Neste trabalho, várias técnicas foram utilizadas para estudar mesofases constituídas por laurato de potássio, cloreto de decilamônio, água e sulfato de brucina. Este sistema foi eleito por apresentar a fase colestérica biaxial, cuja caracterização continua se constituindo um problema digno de investigação. Foram efetuadas medidas reológicas sobre sistemas nemáticos e colestéricos, em diferentes composições e condições. Os valores das viscosidades aparentes foram calculados e o comportamento caracterizado. Para os estudos de RMN, introduziu-se nas amostras uma molécula probe, o racêmico dl alanina, procurando-se verificar se havia diferença na interação dos enantiômeros d e I com a matriz colestérica. Os espectros foram obtidos com variação de temperatura. Compararam-se os dados de variação do parâmetro de ordem, obtidos dos acoplamentos diretos, com a semi largura da linha larga dos espectros de próton, para obter informações sobre o comportamento da alanina e das micelas colestéricas. Todas as fases foram acompanhadas por estudos de microscopia sob luz polarizada, técnica simples e eficiente utilizada para caracterizar tipos de fases de cristais líquidos. / In this work, several techniques were used to study mesophases constituted by potassium laurate, decylammonium chloride, water and brucine sulfate. This system was chosen for presenting a cholesteric biaxial phase, whose characterization continues to be worthy of investigation. Rheological measurements were made on nematic and cholesteric systems, in different compositions and situations. The values of apparent viscosity were calculated and the behaviour was characterized. For the RMN studies, a probe moIecule, the racemic form of dl alanine, was introduced in the sampIes trying to verify difference between in interaction of the enantiomers d and I with the main cholesteric matrix. The spectra were obtained with temperature variation. It was compared the data of variation of the order parameter, obtained from the direct couplings, with the half width of the wide line of the proton spectra, to obtain information about the behaviour of the alanine and of the cholesteric micelles. All the phases were accompanied by microscopy studies under polarized light, simple and efficient technique to characterize types of liquid crystal phases.

Um dos veículos de grande utilização para ativos cosméticos são os sistemas emulsionados, que são constituídos de duas fases líquidas imiscíveis e agentes tensoativos, obtidos por diferentes metodologias de emulsificação. Devido à sua excelente capacidade de solubilizar compostos hidrofílicos e lipofílicos a importância comercial e científica das emulsões entre os diversos sistemas coloidais é inquestionável. O delineamento desses sistemas exige conhecimento dos principais fatores que influenciam sua formação, propriedades físico-químicas e, consequentemente, estabilidade e performance. O uso de óleos vegetais na iensdpúésctrieias vfaergmeataciês uotliecaa gien ocsoassm, péotidcae mtoosrn cai-taser oc baadrau (vDeizp temryaxis a laattraa tVivoog. .)D, neanttirvea daos Bioma Cerrado e cujas sementes contêm um óleo com alto grau de insaturação cseonntdeor qousa nátcididaodse sg rsaixgonsif icoalenitceos teo cloinfoelreóiicso e ofsit oceosntesrtóituisi,n treesp rmesaejonrtaitánrdioos i,m aploérmta ndtee fonte de agentes capazes de atuar no combate aos processos oxidativos diretamente ligados ao envelhecimento e às doenças degenerativas. O objetivo duteilsiztaa npdeos cqoumisao ffaosi eo o ldeeossean ovo ólvleimoe enxtotr aeíd oc adraasc tesreimzaeçnãtoe s ddee sbisatreum (aDs. adliastpae).r sAoss etapas envolvidas no desenvolvimento dos sistemas estão listadas a seguir: 1) Obtenção e caracterização da matéria prima vegetal (óleo); 2) Desenvolvimento das fboarrmu u(lDaç. õaelas:t ae);s teusdtou ddoo dEaq culialísbsrieo dHeid treónfisloo aLtiivpoósfi;l oc o(EnHstLru) çrãeoq udeor iddoia gpraarma ao tóelrenoá rdioe; coabrtaidcotes;r iz3a) çEãnos afíiosisc oin-q vuiítmroi:c aA vea liaeçsãtuod doas s dme uedsatnaçbailsid easdteru tduoras iss mistiecrmoascsó pdiicsapse rdsooss sistemas dispersos mediante simulação da evaporação do produto final após aplicação na pele; estudo do efeito dos sistemas dispersos na dinâmica da membrana de estrato córneo por Ressonância Paramagnética Eletrônica. Os resultados encontrados sugerem que os sistemas dispersos desenvolvidos são potenciais alternativas na liberação de fármacos ou ativos cosméticos ou ainda, podem ser considerados produtos finais de interesse para recuperação da camada lipídica da pele. O uso de metodologia de emulsificação com baixo gasto de energia (emulsificação por inversão de fases) permitiu a obtenção de dois sistemas emulsionados estáveis: um com presença de fase gel lamelar e outro com partículas de tamanho nanométrico. O estudo das propriedades físico-químicas das formulações mostrou inexistência de quaisquer sinais de instabilidade das formulações durante o período de armazenamento em condições de temperatura específicas. A utilização de espectroscopia de Ressonância Paramagnética Eletrônica (RPE) forneceu informações acerca da dinâmica molecular do estrato córneo frente a aplicação do óleo e das formulações, demonstrando o potencial dos mesmos em atuar como veículos de fármacos ou ativos cosméticos visto que os espectros obtidos revelaram diferenças significativas na fluidez dos lipídios do estrato córneo, principal barreira na permeação cutânea. / The commercial and scientific importance of emulsions among the colloidal systems is unquestionable. These systems consist of two immiscible phases that could be obtained by different methods of emulsification. Emulsions have excellent ability to solubilize hydrophilic and lipophilic compounds, so, are widely used as vehicules for drugs and cosmetics. The rational design of these systems requires studies of the main factors that influence their formation, physicochemical properties and, consequently, stability and performance. Nowadays, the use of vegetable oils in the pharmaceutical and cosmetic industries becomes attractive. Dipteryx alata Vog is an oleaginous plant specie native to Cerrado. The seeds of this specie contain an oil with a high degree of unsaturation (oleic and linoleic fatty acids are the major constituents) and significant amounts of tocopherols and phytosterols, representing an important source of agents capable of acting to combat the oxidative processes directly related to aging and degenerative diseases. The objective of this research was the development and characterization of dispersed systems using the oil extracted from the seeds of D. alata (baru). The steps involved in the development of the systems were: 1) Preparation and characterization of vegetable raw material (oil); 2) Development of formulations: Study of Hydrophilic and Lipophilic Balance (HLB) required for baru oil; study of surfactant class; Construction of the ternary diagram; physicochemical characterization and stability studies of dispersed systems obtained; 3) In vitro assays: Evaluation of microscopic structural change of dispersed systems by simulating the evaporation of the final product after application on the skin; study of the effect of dispersed systems in the dynamics of the stratum corneum membrane by Electron Paramagnetic Resonance. The use of low energy emulsification method allowed the development of two stable emulsions: one with presence of lamellar gel phase and another with nanometric size particles. The study of physicochemical properties of the formulations showed absence of any signs of instability of the formulations during the storage period. The use of Electron Paramagnetic Resonance (EPR) spectroscopy provide information about the molecular dynamics of the stratum corneum facing the implementation of oil and formulations, demonstrating the potential of them to act as drug or cosmetic active vehicles

O desenvolvimento de formulações cosméticas multifuncionais tem sido cada vez mais crescente na indústria cosmética. A elaboração de uma formulação que contém diferentes ativos com propósitos diferentes podendo agir sinergicamente, muitas vezes, confere resultados cosméticos eficazes e até mesmo terapêuticos ao usuário. Nesta pesquisa foram desenvolvidas emulsões cosméticas apresentando formação de fases líquido cristalinas à base de manteiga de cupuaçu (Theobroma grandiflorum), manteiga de cacau (Theobroma cacau), o agente hidratante Hidraskin? e aditivos estabilizantes tais como álcool cetoestearílico, lanolina polietoxilada e carbômero. O desenvolvimento das formulações deu-se pelo método de inversão de fases. Estas foram caracterizadas quanto à formação de mesofases líquido cristalinas e avaliadas quanto à estabilidade física. Foram selecionadas quatro emulsões, duas com manteiga de cupuaçu (com e sem Hidraskin?) e duas com manteiga de cacau (com e sem Hidraskin?) que apresentaram maior estabilidade física e formação de fases líquido-cristalinas mais abundante. A adição do ativo hidratante (Hidraskin?) não alterou as características morfológicas das fases líquido cristalinas, identificadas como fase lamelar e a adição de lanolina polietoxilada como aditivo estabilizante promoveu maior estabilidade fisico-química das emulsões, principalmente quando submetidas à temperaturas em torno de 40ºC também sem alteração das fases líquido cristalinas. / Development of multifunctional cosmetic formulations has been growing each day in cosmetic industry. Elaboration of formulations, which presents many actives with different purposes acting together, many times give good and therapeutic results to customers. In this research cosmetic emulsions with liquid crystals were developed based on cupuaçu (Theobroma grandiflorum) or (Theobroma cacau) butter, Hidraskin? as a moisturizer active and actives for stabilization such as cetostearil alcohol, poliethoxilated lanolin and carbomer. Formulations were prepared by the Emulsion Phase Inversion method and characterized on the liquid crystal assembly and evaluated for physical stability. Four emulsions were chosen, two formulated with cupuaçu butter (one with and the other without Hidraskin?) and two with cocoa butter (one with and the other without Hidraskin?), which presented the highest amount of liquid crystals. Addition of Hidraskin? did not change the morphological aspects of liquid crystals, identified as lamellas. Also addition of polyethoxilatted lanolin increased the physical stability of all emulsions prepared, especially when they were submitted to increase of temperature (40ºC).

Orientador: Watson Loh / Texto em português e inglês / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-21T09:28:37Z (GMT). No. of bitstreams: 1 Silva_AnaMariaPercebomSetteda_D.pdf: 24339728 bytes, checksum: 5607616747acea067ac22294eb185712 (MD5) Previous issue date: 2012 / Resumo: Este trabalho se insere em uma linha de pesquisa de nosso grupo sobre a autoassociação de surfatantes iônicos que são neutralizados por contraíons poliméricos, formando os chamados sais complexos. A proposta do presente projeto trata da verificação do efeito de diferentes arquiteturas ou composições químicas de poliânions sobre as propriedades de autoassociação do surfatante catiônico hexadeciltrimetilamônio, utilizando copolímeros aleatórios. A mistura estequiométrica de poli-íons e surfatantes opostamente carregados geralmente leva à separação de uma fase concentrada em sal complexo. Esta fase pode apresentar diferentes estruturas (cristais líquidos ou sistemas micelares) e é interessante para aplicações como moldes para matérias mesoporosos e alguns cosméticos, mas inviabiliza o seu uso em soluções aquosas, como por exemplo, para carreadores de fármacos. Para evitar a separação de fases de sais complexos em água, a estratégia utilizada neste trabalho foi usar copolímeros que possuem comonômeros aniônicos e cadeias laterais hidrofílicas. Dentro do contexto de se estudar complexos de copoli-íons, este projeto também envolve o estudo de sais complexos formados por um copolímero que possui comonômeros hidrofóbicos e hidrofílicos, para verificar seu efeito sobre o comportamento de fases. Para identificar e caracterizar as fases formadas, a principal técnica usada foi a de espalhamento de raios-X a baixos ângulos, que permitiu determinar os diagramas de fases. Também permitiu, em conjunto com o resultado de outras técnicas (espalhamento de luz dinâmico, difusão por ressonância magnética nuclear, tensiometria e fluorescência), mostrar que alterações na estrutura dos polímeros diversifica as estruturas formadas pela autoassociação do surfatante e, consequentemente, suas propriedades / Abstract: This project is part of a research in our group involving the selfassembly of ionic surfactants neutralized by polymeric counterions, forming the so-called complex salts. The main goal of this study is to verify the effect of different architectures or different chemical compositions of polyanions on the self-assembly of the cationic surfactant hexadecyltrimethylammonium, by using different random copolymers. The stoichiometric mixture of poly-ions and oppositely charged surfactants generally leads to the separation of a phase concentrated in complex salt. This phase can display different structures (liquid crystal or micellar systems) and is interesting for applications such as templates for mesoporous materials or cosmetics, but forbids the use in aqueous solutions, such as for drug carriers. To avoid phase separation of complex salts in water, the strategy was to use copolymers with anionic comonomers and hydrophilic neutral side-chains. In the context of studying complex salts of copolyions, this project also involves the study of complex salts formed by a copolymer with both hydrophilic and hydrophobic comonomers, to verify the effect on the phase behavior. In order to identify and characterize the obtained phases, the main technique used was small angle X-ray scattering, which provided information to determine the phase diagrams. These data along with the results from other techniques (dynamic light scattering, nuclear magnetic resonance, surface tension measurements and fluorescence) show that changes on the polymer structure provide a diversification of the surfactant assembles and, as a consequence, of the resulting properties / Doutorado / Físico-Química / Doutora em Ciências

The theory and computation of line defects are discussed in the context of both solids and liquid crystals. This dissertation includes four parts. The Generalized Disclination theory is discussed and applied to numerous interfacial and bulk line defect problems. An augmented Oseen-Frank energy as well as a novel 2D-model is proposed and demonstrated for disclination dynamics in liquid crystal. A model based on kinematics and thermodynamics is devised to predict tactoid dynamics during the process of the isotropic-nematic phase transition in LCLC. In the first part of the thesis, the utility of the notion of generalized disclinations in materials science is discussed within the physical context of modeling interfacial and bulk line defects. The Burgers vector of a disclination dipole in linear elasticity is derived, clearly demonstrating the equivalence of its stress field to that of an edge dislocation. An explicit formula for the displacement jump of a single localized composite defect line in terms of given g.disclination and dislocation strengths is deduced based on the Weingarten theorem for g.disclination theory at finite deformation. The Burgers vector of a g.disclination dipole at finite deformation is also derived. In the second part, a numerical method is developed to solve for the stress and distortion fields of g.disclination systems. Problems of small and finite deformation theory are considered. The fields of various line defects and grain/phase boundary problems are approximated. It is demonstrated that while the far-field topological identity of a dislocation of appropriate strength and a disclinationdipole plus a slip dislocation comprising a disconnection are the same, the latter microstructure is energetically favorable. This underscores the complementary importance of all of topology, geometry, and energetics (plus kinetics) in understanding defect mechanics. It is established that finite element approximations of fields of interfacial and bulk line defects can be achieved in a systematic and routine manner, thus contributing to the study of intricate defect microstructures in the scientific understanding and predictive design of materials. In the third part, nonsingular disclination dynamics in a uniaxial nematic liquid crystal is modeled within a mathematical framework where the kinematics is a direct extension of the classical way of identifying these line defects with singularities of a unit vector field representing the nematic director. We devise a natural augmentation of the Oseen-Frank energy to account for physical situations where infinite director gradients have zero associated energy cost, as would be necessary for modeling half-integer strength disclinations within the framework of the director theory. A novel 2D-model of disclination dynamics in nematics is proposed, which is based on the extended Oseen-Frank energy and takes into account thermodynamics and the kinematics of conservation of defect topological charge. We validate this model through computations of disclination equilibria, annihilation, repulsion, and splitting. In the fourth part, the isotropic-nematic phase transition in chromonic liquid crystals is studied. We simulate such tactoid equilibria and dynamics with a model using degree of order, a variable length director as state descriptors, and an interfacial descriptor. We introduce an augmented Oseen-Frank energy, with non-convexity in both interfacial energy and the dependence of the energy on the degree of order. A strategy is devised based on continuum kinematics and thermodynamics. The model is used to predict tactoid dynamics during the process of phase transition. We reproduce observed behaviors in experiments and perform an experimentally testable parametric study of the effect of bulk elastic and tactoid interfacial energy constants on the interaction of interfacial and bulk fields in the tactoids.

Abstract Xenon atoms and sulfur hexafluoride (SF6) molecules can be dissolved in liquids and liquid crystals or adsorbed in porous materials. Nuclear magnetic resonance (NMR) spectra of 129Xe or 19F nuclei reveal information about their surroundings. This means that xenon atoms and SF6 molecules can be used as probes to indirectly study materials by NMR spectroscopy. The change in the spectra arises from a NMR interaction called shielding. Especially in the case of xenon, shielding reveals even the slightest changes, for example, in the density of a liquid it is dissolved in. Because a change in temperature leads to a change in the density of the liquid as well, temperature change is observed as a shift of the resonance line in the 129Xe NMR spectrum. This property can be utilized in the accurate determination of the sample temperature. Self-diffusion measurements of the gases provide additional information on a larger scale rather than just the immediate surroundings of atoms or molecules. Various liquid crystals were studied using xenon and SF6 as probes proving their applicability. It is often considered that the signal observed in NMR experiments is very weak and limits the full potential of the method. This is true especially with the samples in gaseous form. The Spin-Exchange Optical Pumping (SEOP) hyperpolarization method solves this problem in the case of xenon. A 129Xe NMR signal can be enhanced by a factor of 104–105 by SEOP and this opens access to techniques that are not otherwise possible. The remote detection technique, which separates the encoding and detection steps of the typical NMR experiment both temporally and spatially, is one of these techniques. The potential of the combination of SEOP and remote detection techniques was shown in studies of thermally modified Pinus Sylvestris.

Liquid crystals are a vast and diverse class of materials which ranges from fluids made up of simple rods, polymers and solutions, to elastomers and biological organisms. Liquid crystal phases are neither crystalline, nor a ‘normal’ isotropic liquid, but lie somewhere in between these two common states of matter. Liquid crystals have found enormous use in display devices due to their electro-optic properties. In this thesis, the optical and electro-optical properties of some chiral liquid crystalline phases are studied. The optical and electro-optical behaviour of liquid crystalline blue phases has been investigated via a detailed analysis of the reflection spectrum from thin, vertical field (VF) cells. Spectral analysis in this thesis was performed using a numerical fitting technique based on the Berreman 4x4 matrix method. The validity of the technique was proved through comparisons of independent measurements with the calculated physical parameters. A novel Kerr effect measurement method was proposed in this thesis and a known material was used to verify this new method. The Kerr constant together with its dispersion relation was measured using a white light source. An unusually large Kerr constant, K, is determined in the blue phases of a non-polymer stabilized material, ~ 3x10-9 mV-2 (BPI). The large value of K is attributed to significant pre-transitional values of the dielectric anisotropy and birefringence. K follows an inverse dependence on temperature which is more marked in BPII than BPI, and we consequently suggest that the BPI demonstrates properties best suited to electro-optic devices. The field effects in blue phase include electrostriction and the influence of the Kerr effect was separated from electrostriction phenomena for the first time in this work. Finally in the Kerr effect measurements, the Kerr constant in the optically isotropic dark conglomerate phase of a bent-core material was studied for the first time, with rather low values, ~1x10-11 mV-2. The low Kerr constant can be understood in the context of the physical properties of the material. Supercooling phenomena in the blue phase were studied through an analysis of the optical properties in thin cells. Features including the Bragg reflection peak jump and hysteresis are measured through the reflection spectra. A blue phase sample with a single orientation over an area of millimeters was prepared to help the spectra study of the blue phases. Although some previous reports indicated that there may be a new blue phase in the supercooled region, we find that there is no evidence shows that the supercooled blue phase has a different structure from the BPI.Chiral molecules have been included as dopants in achiral bent-core materials to produce a range of new chiral mixtures. Different host materials and chiral dopants have been used to produce several chiral nematic materials in which the chiral nematic phase, the underlying smectic phase and the blue phases are examined. The order parameter is determined as a function of temperature in the chiral nematic phase, and compared to that determined for several calamitic materials; no discernible difference is found. A study of the pitch divergence in the chiral nematic phase of the bent-core mixtures shows interesting properties at both low temperature (as the smectic phase is approached) and at high temperatures (at the transition to the blue phase). An unusual phase separation of the chiral dopant in the mixtures is reported, and details are deduced through a comparison between different mixtures. It is found that a dopant with similar clearing point to the bent-core material has less likelihood of phase separation. Although the blue phase temperature range is extended in these mixtures in comparison with typical values for calamitic materials, it does not extend beyond 2K in any of the materials. Both blue phase I and the fog phases are observed in these chiral bent core systems, but no BPII is observed in any of the materials studied. The small k33 (~ 2.8 pN at 10 K below clearing point) in the bent-core host material is suggested as one of the reasons that the blue phase range is not enhanced as much as may have been expected from reports by other authors.

Les clustomésogènes sont une nouvelle classe de cristaux liquides hybrides multifonctionnels découverts dans l'équipe CSM de l'Institut des Sciences Chimiques de Rennes en 2008. Ils sont constitués d'un cœur inorganique - des clusters de métaux de transition - auquel sont associés, de manière covalente ou électrostatique, des ligands organiques pro-mésogéniques. Ces matériaux hybrides associent les propriétés d'auto-assemblage des cristaux liquides aux propriétés intrinsèques des clusters métalliques. Le présent travail s'articule autour de clustomésogènes contenant des clusters octaédriques de molybdène, phosphorescents dans le rouge-proche infra-rouge, et aux rendements quantiques compris entre 10% et 50%. Ils sont synthétisés par approche ionique en vue de leur intégration dans des dispositifs optiques. La démarche consiste à rationaliser les relations structures-propriétés afin de contrôler l'arrangement des clustomésogènes à l'échelle nanométrique. Nous créons ainsi des états nématiques sur de larges gammes de température. Le transfert de ces systèmes dans des cellules électro-optiques est renforcé par leur miscibilité dans un certain nombre de cristaux liquides commerciaux. La nature et la concentration de ces derniers permet l'ajustement des températures de fonctionnement et le contrôle de la viscosité de l'état cristal-liquide. Nous montrons qu'il est possible de faire commuter l'intensité de photoluminescence des clustomésogènes de 50% par l'application d'un champ alternatif à la manière des systèmes d'affichage. L'intégration au sein de diodes électroluminescentes constitue le dernier volet de ce travail. La maîtrise de leur structure permet d'envisager leur potentiel dans des dispositifs d'éclairage. L'ensemble de ces études ouvre la voie aux clustomésogènes de molybdène comme alternative réaliste aux émetteurs inorganiques rouges actuels. / Clustomesogens are a new class of hybrid liquid crystals developed since 2008 in our laboratory. They are a combination of an inorganic core, namely transition metal clusters, linked with promesogenic organic ligands through covalent or electrostatic interactions. These hybrid materials associate liquid crystals self-assembling abilities to the metallic clusters intrinsic properties. This work present octahedral molybdenum cluster based clustomesogens, emitting, through phosphorence mechanisms, in the deep red area and exhibiting 10% to 50% quantum efficiency. These materials are produced via an ionic approach by replacing the alkali cations of the ternary solid state compounds with tailored promesogenic organic ones. The ambition of this work is to rationalize the structures-properties relationship to control, at the nanometric scale, the clustomesogens organization. This approach allows us to observe nematic liquid crystalline phases over a wide range of temperatures. As these compounds are miscible with commercial nematic liquid crystals, we could envision their use as emissive species in the design of electroswitchable luminescent liquid crystal cells. By changing the type and concentration of commercial liquid crystals, we could adjust the operating temperature range as well as the viscosity of the mixture. We also establish that it is possible to modulate the clustomesogens' photoluminescence by 50% by applying an alternative electric field, as in display devices. In the last part of this work, we study the integration of clustomesogens as the emissive species into electroluminescent diodes. Being able to control their structure should allow their use in lighting devices. These works pave the way for using Molybdenum clustomesogens as an alternative to inorganic compounds presently used as red light emitters.

Cette thèse porte sur l’influence de la formulation de méthode de nanoprecipitation sur la taille et la structure interne de particules de dérivés squalénés. Ces composés introduits en 2006 par P. Couvreur sont basés sur l’association de principe actif au groupe squalène pour obtenir des propriétés d’auto-assemblage. L’augmentation de l’efficacité thérapeutique des nanoparticules par rapport au principe actif libre et la versatilité de fonctionnalisation ont ouvert une nouvelle stratégie pour les applications biomédicales. Cependant, la compréhension des mécanismes de formation des particules et de leur structure interne reste incomplète. Ces caractéristiques (taille et structure) pouvant influencer l’activité thérapeutique, il est crucial en vue d’une application médicale de déterminer les paramètres clef de la formation des nanoparticules. Dans cette thèse, les particules de squalène deoxycitidine ont été caractérisées par diffusion de neutrons et de rayons X aux petits angles et par cryo-microscopie électronique. Dans une première partie, nous avons identifié les paramètres optimums de formulation pour la nanoprecipitation. Dans une deuxième partie, l’étude de la nature du solvant organique sur la nanoprecipitation a mis en évidence pour certains solvants un mécanisme de nucléation croissance. Les effets de solvants sont cependant faibles par rapport à ce qui est classiquement observé pour les polymères. La troisième partie basée sur la cryo-TEM des particules oriente vers un mécanisme décrit pour les autres cubosomes d’attachements inter lamellaires pour les structures internes cubiques. Enfin, à l’issue de ce travail, nous avons étendu le protocole de nanoprecipitation au D α- Tocophérol Succinate en tentant de stabiliser la phase cristalline hexagonale présente dans le diagramme de phase binaire eau/ α-TOS. / This thesis investigates the influence of the formulation on the size and the internal structure of particles obtained by nanoprecipitation of squalene derivatives. These compounds were introduced in 2006 by P. Couvreur's team as part of a process called squalenoylation. Based on the association of drug with the squalene group it confers to these molecules self-assembling properties and it increased therapeutic efficacy. The particles are prepared by the solvent displacement method ("Ouzo" effect) and were characterized by neutron and X-ray scattering at small angles and by cryo-electron microscopy.We have highlighted the necessary preparation parameters for the reproducible preparation of cubosomes in a dimater of hundred nanometres. A study on the effect of the nature of the organic solvent on Squalene deoxycitidine has highlighted for some of them (isopropanol and DMSO) a nucleation mechanism that could be followed by growth (ethanol and acetone). TEM cryo-microscopy analysis suggests that cubic internal structures form by the mechanism of interlamellar attachments. Finally, we extended the nanoprecipitation method to Dα-Tocopherol Succinate, a derivative of Vitamin E

Several applications, including those in the energy sector that require high thermal efficiency, such as those in the solar energy industry, require a careful thermal analysis of heat exchange components. In this regard, thermal resistance is a major cause of exergy destruction and must be minimised as much as possible, but also adequately designed. In the past, a number of correlations have been developed to predict heat transfer coefficients in compact heat exchangers. The designers of such heat exchangers often exploit the development of thermal boundary layers to achieve higher overall efficiency due to increases in local heat transfer coefficients. However, most of the correlations that have been developed for heat exchangers neglect the specific effect of the thermal boundary layer development in the inlet region, and instead only offer effective average heat transfer coefficients, which most users assume to be constant throughout the heat exchanger. This is often an over-simplification and leads to over-designed heat exchangers. In this study, focus is placed on annular flow passages with uniform heating on the inner wall. This geometry has many applications. This study aims to collect experimental heat transfer data for water at various flow rates and inlet geometries, to process the data and determine local and overall heat transfer coefficients, and to develop an improved local heat transfer coefficient correlation. Experimental tests were performed on a horizontal concentric tube-in-tube heat exchanger with a length of 1.05 m and a diameter ratio of 0.648. The surface of the inner tube was treated with thermochromic liquid crystals (TLCs), which allowed for high-resolution temperature mapping of the heated surface when combined with an automated camera position system in order to determine local heat transfer coefficients. Conventional in-line and out-of-line annular inlet configurations were evaluated for Reynolds numbers from 2 000 to 7 500, as well as the transition from laminar to turbulent flow for a single in-line inlet configuration. It was found that the local heat transfer coefficients were significantly higher at the inlets, and decreased as the boundary layers developed. With the high resolution of the results, the local heat transfer coefficients were investigated in detail. Local maximum and minimum heat transfer coefficients were identified where the thermal boundary layers merged for high turbulent flow cases. The annular inlet geometries only influenced the heat transfer for Reynolds numbers larger than 4 000, for which larger inlets are favoured. Out-of-line inlet geometries are not favoured for heat transfer. A new heat transfer correlation was developed from the experimental data, based on an existing heat transfer correlation for turbulent flow in an annular flow passage, considering the boundary layer development. The new correlation estimated the area-weighted heat transfer coefficients within 10% of the experimental data and closely followed trends for local heat transfer coefficients. / Dissertation (MEng)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / MEng / Unrestricted