L'objectif du projet est la synthèse d'une cornée artificielle biocompatible à base de collagène de type I extrait et purifié à partir de tendons de queues de rats. La synthèse utilise les propriétés mésogènes (cristal-liquides) de la molécule de collagène ainsi qu'une transition sol-gel mimant l'étape de fibrillogenèse qui se déroule in vivo. Des solutions acides de collagène (500 mM en acide acétique) sont dyalisées contre des solutions de diverses concentrations en acide acétique et en acide chlorhydrique puis concentrées jusqu'à 90 mg/mL. Les phases cristal-liquides données par les différentes conditions physico-chimiques sont analysées par microscopie à lumière polarisée et par génération de seconde harmonique. L'une des conditions permet d’obtenir une phase dite en contreplaqué, ce qui est l’organisation des lamelles de fibrilles de collagène dans la cornée.Analysée par microscopie électronique à transmission, la structure des matrices obtenues après fibrillogénèse présente des domaines en contreplaqué indiquant une conservation et une stabilisation de l’organisation cristal-liquide d'origine. L’organisation obtenue est proche de celle du stroma cornéen. Par une optimisation des conditions physico-chimiques, les matrices synthétisées présentent une transparence proche de 90 % et possèdent de bonnes propriétés mécaniques avec un module d’Young proche de 1 MPa. Des cultures cellulaires effectuées sur les matrices transparentes montrent qu’elles sont un très bon support pour la culture de cellules cornéennes, en particulier des cellules épithéliales. Tous ses résultats confortent la méthode utilisée et les essais in vivo constituent l’étape suivante. / In view to generate artificial corneas, dense transparent collagen type-I scaffolds were synthesized exploiting the intrinsic liquid crystals properties of collagen molecules. 3 mg/mL collagen solutions in 500 mM acetic acid were dialyzed against a solution of precise concentrations in acetic and hydrochloric acid. When concentrated, solution provided a liquid-crystal organization resembling plywood, which is the organization of the collagen fibrils in the cornea. This was verified by polarized light and second harmonic generation microscopy experiments. In parallel these collagen solutions were also concentrated by centrifugation-filtration up to 90 mg/mL. The concentrated solutions were pressed into cornea-like shape and submitted to ammonia vapor in order to induce the fibrillogenesis of collagen. The result is a transparent dense fibrillated collagen matrix (transparency 90 %). Transmission electron microscopy revealed that fibrils kept the organization of the concentrated solution. Using a custom made device, mechanical tests showed that the Young modulus reached 900kPa. Human donor limbal explants were sewed on top of the scaffolds and cultured for 14 days. Optical microscopy and immunocytochemical analysis showed the development of an epithelium with characteristics of corneal epithelial cells. Preliminary experiments showed that keratocytes could be successfully inserted during the synthesis process. Thus, the results show the viability of the process of fabrication, and the following step is the in vivo experiment.

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Les nanoparticules métalliques ont des propriétés optiques uniques, dont le contrôle et l'optimisation ont un intérêt grandissant tant pour la recherche fondamentale qu'appliquée. Une propriété spectaculaire de ces nanoparticules est la résonance plasmon de surface localisé, qui est une conséquence des oscillations des électrons libres à l'interface métal/diélectrique.La position spectrale de la résonance plasmon est largement dépendante de la géométrie des nanoparticules, mais aussi de la constante diélectrique du milieu environnant. Un moyen pour contrôler cette résonance consiste donc à faire varier l'indice du milieu qui entoure les nanostructures. Les cristaux liquides nématiques sont un excellent moyen pour modifier et contrôler la résonance plasmon. En effet, par rotation des molécules du cristal liquide on peut induire un changement d'indice qui se traduit par un changement de la réponse optique des nanostructures. L'objectif de la thèse est de simuler des réseaux de nanoparticules d'or, dans un cristal liquide nématique afin de prédire l'influence de l'orientation du CL sur les propriétés optiques de ces nanostructures. Le formalisme numérique utilisé est basé sur la méthode des différences finies dans le domaine temporel (FDTD). Nous avons pris en compte les phénomènes d'ancrage des molécules aux interfaces avec la cellule contenant les cristaux liquides et les structures métalliques, et comparé les résultats avec le cas d'une orientation uniforme des molécules dans la cellule. La possibilité d'avoir une double résonance a été étudiée, ainsi que les gain SERS associés à ces structures spécifiques / Metal nanoparticles have unique optical properties, the control and optimization have a growing interest in fundamental research as same as applied research. A spectacular property of these nanoparticles is the localized surface plasmon resonance ( LSPR ), which is a consequence of the oscillations of free electrons at the interface between metal and dielectric.The spectral position of the plasmon resonance is largely dependent on the geometry of the nanoparticles, but also on the dielectric properties of the surrounding medium. It implies that the variation of the index of the medium surrounding the metallic nanostructures can control the LSPR resonance. Nematic liquid crystals are a great way to modify and control the plasmon resonance. Indeed, rotation of the liquid crystal molecules can induce a change in refractive index which results in a change in the optical response of the nanostructures. The aim of the thesis is to simulate arrays of gold nanoparticles in a nematic liquid crystal in order to predict the influence of the orientation of the LC molcules on the optical properties of these nanostructures. Numerical method we used is based on the finite difference time domain ( FDTD ) method. We have considered anchoring effects of molecules at the interfaces between the cell containing the liquid crystal and the substrates. And the results are compared with the case of uniform orientation of the LC molecules in the cell. The possibility of having double resonances was studied as well as the Surface Enhanced Raman Scattering (SERS ) gain associated with these specific structures

Dans ce travail, les propriétés des oxydes de titane mésoporeux organisés ont été étudiées en détail. La synthèse de ces matériaux a été mise au point auparavant au laboratoire à l’aide d’une méthode combinant le mécanisme transcriptif à partir des cristaux liquides du copolymère bloc P123 et la méthode EISA. Tout d’abord, une optimisation des conditions d’élimination du tensioactif a été effectuée en testant des méthodes d’extraction à partir de solvant et des méthodes thermiques. L’élimination du P123 par l’eau suivie d’un rinçage à l’acétone est efficace, simple et rapide et en même temps favorise la formation de la phase anatase du TiO2. Par contre, les propriétés photocatalytiques de ces TiO2 extraits à l’eau sont médiocres et ne sont améliorées qu’après calcination. En combinant une extraction du P123 à l’eau avec une calcination les oxydes de titane mésoporeux possédent une meilleure activité photocatalytique que celle de l’anatase commercial. Dans un second temps l’incorporation du zinc et du tungstène dans les TiO2 mésoporeux organisés a été investie dans le but d’améliorer leur activité photocatalytique. L’introduction de faibles quantités de zinc (<10% mol) augmente la surface spécifique ; au-delà la mésostructuration est perdue. L’incorporation du tungstène dans le TiO2 mésoporeux n’a pas d’influence sur l’organisation des mésopores, mais des agrégats de WO3 orthorhombique coexistent avec le réseau mésoporeux de TiO2 anatase. Même si la présence d’oxyde de zinc ou de tungstène dans la matrice TiO2 mésoporeux diminue bien l’énergie bandgap, l’activité photocatalytique ne s’en trouve pas améliorée. D’autre part, la synthèse de matériaux à porosité bimodale, en utilisant deux systèmes mixtes de tensioactifs hydrogéné/fluoré, CTABr/RF8(EO)9 et P123/ RF8(EO)9, a été explorée. Sur la base des diagrammes de phase de ces deux systèmes dans l’eau, les solutions micellaires et les cristaux liquides ont été investis pour préparer des silices mésoporeuses en utilisant les deux mécanismes CTM et LCT. Quand le CTABr est présent une seule taille de pores dans le domaine mésoporeux est observée, toutefois il est possible qu’une bimodalité de type micro-mésopores existe. Par contre, l’utilisation de la phase hexagonale du système P123/RF8(EO)9 permet d’obtenir des matériaux à deux tailles de pores distincts dans le domaine mésoporeux. / In this work we will study in detail the properties of the mesoporous TiO2 materials, for which the preparation was developed previously via a method combining Liquid Crystal Templating (LCT) and EISA mechanisms, using P123 as template. We have tested, in the first time, extraction and thermal methods efficiency to eliminate surfactant in order to optimize the P123 elimination step. Removal of P123 using water followed by washing with acetone is effective, easy and promotes the formation of the anatase phase of TiO2. Otherwise, the photocatalytic properties of the obtained TiO2 are not important and can be improved after calcination. Combining extraction using water and calcination give rise to mesoporous TiO2 with better photocatalytic activity than that of commercial anatase. The incorporation of zinc and tungsten in the mesoporous well-ordered TiO2 has been investigated in the third time, in order to improve their photocatalytic activity. The introduction of small amounts of zinc (<10 mol%) increases the surface area; beyond this amount the mesostructure is lost. The incorporation of tungsten in the mesoporous TiO2 does not affect the mesopores organization, and orthorhombic WO3 aggregates are formed beside the mesoporous network of anatase TiO2. Although, the presence of zinc or tungsten oxides in the matrix decreases the bandgap of mesoporous TiO2, the photocatalytic activity is not improved. In the third time, the synthesis of bimodal porosity materials, using a mixed surfactant systems hydrogenated/fluorinated, CTABr/RF8(EO)9 and P123/RF8(EO)9, was explored. Based on the phase diagrams of these two systems in water, micellar solutions and liquid crystals have been investigated to prepare mesoporous silicas using two mechanisms CTM and LCT. When CTABr is present, pores of one size in the mesoporous range are observed, however, it is possible that bimodal type micro-mesopores exist. The use of the hexagonal liquid crystal phase of P123/RF8(EO)9 provides two separate pore sizes materials in the mesoporous range.

Les résultats décrits dans cette thèse démontrent une relation complexe entre le confinement géométrique de molécules à 2D et les propriétés de chiralité. Il a été démontré qu’une chiralité multimodale peut être observée pour des systèmes non chiraux par le biais du confinement 2D. Les molécules H5T forment, sur Au(111), des domaines pour lesquels deux types de chiralité peuvent être observés. Les études sur le système H5T/Au(111) ont prouvé que des interactions simples, de type van der Waals sont susceptibles de créer des chiralités complexes, ce qui donne un caractère générique a ce type de phénomène. Une autre question importante est l’apparition, pour les molécules C-12, des domaines chiraux induits par des interactions intermoléculaires spécifiques: les liaisons hydrogène entre les groupements azobenzènes de molécules voisines. L’orientation des deux domaines chiraux est déterminée par l’orientation de l’un des deux dimères d’azobenzène stable par rapport à l’Au(111).La seconde partie de la thèse est dédiée à l’étude de l’influence du confinement 3D sur la chiralité de gouttes de cristal liquide cholestérique (CLC). Grâce à la nature photo-sensible du dopant chiral utilisé, nous avons été capables de modifier le pas choléstérique du mélange de CLC et par conséquent de déterminer l’expression de la chiralité pour un ratio rayon/pas choléstérique variable. Nous sommes parvenus à contrôler le pas choléstérique au sein de gouttes par irradiation UV et nous avons étudié les variations structurelles que l’irradiation induite. Nous avons observé que le confinement 3D d’un mélange de CLC photo-sensible a une influence positive sur l’inversion de l’hélice dans la goutte. / The first part of the thesis is devoted to studies of the self-assembled monolayers of discotic liquid crystals by the STM measurements at the liquid/solid interface. For the case of a model H5T molecule the self-assembled monolayers have evidenced both: point and organizational types of chirality, despite of the fact that neither the molecule nor the substrate was chiral. For another molecular system, C-12 - a triphenylene peripherally substituted with azobenzene moieties, self-assemblies bearing the chiral nature were also evidenced. Chirality was induced by formation of six dimers of azobenzene subunits coming from the neighboring molecules, which formed “rosettes” of clockwise or counter-clockwise rotation. For the H5T, the chirality was mediated by classical van der Waals interactions between molecules and between molecules and substrate. In the case of C-12 it was shown that the self-assembly originates from the substrate-mediated hydrogen bonding between the azobenzene moieties of neighboring molecules. The second part of the thesis presents studies of the influence of the 3D confinement on the chirality of the photoactive cholesteric liquid crystal (CLC) droplets. Due to the photo-responsive character of a chiral dopant we were able to modify the cholesteric pitch of the CLC mixture and thus to map the expression of chirality for a varying geometrical confinement parameter: radius-to-pitch. We evidenced a successful control of the droplets structure by UV irradiation and we studied the induced structural changes. In particular, the 3D confinement of a photo-responsive CLC mixture was shown to positively support the helix inversion within the cholesteric droplets.

Much of the interest in bent-core compounds in the last few years has centred aroundtheir potential to form nematic liquid crystal phases, which may be both biaxial andpolar. These properties offer possibilities for nematic ferroelectric switching andnonlinear optics applications. In this work, two optical properties, the refractive indices and the second ordernonlinear optical response, were investigated in the high temperature (> 170 °C)nematic phase of a series of bent-core oxadiazole compounds, of varying chain typeand length. An experimental technique, based on the acquisition and analysis of reflectionspectra from liquid crystal cells, and capable of operating at the high temperaturesrequired, was used for the measurement of refractive indices. The extraordinaryrefractive index was found to range from 1.70 to 1.78 over the nematic phase of thebent-core compounds. The ordinary refractive index varied from 1.58 to 1.62. Bothranges of values are higher than is typically observed for rod-like liquid crystals. Thebirefringence took values from ~ 0.10, in the high temperature nematic phase, to~ 0.18, close to the underlying smectic phase. A new experiment was designed, constructed and tested for the second harmonic(SH) measurements. The dependences of the SH on temperature and on scatteringangle are well explained by the theory of SH generation by the flexoelectricpolarisation induced by thermal fluctuations of the director in the nematic phase. Themaximum conversion efficiency was measured to be very low, ~ 1/10000 of apercent. No evidence for the formation of macroscopic biaxial nematic phases was found byeither the refractive indices or SH experiments. However, for the compounds havinglong nematic phases of > 50 °C, different regimes of behaviour in the uniaxialnematic phase were revealed by the SH experiments. This atypical behaviour isconsistent with other reports on these compounds. This study cannot confirm the existence of nanoscale cybotactic clusters in thenematic phases of the bent-core compounds examined but neither is it inconsistentwith them.

Orientador: Watson Loh / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T11:59:07Z (GMT). No. of bitstreams: 1 Ferreira_GuilhermeAugusto_M.pdf: 3614152 bytes, checksum: 568d89fdf3adc43ec1f13c46bc935cad (MD5) Previous issue date: 2015 / Resumo: Surfactantes são moléculas anfifílicas que, em solução, se organizam dando origem a uma série de estruturas de associação, dentre as quais destacam-se os cristais líquidos. Especialmente os brometos de dialquildimetilamônio se associam formando principalmente estruturas líquido-cristalinas lamelares. Nesse trabalho, foram estudadas as propriedades estruturais de fases lamelares formadas pela auto-organização, em solução aquosa, de dois surfactantes dessa classe: o DDAB (brometo de didodecildimetilamônio) e o DODAB (brometo de dioctadecildimetilamônio). Através das técnicas de caracterização utilizadas, foi verificado que, nas condições de concentração e temperatura estudadas, ambos os surfactantes, DDAB e DODAB, se associam em duas fases lamelares, La e Lß, fases essas que diferem pela organização das cadeias carbônicas nas bicamadas e intumescimento. Além de formarem diferentes fases lamelares, essas também apresentaram distintas propriedades estruturais, dependendo do surfactante utilizado. Estudos de calorimetria diferencial de varredura também permitiram acompanhar as transições entre as fases lamelares obtidas causadas por variação da temperatura. As bicamadas formadas pela auto-associação do surfactante DDAB apresentaram um intumescimento menor do que as formadas pelo análogo DODAB, porém, com esse último, houve a formação de bicamadas menos espessas. Misturas preparadas com ambos os surfactantes em diferentes proporções também indicaram a variação das propriedades investigadas, intumescimento e espessura das bicamadas, aumentando o teor de DODAB. A hipótese levantada é que as propriedades estruturais investigadas são fortemente influenciadas pelas forças eletrostáticas atuantes no sistema. A caracterização de amostras formuladas com os tensoativos acima da temperatura de transição para fase fluída e na presença de sal confirmou esta ideia. O maior intumescimento e a pequena espessura das bicamadas formadas pelo DODAB se devem, provavelmente, à interdigitação das cadeias carbônicas e ao efeito de correlação iônica, respectivamente, descritos em mais detalhes nessa dissertação / Abstract: Surfactants are amphiphilic molecules that self-assemble, in solution, giving rise to a number of association structures, among which the liquid crystals stand out. Particularly the dialkyldimethylammonium bromides associate to form mosty lamellar liquid crystalline structures. In this work, we studied the structural properties of lamellar phases formed by self-organization, in aqueous solution, of two surfactants from this class: DDAB (didodecyldimethylammonium bromide) and DODAB (dioctadecyldimethylammonium bromide). Through the used characterization techniques, we found that under the conditions of concentration and temperature studied, both surfactants, DDAB and DODAB are associated in two lamellar phases, La and Lß, phases that differ by the organization of the carbonic chains in bilayers and swelling degree. In addition to forming different lamellar phases, these also showed distinct structural properties, depending on the surfactant used. Studies with differential scanning calorimetry also allowed us to follow the transitions between the lamellar phases caused by temperature variation. The bilayers formed by self-association of DDAB showed a lower swelling degree than those formed by DODAB, however, with the later, there was the formation of thinner bilayers. Mixtures prepared with both surfactants in different proportions also indicated the variation of the investigated properties, swelling degree and bilayer thickness, upon increasing the DODAB content. We propose that the structural properties investigated are strongly influenced by electrostatic forces acting on the system. The characterization of samples formulated with surfactants above the transition temperature to the fluid phase and in the presence of salt confirmed this hypothesis / Mestrado / Físico-Química / Mestre em Química

Neste trabalho apresentamos uma revisão de métodos de simulação de energia eletrostática de sistemas de cargas e uma proposta de adaptação de algoritmo ultilizado na literatura de sistemas gravitacionais para estudo das propriedades estatísticas de sistemas coulombianos. Na primeira parte do estudo, revisamos os fundamentos teóricos do método de Ewald e suas condições de aplicabilidade, procurando esclarecer as referências mais importantes no assunto, que são de difícil compreensão, gerando equívocos na utilização do termo de dipolo. Detalhamos o estudo sobre a análise da convergência da série em que a técnica se baseia, bem como sua interpretação física mostrando a equivalência entre as duas abordagens . Na segunda parte do trabalho analisamos os fundamentos do Fast Multipole Method desenvolvido para interação gravitacional, para o qual construímos programas em linguagem C para uma versão na rede. Criamos um algoritmo que denominamos Fast Multipole Monte Carlo (FMMC) e desenvolvemos um programa para cálculo das propriedades termodinâmicas de sistemas coulombianos. Os programas são testados comparando resultados para a energia e propriedades térmicas do modelo LRPM com resultados de simulação através de cálculo direto. / In this work we present a review of methods of simulation for the electrostatic energy of charged systems and an adaptation of an algorithm from the literature on gravitational systems for the study of the statistical properties of Coulomb systems. In the first part of the work, we review the fundamentals for the theoretical method of Ewald and its conditions of applicability, seeking to clarify the most important references on the subject, which because of the involved mathematics, have led to misuse of the so-called dipole correction. We detail the study on the convergence of the series for the electrostatic potential on which the Ewald technique is based, as well as the physical interpretation given elsewhere, showing the equivalence between the two approaches. In the second part of this work, we analyse the foundations of the Fast Multipole Method developed for gravitational interactions, and present programs in C language for a network version of neutral charged systems. Finally, an algorithm, which we name Fast Multipole Monte Carlo, and the corresponding code for calculating the thermodynamic properties of Coulomb systems are presented. The programs are tested by comparing results for the energy and thermal properties of the Lattice Restricted Primitive model with results of simulations based on direct calculations for the Coulomb energies.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23160号 / 工博第4804号 / 新制||工||1751(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 関 修平, 教授 今堀 博, 教授 梶 弘典 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM