A stable aqueous nanocomposite dispersion containing cellulose whiskers and a polymer matrix was prepared via miniemulsion polymerization. We were able to prepare a stable dispersion with a 250 wt % solid content and a cellulose whiskers content ranging from 1 up to 5 wt % based on polymer content. Cellulose nanocrytals suspension was mixed with monomers phase in presence of anionic or cationic surfactant and a stabilizing additive acting as a hydrophobe. After sonication for a short time to obtain a stable emulsion of small droplet polymerisation reaction was trigged by the addition of the initiator. The nanocomposite dispersion was characterized using dynamic light scattering, ζ-potential measurement, transmission electron microscopy (TEM), atomic force microscopy (AFM) and FE-SEM. It was found that the particle size of the prepared suspensions is in the range of 90-600 nm, and the final nanocrystals composite is stable for months.Films obtained by casting followed by water evaporation and particle coalescence were analyzed by differential scanning calorimetry, dynamic mechanical analysis, and tensile testing. The nanocomposite maintained high transparency, and their storage elastic modulus increased tediously with the increasing nanowhiskers content. / Des dispersions de nanocomposites stables à matrice polymérique et à base de whiskers de cellulose ont été préparées par polymérisation en miniémulsion, dont on peut atteindre 5 % en masse. Ce procédé permet d’obtenir une distribution homogène des nanofibres autour des particules de polymère, et empêche ainsi les risques d’agglomération.La caractérisation de ces dispersions a été réalisée en recourant à divers techniques comme la diffusion dynamique de la lumière, zetamètrie, le microscope électronique à transmission (MET), à force atomique (AFM) et à effet de champs. Nous avons montré que l’accroissement du taux de nanoparticules s’accompagne par une augmentation de la taille des particules de polymères.Les propriétés des films de nanocomposites, obtenus après évaporation de l’eau et coalescence des particules ont été analysées par calorimétrie différentiel à balayage (DSC), analyse mécanique dynamique (DMA) et par essai de traction.

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.

This research aims to add to the current knowledge available for miniemulsion polymerization reactions and to use this knowledge to synthesize multifunctional nanosized latex particles that have the potential to be used in catalysis. The physical properties of the latex can be adjusted to suit various environments due to the multiple functional groups present. For this research, styrene, pentafluorostyrene, azidomethyl styrene, pentafluorostyrene with azidomethyl styrene and pentafluorostyrene with styrene latexes were produced, and analyzed by dynamic light scattering. The latexes were synthesized using a miniemulsion polymerization technique found through this research. Potassium oleate and potassium 1,1,2,2,3,3,4,4-nonafluorobutane-1-sulfonate were used as surfactants during the miniemulsion polymerization reaction to synthesize pentafluorostyrene with azidomethyl styrene latex. Transmission electron microscopy data and dynamic light scattering data have been collected to analyze the structure of this latex, and it has been synthesized using a number of conditions, differing in reaction time, surfactant amount and sonication methods. We have also improved the solubility of the latex through a copper(I) catalyzed 1,3-dipolar azide-alkyne reaction, by clicking (polyethylene glycol)5000 onto the azide functional groups.

A stable aqueous nanocomposite dispersion containing cellulose whiskers and a polymer matrix was prepared via miniemulsion polymerization. We were able to prepare a stable dispersion with a 250 wt % solid content and a cellulose whiskers content ranging from 1 up to 5 wt % based on polymer content. Cellulose nanocrytals suspension was mixed with monomers phase in presence of anionic or cationic surfactant and a stabilizing additive acting as a hydrophobe. After sonication for a short time to obtain a stable emulsion of small droplet polymerisation reaction was trigged by the addition of the initiator. The nanocomposite dispersion was characterized using dynamic light scattering, ζ-potential measurement, transmission electron microscopy (TEM), atomic force microscopy (AFM) and FE-SEM. It was found that the particle size of the prepared suspensions is in the range of 90-600 nm, and the final nanocrystals composite is stable for months.Films obtained by casting followed by water evaporation and particle coalescence were analyzed by differential scanning calorimetry, dynamic mechanical analysis, and tensile testing. The nanocomposite maintained high transparency, and their storage elastic modulus increased tediously with the increasing nanowhiskers content.

Conventional free-radical miniemulsion polymerization has been well studied since early 1970s. Conventional free-radical miniemulsion polymerizations have inherent limitations associated with uncontrolled free-radical polymerization mechanism. The goal of this work is to develop a variety of unconventional miniemulsion polymerization techniques by applying new polymerization techniques (typically in solution or bulk) to miniemulsion systems to overcome their inherent limitations and extend the application of free-radical miniemulsion polymerization. This work focused on the exploration of kinetic and mechanistic aspects of unconventional miniemulsion polymerizations. First, enzyme initiated free-radical miniemulsion polymerization, in contrast with those conventional chemical initiated miniemulsion polymerization, is demonstrated for the first time as an answer to the challenges associated with using the hydrophobic of vinyl monomers in aqueous enzymatic reactions. A procedure for enzyme initiated free-radical miniemulsion polymerization was formulated and stable poly(styrene) latexes were successfully synthesized. The kinetics of enzyme initiated free-radical miniemulsion polymerization and the effect of reaction conditions on the polymerization was elucidated. Second, RAFT miniemulsion polymerization of hydrophobic monomers was performed in CSTR trains and the transient states, previously identified by others in our group, were elucidated. Next, RAFT miniemulsion polymerization of a partially water soluble monomer was studied. RAFT miniemulsion polymerizations of gamma-methyl-alpha-methylene-gamma-butyrolactone, a partially water soluble lactone monomer derived from renewable sources, was successfully formulated. Homogeneous nucleation was found to play an important role in the free-radical "miniemulsion" homopolymerization of MeMBL. By using styrene as a comonomer, the RAFT miniemulsion polymerizations of MeMBL and styrene were well controlled and narrowly distributed copolymers of MeMBL/styrene were produced. Following the study of the partially water monomer, RAFT inverse miniemulsion polymerization was proposed for the polymerization of hydrophilic monomers. The kinetics of RAFT inverse miniemulsion polymerization of acrylamide exhibited the typical behavior of controlled polymerizations up to high conversions. The effects of reaction parameters on the polymerization rate and particle size were investigated. The dominant locus of radical generation for particle nucleation and the fate of desorbed monomeric radicals in inverse miniemulsion polymerizations were evaluated. Finally in this work, conclusions and implications are presented and ideas for future work are suggested.

No description available.

Neste trabalho, dois macro-agentes de transferência de cadeia para polimerizações via RAFT, à base de poli(óxido de etileno), isto é, PEO-CPADB e PEO-CPP, foram sintetizados via duas rotas químicas e utilizados como estabilizantes coloidais e como agentes de controle de massa molecular na polimerização em miniemulsão do estireno. Látices de poliestireno (PS), estabilizados estericamente pelos segmentos de PEO, foram obtidos utilizando 2,2\'-azobis(isobutironitrila) como iniciador e hexadecano como co-estabilizador. O consumo de monômero foi determinado via análise gravimétrica. O tamanho de partícula e a distribuição de tamanhos de partículas (PSD) foram determinados por espalhamento de luz (LS). As massas moleculares e a distribuição de massas moleculares (nwMM) dos polímeros foram determinadas por cromatografia de exclusão de tamanho (SEC). Os resultados mostraram que o diâmetro das gotas e das partículas de polímero, assim como a estabilidade coloidal dos látices são fortemente dependentes do tipo e da quantidade de agente de transferência de cadeia utilizado nas polimerizações. Deslocamentos das curvas de distribuição de massas moleculares para massas moleculares maiores, em função da conversão, indicaram que a maioria das cadeias poliméricas apresentava características de cadeias vivas. Análises de GPC também mostraram que a polimerização foi bem controlada quando uma quantidade do macro-agente RAFT PEO-CPP, igual a 4,4 x 10-3 mol.L-1 foi utilizada, o que foi indicado pelo baixos índices de polidispersão obtidos (1,05-1,42). / In this work, two poly(ethylene oxide)-based macro-RAFT agents, ie, PEO-CPADB and PEO-CPP, were synthesized via two chemical routes and used as a stabilizer and a control agent in the miniemulsion polymerization of styrene. Polystyrene (PS) latexes sterically stabilized by the PEO segments were obtained using 2,2?-azobis(isobutyronitrile) as initiator and hexadecane as co-stabilizer. Monomer consumption was monitored by gravimetric analysis. The latex particle size and the particle size distribution (PSD) were measured by light scattering (LS). Molar masses and molar mass distributions (nwMM) of the polymers were determined by size exclusion chromatography (SEC). The results showed that the droplet/particle sizes and the latexes stability are strongly dependent on the type and on the amount of macro-RAFT agent used in the polymerizations. Shifts of the SEC chromatograms toward higher molar masses with conversion indicated that the majority of the polymer chains are living chains. Size Exclusion Chromatography (SEC) analysis also showed that polymerization was well controlled when an amount of macro-RAFT PEO-RAFT agent equal to 4.4 x 10-3 mol. L-1 was used, since low polidispersity indices (1.05-1.42) was achieved.

Neste trabalho, dois macro-agentes de transferência de cadeia para polimerizações via RAFT, à base de poli(óxido de etileno), isto é, PEO-CPADB e PEO-CPP, foram sintetizados via duas rotas químicas e utilizados como estabilizantes coloidais e como agentes de controle de massa molecular na polimerização em miniemulsão do estireno. Látices de poliestireno (PS), estabilizados estericamente pelos segmentos de PEO, foram obtidos utilizando 2,2\'-azobis(isobutironitrila) como iniciador e hexadecano como co-estabilizador. O consumo de monômero foi determinado via análise gravimétrica. O tamanho de partícula e a distribuição de tamanhos de partículas (PSD) foram determinados por espalhamento de luz (LS). As massas moleculares e a distribuição de massas moleculares (nwMM) dos polímeros foram determinadas por cromatografia de exclusão de tamanho (SEC). Os resultados mostraram que o diâmetro das gotas e das partículas de polímero, assim como a estabilidade coloidal dos látices são fortemente dependentes do tipo e da quantidade de agente de transferência de cadeia utilizado nas polimerizações. Deslocamentos das curvas de distribuição de massas moleculares para massas moleculares maiores, em função da conversão, indicaram que a maioria das cadeias poliméricas apresentava características de cadeias vivas. Análises de GPC também mostraram que a polimerização foi bem controlada quando uma quantidade do macro-agente RAFT PEO-CPP, igual a 4,4 x 10-3 mol.L-1 foi utilizada, o que foi indicado pelo baixos índices de polidispersão obtidos (1,05-1,42). / In this work, two poly(ethylene oxide)-based macro-RAFT agents, ie, PEO-CPADB and PEO-CPP, were synthesized via two chemical routes and used as a stabilizer and a control agent in the miniemulsion polymerization of styrene. Polystyrene (PS) latexes sterically stabilized by the PEO segments were obtained using 2,2?-azobis(isobutyronitrile) as initiator and hexadecane as co-stabilizer. Monomer consumption was monitored by gravimetric analysis. The latex particle size and the particle size distribution (PSD) were measured by light scattering (LS). Molar masses and molar mass distributions (nwMM) of the polymers were determined by size exclusion chromatography (SEC). The results showed that the droplet/particle sizes and the latexes stability are strongly dependent on the type and on the amount of macro-RAFT agent used in the polymerizations. Shifts of the SEC chromatograms toward higher molar masses with conversion indicated that the majority of the polymer chains are living chains. Size Exclusion Chromatography (SEC) analysis also showed that polymerization was well controlled when an amount of macro-RAFT PEO-RAFT agent equal to 4.4 x 10-3 mol. L-1 was used, since low polidispersity indices (1.05-1.42) was achieved.

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.

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.