamiques des polymères confinés en géométrie nanoparticules." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI035/document.
Full textAbstract:
L’effet du confinement sur les propriétés physiques des polymères est un sujet d’une importance à la fois fondamentale et académique et est le centre d’un débat scientifique soutenu. La relation entre la transition vitreuse (Tg) et la dynamique des polymères en confinement est notamment le centre d’un débat controversé au sein de la communauté scientifique depuis les deux dernières décennies. Alors que la transition vitreuse mesurée par expansion thermique est diminuée de manière remarquable en films minces, sa dynamique alpha est invariante : ce phénomène est aperçu comme une rupture avec la loi de superposition temps température. Pour chercher l’origine des controverses scientifiques qui en résultent et répondre aux questions posées dans ce débat, on s’intéresse, dans ce travail de recherche, aux propriétés calorifiques des polymères à base de nanoparticules, avec une surface spécifique élevée, confinés en structure compacte. Bien que cette géométrie présente quelques avantages comme une importante surface spécifique et une méthode de préparation générant moins de contraintes résiduelles, relativement peu d’études ont été réalisées sur cette géométrie de confinement comparé à celles portant sur les films minces.L’objectif principal de cette thèse est d'étudier le comportement de la Tg et de la dynamique du polystyrène confinés sous forme de nanoparticules dans une structure compacte où les particules sphériques sont séparées par des vides et en les comparants aux polymères massiques correspondants. Nous étudions la cinétique de fermeture des vides inter-particules dans cette géométrie compacte en fonction de la surface libre pour extraire la dynamique α du polystyrène confiné. Nous avons utilisé les résultats des thermogrames de calorimétrie à balayage différentielle (DSC) de ces particules pour obtenir des informations sur la capacité calorifique Cp. Nous montrons que la capacité calorifique du polystyrène confiné est similaire à celle du polymère massique correspondant dans le régime vitreux et s’écarte de ce comportement entre Tg -30°C et Tg. Cet écart devient de plus en plus important avec l’augmentation de la surface libre. Ce phénomène a été attribué à l'existence d'une couche mobile à la surface libre du polystyrène ou à l'existence d'une couche possédant un coefficient de dilatation important. Par contre, nous montrons également que la dynamique α du polymère confiné présente le même comportement que le polymère massique dans cette gamme de température.Le deuxième volet de cette thèse vise à étudier le mécanisme de vieillissement vitreux du polystyrène confiné dans la géométrie des particules en structure compacte. Nous avons calculé la recouvrance enthalpique lors du vieillissement du polystyrène dans les cas confiné et massique à des différents températures et temps de vieillissement. Nous montrons que le vieillissement vitreux dépend de la méthode de préparation du polymère et est fortement affecté par le confinementThe impact of confinement on the physical properties of polymers is an important topic for both fundamental and academic aspects and has gathered an intensive interest within the polymer physics community. In particular the relationship between the glass transition (Tg) and the dynamic of confined polymers has remained the center of a controversial debate over the past two decades. While the glass transition measured by thermal expansion is remarkably decreased in thin films, the alpha dynamic of polymers was found to be invariant, which can be seen as incoherence with the time-temperature superposition. To search the origin of these controversies and answer the questions posed in this debate, we focus the study on the thermal properties of confined polystyrene in the compact structure with a high surface area such as nanoparticles. Even though the particles geometry exhibit several advantages such as higher free surface and mild processing method, only few studies have been carried out on it compared to that on the thin films.The main objective of this thesis is to investigate the behavior of Tg and the dynamics of confined polystyrene in particles in the close packed structure, where the spherical particles are separated by voids, and to compare them to their corresponding bulk. We investigate the kinetic of void closure to quantify the α-dynamic of confined polystyrene in particles. We extract information about the heat capacity (Cp) from differential scanning calorimetry (DSC) thermograms. We show that the Cp of confined polystyrene is similar to that of bulk in the glassy regime and deviates from it between Tg -30 ° C and Tg. The magnitude of this deviation increases with increasing the free surface area. This was interpreted by the existence and the propagation of a mobile layer on the free surface or the existence of a zone with higher expansion coefficient. On the other hand, the α-dynamic probed via the void closure in the area where Cp increases was found to exhibit a bulk behavior.A second objective of this thesis is to investigate the physical aging of confined polystyrene in particles in the glassy regime. We quantify the enthalpy recovery during aging of both confined polystyrene and their corresponding bulk at various temperatures and aging times. We show that the physical aging process depends on the processing history of the polymer and is highly affected by the confinement
44
Rodrigues, Guimarães Thiago. "Synthesis of magnetic polymer latex particles by reversible addition-fragmentation chain transfer (RAFT) polymerization in aqueous dispersed media." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1107/document.
Full textAbstract:
Dans le cadre de ce travail de thèse, la polymérisation de type RAFT a été exploitée pour synthétiser des particules de latex magnétiques décorées de polymères stimulables. Cinq (co)polymères hydrophiles ont tout d'abord été préparés via la (co)polymérisation RAFT en solution d'acide acrylique (AA) et de méthacrylate de 2-diméthylaminoéthyle (MADAME). Les agents macromoléculaires obtenus (macroRAFT) : des homopolymères de PAA ou PMADAME ainsi que des copolymères P(AA-co-MADAME), présentent une sensibilité au pH et à la température. Ces macroRAFT hydrophiles ont ensuite été utilisés dans des réactions d’extension de chaîne avec du styrène conduisant à la formation de copolymères à blocs amphiphiles bien définis. Puis, des dispersions aqueuses d’agrégats (clusters) de nanoparticules d’oxyde de fer (OF) ont ensuite été préparées via un procédé de mini-émulsification/évaporation de solvant, en utilisant les copolymères à blocs comme stabilisants. Après optimisation des conditions expérimentales (sonication, concentration de macroRAFT, pH), des agrégats de taille contrôlée (45 à 300 nm) ont pu être obtenus. Ces clusters ont ensuite été utilisés comme semence lors de la polymérisation en émulsion du styrène, conduite en présence d’un agent de réticulation. Les clusters d'OF ont été individuellement encapsulés par une couche de polymère, formant des particules magnétiques stabilisées par le segment hydrophile des copolymères à blocs. Enfin, les particules magnétiques décorées de copolymères de P(AA-co-MADAME) ont été utilisées avec succès pour la capture et le relargage de bactéries grâce à la modulation de leurs propriétés de surface en fonction du pHIn this work reversible addition-fragmentation chain transfer (RAFT) polymerization was exploited to synthesize magnetic latex particles decorated with stimuli-responsive polymer brushes. First, five hydrophilic (co)polymers with various compositions were successfully prepared by RAFT solution (co)polymerization of acrylic acid (AA) and 2-dimethylaminoethyl methacrylate (DMAEMA) for different AA to DMAEMA molar ratios. The obtained macromolecular RAFT agents (macroRAFTs), PAA or PDMAEMA homopolymers and P(AA-co-DMAEMA) copolymers, displayed interesting pH- and thermo-responsive properties. These hydrophilic macroRAFTs were then chain extended with styrene leading to the formation of well-defined amphiphilic block copolymers. An aqueous dispersion of iron oxide clusters was next prepared using a strategy based on emulsification/solvent evaporation in which the block copolymers were used as stabilizers. By varying the experimental conditions (sonication power, macroRAFT concentration and pH of the medium), the cluster size could be controlled from 45 up to 300 nm. These clusters were then used as seeds in styrene emulsion polymerization in the presence of a crosslinker. The iron oxide clusters were individually encapsulated into a polymer shell generating latex particles, stabilized by the hydrophilic segment of the block copolymers, and displaying interesting magnetic properties. At last, these magnetic beads were evaluated as carriers in the magnetic separation of bacteria. The magnetic latex particles decorated with P(AA-co-DMAEMA) copolymers were successfully employed for the capture and trigger release of bacteria, allowing their concentration in a biological sample
45
Abdelsayed, Victor Maher. "Experimental Studies on Nucleation, Nanoparticle's Formation and Polymerization from the Vapor Phase." VCU Scholars Compass, 2004. http://scholarscompass.vcu.edu/etd/1109.
Full textAbstract:
This research is divided into three major parts. In part I, the critical supersaturations required for the homogeneous nucleation of 2,2,2-trifluorothanol (TFE) vapor have been measured over a temperature range (266-296 K) using an upward thermal diffusion cloud chamber (DCC). The measured supersaturations are in agreement with the predictions of both the classical and the scaled theory of nucleation. Moreover, the condensation of supersaturated TFE vapor on laser-vaporized magnesium nanoparticles has been studied under different experimental conditions, such as the supersaturation, the pressure and the electric field. In part II, the laser vaporization controlled condensation (LVCC) technique was used to prepare Au-Ag alloy nanoparticles in the vapor phase using designed targets of compressed Au and Ag micron-sized powder mixtures of selected composition. The results showed that the optical properties of these nanoparticles could be tuned depending on the alloy composition and the laser wavelength. Different intermetallic nanoparticles (FeAl and NiAl) from the vapor phase has also been prepared, using the same approach.In this work, the fraction of the charged particles generated during the laser vaporization process was used to prepare a new class of nanoparticle assemblies in the LVCC chamber under the influence of an electric field. The results showed that the electric field required to induce the formation of these nanoassemblies is material and field dependent. By coupling the LVCC chamber with the differential mobility analyzer, size-selected nanoparticles have been prepared in the vapor phase. The prepared nanoparticles were characterized by different techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy. In part III, new methods were developed to prepare nanoparticle-polymer composites from the vapor phase. In the first method, the LVCC method was used to prepare a carbonaceous cross-linked resin, with different nanoparticles (Ni, Pt and FeAl) embedded inside. In the second method, free radical-thermally initiated polymerization was used to polymerize a monomer vapor of styrene on the surfaces of activated Ni nanoparticles.
46
Li, Keran. "Surfactant-free synthesis of magnetic latex particles." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10211/document.
Full textAbstract:
Ce travail de thèse décrit l'élaboration de latex hybrides oxyde de fer (OF)/polymère par polymérisation en émulsion sans tensioactif. Des nanoparticules d'OF cationiques ont été tout d'abord synthétisées par co-précipitation de sels de fer dans l'eau. Des latex hybrides magnétiques ont été ensuite obtenus par deux voies de polymérisation. La première consiste en la synthèse de particules de latex de morphologie 'carapace' par polymérisation en émulsion Pickering du styrène et du méthacrylate de méthyle (MMA). Un comonomère auxiliaire (acide (méth)acrylique ou acide 2-acrylamido-2-méthyl-1-propane sulfonique) a été utilisé pour favoriser l'adsorption des OF à la surface des particules de polymère produites. Les analyses par MET indiquent la présence d'OF à la surface des particules de polymère (structure carapace). L'analyse thermogravimétrique a permis de quantifier l'efficacité d'incorporation des OF, i.e. la fraction d'OF initialement introduits effectivement adsorbés à la surface des particules. L'efficacité d'incorporation augmente avec la quantité de comonomère auxiliaire, le pH et la concentration en OF et dépend de la nature du monomère hydrophobe. Dans la deuxième voie, les OF ont été encapsulés par polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT) en émulsion aqueuse. La stratégie utilisée repose sur l'utilisation de macroagents RAFT amphiphiles comportant des groupements acide carboxylique connus pour interagir avec la surface des OF. L'interaction entre les macroRAFTs et les OF a été étudiée à travers le tracé de l'isotherme d'adsorption. Des analyses SAXS et DLS indiquent la formation de clusters d'oxyde de fer. Ces derniers ont été ensuite engagés dans la polymérisation en émulsion du styrène ou d'un mélange de MMA et d'ABu (ratio massique : 90/10) pour former une écorce de polymère à leur surface. Les particules carapace et les OF encapsulés affichent un comportement superparamagnétiqueThis work describes the elaboration of polymer/iron oxide (IO) hybrid latexes through surfactant-free emulsion polymerization. Cationic iron oxide nanoparticles stabilized by nitrate counterions were first synthesized by the co-precipitation of iron salts in water. Magnetic hybrid latexes were next obtained by two polymerization routes carried out in the presence of IO. The first route consists in the synthesis of polymer latexes armored with IO via Pickering emulsion polymerization of methyl methacrylate (MMA) or styrene (St). An auxiliary comonomer (namely methacrylic acid, acrylic acid or 2-acrylamido-2-methy-1- propane sulfonic acid) was used to promote IO particle adhesion to the surface of the generated polymer particles. TEM showed the presence of IO at the surface of the polymer particles and the successful formation of IO-armored polymer particles. TGA was used to quantify the IO incorporation efficiency, which corresponds to the fraction of IO effectively located at the particle surface. The incorporation efficiency increased with increasing the amount of auxiliary comonomer, suspension pH and IO content or with increasing monomer hydrophobicity. In the second route, IO encapsulation was investigated via reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. The developed strategy relies on the use of water-soluble amphipathic macromolecular RAFT agents containing carboxylic acid groups, designed to interact with IO surface. The interaction between the macroRAFT agents and IO was investigated by the study of the adsorption isotherms. Both DLS and SAXS measurements indicated the formation of dense IO clusters. These clusters were then engaged in the emulsion polymerization of St or of MMA and nbutyl acrylate (90/10 wt/wt) to form a polymer shell at their surface. Both IO-armored latex particles and polymer-encapsulated clusters display a superparamagnetic behavior
47
Miles, Craig. "Synthesis and Characterization of Mesoporous PMMA/POSS Particles." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1305145439.
Full text
48
Chen, Tao, Rainer Jordan, and Stefan Zauscher. "Polymer brush patterning using self-assembled microsphere monolayers as microcontact printing stamps." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138826.
Full textAbstract:
Self-assembled microsphere monolayers (SMMs) hold significant promise for micro- and nanopatterning. Here we exploit, for the first time, SMMs as stamps for microcontact printing (μCP) and demonstrate this to fabricate patterned initiator templates that can subsequently be amplified into polymer brushes by surface initiated atom transfer radical polymerization (SI-ATRP). SMM stamps avoid the need for expensive and sophisticated instrumentation in pattern generation, and provide a broad range of accessible surface chemistries and pitch size control.
49
Hubert, Céline. "Ingénierie de particules et assemblages à l’échelle colloïdale." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0185/document.
Full textAbstract:
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 chaînesThe 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
50
Genevaz, Nicolas. "Particules greffées d'homopolymères et de copolymères pour l'élaboration de nanocomposites modèles : dispersion des particules, dynamique des chaînes greffées en relation avec les propriétés rhéologiques." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4774.
Full textAbstract:
Les nanocomposites polymère intéressent depuis de nombreuses années la communauté scientifique, du fait, notamment, de leurs bonnes propriétés mécaniques. Il est établi que l'amélioration des propriétés mécaniques observées dans les nanocomposites est principalement due à des effets de structure (dispersion des particules) et à des effets d'interface (interactions particule/matrice et particule/particule). Cependant, de nombreux résultats expérimentaux restent difficiles à expliquer. Dans ce contexte, nous avons synthétisé des nanocomposites modèles constitués de nanoparticules de silice greffées de chaînes de polystyrène (PS) (ou de PS-b-poly(acrylate de tertio-butyle)) par polymérisation radicalaire contrôlée par les nitroxydes (NMP) et réparties dans une matrice de PS. Ces nanocomposites ont ensuite été caractérisés en couplant la diffusion de rayons X et la microscopie électronique à transmission. En variant la taille des chaînes de la matrice, nous sommes parvenus à obtenir différentes répartitions spatiales de particules allant de la dispersion totale à l'agrégation en passant par un état intermédiaire s'apparentant à un réseau connecté aux fractions volumiques élevées. Les propriétés mécaniques de ces nanocomposites ont été étudiées par des mesures de cisaillement aux faibles fréquences puis reliées aux différentes dispersions observées. Enfin, nous avons mesuré la dynamique locale et intermédiaire des chaînes de polymères greffées dans les matériaux préparés en couplant la diffusion quasiélastique des neutrons (rétrodiffusion et écho de spin) et la résonance magnétique nucléaire. Ces mesures ont ensuite été reliées aux propriétés mécaniques des nanocompositesPolymer nanocomposites interest for many years the scientific community, due in particular, to their good mechanical properties. It is established that the improvement of these properties observed in nanocomposites are mainly due to structural effects (particles dispersion) and interfacial effects (particle/matrix and particles/particles interactions). However, many experimental results are difficult to explain. In such a context, we have synthesized model nanocomposites based on silica nanoparticles grafted with polystyrene (PS) chains (or PS-b-poly(ter-butyl acrylate)) by nitroxide mediated polymerization and dispersed in a PS matrix. Then, these nanocomposites have been characterized by combining X-ray scattering and transmission electronic microscopy. By varying the length of the matrix chains, we have obtained different fillers structure going from individual nanoparticles dispersion to aggregate, up to an intermediate state (equivalent to an interconnected network for high volume fraction). Mechanical properties of these nanocomposites were studied by the mean of shear measurements at low frequency and linked to the different states of dispersion observed. Finally, we have measured local and intermediate dynamics of the grafted polymer chains by combining quasielastic neutron scattering (backscattering and spin echo) and nuclear magnetic resonance. Then, we have linked these measurements with the mechanical properties of the materials