La plupart des solides dans la vie quotidienne, tels que les métaux et les céramiques, sont des systèmes cristallins dans lesquels les atomes ou molécules sont arrangés sur une structure périodique. Les solides cristallins sont rarement composés d'un cristal unique, mais sont en général des systèmes polycristallins formés par un grand nombre de grains cristallins avec une même structure cristalline, mais différente orientation. On appelle joints de grain (JG) les réseaux 2D de défauts qui séparent deux grains d'orientation différente. Les polycristaux jouent un rôle important en science et technologie et une connaissance complète de leurs propriétés mécaniques est de grand intérêt. La plasticité des polycristaux est liée à leur microstructure, mais les mécanismes qui régissent leur comportement plastique sont encore mal compris, en partie du fait de limitations techniques pour les systèmes atomiques. D'autre part, les colloïdes, dont l'étude expérimentale est souvent plus aisée que celle des systèmes atomiques, du fait de temps et taille caractéristiques plus grands, sont souvent considérés comme des systèmes modèles pour les atomes. L'objectif de la thèse est l'étude des propriétés mécaniques d'un polycristal colloïdal formé par une suspension aqueuse d'un copolymère tribloc commercial (Pluronic F108), dopé par une faible quantité de nanoparticules (NPs). Le polymère présente une phase micellaire cristalline pour une gamme de température et de concentration. De manière similaire à ce qui est fait couramment pour les systèmes atomiques, on peut contrôler le taux de cristallisation en faisant varier la vitesse à laquelle l'échantillon est porté de la phase liquide à basse température (T ~ 0°C) à la phase micellaire cristalline à température ambiante. Une caractéristique importante est que la taille des grains peut être facilement contrôlée en faisant varier la vitesse d'augmentation de la température ou la concentration en NPs. Dans un premier temps, nous avons caractérisé la structure du polycristal par diffusion de neutrons (SANS) et de lumière. Les mesures par SANS ont permis de sonder la structure du polycristal à l'échelle du nanomètre, i.e. sur des échelles de longueur comparable à celle des micelles et des NPs. Nous avons constaté que la structure cristalline micellaire est conservée indépendamment de l'histoire thermique de l'échantillon et de la concentration en NPs. De plus, nous avons montré que la distribution des NPs dans l'échantillon est hétérogène: les grains sont pauvres en NPs alors que les JG sont enrichies en NPs. Par conséquent, les NPs ségrégent dans les JG et et jouent un rôle analogue aux impuretés dans les cristaux atomiques. En outre, en raison de leur ségrégation, les NPs sont structurées sur une échelle de longueur beaucoup plus grande que leur taille. Nous avons étudié la structure mésoscopique des NPs par diffusion statique de la lumière, grâce à un appareil de diffusion de la lumière (MALS) spécialement construit pour accéder à la plage correcte de vecteurs d'onde. D'autre part, afin d'étudier les propriétés mécaniques des polycristaux, des mesures de diffusion dynamique de la lumière ont été réalisée dans la configuration MALS sur un échantillon soumis à des déformations de cisaillement cycliques. Dans la configuration MALS, l'intensité diffusée étant dominée par les NPs dans les JG, la technique permet de sonder la dynamique du réseau de JG induite par le cisaillement. Expérimentalement, on calcule la corrélation de l'intensité diffusée mesurée après un nombre donné de cycles de déformation. Les données montrent systématiquement une décroissance de la corrélation après un nombre caractéristique de cycles, démontrant ainsi l'existence de plasticité dans les échantillons. À l'avenir, des échantillons avec des tailles de grain différentes seront étudiés. De telles expériences pourraient faire la lumière sur les liens entre plasticité d'un polycristal colloïdal et microstructure. / Most everyday life solids, such as metals and ceramics, are crystalline systems in which atoms or molecules are arranged in a regular periodic structure. Crystalline solids are rarely composed of one single crystal, but are usually polycrystalline systems made of a large number of crystalline regions (grains), which share a common crystal structure, but with different lattice orientations. The interfaces where crystallites meet are denoted as grain boundaries (GBs). Polycrystalline materials play an important role in science and technology and a complete knowledge of their mechanical properties, including their elasticity and plasticity, is of great interest. It is well known that the plasticity of polycrystals is related to their microstructure, but the mechanism governing the plastic behavior is still poorly understood, partly because of the limits of experimental techniques and simulations for atomic polycrystals. On the other hand, colloids are often regarded as model systems for atoms, since many of the forces governing the behavior of condensed matter govern also that of colloidal suspensions, whose experimental study is often easier than that of atomic systems because of the larger characteristic time- and length-scales. In particular, colloidal crystalline systems can be used to investigate mechanical properties of polycrystals. The aim of the PhD thesis is the investigation of the mechanical properties of a colloidal polycristal formed by an aqueous suspension of a commercial triblock copolymer called Pluronic F108, doped with a small amount of nanoparticles (NPs). The polymer presents a micellar crystalline phase for a given range of temperature and concentration. Similarly to what is commonly done for atomic systems, we can control the crystallization rate by varying the speed at which the sample is brought from the fluid, at low temperature (T ~ 0°C), to the crystal phase at room temperature. An important characteristic of our system is that the grain size can be easily tuned by changing the temperature rate or the nanoparticles concentration. We have first characterized the structure of the Pluronic polycrystal using neutron (SANS) and light scattering. The SANS measurements have permitted to investigate the (doped) Pluronic polycrystal at nanometer length scale, i.e. at the length scale of the micelles and nanoparticles. We have found that the micellar crystal structure is preserved independently of the thermal history of the sample and the amount of added nanoparticles. Moreover, we have shown that the NPs distribution into the sample is heterogeneous: grains are poor in NPs whereas GBs are enriched in NPs. Hence, NPs segregate into the GBs as impurities in atomic crystals. In addition, because of their segregation in the GBs, NPs form structures on a length scale much larger than their size, that we have investigated with static light scattering, thanks to a novel light scattering apparatus (MALS) specifically built to access the correct range of wave-vectors. On the other hand, in order to investigate the mechanical properties of the Pluronic crystal, dynamic light scattering measurements have been performed with the MALS setup on the Pluronic polycrystal submitted to cyclic shear deformations. Since, in the range of wave-vectors covered by the MALS apparatus, the scattered intensity is dominated by the NPs segregated in the GBs, the techniques allows the shear-induced dynamics of the GB network to be probed. Experimentally, one computes the correlation of the scattered intensity measured after a given number of shear deformation cycles. Data systematically show that the correlation decays after a characteristic number of cycles, demonstrating the existence of plasticity. In future, samples with different grain size will be investigated with this technique. Such experiments could shed light on how the plasticity of a colloidal polycrystal is related to its polycrystalline microstructure.

La bêta lactoglobuline (βlg) est une protéine globulaire qui forme le constituant majoritaire du sérum du lait ou petit lait. Par chauffage la protéine se dénature irréversiblement, puis s’assemble pour former des agrégats ou gels présentant des structures très différentes selon les conditions environnementales, en particulier de pH et de force ionique. Des travaux récents ont montré la possibilité de créer des agrégats stables de βlg de forme sphérique, de 100 à 400 nm de diamètre dans une plage de pH bien spécifique. Ces particules sphériques que nous appelons microgels, sont potentiellement très intéressantes pour des applications dans l’agroalimentaire (blanchissement, stabilisation d’interfaces et encapsulation). L’objectif de la thèse est d’étudier le mécanisme de formation de ces microgels et leurs propriétés structurales dans différentes conditions environnementales afin de pouvoir créer de nouvelles fonctionnalités. La première partie de la thèse a consisté à étudier l’influence du pH sur la formation des microgels. Les suspensions stables de microgels sont formées par chauffage de la solution de βlg en absence de sel jusqu’à 50 g.L-1 de protéine si le pH est placé dans une gamme très étroite entre 5,75 et 6,1. La densité de ces particules sphériques est environ 150 g.L-1 et leur rayon hydrodynamique diminue de 200 nm à 75 nm en augmentant le pH. La formation de ces microgels entraine une augmentation de pH, qui est nécessaire pour obtenir une suspension stable. L’augmentation spontanée du pH pendant la formation des microgels entraine une augmentation de leur densité de charge à la surface qui a pour conséquence d'empêcher leur agrégation. Ce mécanisme d’auto-stabilisation n’est plus suffisant si le pH initial est inférieur à 5,75 et on observe alors la précipitation des microgels. Les microgels ne sont plus formés au-delà d’une valeur critique du pH initial. Dans ce cas, les agrégats fibrillaires sont formés avec un rayon hydrodynamique d’environ 15 à 20 nm. La seconde partie de ce travail traite de la formation des microgels induite par l’ajout des ions calcium. Nous avons montré que des suspensions stables de microgels peuvent être obtenues en chauffant les solutions de βlg en présence des ions calcium. Les conditions de formation des microgels ont été étudiées à différents pH entre 5.8 et 7.5 et différentes concentrations de protéine entre 5 et 100 g.L-1. Il existe un rapport molaire critique calcium/protéine (R) pour former des microgels qui est indépendant de la concentration de protéine. R diminue en diminuant le pH. Les microgels ont un rayon hydrodynamique qui varie entre 100 et 300 nm et leur densité est comprise entre 200 et 450 g.L-1. La détermination de quantité de calcium lié aux microgels indique que le paramètre crucial pour la formation des microgels est la densité des charges nettes des protéines natives. Les suspensions de microgels sont stables dans certaines gammes étroites de R mais s’agrègent et précipitent ou gélifient à des concentrations de calcium plus élevées. Dans la troisième partie, nous avons continué à étudier la formation des microgels dans les étapes initiales et observer leur croissance en présence des ions calcium. On a proposé un mécanisme de formation des microgels de βlg, qui commence par un processus de nucléation et croissance. Des nucléi de tailles bien définies sont formés à la première étape, puis ils continuent à grossir jusqu’à la taille finale des microgels. A des faibles concentrations de calcium les microgels sont stables. A des concentrations plus élevées, les microgels peuvent s’agréger pour former des agrégats plus grands et finalement un gel. La structure des gels de microgels est hétérogène à l’échelle de la microscopie confocale et similaire à celle formée en présence de NaCl 0.3M. Pourtant le processus de formation de ces gels n’est pas le même... / Beta lactoglobulin (βlg) is a major whey protein in the bovine milk. Upon heating above its denaturation temperature (which is pH-dependent), this globular protein undergoes molecular changes leading to the irreversible aggregation. Depending on the pH and ionic strength, either protein aggregates or gels exhibiting various structures and morphologies have been described. Very recently, it was found that in a narrow range of the pH close to iso-electric point, stable suspensions of rather monodisperse spherical particles with a radius of about a hundred nanometers were formed. These spherical particles which were called microgels might be of special interest for the production of liquid dispersions of β-lactoglobulin aggregates exhibiting various functionalities for food applications. The project on which I report here was a collaboration with the Nestlé Reseach Center (Lausanne, Switzerland) and its objective was to study the formation and structural properties of the microgels in different environmental conditions. The first part of the project is to study the influence of the pH on the formation of microgels. Stable suspensions of protein microgels are formed by heating salt free βlg solutions at concentrations up to about C = 50 g.L-1 if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g.L-1 and the average hydrodynamic radius decreases with increasing pH from 200 nm to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm. The second part of the work is about the formation of microgels driven by the addition of calcium ions. We found that stable suspensions of spherical protein particles (microgels) can be formed by heating βlg solutions in the presence of calcium ions. The conditions for the calcium induced microgel formation were studied at different pH between 5.8 and 7.5 and different protein concentrations between 5 – 100 g.L-1. The results showed that a critical molar ratio of calcium to proteins (R) is needed to form microgels independent of the protein concentration. R decreases with decreasing pH. The microgels have a hydrodynamic radius ranging from 100 to 300 nm and their internal protein concentration ranges from 0.2 to 0.45 g.mL-1. The determination of calcium bound to the microgels suggests that the crucial parameter for microgel formation is the net charge density of the native proteins. The microgel suspensions are stable in a narrow range of R but aggregate at higher Ca2+ concentrations. In the third part, we continued to investigate the formation of microgels at initial step and how it is growing in the presence of calcium ions. We have proposed a mechanism of formation of blg microgels which follows a nucleation and growing process. The nucleus with define size are formed at the initial state and that is growing in size to reach final size of aggregates. At low calcium concentration it stabilizes and then we obtain a stable suspension of microgels. But at high concentrations, the microgels here can jump to form big aggregates and finally a gel. The structure of gel from microgels is heterogenous at the scale of confocal microscopy and similar to those formed in the presence of NaCl 0.3 M. However the process of formation of these gels is not the same...

A técnica de Espalhamento Dinâmico de Luz (do inglês Dynamic Light Scattering, ou DLS), também conhecida por técnica de Espectroscopia por Correlação de Fótons (do inglês Photon Correlation Spectroscopy, ou PCS), é amplamente utilizada na caraterização estrutural de sistemas coloidais, fornecendo informações importantes sobre tamanhos ca- ractersticos, tempos de correlação e efeitos de polarização no sistema. A facilidade de execução dos experimentos e praticidade das análises é uma das principais vantagens desta técnica. Especificamente para sistemas diludos compostos por partculas em solução, ela pode fornecer informações diretas sobre o raio hidrodinâmico das partculas do meio. No entanto, a obtenção desse parâmetro requer a utilização de métodos de ajuste e análise dos dados experimentais que assumem diversas caractersticas do sistema e possuem li- mitações intrnsecas devido à própria resolução do método frente presença de partculas de variados tamanhos e concentrações, polidispersões contnuas de tamanho, entre vários outros fatores. Existem casos, por exemplo, onde o mesmo conjunto experimental pode ser descrito por dois modelos diferentes. Neste projeto, é proposto um estudo sistemático das limitações dos métodos de análise frente a dados simulados e experimentais, de modo a permitir a aplicabilidade destes métodos a vários tipos de sistemas. Serão investigados casos de sistemas monodispersos e polidispersos, monomodais e multimodais, através da geração de dados simulados que mimetizem a presença desses grupos de partculas, em di- ferentes proporções e polidispersões. Como resultado, teremos indicações da precisão com que estes métodos de modelagem conseguem reproduzir os valores inseridos na simulação. Além disso, experimentos reais serão realizados utilizando amostras padrão de modo a aplicar os métodos de análise a estes dados bem como contrapor os resultados obtidos pelas simulações e pelos dados experimentais. / The Dynamic Light Scattering technique, also known as Photon Correlation Spectros- copy, is widely used for the structural characterization for colloidal systems, providing important information on characteristic length scales, correlation times and polarization effects. The relative simple experimental setup and easy-to-use modeling methods are one of the main advantages of this technique. Specifically for diluted systems of particles in solution, one can obtain direct information on the hydrodynamic for the particles in the system. However, in order to retrieve this parameter it is necessary to use modeling and analysis methods for the experimental methods which assumes intrinsic characteristics on the system and have intrinsic limitations due to the resolution of the method when particles with several sizes, concentrations, etc. In several cases, the same experimental data can be described by several different models. In this project it is proposed a systematic study on the limitations on the analysis methods upon simulated and experimental data in order to investigate the applicability of these methods for several system types. Monodisperse and polydisperse systems are investigated, either composed by one type of particles (monomo- dal) or several types of particles (multimodal). As a result, one can obtain indications on the accuracy that the modeling methods can reproduce the simulated parameters. Finally, real experiments were performed using standard samples in order to test the modeling methods and to calibrate the simulation procedures.

A cold atomic cloud is a versatile object, because it offers many handles to control and tune its properties. This facilitates studies of its behavior in various circumstances, such as sample temperature, size and density, composition, dimensionality and coherence time. The range of possible experiments is constrained by the specifications of the atomic species used. In this thesis presents the work done in the experiment for laser cooling of strontium atoms, focusing on its stability, which should provide cold and ultracold samples for the study of collective effects in light scattering. From the initial apparatus, innumerous changes were performed. The vacuum system got improved and now reached lower ultra high vacuum due to the pre-baking done to its parts and adding a titanium-sublimation stage. The quadrupole trap were improved by the design and construction of a new pair of coils. The stability of the blue, green and red laser systems and the loss prevention of laser light were improved, giving rise to a robust apparatus. Another important point is the development of homemade devices to reduce the costs and to be used as a monitor of different parts of an cold atoms experiment. From this homemade devices, we could demonstrate a dramatic linewidth narrowing by injection lock of an low cost 461 nm diode laser and its application to our strontium experiment. In the end, this improved experimental apparatus made possible the study of a new scattering effect, the mirror assisted coherent back-scattering (mCBS). / Uma nuvem atômica fria é um objeto versátil porque oferece muitas formas de controlar e ajustar suas propriedades. Isso facilita o estudo de seu comportamento em várias circunstâncias, tais como temperatura da amostra, tamanho e densidade, composição, dimensionalidade e tempo de coerência. A extensão de experimentos possíveis é limitada pelas especificações da espécie atômica utilizada. Nessa tese, eu apresento o trabalho feito em um experimento para resfriamento de átomos de estrôncio, focando em sua estabilidade, que deve gerar amostras frias e ultras-frias para o estudo de efeitos coletivos em espalhamento de luz. Do aparato inicial, inúmeras mudanças foram feitas. O sistema de vácuo foi melhorado e agora atinge vácuos ultra altos mais baixos, devido ao pré-cozimento feito em suas partes e a adição de um estágio de sublimação de titânio. A estabilidade e a prevenção de perdas de luz dos sistemas de laser azul, verde e vermelho foram melhorados, levando a um sistema mais robusto. Outro ponto importante é o desenvolvimento de dispositivos caseiros para reduzir os custos e para ser usado como monitor de diferentes partes de um experimento de átomos frios. Destes dispositivos, pudemos demonstrar a redução dramática da largura de linha de um diodo laser de 461 nm de baixo custo devido a estabilização por injeção. No fim, esse aparato experimental melhorado fez possível o estudo de um novo efeito de espalhamento, o retro espalhamento coerente da luz assistido por espelho.

A técnica de Espalhamento Dinâmico de Luz (do inglês Dynamic Light Scattering, ou DLS), também conhecida por técnica de Espectroscopia por Correlação de Fótons (do inglês Photon Correlation Spectroscopy, ou PCS), é amplamente utilizada na caraterização estrutural de sistemas coloidais, fornecendo informações importantes sobre tamanhos ca- ractersticos, tempos de correlação e efeitos de polarização no sistema. A facilidade de execução dos experimentos e praticidade das análises é uma das principais vantagens desta técnica. Especificamente para sistemas diludos compostos por partculas em solução, ela pode fornecer informações diretas sobre o raio hidrodinâmico das partculas do meio. No entanto, a obtenção desse parâmetro requer a utilização de métodos de ajuste e análise dos dados experimentais que assumem diversas caractersticas do sistema e possuem li- mitações intrnsecas devido à própria resolução do método frente presença de partculas de variados tamanhos e concentrações, polidispersões contnuas de tamanho, entre vários outros fatores. Existem casos, por exemplo, onde o mesmo conjunto experimental pode ser descrito por dois modelos diferentes. Neste projeto, é proposto um estudo sistemático das limitações dos métodos de análise frente a dados simulados e experimentais, de modo a permitir a aplicabilidade destes métodos a vários tipos de sistemas. Serão investigados casos de sistemas monodispersos e polidispersos, monomodais e multimodais, através da geração de dados simulados que mimetizem a presença desses grupos de partculas, em di- ferentes proporções e polidispersões. Como resultado, teremos indicações da precisão com que estes métodos de modelagem conseguem reproduzir os valores inseridos na simulação. Além disso, experimentos reais serão realizados utilizando amostras padrão de modo a aplicar os métodos de análise a estes dados bem como contrapor os resultados obtidos pelas simulações e pelos dados experimentais. / The Dynamic Light Scattering technique, also known as Photon Correlation Spectros- copy, is widely used for the structural characterization for colloidal systems, providing important information on characteristic length scales, correlation times and polarization effects. The relative simple experimental setup and easy-to-use modeling methods are one of the main advantages of this technique. Specifically for diluted systems of particles in solution, one can obtain direct information on the hydrodynamic for the particles in the system. However, in order to retrieve this parameter it is necessary to use modeling and analysis methods for the experimental methods which assumes intrinsic characteristics on the system and have intrinsic limitations due to the resolution of the method when particles with several sizes, concentrations, etc. In several cases, the same experimental data can be described by several different models. In this project it is proposed a systematic study on the limitations on the analysis methods upon simulated and experimental data in order to investigate the applicability of these methods for several system types. Monodisperse and polydisperse systems are investigated, either composed by one type of particles (monomo- dal) or several types of particles (multimodal). As a result, one can obtain indications on the accuracy that the modeling methods can reproduce the simulated parameters. Finally, real experiments were performed using standard samples in order to test the modeling methods and to calibrate the simulation procedures.

Thesis. 1975. B.S. cn--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / B.S.cn

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Microfiche copy available in Archives and Engineering. / Vita. / Includes bibliographical references. / Ph.D.

Antibodies and antibody fragments are the largest class of biotherapeutics in development with many products already available in the clinic. Antibodies are promising due to their naturally high affinity and specificity for biological targets. A key stumbling block to biopharmaceutical development compared to small molecule drugs is the general requirement for a stable liquid formulation, which is often difficult to obtain due to issues with aggregation, phase separation, particle formation, and chemical instabilities. Aberrant solution behaviour limits the production, storage and delivery of the monoclonal antibody. Biopharmaceutical solution behaviour is determined by weak, transient protein-protein and protein-solvent interactions. An attractive interaction potential between proteins in solution can lead to association. Irreversible association occurs when proteins undergo large scale structural changes and aggregate. Reversible association is less severe, but can lead to undesirable solution properties such as high viscosity, phase separation and opalescence, which can lead to difficulties throughout the downstream processing and formulation steps. These problems can become exacerbated during formulation of antibodies when trying to achieve high protein concentrations often required for effective antibody dosage. Firstly, we studied the domains of the Fab fragment using statistical models and continuum electrostatic calculations and found that the CH1 domain is more soluble than the other domains and has properties of intrinsically disordered like proteins which is supported by observations in the literature. We then investigated the immunoglobulin superfamily and found 11 proteins which may have a similarly disordered nature. We present a new web server for predicting protein solubility from primary sequence using an in-house algorithm that weighs the contribution of various sequence properties for predicting solubility. Lastly, we conducted physical characterisation of an antibody and human serum albumin in pharmaceutically relevant buffers and found that the interaction potential can be modelled using spherical models from low to high protein concentration. We hope that the work outlined in this thesis will contribute to the theoretical understanding and modelling of protein solution behaviour.

Made available in DSpace on 2014-12-17T15:41:58Z (GMT). No. of bitstreams: 1 VictorAVO_DISSERT.pdf: 1098770 bytes, checksum: b51c2db6f7a42c08650cb24f90bc77c8 (MD5) Previous issue date: 2012-03-30 / Dynamic light scattering was used to monitor relaxation processes in chitosan solutions at concentrations within the semi-dilute and concentrated regimes, Kowhlrausch-Williams-Watts (KWW) equation being successfully fitted to intensity correlation function data. The dependence of KWW equation parameters on chitosan concentration indicated that an increase in concentration from semi-dilute to concentrated regimes resulted in narrowing the distribution of relaxation rates; temperature dependence indicated the relaxation process as described as an energy activated process, whose parameters were function of the interaction between chitosan chains (enthalpy of activation) and rigidity of chitosan conformations (pre-exponential factor) / O espalhamento din?mico de luz foi utilizado para monitorar processos de relaxa??es em solu??es de quitosana em concentra??es dentro dos regimes semidilu?das e concentradas, a equa??o Kowhlrausch-Williams-Watts (KWW) foi ajustada com ?xito para os dados de intensidade de fun??o de correla??o. A depend?ncia dos par?metros da equa??o KWW sobre a concentra??o de quitosana indicam que um aumento na concentra??o de semidilu?da ? concentrada resultou no estreitamento da distribui??o das taxas de relaxa??o; a depend?ncia da temperatura indicada no processo de relaxa??o, foi descrito como energia de ativa??o do processo, cujos par?metros foram fun??es da intera??o entre as cadeias de quitosana (entalpia de ativa??o) e rigidez das conforma??es de quitosana (fator pr?-exponencial)

Made available in DSpace on 2014-12-17T15:42:02Z (GMT). No. of bitstreams: 1 AnaMariaSM.pdf: 217960 bytes, checksum: 2de591943a3cac6bc496d8cf75adf593 (MD5) Previous issue date: 2008-01-25 / Modified polyacrylamides with ≅ 0.2 mol % of N,N-dihexylacrylamide and hydrolysis degree from 0 to 25 % were synthesized by micellar copolymerization. The hydrophobic monomer was obtained by the reaction between acryloyl chloride and N,Ndihexylamine and characterized by infrared (IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The polymer molecular structures were determined through 1H and 13C NMR spectroscopy and the polymers were studied in dilute and semi-dilute regimes by viscometry, rheometry, static light scattering and photon correlation spectroscopy, at the temperature range from 25 to 55 ?C. The data obtained by viscometry showed that the intrinsic viscosity from the hydrolyzed polymers is larger than the precursor polymers at the same ionic strength. The comparison between the charged polymers showed that the polymer with higher hydrolysis degree has a more compact structure in formation water (AFS). The increase of temperature led to an enhanced reduced viscosity to the polymers in Milli-Q water (AMQ), although, in brine, only the unhydrolyzed polymer had an increase in the reduced viscosity with the temperature, and the hydrolyzed derivatives had a decrease in the reduced viscosity. The static light scattering (SLS) analyses in salt solutions evidenced a decrease of weight-average molecular weight (⎯Mw) with the increase of the hydrolysis degree, due to the reduction of the thermodynamic interactions between polymer and solvent, which was evidenced by the decrease of the second virial coefficient (A2). The polymers showed more than one relaxation mode in solution, when analyzed by photon correlation spectroscopy, and these modes were attributed to isolated coils and aggregates of several sizes. The aggregation behavior depended strongly on the ionic strength, and also on the temperature, although in a lower extension. The polymers showed large aggregates in all studied conditions, however, their solutions did not displayed a good increase in water viscosity to be used in enhanced oil recovery (EOR) processes / Poliacrilamidas modificadas com ≅ 0,2 mol % de N,N-dihexilacrilamida e grau de hidr?lise de 0 a 25 % foram sintetizadas por copolimeriza??o micelar. O mon?mero hidrof?bico foi obtido pela rea??o entre cloreto de acrilo?la e N,N-dihexilamina e foi caracterizado por espectroscopia no infravermelho (IV) e resson?ncia magn?tica nuclear de pr?ton (1H RMN). As estruturas moleculares dos pol?meros foram determinadas atrav?s de espectroscopia de RMN 1H e 13C e os pol?meros foram estudados em regime dilu?do e semidilu?do por viscosimetria, reometria, espalhamento de luz est?tico e espectroscopia de correla??o de f?tons, na faixa de temperatura de 25 a 55 ?C. Os dados obtidos por viscosimetria mostraram que as viscosidades intr?nsecas dos pol?meros hidrolisados s?o maiores que a do pol?mero precursor na mesma for?a i?nica e a compara??o entre os pol?meros carregados mostrou que o pol?mero com maior grau de hidr?lise tem uma estrutura mais compacta em ?gua de forma??o sint?tica (AFS). A eleva??o da temperatura induziu um aumento na viscosidade reduzida dos pol?meros em ?gua Milli-Q (AMQ). Em solu??o salina, apenas o pol?mero neutro apresentou aumento na viscosidade reduzida com a temperatura, enquanto os derivados hidrolisados apresentaram uma diminui??o na viscosidade reduzida. A partir do espalhamento de luz est?tico (SLS), em meio salino, foi evidenciada uma diminui??o da massa molar ponderal m?dia (⎯Mw) com o aumento do grau de hidr?lise, que foi atribu?da ? redu??o das intera??es termodin?micas entre pol?mero e solvente, o que p?de ser deduzido pela diminui??o do segundo coeficiente do virial (A2). Os pol?meros apresentaram mais de um modo de relaxa??o em solu??o, quando analisados por espectroscopia de correla??o de f?tons, e esses modos foram atribu?dos a cadeias isoladas e a agregados de diversos tamanhos. O comportamento de agrega??o dependeu fortemente da for?a i?nica, e tamb?m da temperatura, embora de uma forma menos pronunciada. Os pol?meros apresentaram grandes agregados em todas as condi??es estudadas, contudo, suas solu??es n?o mostraram um bom aumento na viscosidade da ?gua para serem usados em processos de recupera??o melhorada de petr?leo (EOR)