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DITERLIZZI, MARIANNA. « Polymeric Water-Processable Nanoparticles towards sustainable organic photovoltaics ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/376407.
Texte intégralRésumé :
Il mio progetto di dottorato è focalizzato sullo sviluppo di inchiostri a base acquosa costituiti da nanoparticelle (NPs) polimeriche per applicazioni optoelettroniche ed elettroniche. In particolare, lo scopo della mia ricerca è la preparazione di strati attivi di dispositivi fotovoltaici organici (OPV) sostenibili. Questo obiettivo è raggiunto attraverso sospensioni acquose di NPs processabili in acqua, preparate a partire da miscele di polimeri semiconduttori donatori e accettori di elettroni. Gli inchiostri acquosi sono stati ottenuti attraverso il metodo della miniemulsione, modificato affinché non fosse necessaria l'aggiunta di surfattanti per garantire la stabilità colloidale. L'approccio sviluppato prevede l'utilizzo di copolimeri a blocchi (BCPs) anfifilici del tipo rod-coil, caratterizzati da un blocco rigido (un polimero semiconduttore di tipo p) legato covalentemente a un segmento flessibile idrofilo in grado di interagire con il mezzo acquoso, stabilizzando le interfacce acquose/non acquose. I BCPs anfifilici sono in grado di auto-assemblarsi sia puri che in miscela con materiali accettori, portando alla formazione di nanostrutture costituite da domini con dimensioni adatte alla percolazione della carica nello strato attivo della cella solare organica (OSC).
In primo luogo, come materiali elettron-donatori sono stati considerati dei polimeri low band-gap (LBG). Nella parte iniziale della tesi è descritta la sintesi di quattro BCPs basati sul polimero poli[2,6-(4,4-bis-(2-etilesil)-4H-ciclopenta[2,1-b;3,4-b']ditiofene)-alt-4,7(2,1,3-benzotiazolo)] (PCPDTBT), con un segmento di poli-4-vinilpiridina (P4VP) come coil. I BCPs sono stati utilizzati in miscela con il derivato fullerenico PC61BM come materiale elettron-accettore per ottenere inchiostri acquosi, che sono stati poi depositati per fabbricare strati attivi. In seguito, sono stati condotti diversi esperimenti per trovare la correlazione tra la morfologia interna e la composizione delle NPs con l'efficienza dei dispositivi OPV.
Successivamente, sono stati studiati altri polimeri LBG dotati di un parziale grado di cristallinità, al fine di migliorare l'efficacia del metodo sviluppato. Pertanto, nella seconda parte della tesi si discute la sintesi e la caratterizzazione di un nuovo BCP anfifilico basato sul poli[[4,8-bis[(2-etilesil)ossi]benzo[1,2-b:4,5-b']ditiofene-2,6-diil][3-fluoro-2-[(2-etilesil)carbonil]tieno[3,4-b]tiofenediil]] (PTB7) come blocco rigido, che è più rigido e più cristallino del PCPDTBT. Come blocco coil è stato scelto un segmento costituito da 15 unità di 4VP. Quindi sono state preparate le NPs tramite self-assembly del PTB7-b-P4VP miscelato con il derivato fullerenico PC71BM. Le sospensioni acquose ottenute sono state impiegate per fabbricare dispositivi OPV in configurazione diretta, e la cella migliore che è stata ottenuta presenta un’efficienza pari a 0.85%, che è un valore ancora molto lontano dal benchmark, ma è comunque superiore all'efficienza del dispositivo ottenuto depositando la miscela PC71BM:PTB7-b-P4VP da solventi alogenati.
Infine, è stato preso in considerazione l'uso di tensioattivi nella preparazione delle NPs, in quanto le sospensioni acquose che ne risultano sono più stabili e più facili da maneggiare e conservare, facilitando il processo di scale-up a livello industriale. In quest’ultima parte della tesi, sono stati studiati altri polimeri semiconduttori come materiali elettron-donatori. In particolare, sono stati sintetizzati e caratterizzati due nuovi polimeri semiconduttori LBG e uno a medio band-gap. Questi materiali saranno miscelati con accettori fullerenici e non per ottenere inchiostri a base acquosa che saranno depositati come strati attivi di dispositivi optoelettronici, analogamente a quanto fatto per i materiali precedenti.My PhD project is focused on the development of polymeric nanoparticle-based aqueous inks for optoelectronic and electronic applications. Specifically, the aim of my research is the fabrication of sustainable active layers of organic photovoltaic (OPV) devices processable in water. This goal is reached through water-processable nanoparticle (WPNP) aqueous suspensions, prepared from semiconducting polymers as electron-donor and acceptor materials. The aqueous inks are obtained through a modified miniemulsion method, which unlike the standard process does not imply the addition of any surfactant to ensure the colloidal stability. The adapted approach involves the use of amphiphilic rod-coil block copolymers (BCPs), characterized by a rigid block (a p‐type semiconducting polymer) covalently linked to a hydrophilic flexible segment able to interact with aqueous medium, stabilizing the aqueous/non-aqueous interfaces. The amphiphilic BCPs are able to self-assemble both neat and in blend with acceptor materials, leading to the formation of nanostructures consisting of domains with dimensions suitable for the charge percolation in the resulting active layer of the organic solar cell (OSC). Primarily, low-band-gap (LBG) polymers were considered as electron donor materials to match the solar radiation absorption. Firstly, the synthesis of four different poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b’]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT)-based amphiphilic BCPs, with a tailored segment of poly-4-vinylpiridine (P4VP) as coil, was presented. The BCPs were used in blend with the [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as acceptor material to prepare WPNP aqueous inks, which were deposited to obtain the active layers. The correlation between the internal morphology and composition of the WPNPs, and the dimensions of the donor/acceptor nanodomains with the efficiency of the resulting OSCs was deeply studied. In a second time, we explored other LBG polymers endowed with a partial order to improve the effectiveness of the approach. Therefore, the synthesis and the deep characterization of a new amphiphilic BCP based on the poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) as rigid donor polymer, which is stiffer and more crystalline than PCPDTBT, were described. A segment of 15 repeating units of 4VP was selected as coil. We prepared WPNPs coming from the self-assembly of the PTB7-b-P4VP blended with the [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). Subsequently, the WPNPs were employed to fabricate OSCs in direct configuration, and the best gained OPV device exhibited a PCE of 0.85%, which is still very far from the benchmark, but it is higher than the efficiency of the device obtained depositing the PC71BM:PTB7-b-P4VP from halogenated solvents. Lastly, the use of surfactants in the WPNP preparation was considered, as the resulting aqueous suspensions are more stable and easier to handle and store, enhancing the industrial scale-up process. Other semiconducting polymers were selected as electron-donor materials in the active blends. Particularly, two new LBG semiconducting BDT-based polymers, and a medium band-gap one, were synthetized and characterized. These materials will be blended with fullerene and non-fullerene acceptor (NFA) materials to obtain aqueous inks that will be deposited as active layers of optoelectronic devices, similarly to previous materials.
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Holtze, Christian H. W. « Neue Einflüsse und Anwendungen von Mikrowellenstrahlung auf Miniemulsionen und ihre Kompositpolymere ». [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974875694.
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Bechthold, Nina. « Polymerisation in Miniemulsion ». Phd thesis, [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961879416.
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Barnette, Darrell Thomas. « Continuous miniemulsion polymerization ». Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/12518.
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Jasinski, Florent. « Photopolymérisation radicalaire en miniemulsion ». Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH7111/document.
Texte intégralRésumé :
Les problématiques et potentialités de la photopolymérisation radicalaire en miniémulsion ont été discutées, en partant de l’étude des propriétés optiques des miniémulsions de monomère jusqu’à la synthèse de nouvelles nanoparticules polysulfures semi-cristallines par réaction thiol-ène. En premier lieu, l'interaction entre les propriétés optiques de miniémulsion de monomère et l'efficacité de photopolymérisation a été clarifiée. Nous avons établi le rôle majeur de la diffusion optique sur les cinétiques de photopolymérisation de nanogouttelettes acrylates, tandis que l'absorption s’est révélé de moindre importance. Que ce soit en milieu dilué ou concentré (modèle de Kubelka-Munk), la diffusion de la lumière est atténuée lorsque la taille de gouttelettes diminue. La conséquence immédiate est une amélioration significative de la pénétration de la lumière induisant une accélération des cinétiques de polymérisation. Néanmoins, cette conclusion doit être pondérée car l’effet de compartimentage de la polymérisation radicalaire n’a pu être dissocié des effets optiques. On notera qu’en milieu concentré (contenu en solide de 30 % massique), au-delà de 150 nm pour le diamètre de gouttelette, le coefficient de diffusion atteint un palier et devient indépendant de la taille des gouttelettes. La chute d’absorbance, observée par spectroscopie UV-visible, tout au long de l’irradiation pour des miniémulsions acrylates de faible taille (40 nm) a mis en évidence un mécanisme de polymérisation par diffusion de monomère des gouttelettes non nucléées vers les particules en croissance. Cette analyse non invasive (aucune dilution n’a été nécessaire) présente un intérêt évident pour l’étude du mécanisme de nucléation. Nous avons ensuite démontré que la photopolymérisation pouvait être réalisée en utilisant le caractère auto-amorçant des acrylates sous irradiation UV court ( < 300 nm). Ce type d’amorçage photochimique a permis d’éviter l’emploi de photoamorceur, limitant ainsi les risques liés à leur présence résiduelle dans le matériau final. Les photopolymérisations ont été réalisées dans un microréacteur modèle (cuve spectroscopique d’épaisseur 0,1 à 1 mm). La variation de plusieurs paramètres expérimentaux a permis d’identifier un ensemble de paramètres clés influençant les cinétiques de polymérisation tels que la taille des gouttelettes, corroborant ainsi les résultats de l’étude optique. Les longueurs d’onde d’irradiation et le chemin optique ont joué un rôle tout aussi déterminant ; le décalage vers des longueurs d’onde courtes et la diminution de l’épaisseur de l’échantillon accélèrent à la fois la création de radicaux amorceurs et le nombre d’entités nucléées. La versatilité du procédé a été démontrée en polymérisant rapidement (conversion totale en moins de 20 min) une large gamme de monomères acrylate, méthacrylate ou à base d’acétate de vinyle. En ce qui concerne le mécanisme d’auto-amorçage, nous avons prouvé que les espèces amorçantes provenaient vraisemblablement d’un biradical photoinduit, pouvant arracher ou transférer un hydrogène sur des molécules de monomère pour former des monoradicaux amorceurs. Par le biais de ce mécanisme original, la génération de radicaux est constante tout au long de la polymérisation ce qui pour effet d’impacter les caractéristiques des copolymères formés : l’indice de polymolécularité tend à augmenter et les masses molaires à diminuer par rapport à un processus photoamorcé conventionnel. Ces photopolymérisations ont été réalisées dans un photoréacteur annulaire à immersion et ont montré les mêmes évolutions en fonction de la taille de gouttelettes que lors d’expériences en cuve spectroscopique non agitées. A titre d’exemple, une conversion totale est atteinte en 1 h pour des tailles de gouttelettes de 60 nm et un contenu en solide de 30 %. L’auto-amorçage photoinduit a permis de générer rapidement une grande quantité de chaînes en croissance au sein des gouttelettes. [...]Issues and potentials of miniemulsion radical photopolymerization were discussed, starting from monomer miniemulsions’ optical properties to the synthesis of new semi-crystalline polysulfide nanoparticles by thiol-ene reaction. First, the relationship between the optical properties of miniemulsion and the polymerization efficiency was clarified. We established the major role of optical scattering on the acrylate nanodroplets’ photopolymerization kinetic, while the absorption was found to play a minor role. Whether diluted or concentrated medium (Kubelka-Munk model), light scattering is attenuated when droplet size decreased. The corollary is a significant improvement of UV light penetration within the reactor vessel leading to an acceleration of the polymerization kinetics. However, this conclusion was mitigated by the fact that compartmentalization effect could not be easily dissociated from optical effects. Note that in concentrated medium (solids content of 30 wt %), beyond 150 nm droplet diameter, the scattering coefficient leveled off regardless of droplet size. An absorbance drop was observed using UV-visible spectroscopy throughout the irradiation of the smallest acrylate miniemulsions (40 nm). This result suggested a polymerization mechanism occurring by monomer diffusion from non-nucleated droplets to growing particles. This non-invasive analysis (no dilution was required) is of high interest to study the nucleation mechanism.In a second part, we demonstrated that acrylate miniemulsion photopolymerization could be performed through a monomer self-initiation mechanism induced by short-wavelength UV irradiation ( < 300 nm). Such original photochemical initiation avoided the use of photoinitiator, thus limiting the risks associated with their residual presence in the final material. The self-initiated photopolymerizations were carried out in a model microreactor (spectroscopic cell of 0.1 to 1 mm thick). The variation of several parameters allowed us to identify key parameters influencing polymerization kinetics such as droplet size, thus corroborating the results of the optical study. The irradiation wavelength and the optical path played a crucial role; the shift towards shorter wavelengths and the sample thickness reduction accelerated both the generation of initiating radicals and the number of nucleated entities. The versatility of the method was demonstrated by fast polymerization (complete conversion achieved within 20 minutes) employing a wide range of acrylate, methacrylate and vinyl acetate monomers. Regarding the self-initiating mechanism, one proved that the initiating species likely originated from a biradical able to abstract or transfer hydrogen from monomer molecules, thereby forming initiating monoradicals. Through this original mechanism, the generation of radicals was constant throughout the polymerization, which impacted the characteristics of the copolymer chains: the polydispersity index tended to increase and the molar masses decreases when compared with a conventional photoinduced process. These photopolymerizations were also carried out in an annular immersion photoreactor and showed the same trends regarding the effect of droplet size as the experiments conducted in unstirred spectroscopic tank. For example, a complete conversion was reached after 1 h for a 60 nm acrylate miniemulsion with a solids content of 30 wt %. As a result, a self-initiated polymerization can generate rapidly a large amount of insoluble growing polymer chains within the droplets. This unique feature was exploited to overcome Ostwald ripening without the addition of a specific costabilizer. Photochemical self-initiation could also be used to form surfactant-free nanolatex via Pickering-stabilized miniemulsion photopolymerization. Indeed, Laponite clay adsorbed at the surface of the droplets showed an excellent UV transparency up to 200 nm. [...]
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Qi, Genggeng. « Unconventional radical miniemulsion polymerization ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26547.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jones, Christopher W.; Committee Chair: Schork, F. Joseph; Committee Member: Koros, William J.; Committee Member: Lyon, Andrew; Committee Member: Nenes, Athanasios. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ghazy, Omayma. « Binary blend nanoparticles with defined morphology ». [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-63345.
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Doucet, Jean-Baptiste. « Novel route to mono- and diglycerides synthesis in miniemulsion catalyzed by lipases ». [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-63562.
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Ethirajan, Anitha. « Polymeric nanoparticles synthesized via miniemulsion process as templates for biomimetic mineralization ». [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-65496.
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Kobitskaya, Elena. « Synthesis of hydrophobically modified polyacrylamide in inverse miniemulsion ». [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-65587.
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Etmimi, Hussein Mohamed. « Hydrophobic core/shell particles via miniemulsion polymerization ». Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019/539.
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Samer, Charles J. « Dynamic modeling of continuous miniemulsion polymerization reactors ». Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10228.
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Grabs, Ilka-Marina. « Synthese funktionalisierter Nanopartikel durch Copolymerisation in Miniemulsion ». Clausthal-Zellerfeld Papierflieger, 2009. http://d-nb.info/99561881X/04.
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Wiechers, Susann Amélie. « Copolymerisation saurer und basischer Monomere in inverser Miniemulsionen ». Clausthal-Zellerfeld Universitätsbibliothek Clausthal, 2010. http://d-nb.info/100354729X/34.
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Dobre, Adrian Cosmin. « Reaktionskalorimetrische Untersuchung der Polymerisation eines Zuckerderivates in Miniemulsionen ». Göttingen Sierke-Verl, 2009. http://d-nb.info/996716696/04.
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Ramírez, Ríos Liliana Patricia. « Superpara- and paramagnetic polymer colloids by miniemulsion processes ». [S.l. : s.n.], 2004. http://pub.ub.uni-potsdam.de/2004/0026/ramirez.pdf.
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Ramírez, Ríos Liliana Patricia. « Superpara- and paramagnetic polymer colloids by miniemulsion processes ». Phd thesis, Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/137/.
Texte intégralRésumé :
Polymerverkapselte magnetische Nanopartikel versprechen, in der Zukunft sehr erfolgreich bei Anwendungen in der Biologie und der Medizin eingesetzt werden zu können z. B. in der Krebstherapie und als Kontrastmittel bei der magnetischen Kernspinresonanztomographie. Diese Arbeit zeigt, dass durch die interdisziplinäre Kombination verschiedener Techniken Herstellungsverfahren und Eigenschaften solcher Partikel verbessert werden können. Unter Miniemulsionen versteht man wässrige Dispersionen relativ stabiler Öltröpfchen, zwischen 30 und 50 nm Größe. Ein Nanometer (nm) ist der 1.000.000.000ste Teil eines Meters. Ein Haar ist ungefähr 60.000 Nanometer breit.
Hergestellt werden Miniemulsionen durch Scherung eines Systems bestehend aus Öl, Wasser, Tensid (Seife) und einer weiteren Komponente, dem Hydrophob, das die Tröpfchen stabilisieren soll. Die Polymerisation von Miniemulsionen ermöglicht die Verkapselung anorganischer Materialen z. B. magnetischer Teilchen oder Gadolinium-haltiger Komponenten. Zu Optimierung des Verkapselung, ist es notwendig, die richtige Menge eines geeigneten Tensids zu finden.
Die magnetischen polymerverkapselten Nanopartikel, die in einer wässrigen Trägerflüssigkeit dispergiert sind, zeigen in Abhängigkeit von Partikelgröße, Zusammensetzung, elektronischer Beschaffenheit, etc. ein sogenanntes superpara- oder paramagnetisches Verhalten. Superpara- oder paramagnetisches Verhalten bedeutet, dass die Flüssigkeiten in Anwesenheit äußerer Magnetfeldern ihre Fließfähigkeit beibehalten. Wenn das Magnetfeld entfernt wird, haben sie keine Erinnerung mehr daran, unter dem Einfluss eines Magnetfeldes gestanden zu haben, d. h., dass sie nach Abschalten des Magnetfeldes selbst nicht mehr magnetisch sind.
Die Vorteile des Miniemulsionsverfahrens sind der hohe Gehalt und die homogene Verteilung magnetischer Teilchen in den einzelnen Nanopartikeln. Außerdem ermöglicht dieses Verfahren nanostrukturierte Kompositpartikel herzustellen, wie z. B polymerverkapselte Nanopartikel mit Nanoschichten bestehend aus magnetischen Molekülen.
Combining the magnetic properties of a given material with the tremendous advantages of colloids can exponentially increase the advantages of both systems. This thesis deals with the field of magnetic nanotechnology. Thus, the design and characterization of new magnetic colloids with fascinating properties compared with the bulk materials is presented.
Ferrofluids are referred to either as water or organic stable dispersions of superparamagnetic nanoparticles which respond to the application of an external magnetic field but lose their magnetization in the absence of a magnetic field.
In the first part of this thesis, a three-step synthesis for the fabrication of a novel water-based ferrofluid is presented. The encapsulation of high amounts of magnetite into polystyrene particles can efficiently be achieved by a new process including two miniemulsion processes. The ferrofluids consist of novel magnetite polystyrene nanoparticles dispersed in water which are obtained by three-step process including coprecipitation of magnetite, its hydrophobization and further surfactant coating to enable the redispersion in water and the posterior encapsulation into polystyrene by miniemulsion polymerization. It is a desire to take advantage of a potential thermodynamic control for the design of nanoparticles, and the concept of "nanoreactors" where the essential ingredients for the formation of the nanoparticles are already in the beginning. The formulation and application of polymer particles and hybrid particles composed of polymeric and magnetic material is of high interest for biomedical applications. Ferrofluids can for instance be used in medicine for cancer therapy and magnetic resonance imaging.
Superparamagnetic or paramagnetic colloids containing iron or gadolinium are also used as magnetic resonance imaging contrast agent, for example as a important tool in the diagnosis of cancer, since they enhance the relaxation of the water of the neighbouring zones. New nanostructured composites by the thermal decomposition of iron pentacarbonyl in the monomer phase and thereafter the formation of paramagnetic nanocomposites by miniemulsion polymerization are discussed in the second part of this thesis. In order to obtain the confined paramagnetic nanocomposites a two-step process was used. In the first step, the thermal decomposition of the iron pentacarbonyl was obtained in the monomer phase using oleic acid as stabilizer. In the second step, this iron-containing monomer dispersion was used for making a miniemulsion polymerization thereof.
The addition of lanthanide complexes to ester-containing monomers such as butyl acrylate and subsequent polymerization leading to the spontaneous formation of highly organized layered nanocomposites is presented in the final part of this thesis. By an one-step miniemulsion process, the formation of a lamellar structure within the polymer nanoparticles is achieved. The magnetization and the NMR relaxation measurements have shown these new layered nanocomposites to be very apt for application as contrast agent in magnetic resonance imaging.
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Xie, Min. « Nitroxide-mediated living radical styrene polymerization in miniemulsion ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/MQ54494.pdf.
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Tsavalas, John George. « A molecular level investigation of hybrid miniemulsion polymerization ». Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/11153.
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Bailly, Nathalie. « AB diblock copolymers via RAFT-mediated miniemulsion polymerization ». Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2707.
Texte intégralRésumé :
Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008.The Reversible addition fragmentation chain transfer (RAFT) technique is a robust and versatile technique that enables the synthesis of polymers of controlled molecular weight and polydispersity. The application of the RAFT technique in heterogeneous aqueous media has attracted great interest in academics and industry due to it being more environmentally friendly, besides its other advantages. To date, the synthesis of well-defined high molecular weight polymers via the RAFT process under industrially relevant conditions still remains a challenge for polymer chemists. The study addresses the application of the RAFT process in heterogeneous media, namely in miniemulsion polymerization, for the synthesis of AB diblock copolymers of n-butyl methacrylate and styrene. AB diblock copolymers of high molecular weight were successfully prepared via a twostep method. In the first step, a dithiobenzoate monofunctional RAFT agent was used in bulk polymerization with the first monomer, n-butyl methacrylate. After the polymerization, the majority of the polymer chains contained the thiocarbonyl-thio RAFT agent functionality, which makes the chains potentially active for chain extension. The polymeric RAFT agent (also referred to as the starting block) obtained in the first step was chain extended in the second step, in miniemulsion, upon further addition of fresh initiator and the second monomer, styrene. The effects of the initiator/RAFT agent concentration ratio on the miniemulsion systems were investigated. The miniemulsion systems used for the high molecular weight AB diblock copolymers exhibited living features despite the high polydispersity indices. Kinetic results showed an increase in the rate of polymerization throughout the polymerization. Size exclusion chromatography (SEC) results indicated significant broadening in the molecular weight distributions and a steep increase in the polydispersity during the polymerization. It was concluded that the broad molecular weight distributions and steep increase in the polydispersity was not only related to the initiator concentration but possibly due to other factors such as inhomogeneity in the miniemulsion system and a transition in the kinetic behavior during the polymerization. Secondary particle formation emerged from kinetic data and transmission electron microscopy (TEM) results, but this were not supported by the SEC results. The effect of the use of a water-soluble initiator on the miniemulsion system was also investigated. Results indicated a similar behavioral pattern as observed in the AIBNinitiated systems, and not much improvement in terms of the molecular weight distributions and polydispersity was seen. The effect of the molecular weight of the diblock copolymers on the miniemulsion system was investigated. Poly(n-butyl methacrylate)-b-poly(styrene) diblock copolymers of lower molecular weight were synthesized via the two-step process. Kinetic results indicated a similar behavioral trend as to that of the high molecular weight diblock copolymers synthesized, however SEC chromatograms showed narrower molecular weight distributions and low polydispersity indices.
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Lima, Ana Paula Dantas de. « Enzimatic hydrolysis and glycerolysis of triglyceride in miniemulsion ». Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13753.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoCoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
O objetivo desse trabalho foi investigar a produÃÃo de mono (MG) e diglicerÃdeos (DG) a partir da hidrÃlise e/ou glicerÃlise enzimÃtica de um triglicerÃdeo (TG), utilizando-se a tÃcnica de miniemulsÃo. Utilizou-se como substrato o triglicerÃdeo do Ãcido caprÃico, a tricaprilina. Dois tipos de lipases foram utilizadas neste estudo a fim de se estudar a regioseletividade da reaÃÃo de hidrÃlise em miniemulsÃo. A lipase Rhizopus arrhizus (RAL) com regiosseletividade especÃfica sn-1,3 e a lipase Pseudomonas cepacia (PS) devido a sua ausÃncia de regioseletividade. Uma vez que hidrÃlise e glicerÃlise ocorrem na interface Ãleo-Ãgua, diferenÃas na Ãrea interfacial pela variaÃÃo da quantidade de surfactante e a influÃncia da concentraÃÃo das lipases tambÃm foram estudadas. AlÃm disso, a glicerÃlise foi estudada pela adiÃÃo de glicerol na preparaÃÃo da miniemulsÃo com o objetivo de direcionar a formaÃÃo dos produtos para uma maior quantidade de monoglicerÃdeos. Os produtos das reaÃÃes foram caracterizados e quantificados pelas tÃcnicas de H1-RMN e HPLC. Por HPLC obteve-se as quantidades totais de cada componente (MG, DG, Ãcido graxo livre e glicerol) enquanto que por RMN, pode-se calcular as quantidades individuais de cada produto formado (1-MG, 2-MG, 1,2-DG e 1,3-DG). Observando-se as concentraÃÃes dos produtos formados na hidrÃlise catalisada pela lipase PS, pÃde-se concluir que essa lipase, conhecida por sua nÃo-especificidade, catalisou a reaÃÃo preferencialmente na posiÃÃo sn-2, tendo como principais produtos 1,3-DG e 1-MG, com concentraÃÃes mÃximas de 29% e 22%, respectivamente. Por outro lado, a hidrÃlise catalisada pela lipase RAL, teve como principais produtos 1,2-DG e 2- MG, com concentraÃÃes mÃximas de 24% e 18%, respectivamente. Os resultados corroboram com a preferÃncia dessa lipase pela posiÃÃo sn-1,3. Observou-se para a glicerÃlise em miniemulsÃo catalisada pela lipase RAL, que a adiÃÃo de glicerol mudou o perfil de formaÃÃo de 1-MG e 2-MG, alcanÃando um mÃximo de 10-12% e 32-35%, respectivamente, apÃs 4h, comparado com 8 e 22-25% durante hidrÃlise. JÃ para glicerÃlise catalisada pela lipase PS, os resultados mostraram que essa lipase, que apresentou preferÃncia pela posiÃÃo sn-2 na hidrÃlise, passou a ter comportamento similar ao da lipase RAL, sn-1,3 especÃfica.
The aim of this study was to investigate the production of mono (MG) and diglycerides (DG) from the enzymatic hydrolysis and/or glycerolysis of a triglyceride (TG), using the technique of miniemulsion. As substrate, the triglyceride of the caproic acid, the tricaprylin was used. Two types of lipases were used in this study in order to examine the regioselectivity of the hydrolysis reaction in miniemulsion. The Rhizopus arrhizus lipase (RAL) known as specific sn-1,3 and the Pseudomonas cepacia (PS) known as non-specific lipase. Since hydrolysis and glycerolysis occur in the oil-water interface, differences in the interfacial area by varying the amount of surfactant concentration and the influence of the lipase were also studied. Additionally, glycerolysis was studied by adding glycerol to prepare the miniemulsion in order to increase amount of monoglycerides as products. The products were characterized and quantified by the 1H-NMR and HPLC techniques. HPLC afforded the quantification of total amount of each component (MG, DG, free fatty acid and glycerol) whereas by NMR, it was possible to calculate the amounts of each individual isomers (1-MG, 2-MG, 1,2-DG e 1,3-DG). The concentrations of the isomers formed in the lipase PS catalyzed hydrolysis showed that this lipase, known for its non-specificity, catalyzed the reaction preferentially at the sn-2 position, having as main products 1,3-DG and 1-MG, with maximum concentrations of 29% and 22%, respectively. On the other hand, hydrolysis catalyzed by lipase RAL has as main products 1,2-DG and 2-MG with maximum concentrations of 35% and 25% respectively, at 4h. The results corroborate the preference of the lipase for the sn-1,3 position. The initial addition of glycerol to the reaction catalyzed with lipase RAL did not significantly affect the reaction profiles and the formation rates of the diglycerides. However, the introduction of glycerol changes the profile of the formation of 1- and 2-monocaprylin, reaching the concentration maximum of 10-12% and 32-35% after 4h compared to 8% and 22-25% during the hydrolysis reaction, respectively. Lipase PS, an unspecific enzyme (slight preference for the sn-2-position in hydrolysis in miniemulsion) showed in presence of glycerol a behavior similar to RAL, a sn-1,3 specific lipase.
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Volz, Marissa. « Synthese neuartiger Initiatorsysteme und röntgenopaker Hybridpartikel in Miniemulsion zur Anwendung in polymeren Dentalwerkstoffen ». [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-64782.
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Smith, Jodi. « Kinetic study of stable free radical polymerization in miniemulsion ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ63370.pdf.
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Riedel, Denise [Verfasser]. « Molecular imprinting of proteases via miniemulsion polymerization / Denise Riedel ». Ulm : Universität Ulm, 2019. http://d-nb.info/1190727269/34.
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Weiss, Andreas. « Kristallisationsphänomene in Miniemulsion und Bildung anorganischer Filme aus Nanopartikeln ». [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-57915.
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Delbé, Michèle [Verfasser], et S. [Akademischer Betreuer] Bräse. « Photochemisch initiierte Polymerisation in Miniemulsionen / Michèle Delbé. Betreuer : S. Bräse ». Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1058165224/34.
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Holzapfel, Verena. « Funktionalisierte fluoreszierende und magnetische Polymernanopartikel für biomedizinische Anwendungen ». [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-57808.
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Jagielski, Nicole. « Synthese strukturierter Hybridnanopartikel und neuartiger filmbildender Polymerdispersionen via Miniemulsionsprozess ». [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-59759.
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Steiert, Nico. « Reaktionen im begrenzten Raum zur Herstellung und Verkapselung von Pigmenten ». [S.l. : s.n.], 2009. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-66471.
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Ma, John W. « Mechanistic model studies of living nitroxide-mediated styrene miniemulsion polymerization ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2002. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65680.pdf.
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Dong, Hai. « Water-borne oil-modified polyurethane coatings via hybrid miniemulsion polymerization ». Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/8514.
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Samer, Charles J. « Polymer-stabilized miniemulsion polymerization in a continuous stirred-tank reactor ». Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/11142.
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Nabih, Nermeen [Verfasser]. « Hybrid inorganic-polymer coatings prepared via miniemulsion process / Nermeen Nabih ». Mainz : Universitätsbibliothek Mainz, 2011. http://d-nb.info/1031790691/34.
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Ouzineb, Keltoum. « Emulsion and miniemulsion polymerization : stabilization, tubular reactor and practical applications ». Lyon 1, 2003. http://www.theses.fr/2003LYO10022.
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L'objectif de cette thèse est de proposer des applications innovantes pour la polymérisation en émulsion et en mini-émulsion dans différents procédés : réacteur fermé parfaitement agité, semi-continu et continu. Des résultats similaires au réacteur fermé furent obtenus dans le réacteur tubulaire continu pour des taux de solides inférieurs à 30 % en poids. La polymérisation en mini-émulsion s'est alors révélée comme un candidat prometteur en vue d'éliminer les problèmes de démixtion rencontrés à des taux de solide plus important. Dans une étude préliminaire en réacteur fermé nous avons mis en évidence la nucléation complète des gouttelettes de monomères et leurs compartimentalisations. Des procédés de synthèse de latex à haut extrait sec et de viscosité faible avec un contrôle de la distribution des masses molaires ont été ainsi proposés. En mini-émulsion des réactions à taux de solides supérieurs à 30 % en poids ont été réalisées dans le réacteur tubulaire continu
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Russum, James. « Controlled Radical Polymerizations in Miniemulsions : Advances in the Use of RAFT ». Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-10112005-105314/.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2006.Jones, Christopher, Committee Chair ; Schork, F. Joseph, Committee Co-Chair ; Weck, Marcus, Committee Member ; Meredith, Carson, Committee Member ; Agrawal, Pradeep, Committee Member.
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Holtze, Christian H. W. « Neue Einflüsse und Anwendungen von Mikrowellenstrahlung auf Miniemulsionen und ihre Kompositpolymere ». Phd thesis, Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/249/.
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Miniemulsionen bestehen aus zwei miteinander nicht mischbaren Flüssigkeiten, von der die eine in Form kleiner Tröpfchen fein in der anderen verteilt (dispergiert) ist. Miniemulsionströpfchen sind mit Durchmessern von ungefähr 0,1 Mikrometer kleiner als herkömmliche Emulsionen und können u. a. als voneinander unabhängige Nanoreaktoren für chemische Reaktionen verwendet werden. Man unterteilt sie in direkte Miniemulsionen, in denen ein Öl in Wasser dispergiert ist, und inverse Miniemulsionen, in denen Wasser in Öl dispergiert wird. In dieser Arbeit wird das besondere chemische und physikalische Verhalten solcher Miniemulsionen unter dem Einfluß von Mikrowellenstrahlung untersucht. Dabei werden sowohl für Öl-in-Wasser als auch für Wasser-in-Öl-Miniemulsionen grundlagenwissenschaftliche Entdeckungen beschrieben und durch neue Modelle erklärt. Der praktische Nutzen dieser bislang unbeschriebenen Effekte wird durch ingenieurwissenschaftliche Anwendungsbeispiele im Bereich der Polymerchemie verdeutlicht.
1. Polymerisation mit "überlebenden Radikalen" (Surviving Radical Polymerization)
Für die Herstellung von sog. Polymerlatizes (Kunststoffdispersionen, wie sie u. a. für Farben verwendet werden) aus direkten Styrol-in-Wasser Miniemulsionen werden die Styroltröpfchen als Nanoreaktoren verwendet: Sie werden mit Hilfe von Radikalen durch eine Kettenreaktion zu winzigen Polymerpartikeln umgesetzt, die im Wasser dispergiert sind. Ihre Materialeigenschaften hängen stark von der Kettenlänge der Polymermoleküle ab. In dieser Arbeit konnten durch den Einsatz von Mikrowellenstrahlung erstmals große Mengen an Radikalen erzeugt werden, die jeweils einzeln in Tröpfchen (Nanoreaktoren) auch noch lange Zeit nach dem Verlassen der Mikrowelle überleben und eine Polymerisationskettenreaktion ausführen können. Diese Methode ermöglicht nicht nur die Herstellung von Polymeren in technisch zuvor unerreichbaren Kettenlängen, mit ihr sind auch enorm hohe Umsätze nach sehr kurzen Verweilzeiten in der Mikrowelle möglich – denn die eigentliche Reaktion findet außerhalb statt. Es konnte gezeigt werden, dass durch Einsatz von Zusatzstoffen bei unvermindert hohem Umsatz die Polymerkettenlänge variiert werden kann. Die technischen Vorzüge dieses Verfahrens konnten in einer kontinuierlich betriebenen Pilotanlage nachgewiesen werden.
2. Aufheizverhalten inverser Miniemulsionen in Mikrowellenöfen
Das Aufheizverhalen von Wasser-in-Öl Miniemulsionen mit kleinen Durchmessern durch Mikrowellen ist überaus träge, da sich nur das wenige Wasser in den Tröpfchen mit Mikrowellen aufheizen lässt, das Öl jedoch kaum. Solche Systeme verhalten sich gemäß der "Theorie des effektiven Mediums". Werden aber etwas größere Tröpfchen im Mikrometerbereich Mikrowellen ausgesetzt, so konnte eine wesentlich schnellere Aufheizung beobachtet werden, die auf eine Maxwell-Wagner-Grenzflächenpolarisation zurückgeführt werden kann. Die Größenabhängigkeit dieses Effekts wurde mit Hilfe der dielektrischen Spektroskopie quantifiziert und ist bislang in der Literatur nie beschrieben worden. Zur genauen Messung dieses Effekts und zu seiner technischen Nutzung wurde ein neuartiges Membranverfahren für die Herstellung von großen Miniemulsionströpfchen im Mikrometerbereich entwickelt.
3. Herstellung von Kompositpolymeren für Mikrowellenanwendungen
Um die untersuchte Maxwell-Wagner-Grenzflächenpolarisation technisch nutzen zu können, wurden als dafür geeignete Materialien Kompositpolymere hergestellt. Das sind Kunststoffe, in denen winzige Wassertropfen oder Keramikpartikel eingeschlossen sind. Dazu wurden neuartige Synthesewege auf der Grundlage der Miniemulsionstechnik entwickelt. Ihr gemeinsames Ziel ist die Einschränkung der üblicherweise bei Polymerisation auftretenden Entmischung: In einem Verfahren wurde durch Gelierung die Beweglichkeit der emulgierten Wassertröpfchen eingeschränkt, in einem anderen wurde durch das Einschließen von Keramikpartikeln in Miniemulsionströpfchen die Entmischung auf deren Größe beschränkt. Anwendungen solcher Kompositpolymere könnten künstliche Muskeln, die Absorption von Radarstrahlung, z. B. für Tarnkappenflugzeuge, oder kratzfeste Lacke sein.
Bei diesen Experimenten wurde beobachtet, daß sich u. U. in der Miniemulsion große Tröpfchen bilden. Ihr Ursprung wird mit einer neuen Modellvorstellung erklärt, die die Einflüsse auf die Stabilität von Miniemulsionen beschreibt.
Miniemulsions are composed of two immiscible fluids. One of which is distributed as small droplets (dispersed) in the other one. Having diameters of down to 0.05 micrometers, droplets of miniemulsions are smaller than those of conventional emulsions. Among other applications, they can be employed as independent nano-reactors for chemical reactions. They are subdivided in direct miniemulsions, for which an oil is dispersed in an aqueous phase, and inverse miniemulsions, for which water is dispersed in an oil phase. In this work, the specific chemical and physical behaviour of miniemulsions under the influence of microwave-radiation was investigated. For water-in-oil as well as for oil-in-water miniemulsions fundamental discoveries are described and explained by new models. The practical importance of these new effects is exemplified by applications in the field of polymer-chemistry.
1. Polymerization with "surviving radicals"
For the production of so-called polymer-latices (dispersions of plastics, as they are used in paints and coatings) from direct styrene-in-water miniemulsions, the styrene-droplets can be considered as separate nano-reactors. Upon radical polymerization, they may be transformed to polymer particles dispersed in water in a 1:1 conversion. Their material properties strongly depend on the chain-length of the polymer molecules. In this work, using microwave radiation, for the first time great quantities of radicals could be generated that survive within the individual droplets (nano-reactors) even for a long time after leaving the microwave oven, carrying out polymerization. This method is suited for the production of polymers with great chain-lengths that cannot be obtained with other technically relevant methods. Moreover, it yields great conversion after very short residence-times in the microwave-oven: the actual reaction takes place outside of the oven. Employing additives allows the variation of chain-length at the same great net rates of conversion. The technical promises of this method could be demonstrated in a continuously operated pilot plant.
2. Heating behaviour of inverse miniemulsions with microwave-radiation
The heating of water-in-oil miniemulsions with small droplets using microwaves is very slow, as only the water absorbs microwave-radiation and not the oil. The system behaves according to the "effective medium theory". If slightly larger droplets with diameters of about a micron are subjected to microwaves, they are being heated much more readily, which can be attributed to a Maxwell-Wagner-effect. The size-dependence of this effect has never been described in the literature. It could be quantified with dielectric spectroscopy. For the controlled production of big miniemulsion droples on the micron-scale and for the technical application of the size-dependence, a continuously operated membrane-emulsification device was developed.
3. Production of composite polymers for microwave-applications
Suitable composite polymers were produced in order to technically exploit the size-dependence of the Maxwell-Wagner-effect. They may contain sub-micron sized water droplets or ceramic nanoparticles. For their synthesis, new strategies on the basis of miniemulsion-systems were developped, which avoid the usual phase-separation upon polymerization. In one approach, the mobility of the dispersed water droplets was limited through the gelation of the oil phase, in another approach phase separation of ceramic nanoparticles entrapped within miniemulsion droplets was restricted to the dimensions of the droplets. Applications of such composite polymers could be the development of artificial muscles, the absorption of radar radiation (e.g. for stealth applications) or scratch-resistant coatings.
In these experiments the existence of stable big droplets in miniemulsions was discovered. Their origin can be explained by a new model that describes the influences on miniemulsion stability.
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Wiechers, Susann Amélie [Verfasser]. « Copolymerisation saurer und basischer Monomere in inverser Miniemulsionen / Susann Amélie Wiechers ». Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2010. http://d-nb.info/100354729X/34.
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Schatzinger, Andreas. « Enzymkatalysierte Kondensationsreaktionen in wässrigen Miniemulsionen und radikalische Polymerisationen in ionischen Flüssigkeiten ». [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-63669.
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Emiliani, Laura. « Raft miniemulsion (co)polymerization of methyl methacrylate and n-butyl acrylate ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8606/.
Texte intégralRésumé :
This thesis work is part of a larger synthesis project about alkyd resins from natural sources, copolymerized with methyl acrylate and n-butyl acrylates, which wil be used for coatings purpose.
The aim is to control the copolymerization of methyl acrylate and n-butyl acrylate in RAFT miniemulsion. The research was divided into three parts. First the homopolymerization of methyl methacrylate and n-butyl acrylate was studied by varying different parameters such as the amount of surfactant, the amount of initiator, pH, and especially the RAFT agent. Then two macro RAFT agents were synthesized, as suggested by the existing literature. Finally, the two monomers were copolymerized using both the RAFT used for the homopolymerization and those synthesized in the second stage.
To verify the obtained control over the polymerization, the synthesized polymers were analyzed by gel permeation chromatography, GPC, thus finding their molecular weight and its polydispersity.
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Hermant, Marie-Claire. « An investigation into the mechanistic behaviour of RAFT-mediated miniemulsion polymerizations ». Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/248.
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Tong, Zhaohui. « Water-based suspension of polymer nanoclay composite prepared via miniemulsion polymerization ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19763.
Texte intégralRésumé :
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Yulin Deng; Committee Member: Howard (Jeff) L. Empie; Committee Member: J. Carson Meredith; Committee Member: Jeffery S. Hsieh; Committee Member: Timothy Patterson.
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Chakraborty, Sourav. « Synthesis of magnetic polymer nanoparticles using RAFT mediated miniemulsion polymerization in presence of amphiphilic ionic liquid as surfactant ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-164920.
Texte intégralRésumé :
Polymer magnetic composite (PMC) nanoparticles have gained a large attention due to their potential use in several biomedical applications from biomedical to engineering field. Among the different heterogeneous polymerization techniques that are generally used to prepare hybrid polymer particles, miniemulsion polymerization is proved to be an efficient one. The occurrence of preferential droplet nucleation in case of miniemulsion polymerization results in a 1:1 copy of monomer droplets to the polymer particles and such a mechanistic pathway offers a suitable environment for the preparation of hybrid polymer nanoparticles in the range between 50 to 500 nm.
The surfactant in miniemulsoin plays a significant role to stabilize the droplets/particles and also in the encapsulation of nanoparticles. In the present study, a new class of surfactant, called amphiphilic ionic liquid, has been employed in the field of miniemulsion. The amphiphilic ionic liquid has amazing ability to impart surface tunable characteristics to the polymer particles when present on the surface of the particles. Thus the aim of the present work is to synthesize polymer magnetic composite nanoparticles with good colloidal stability, high content of magnetic nanoparticles as well as the chance for further surface functionality. Such magnetic nanoparticles may find applications in various fields.
At first, the aim of the work was to establish a suitable recipe with ionic liquid as surfactant for the execution of miniemulsion polymerization. Monodisperse polystyrene nanoparticles were possible to be synthesized reproducibly. The established recipe was utilized to carry out the synthesis of PMC nanoparticles. Iron oxide (Fe3O4) was taken as magnetic nanoparticles (MNP) and it was hydrophobized with oleic acid to disperse in styrene. The concentration of feed MNP was varied to observe its influence on the characteristics of PMC nanoparticles. Stable dispersion of magnetic polystyrene particles was possible to be synthesized up to 8 wt% feed MNP. But feeding 12 wt% MNP resulted in the development of large amount of coagulum associated with instability in the dispersion. TGA investigation confirmed a significantly lower MNP content (8.2 wt%) of the composite compared to the feed amount. TEM investigation showed inhomogeneous distribution of MNP among polystyrene particles and agglomeration of MNP was observed on the surface of polystyrene particles.
Considering the inability of the single step miniemulsion polymerization for the preparation of high MNP content polymer particles, it was aimed to find a new strategy which can produce such material. Inspired from the affinity of carboxylic acid group towards the surface of MNP, it was aimed to synthesize carboxyl functionalized polystyrene which was expected to improve the interaction between polymer and magnetic nanoparticles. For this purpose, RAFT mediated miniemulsion polymerization was performed in presence of a carboxyl functionalized chain transfer agent (CTA). The colloidal stability was much better compared to the previous case of non-RAFT experiments. From a feed MNP of 8 wt%, a high final MNP content up to ~27 wt% could be achieved and all the dispersions were highly stable. The higher MNP content in the final composites compared to the feed ratio was a result of the low monomer conversion and could be adjusted by a proper tuning of AIBN to CTA mole ratio.
Another significant influence of the carboxyl functionalized CTA was observed on the morphology of the composite nanoparticles. The MNP were distributed homogeneously among the PS particles. Regarding the dispersion of MNP in the individual polystyrene particles, it was observed that higher amount of CTA resulted in a homogeneous dispersion of MNP whereas higher amount of initiator ended up producing asymmetric Janus like morphology.
Apart from that, due to the involvement of CTA in the polymerization, much lower molecular weight of the polystyrene chains was developed compared to the free radical process and the molecular weight distribution of PS in the composite nanoparticles became much narrower through the RAFT polymerization. Thus a relatively good control over the polymerization process was achieved through RAFT polymerization which was confirmed by a nearly linear increase of molecular weight (Mn) with time of polymerization and thus, monomer conversion.
In the recipe of miniemulsion, costabilizer plays an important role to retard monomer diffusion from smaller to larger droplets. Hexadecane, being the most frequently used costabilizer for miniemulsion, has been employed in this study so far. But its volatile nature restricts its utilization in several applications. For the replacement of hexadecane, a carboxyl functionalized polystyrene is employed as a costabilizer as well as a macro CTA in miniemulsoin polymerization of styrene. For this purpose, low molecular weight carboxyl bi-functionalized polystyrene (9000 g/mole) was synthesized by thermal bulk RAFT polymerization. The carboxylated polystyrene worked successfully as a costabilizer in miniemulsion and molecular weight investigation confirmed the integration of the carboxyl functionalized macro CTA into the developing polystyrene chain via RAFT polymerization. This strategy was employed successfully to synthesize stable dispersion of PMC nanoparticles with a reasonable content of MNP in the system. A homogeneous morphology was observed regarding the distribution of MNP among the polystyrene particles.
The strategy of using macro CTA as costabilizer can be utilized to synthesize various functional copolymers with control architecture without any added monomer and CTA in the system. Moreover, presence of functionality within the monomer droplets can be effective to encapsulate several nanomaterials using miniemulsion polymerization.
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Mellon, Véronique. « Synthesis and characterization of waterborne polymer/laponite nanocomposite latexes through miniemulsion polymerization ». Lyon 1, 2009. http://www.theses.fr/2009LYO10028.
Texte intégralRésumé :
Ce travail décrit l’élaboration et la caractérisation de latex composites polymère/argile élaborés par polymérisation en miniémulsion. Deux approches appelées voie I et voie II ont été explorées. La différence principale entre ces deux voies de synthèse réside dans la localisation de l’argile au début de la polymérisation. L’argile est disperse��e dans la phase aqueuse pour la voie I et dans le mélange de monomères pour la voie II. La synthèse des particules composites polymère/Laponite fait intervenir quatre étapes : i) la modification chimique de surface de la Laponite, ii) la dispersion de l’argile modifiée soit dans l’eau soit dans la phase organique, iii) la formation de nano-gouttelettes en présence de Laponite modifiée et iv) la polymérisation en miniémulsion. La modification chimique de la Laponite constitue une étape déterminante et a été étudiée en détails. Dans la voie I, un amorceur de polymérisation radicalaire a été intercalé entre les feuillets de la Laponite par échange cationique tandis que dans la voie II, la Laponite a été rendue organophile par intercalation de tensioactifs cationiques et greffage d’organosilanes polymérisables. Par la suite, une attention particulière a été portée au mécanisme de polymérisation, à la stabilité colloïdale des particules de latex ainsi qu’à leur morphologie. Il a été montré que la stabilité des latex est étroitement liée à l’état de dispersion de l’argile dans l’eau ou dans la phase organique. Tandis que dans la voie I, les plaquettes d’argiles sont en surface des particules de latex, dans la voie II, elles sont encapsulées au sein des particules polymères. Les films issus de ces latex présentent des propriétés mécaniques amélioréesThis work describes the elaboration and characterization of polymer/Laponite nanocomposite latexes through miniemulsion polymerization. Two synthetic approaches, called Route I and Route II, have been investigated. The main difference between these two strategies relies on clay localization at the beginning of polymerization. The clay is dispersed in the water phase for Route I and in the monomer phase for Route II. Synthesis of the polymer/clay nanocomposite involves four steps: i) chemical modification of Laponite, ii) dispersion of the organoclay either in water or in the monomer phase, iii) nanodroplet formation in the presence of organically-modified Laponite and iv) miniemulsion polymerization. Clay modification is a determinant step and was studied in details. In Route I, a free radical initiator was intercalated into Laponite through cation exchange while in Route II, Laponite was modified by cationic surfactants or through grafting of polymerizable organosilane molecules. Then, a particular attention was paid to polymerization mechanism, colloidal stability and particle morphology. It was shown that the latex stability was closely related to the initial dispersion state of the clay in the aqueous or organic phases. The better was the clay dispersion, the greater was the latex colloidal stability. While in Route I, the clay platelets were located at the particle surface in an armoured-like morphology, in Route II, the clays were encapsulated inside the polymer particles. The films elaborated from these latexes showed enhanced mechanical properties
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Thongnuanchan, Bencha. « A low temperature alkoxyamine designed for use in nitroxide-mediated miniemulsion polymerization ». Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/a-low-temperature-alkoxyamine-designed-for-use-in-nitroxidemediated-miniemulsion-polymerization(9dddd46a-9756-41a2-8b66-66fac7d360c9).html.
Texte intégralRésumé :
The basis for this research project is based on the discovery in the previous research that 2,2' ,5-trimethyl-3-( I-phenylethoxy)-4-tert-butyl-3-azahexane, (Styryl- TITNO) is able to control bulk polymerization of styrene at temperature as low as 70°C. The principle objective of this project was to evaluate the feasibility of using Styryl- TITNO to control radical solution and miniemulsion polymerizations at temperatures below 100°C. Styryl- TITNO was shown to effect solution polymerizations of both n-butyl acrylate (BA) and styrene below 100°C. Polymerization temperature was shown to be a crucial parameter for achieving control in Styryl- TITNO -mediated polymerizations. Good control of the number-average molecular weight (Mn) and molecular weight dispersity for the polymerization of BA was observed at 90°C. However, a lower temperature of 70 °C is required for good control of styrene polymerization. Living characteristics of polymer chains were demonstrated by a sequential chain extension of TITNO -terminated PBA with styrene at 90°C to form poly(n-butyl acrylate)- block-poly[(n-butyl acrylate)-co-styrene], [pBA-b-P(BA-co-PS)], block copolymers. An improvement in livingness in these reactions was observed when the second P(BAlstyrene) block was formed at 70°C after the first PBA block was produced at 90°C. Kinetics studies facilitated determination of the activation-deactivation equilibrium constant (K), which for styrene polymerization at 90°C (K = 4.1 x 10.9 mol L-J at 90°C and 3.0 x 10-9 mol L-J at 70 "C) is nearly an order of magnitude higher than that for BA polymerization at the same temperature (K = 8.5 x 10-11 mol L-I). This is the reason why BA polymerization shows better control than styrene polymerization at 90°C. The activation energy (Ea) for thermolysis of Stryl- TITNO is 104.1 kJ mol", which is relatively low compared to the literature values of Ea for various styryl alkoxymines. This explains why Styryl- TITNO is able to effect polymerization at temperatures as low as 70 "C. The studies of Styryl- TITNO-mediated miniemulsion polymerizations at 90 "C indicate that accumulation of free TITNO• in the particles is an issue for use of Styryl- TITNO in miniemulsion polymerizations. The use of L-ascorbic acid (L-AA) and L-ascorbic acid 6-palmitate (L-AAP) as nitroxide scavengers to reduce the level of free TITNO • in the polymerization was investigated. The best result was observed for the polymerization of BA in the presence of 5.35 mol% of L-AAP relative to Styryl- TITNO, which attained 48% conversion after 5 h. The chain extension of isolated TITNO -terminated PBA, TITNO -PBA, was used to examine the livingness of - polymer -chains before the rate of polymerization was severely retarded. The livingness of TITNO-PBA was evidenced by a shift of the staring PBA molecular weight distribution towards higher molecular weight, which provides solid evidence that the majority of polymer chains remained living. Thus, it can be concluded with certainty that the accumulation of free TITNO• was mainly responsible for the suppression of polymerization in miniemulsion polymerizations mediated by Styryl- TITNO.
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Fuchs, Adrian Vaughan. « The encapsulation of gold nanoparticles using RAFT, ATRP and miniemulsion polymerisation techniques ». Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/31708/3/Adrian_Fuchs_Thesis.pdf.
Texte intégralRésumé :
The investigation into the encapsulation of gold nanoparticles (AuNPs) by poly(methyl methacrylate) (PMMA) was undertaken. This was performed by three polymerisation techniques including: grafting PMMA synthesised by reversible addition-fragmentation chain transfer (RAFT) polymerisation to AuNPs, grafting PMMA synthesised by atom transfer radical polymerisation (ATRP) from the surface of functionalised AuNPs and by encapsulation of AuNPs within PMMA latexes produced through photo-initiated oil-in-water (o/w) miniemulsion polymerisation. The grafting of RAFT PMMA to AuNPs was performed by the addition of the RAFT functionalised PMMA to citrate stabilised AuNPs. This was conducted with a range of PMMA of varying molecular weight distribution (MWD) as either the dithioester or thiol end-group functionalities. The RAFT PMMA polymers were characterised by gel permeation chromatography (GPC), ultraviolet-visible (UV-vis), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), Fourier transform Raman (FT-Raman) and proton nuclear magnetic resonance (1H NMR) spectroscopies. The attachment of PMMA to AuNPs showed a tendency for AuNPs to associate with the PMMA structures formed, though significant aggregation occurred. Interestingly, thiol functionalised end-group PMMA showed very little aggregation of AuNPs. The spherical polymer-AuNP structures did not vary in size with variations in PMMA MWD. The PMMA-AuNP structures were characterised using scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive X-ray analysis (EDAX) and UV-vis spectroscopy. The surface confined ATRP grafting of PMMA from initiator functionalised AuNPs was polymerised in both homogeneous and heterogeneous media. 11,11’- dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane] (DSBr) was used as the surface-confined initiator and was synthesised in a three step procedure from mercaptoundecanol (MUD). All compounds were characterised by 1H NMR, FTIR-ATR and Raman spectroscopies. The grafting in homogeneous media resulted in amorphous PMMA with significant AuNP aggregation. Individually grafted AuNPs were difficult to separate and characterise, though SEM, TEM, EDAX and UV-vis spectroscopy was used. The heterogeneous polymerisation did not produce grafted AuNPs as characterised by SEM and EDAX. The encapsulation of AuNPs within PMMA latexes through the process of photoinitiated miniemulsion polymerisation was successfully achieved. Initially, photoinitiated miniemulsion polymerisation was conducted as a viable low temperature method of miniemulsion initiation. This proved successful producing a stable PMMA with good conversion efficiency and narrow particle size distribution (PSD). This is the first report of such a system. The photo-initiated technique was further optimised and AuNPs were included into the miniemulsion. AuNP encapsulation was very effective, producing reproducible AuNP encapsulated PMMA latexes. Again, this is the first reported case of this. The latexes were characterised by TEM, SEM, GPC, gravimetric analysis and dynamic light scattering (DLS).
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Matahwa, Howard. « Synthesis and characterization of surfmers for latex stabilization in RAFT-mediated miniemulsion polymerization ». Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1105.
Texte intégral
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Udagama, Ravindra. « Synthesis of polymer-polymer hybrids by miniemulsion polymerisation and characterisation of hybrid latex ». Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00916670.
Texte intégralRésumé :
The objectives of work presented in this thesis are to understand droplet and particle formulation processes in order to make useful polymer-polymer hybrids in aqueous dispersions and use our fundamental understanding of these processes to: 1. Improve monomer conversion as much as possible. 2. Understand impact of these processes on hybrid film properties. Specific case studies of interest under commercially feasible conditions (i.e. solids content of 50wt %) were done based on two systems namely alkyd-acrylic and polyurethane-acrylic. Miniemulsification, miniemulsion polymerisation and characterisation of hybrid latex, chemical incorporation of alkyd and polyurethane to acrylic monomers were studied in detail. We have been able to successfully synthesise and characterise hybrid latex of about 100nm in particle diameter and high solids content (50wt %) to be used in coating and adhesive applications
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Antonello, Alice [Verfasser]. « Crystallization of complex inorganic systems within the confinement of miniemulsion droplets / Alice Antonello ». Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1136638776/34.
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Vosloo, Johannes Jacobus. « Controlled free radical polymerization in miniemulsion using Reversible Addition-Fragmentation Chain Transfer (RAFT) ». Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52174.
Texte intégralRésumé :
Thesis (MSc)--Stellenbosch University, 2001.ENGLISH ABSTRACT: A novel approach to conducting controlled free radical polymerization in aqueous systems using Reversible Addition-Fragmentation Chain Transfer (RAFT) has been studied. When conducting RAFT in aqueous systems, reaction conditions must be chosen such that monomer transport across the aqueous-phase is either eliminated or facilitated. This is to prevent the formation of the red layer associated with RAFT in emulsions. The formation of the red layer is ascribed to the inability of waterinsoluble, dithiobenzoate-endcapped oligomers to be sufficiently transported across the aqueous phase. The novel approach in this study focussed on eliminating monomer transport and comprises two fundamental steps: the synthesis of dithiobenzoate-encapped oligomers in bulk followed by miniemulsification of these oligomers to yield a polymerizable miniemulsion. Dithioesters that act as chain transfer agents in the RAFT -process were synthesized in situ, thereby eliminating laborious and time-consuming organic purification procedures of dithioesters. In situ formation of the RAFT-agents involved conducting the reaction between di(thiobenzoyl) disulfide and conventional azo-initiators of differing structures in the presence of monomer. The structure of the chosen azo-initiator played a role in the efficiency of the RAFT process when the reaction was conducted in the presence of monomer to control the free radical polymerization process. Synthesis of the oligomers was performed by heating di(thiobenzoyl) disulfide and a selected azo-initiator, in the presence of monomer for a specific reaction duration in bulk. After the reaction was stopped, these oligomers were then miniemulsified by adding water, surfactant and cosurfactant, followed by the application of shear to form the resulting mini emulsion. The free radical polymerization of the dithiobenzoate-endcapped oligomers in the miniemulsion proceeded in a controlled manner with molecular weight increasing in a linear fashion with increasing conversion, while polydispersities remained low. The familiar red layer formation associated with RAFT polymerization in conventional emulsions was not observed under these conditions. The effects of changing the cosurfactant (hydrophobe) as well as changing the degree of polymerization of the emulsified oligomers were also investigated and described.
AFRIKAANSE OPSOMMING: Hierdie studie is geloods om 'n nuwe benadering tot die beheerde vry-radikaal polimerisasie in water gebaseerde sisteme te ondersoek. Daar is spesifiek gekyk na die uitvoer van die RAFT (Reversible Addition-Fragmentation Chain Transfer) proses in emulsies. Wanneer RAFT in emulsies toegepas word, moet die toestande waaronder die reaksie uitgevoer word, versigtig opgestel word. Die toestande moet so gekies word dat die vervoer van monomere deur die waterfase óf geëlimineer word óf gefasiliteer word. Dit word gedoen om die faseskeiding in die vorm van 'n rooi laag, wat so kenmerkend van RAFT -polimerisasie in emulsies is, te voorkom. Hierdie faseskeiding vind plaas omdat die vervoer van ditiobensoaat endgroep-bevattende oligomere deur die waterfase tydens interval II, moeilik is a.g.v. hulle oplosbaarheid in water. Die nuwe benadering wat hier bestudeer is, het twee basiese stappe. Eerstens word die ditiobensoaat endgroep-bevattende oligomere in bulk gesintetiseer. Dit word gevolg deur die emulsifisering van die oligomere. Hierna vind verdere polimerisasie van die oligomere plaas deur die dormante oligomere te heraktiveer. Die ditio-esters wat as kettingoordrag agente optree in die RAFT proses, word in situ gesintetiseer. Hierdie modifikasie sny tydrowende organiese suiweringsmetodes uit. Die in situ RAFT agente word gesintetiseer deur di(tiobensoïel) disulfied met verskillende konvensionele azo-inisieerders te laat reageer. Die struktuur van die spesifieke azoinisieerder het wel 'n rol gespeel in die effektiwiteit van die RAFT proses om molekulêre massa te beheer as bg. reaksie in die teenwoordigheid van monomere uitgevoer is. Die sintese van die oligomere is gedoen deur di(tiobensoïel) en 'n azo-inisieerder te verhit in die teenwoordigheid van monomere. Die reaksie is gedoen in bulk en die graad van polimerisasie van die oligomere is beheer deur die reaksie te stop by verskillende tydstippe. Nadat die bulk reaksie gestop is, is hierdie oligomere ge-emulsifiseer deur die oligomere te meng met 'n seep, hidrofoob en water. Hierdie mengsel word dan onderwerp aan 'n vermengingskrag om 'n polimeriseerbare mini-emulsie te vorm. Die voortsetting van die polimerisasie van die oligomere in die mini-emulsie het op 'n beheerde wyse verloop, m.a.w. molekulêre massa wat linieêr toeneem met stygende omsetting. Polidispersiteit indekse van die polimere het deurentyd laag gebly in die stabielste sisteme. Onder hierdie toestande was daar geen kenmerkende rooi laagvorming te bespeur nie. Die effekte wat die verandering van die hidrofoob, asook die verandering van die graad van polimerisasie van die oligomere op die sisteem gehad het, is onder andere ook ondersoek en beskryf.
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Dolcet, Paolo. « Synthesis and Chemico-Physical and Structural Characterization of Nanocrystalline Inorganic Materials obtained via Miniemulsions ». Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423646.
Texte intégralRésumé :
In this PhD thesis, several inorganic nanostructures were synthesized through a wetchemistry synthetic route. In particular, the miniemulsion approach was exploited to induce the formation in confined space of pure and doped binary (oxides, sulfides and fluorides) and ternary (hydroxides) compounds, of metal/oxide nanocomposites and of hybrid organic/inorganic nanoparticles. Through this methodology, the investigated systems were obtained in crystalline form already at room temperature.
Various miniemulsion formulations were used to control the size and morphology of the investigated systems, achieving different emulsion stabilities and yields of crystalline powders.
The obtained materials were thoroughly characterized through a wide array of techniques from the compositional, structural and functional points of view. In particular, XRD (X-Ray Diffraction) was employed to assess the formation of crystalline materials and to calculate average crystallite sizes (through Rietveld refinement), and the data thus obtained were compared with micrographs collected through TEM (Transmission Electron Microscopy). This latter microscopy, coupled with SEM (Scanning Electron Microscopy), was also used to investigate the morphology of the synthesized nanostructures. In addition, the surface composition was explored through XPS (X-ray Photoelectron Spectroscopy) and, especially in the case of systems doped with transition metal or lanthanide ions, atomic ratios were compared to those obtained through ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) or ICP-MS (Inductively Coupled Plasma-Mass Spectroscopy). TGA-DSC (ThermoGravimetric Analysis-Differential Scanning Calorimetry) allowed to evaluate the presence and amount of residual surfactant moieties adsorbed on the materials surfaces.
In the case of the doped systems, XAS (X-ray Absorption Spectroscopy) measurements were performed in order to study in detail the local structure of the doping ions, also with respect to the hosting matrices. The obtained data were further correlated to the photoluminescence properties. These materials, also due to the biocompatibility of the selected matrices, might indeed be potentially applied for optical bioimaging. At this regard, cytotoxicity and cell viability assays were also performed on selected systems.In questa tesi di dottorato, diverse nanostrutture inorganiche sono state sintetizzate mediante un approccio sintetico per via umida. In particolare, l’approccio della miniemulsione è stato sfruttato per indurre la formazione in spazio confinato di composti binari (ossidi, solfuri e fluoruri) e ternari (idrossidi), sia in forma pura che drogati, e di nanocompositi metallo/ossido e nanoparticelle ibride organiche/inorganiche. Attraverso questa metodologia, i sistemi investigati sono stati ottenuti in forma cristallina già a temperatura ambiente. Miniemulsioni con varie formulazioni sono state usate per controllare le dimensioni e la morfologia dei sistemi investigati, ottenendo emulsioni con stabilità differenti e diversa resa in termini di prodotti cristallini. I materiali ottenuti sono stati caratterizzati in dettaglio attraverso numerose tecniche, sia dal punto di vista composizionale che da quello strutturare e funzionale. In particolare, l’XRD (X-Ray Diffraction) è stato utilizzato per valutare la formazione di materiali cristallini e, attraverso rifinimento Rietveld, calcolare le dimensioni medie dei cristalliti; i dati così ottenuti sono stati confrontati con le micrografie TEM (Transmission Electron Microscopy). Quest’ultima microscopia, affiancata al SEM (Scanning Electron Microscopy), è stata anche utilizzata per investigare la morfologia delle nanostrutture sintetizzate. In aggiunta, la composizione superficiale è stata esplorata attraverso XPS (X-ray Photoelectron Spectroscopy) e, specialmente nel caso dei sistemi drogati con ioni di metalli di transizione o lantanidi, i rapporti molari registrati sono stati confrontati con quelli ottenuti attraverso ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) o ICP-MS (Inductively Coupled Plasma-Mass Spectroscopy). Analisi TGA-DSC (ThermoGravimetric Analysis-Differential Scanning Calorimetry) hanno invece permesso di valutare la presenza e la quantità di residui di tensioattivi adsorbiti sulla superficie del materiale. Nel caso dei sistemi drogati, sono state effettuate misure XAS (X-ray Absorption Spectroscopy) al fine di studiare in dettaglio la struttura locale intorno agli ioni droganti, in relazione alle matrici ospitanti. I dati così ottenuti sono stati inoltre correlati con le proprietà di fotoluminescenza. Questi materiali, anche grazie alla biocompatibilità delle matrici selezionate, potrebbero potenzialmente essere utilizzati nel campo del bioimaging ottico. A questo riguardo sono state quindi effettuate prove di citotossicità e di influenza sulla vitalità cellulare su alcuni dei sistemi sintetizzati.