Materiais nanocompósitos híbridos polímero-argila nos quais lamelas nanométricas de argila montmorilonita são encapsuladas e dispersas em matriz polimérica são em geral mais rígidas, tenazes e resistentes do que os materiais poliméricos convencionais e tem o potencial de aplicações em revestimentos e filmes com propriedades de barreira. Dentre as várias técnicas de preparação de nanocompósitos poliméricos, as técnicas de polimerização \"in-situ\" em emulsão e mini-emulsão vem sendo empregada na síntese de látices híbridos com lamelas de argilas encapsuladas pelo polímero. Neste trabalho foram preparados látices híbridos de poliestireno e argila montmorilonita esfoliada através de dois métodos: no primeiro, a polimerização em emulsão e miniemulsão convencional na presença de argila modificada com sal quaternário de amônio é realizada com surfatante catiônico; no segundo método, um surfatante aniônico reativo foi usado para modificar uma argila natural sódica e empregada na polimerização em emulsão. Os resultados obtidos tanto para a polimerização em emulsão como em miniemulsão empregando idênticos reagentes (argila organofílica modificada e surfatante catiônico) mostraram boa conversão, aumento na velocidade de polimerização com aumento da concentração de surfatante e de argila, aumento na temperatura de pico na máxima velocidade de decomposição (TG), aumento no módulo de armazenamento no patamar vítreo e no patamar borrachoso (DMTA) com aumento da concentração de argila, encontrando um valor mínimo em ambos a 5% de argila. Apesar dessas características positivas, não foi obtida a encapsulação das lamelas da argila que era o objetivo principal do trabalho. Por outro lado, o método de polimerização em emulsão não convencional com surfatante reativo mostrou baixa eficiência na conversão mas que se mostrou eficaz na encapsulação das lamelas da argila para os látices com baixa conversão e elevado diâmetro de partícula. / Polymer-clay nanocomposite materials, in which nanometer-thick layers of clay dispersed in polymers, are generally stiffer, stronger, and tougher than normal polymeric materials and can be potentially useful in a variety of applications. These polymer-clay nanocomposites can be prepared in several ways, namely by emulsion \"in-situ\" polymerisation where polymer chains are coagulated on silicate layers producing capped silicate layers are more or less uniformly dispersed in aqueous medium. The objective of this work is to prepare polymer-clay hybrid latexes with exfoliated clay platelets encapsulated inside latex particles in order to improve the exfoliation of the clay platelets in the final polymeric film. To achieve this objective two separate approaches have been investigated, first by conventional emulsion polymerization and miniemulsion polymerization in the presence of montmorillonite clay modified by cationic surfactant and in the other approach a reactive anionic surfactant was used to modify the natural montmorillonite clay layers by emulsion polymerization. The results for both the emulsion polymerization as in miniemulsion using identical reagents (organoclay modified and cationic surfactant) showed good conversion, polymerization rate increased with increasing concentration of surfactant and clay, increased peak temperature at maximum speed decomposition (TG), an increase in storage modulus in the glassy plateau and the rubbery plateau (DMTA) with increasing concentration of clay, finding a minimum value in both the 5% clay. Despite these positive characteristics, encapsulation was not obtained from lamellar clay that was the main objective. Moreover, the method of emulsion polymerization with non-conventional reactive surfactant showed low conversion efficiency but has proved effective in the encapsulation of the lamellae of the clay for the lattices with low conversion and high particle diameter.

Partículas poliméricas com propriedades magnéticas podem ser utilizadas tanto em aplicações terapêuticas in vivo, como agentes de liberação controlada de princípios ativos, ex vivo, na extração de células cancerígenas do organismo, ou ainda in vitro, em diagnósticos. A necessidade de materiais inteligentes e biocompatíveis, como agentes de encapsulação destas partículas magnéticas, leva ao uso de polímeros sensíveis a estímulos. Em aplicações terapêuticas, esta tecnologia é baseada na localização das partículas através da aplicação de um campo magnético e na concentração da droga na área de interesse. Esta etapa é seguida pela liberação da droga, utilizando-se as propriedades sensíveis dos polímeros. Dessa forma, este trabalho de tese se dedica ao estudo da obtenção de nanopartículas constituídas de uma matriz polimérica sensível a estímulos e de partículas de óxido de ferro (?-Fe2O3 e Fe3O4). Inicialmente, nanogéis à base de poli(NVCL-co-AA) foram obtidos através do método de polimerização por precipitação. A Poli(Nvinilcaprolactama) (PNVCL) é um polímero termo-sensível, que possui temperatura crítica inferior de solubilização (LCST) próxima à temperatura fisiológica (35-38 ºC) e é conhecida, ainda, por possuir maior biocompatibilidade, em comparação a outros polímeros do gênero. O poli(ácido acrílico) (PAA), por sua vez, é um polímero que apresenta sensibilidade ao pH. Nesta etapa estudou-se a influência de alguns parâmetros de síntese nos diâmetros de partículas, na polidispersidade e na sensibilidade à temperatura dos nanogéis. A sensibilidade ao pH também foi estudada em função da concentração de ácido acrílico adicionado nas sínteses. Em seguida, realizou-se o estudo da encapsulação de nanopartículas magnéticas complexadas com dextrana em nanogéis de PNVCL, utilizando-se a técnica de polimerização em miniemulsão inversa. Os nanogéis magnéticos sensíveis à temperatura foram caracterizados quanto ao diâmetro de partículas (DP) e distribuição do diâmetro de partículas (DDP), pela técnica de espalhamento de luz. A sensibilidade à temperatura dos nanogéis magnéticos também foi estudada por espalhamento de luz, através de medidas de diâmetro de partículas em diferentes temperaturas. As medidas de magnetização foram obtidas em um magnetômetro de amostra vibrante (MAV). Análises de infra vermelho (FTIR) e de difratometria de raios X revelaram qualitativamente a encapsulação das nanopartículas magnéticas. A eficiência de incorporação das nanopartículas de óxido de ferro foi estudada através de análises termogravimétricas (TGA) e medidas de magnetização. As características morfológicas dos nanogéis magnéticos foram observadas por microscopia eletrônica de transmissão (TEM). / Polymeric particles with magnetic properties can be useful for in vivo therapeutic applications, as agents for controlled drug release, for ex vivo applications, as agents for the extraction of cancer cells, and finally, for the diagnosis in vitro. The search for biocompatible and smart materials as agents for the encapsulation of magnetic particles, leads to the use of stmuli-responsive polymers. In therapeutic applications, this technology is based on the localization and the concentration of the particles containing the drug in the area of interest by applying a magnetic field. This step is followed by the release of the drug, using the sensitive properties of the polymers. In this context, this thesis is devoted to the preparation of nanoparticles constituted by a stimuli-responsive polymer matrix and particles of iron oxide (?-Fe2O3 e Fe3O4). First of all, we performed the synthesis of poly(NVCL-co-AA)-based nanogels using the precipitation polymerization method. Poly(N-vinilcaprolactama) (PNVCL) is a thermo-responsive polymer which presents the lower critical solution temperature (LCST) near the physiological temperature (35-38 °C) and it is well known by its greater biocompatibility, in comparison with other themallysensitive polymers. On the other hand, the poly(acrylic acid) (PAA) is known by its sensibility to changes in the enviromental pH. In this stage, the influence of some synthesis parameters on the particles diameter, polydispersity and themally-sensitive behavior of the nanogels was evaluated. The pH-sensibility behavior was also studied as a function of the AA concentration in the synthesis. As a second step, the study of the incorporation of dextran-coated magnetic nanoparticles in the PNVCL-based nanogels using the inverse miniemulsion polymerization was preformed. The thermo-responsive magnetic nanogels were characterized in terms of particles diameter (PD) and particles size distribution (PSD) using light scattering. The temperature sensitivity of the magnetic nanogels was also studied by light scattering, with measurements of particles diameter as a function of temperature. The magnetization measurements were obtained on a vibrating sample magnetometer (VSM). Analysis of infra-red (FTIR) and X-ray diffraction revealed qualitatively the incorporation of magnetic nanoparticles. The incorporation efficiency of iron oxide nanoparticles was studied by thermo-gravimetric analysis (TGA) and magnetic measurements. The morphological characteristics of the magnetic nanogels were observed by transmission electron microscopy (TEM).

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. <br /> <br /> 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.<br /> <br /> 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. <br /> <br /> 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. <br /> <br /> 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. <br /> <br /> 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. <br /> <br /> 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 &quot;nanoreactors&quot; 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.<br /> <br /> 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. <br /> <br /> 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.

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.

Devido à importância industrial e tecnológica dos látices estabilizados com poli(álcool vinílico)/PVA e a dificuldade encontrada na etapa de polimerização em emulsão, na presença de monômeros hidrofóbicos e de PVA\'s com alto grau de hidrólise (>92%), a síntese de novos estabilizantes poliméricos derivados de PVA para utilização em reações de polimerização em emulsão e em miniemulsão se torna muito atraente e desafiadora. O objetivo principal deste trabalho foi sintetizar novos estabilizantes poliméricos do tipo poli(álcool vinílico-co-neodecanoato de vinila)/PVA-VV com alto grau de hidrólise e conseqüentemente com propriedades diferenciadas, para serem utilizados como estabilizantes nas reações de polimerização em emulsão e em miniemulsão do acetato de vinila (VAc) com o neo-nonanoato de vinila (VEOVA-9), visando a obtenção de adesivos com propriedades diferenciadas para colagem de madeiras. Os novos estabilizantes poliméricos foram obtidos em duas etapas: i) copolimerização em solução do VAc com o neo-decanoato de vinila (VEOVA-10); ii) hidrólise alcalina (NaOH/Metanol) do poli(acetato de vinila-coneodecanoato de vinila). As miniemulsões de VAc com VEOVA-9 com diferentes tipos de estabilizantes poliméricos foram preparadas em um homogeneizador de alta pressão do tipo \"Manton Gaulin\". Foi estudado o efeito dos estabilizantes poliméricos (PVA e PVA-VV) na etapa de emulsificação (diâmetro médio das gotas, polidispersão, estabilidade das miniemulsões) e na copolimerização em emulsão e em miniemulsão do VAc com o VEOVA-9, em processo batelada. O efeito do tipo de iniciador (persulfato de amônio/APS e hidroperóxido de tércio butila/TBHP e peróxido benzoato de tércio butila/TBPB, juntamente com o formaldeído sulfoxilato de sódio/SFS) na cinética da polimerização em miniemulsão do VAc com o VEOVA-9 foi estudado em processo semi-contínuo. A distribuição dos estabilizantes poliméricos (PVA e PVA-VV) entre a fase aquosa e a superfície das partículas de polímero (adsorvido/enxertado) foi determinada e correlacionada com a viscosidade e a estabilidade coloidal dos látices. Látices na condição ideal de cópia (1:1) das gotas de monômero para as partículas de polímero foram obtidos via polimerização em miniemulsão, apresentando propriedades diferenciadas, tais como, menores valores de viscosidade, menor concentração de coágulos e maior estabilidade de estocagem, em comparação com os látices obtidos em emulsão. / Due to the technological and industrial importance of latexes stabilized with poly(vinyl alcohol)/PVA and the difficulties related to the emulsion polymerization of hydrophobic monomers and the use of PVA having a high degree of hydrolysis (> 92%), the synthesis of new PVA based polymeric stabilizers for use in emulsion and miniemulsion polymerizations becomes very attractive and challenging. The aim of this work was to synthesize a new class of polymeric stabilizer, poly(vinyl alcohol-co-vinyl neo-decanoate)/PVA-VV, with a high degree of hydrolysis and differentiated properties to be used as stabilizers in the emulsion and miniemulsion copolymerization of vinyl acetate (VAc) with vinyl neo-nonanoate (VEOVA-9), that can be used as adhesive for wood bonding. New PVA based polymeric stabilizers with high degree of hydrolysis (94 - 98%) were synthesized in two steps: i) solution copolymerization of vinyl acetate (VAc) with vinyl neo-decanoate (VEOVA-10) and ii) alkaline hydrolysis (NaOH/Methanol) of poly(vinyl acetate-co-vinyl neodecanoate). Miniemulsions of VAc/VEOVA-9 were prepared using the different polymeric stabilizers in a \"Manton Gaulin\" high pressure homogenizer. The effect of different initiators (ammonium persulfate/APS or tert-butyl hydro peroxide/TBHP and tert-butyl peroxide benzoate/TBPB in the presence of sodium formaldehyde sulfoxylate/SFS) in the polymerization kinetic was evaluated. The effect of the type and concentration of polymeric stabilizer, in the emulsification step (average diameter of drops, stability of miniemulsions) as well in the polymerizations (rate of consumption of monomers, particle size and particles number) was investigated in this work. The partition of the polymeric stabilizers between the aqueous phase and the polymer particle surface (grafted/adsorbed) was determined and correlated with the viscosity and colloidal stability of latexes. Latexes with differentiated properties such as low-viscosity, lower grits content and improved storage stability, were obtained by miniemulsion polymerization with an ideal condition copy (1:1) of the monomer droplets to the polymer particles.

Partículas poliméricas com propriedades magnéticas podem ser utilizadas tanto em aplicações terapêuticas in vivo, como agentes de liberação controlada de princípios ativos, ex vivo, na extração de células cancerígenas do organismo, ou ainda in vitro, em diagnósticos. A necessidade de materiais inteligentes e biocompatíveis, como agentes de encapsulação destas partículas magnéticas, leva ao uso de polímeros sensíveis a estímulos. Em aplicações terapêuticas, esta tecnologia é baseada na localização das partículas através da aplicação de um campo magnético e na concentração da droga na área de interesse. Esta etapa é seguida pela liberação da droga, utilizando-se as propriedades sensíveis dos polímeros. Dessa forma, este trabalho de tese se dedica ao estudo da obtenção de nanopartículas constituídas de uma matriz polimérica sensível a estímulos e de partículas de óxido de ferro (?-Fe2O3 e Fe3O4). Inicialmente, nanogéis à base de poli(NVCL-co-AA) foram obtidos através do método de polimerização por precipitação. A Poli(Nvinilcaprolactama) (PNVCL) é um polímero termo-sensível, que possui temperatura crítica inferior de solubilização (LCST) próxima à temperatura fisiológica (35-38 ºC) e é conhecida, ainda, por possuir maior biocompatibilidade, em comparação a outros polímeros do gênero. O poli(ácido acrílico) (PAA), por sua vez, é um polímero que apresenta sensibilidade ao pH. Nesta etapa estudou-se a influência de alguns parâmetros de síntese nos diâmetros de partículas, na polidispersidade e na sensibilidade à temperatura dos nanogéis. A sensibilidade ao pH também foi estudada em função da concentração de ácido acrílico adicionado nas sínteses. Em seguida, realizou-se o estudo da encapsulação de nanopartículas magnéticas complexadas com dextrana em nanogéis de PNVCL, utilizando-se a técnica de polimerização em miniemulsão inversa. Os nanogéis magnéticos sensíveis à temperatura foram caracterizados quanto ao diâmetro de partículas (DP) e distribuição do diâmetro de partículas (DDP), pela técnica de espalhamento de luz. A sensibilidade à temperatura dos nanogéis magnéticos também foi estudada por espalhamento de luz, através de medidas de diâmetro de partículas em diferentes temperaturas. As medidas de magnetização foram obtidas em um magnetômetro de amostra vibrante (MAV). Análises de infra vermelho (FTIR) e de difratometria de raios X revelaram qualitativamente a encapsulação das nanopartículas magnéticas. A eficiência de incorporação das nanopartículas de óxido de ferro foi estudada através de análises termogravimétricas (TGA) e medidas de magnetização. As características morfológicas dos nanogéis magnéticos foram observadas por microscopia eletrônica de transmissão (TEM). / Polymeric particles with magnetic properties can be useful for in vivo therapeutic applications, as agents for controlled drug release, for ex vivo applications, as agents for the extraction of cancer cells, and finally, for the diagnosis in vitro. The search for biocompatible and smart materials as agents for the encapsulation of magnetic particles, leads to the use of stmuli-responsive polymers. In therapeutic applications, this technology is based on the localization and the concentration of the particles containing the drug in the area of interest by applying a magnetic field. This step is followed by the release of the drug, using the sensitive properties of the polymers. In this context, this thesis is devoted to the preparation of nanoparticles constituted by a stimuli-responsive polymer matrix and particles of iron oxide (?-Fe2O3 e Fe3O4). First of all, we performed the synthesis of poly(NVCL-co-AA)-based nanogels using the precipitation polymerization method. Poly(N-vinilcaprolactama) (PNVCL) is a thermo-responsive polymer which presents the lower critical solution temperature (LCST) near the physiological temperature (35-38 °C) and it is well known by its greater biocompatibility, in comparison with other themallysensitive polymers. On the other hand, the poly(acrylic acid) (PAA) is known by its sensibility to changes in the enviromental pH. In this stage, the influence of some synthesis parameters on the particles diameter, polydispersity and themally-sensitive behavior of the nanogels was evaluated. The pH-sensibility behavior was also studied as a function of the AA concentration in the synthesis. As a second step, the study of the incorporation of dextran-coated magnetic nanoparticles in the PNVCL-based nanogels using the inverse miniemulsion polymerization was preformed. The thermo-responsive magnetic nanogels were characterized in terms of particles diameter (PD) and particles size distribution (PSD) using light scattering. The temperature sensitivity of the magnetic nanogels was also studied by light scattering, with measurements of particles diameter as a function of temperature. The magnetization measurements were obtained on a vibrating sample magnetometer (VSM). Analysis of infra-red (FTIR) and X-ray diffraction revealed qualitatively the incorporation of magnetic nanoparticles. The incorporation efficiency of iron oxide nanoparticles was studied by thermo-gravimetric analysis (TGA) and magnetic measurements. The morphological characteristics of the magnetic nanogels were observed by transmission electron microscopy (TEM).

No description available.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

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 polymérisation / The 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

Le poly (acide lactique) (PLA), est un polymère synthétisé à partir de ressources renouvelables, qui est l'objet de beaucoup d'études à l'heure actuelle mais qui souffre d'une faible résistance au choc. Le but de ce travail est de rechercher des pistes permettant la préparation d'un matériau à base de PLA avec une résistance au choc améliorée tout en minimisant la perte de résistance à la traction. Les travaux présentés ici ont étudié le rôle de nanoparticules élastomères de poly (acrylate de butyle) (PBA) chargées de laponite (LRD) (PBA-LRD) ainsi que de nanocomposites coeur-écorce (PBA-LRD)/poly(méthacrylate de méthyle) (PMMA) en tant qu'agents de renforcement d'une matrice de PLA. Ces nanoparticules ont été dispersées dans la matrice PLA à l'état fondu. La synthèse de ces nanoparticules a été effectuée par polymérisation en émulsion ou miniémulsion. La laponite a été incorporée dans les nanoparticules afin de minimiser la perte de la rigidité tout en améliorant la résistance au choc de PLA. Trois types de tensioactifs et des modifications de surface de la laponite ont été testées pour améliorer l'adhérence entre les particules de PBA et la matrice de PLA. Enfin une écorce de PMMA a été utilisée pour assurer la bonne adhérence entre les particules de PBA et de matrice PLA. Nous avons montré que les particules coeur-écorce ont permis d'augmenter la résistance au choc au 3 fois du PLA tout en réduisant la diminution du module d'Young et la perte de résistance à la traction (~25%). Les propriétés de les particules synthétiques et les propriétés des mélange du PLA avec les particules PBA ou particules coeur-écorce ont été étudiées par diverses techniques de caractérisation (DLS, FTIR, ATG, MET, MEB, RMN 1H, DSC, DMTA...) / Poly (lactic acid) (PLA), come from renewable resources, one of the most important biopolymers, suffers from weak impact resistance. The aim of this work is to develop a process that will allow preparing a PLA with improved impact resistance while minimizing loss in tensile strength. The work presented here examined in detail the synthesis of poly(butyl acrylate) (PBA) nanoparticles charged with laponite (LRD) (PBA-LRD) and (PBA-LRD) / poly(methyl methacrylate) (PMMA) core-shell nanocomposites. They were dispersed phase in PLA matrix and were synthesized by emulsion or miniemulsion polymerization. The clay such as laponite was included in these nanoparticles to minimize the loss of rigidity while improving the impact resistance of PLA. Note that three types of surfactants and some modify agents for LRD have been tried to improve the adhesion between the PBA particles and matrix PLA, PMMA was finally used to ensure a good adhesion between the PBA particles and the matrix. To this end, we explored successively the PLA blend, using PBA nanocomposites and the PBA/PMMA core-shell nanoparticles as reinforcing agents, with improved impact resistance, showing that core-shell particles allowed increasing of 3 times of impact strength of the PLA with a minimum amount of loss (~25%) in Young?s modulus and tensile strength. The properties of the synthetic particles and the properties of PLA blends have been demonstrated by various characterization techniques (DLS, FTIR, TGA, TEM, SEM, 1H-NMR, DSC, DMTA ...)