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Master of Science / Department of Animal Sciences and Industry / J. Scott Smith / Emulsifiers have been and remain highly functional ingredients in the food industry. Emulsifiers contain both hydrophilic and lipophilic parts, resulting in their ability to be useful in foods at very low levels. However, knowledge of why emulsifiers work and how to use them most effectively is reserved for the few scientists who specialize in the discipline. Therefore, a comparison of current emulsifier theory with known emulsifier usage in the industry is beneficial to all who use these ingredients. Current emulsifier theory effectively describes how emulsifiers behave in food systems. Emulsion theory details how emulsifiers facilitate the formation and stability of emulsions through study of the kinetics of food systems. Emulsion theory further relates the ability of emulsifiers to interact with other substances in a food system. The main interactions concerning emulsifiers are their ability to form mesophases with water, to strengthen or weaken protein interactions, to form complexes with starches, and to promote or subdue fat crystallization. However, industrial applications of emulsifiers indicate areas where exceptions to theory exist. While emulsion theory has been found to effectively describe the individual interactions and functions in food, the simplicity of the models indicates that complex food system models are still needed to truly understand how to maximize the functionality of emulsifiers.

Liquid crystalline materials forming columnar mesophases are of importance for both the fundamental research and technological applications due to their supramolecular architecture allowing for one-dimensional charge transport. The potential applications of these materials include light emitting diodes, solar cells, field effect transistors and photovoltaic cells. However, to design a LC material suitable for a particular application, a fundamental understanding of the structure-property relationships is needed. In the present thesis, a variety of systems forming columnar mesophases have been explored. They include small molecular weight compounds (triphenylene, phthalocyanine derivatives and star-shaped mesogens) and polymer materials. The research was focused on the study of the influence of the molecular architecture and specific interactions such as hydrogen bonding on the supramolecular organization in the mesophase, as well as on the influence of columnar mesophase on crystal growth. The main results of the thesis are summarized below. The influence of hydrogen bonding on the structure and charge carrier mobility was investigated for a triphenylene derivative, hexaazatriphenylene, having lateral alkyl chains linked to the core via amide groups. These linking groups provide the possibility to form inter- and intra-molecular hydrogen bonds. Acting as “clamps”, the inter-molecular hydrogen bonds are found to enforce the attractive interactions between the molecules in the column. Thus, the columnar mesophase formed by this system is characterized by the smallest inter-disk distance ever found in columnar mesophases (3.18 Å). The improved intra-columnar order brings about a higher charge carrier mobility (0.02 cm2/Vs) as compared to other triphenylene derivatives without hydrogen bonds. Phthalocyanine derivatives, which are liquid crystalline at ambient temperature, could be suitable for opto-electronic applications due to their improved processibility and self-healing of structural defects. Our interest in these systems was inspired by the fact that, in spite of numerous studies performed to date, only very a few phthalocyanine derivatives were found to exhibit columnar mesophases at ambient temperature. We observed that by introducing branches in alkyl chains close to the core, we were able to render the material LC at ambient temperature. Analysis of X-ray diffraction patterns measured on oriented samples showed that these systems form hexagonal and rectangular ordered columnar mesophases. This finding is in contradiction with the general view stating that non-hexagonal mesophases can be only disordered. Since the absolute majority of applications require fabrication of films, it was very important to achieve the visualization of the organization of the phthalocyanine derivatives at the nanometer scale. AFM images on thick spin-coated films with columnar resolution are presented for the first time. They allowed the examination of columnar curvatures and breaks at the boundaries between different single crystal-like domains. The possibility of templating columnar crystal growth was studied for a star-shaped mesogen using a combination of direct- and reciprocal-space techniques. AFM images with columnar resolution showed that the crystal growth initiated in the monotropic columnar mesophase occurs almost in register with the mesomorphic template. In the final crystalline structure, the placement of the crystalline columns is controlled by the mesomorphic tracks at the scale of an individual column, i.e. at the scale of approximately 3.5 nm. The mesophase-assisted crystallization was also studied for the case of a polymer material forming columnar mesophase, poly(di-n-propylsiloxane). X-ray diffraction on oriented fibers allowed us to correct the previous indexation and solve the structure of the unit cell. The crystallization process was studied on samples crystallized in different conditions. It was found that, depending on crystallization conditions, both folded-chain and extended-chain crystals can be obtained. Thus, crystallization of the material from the mesophase results in the formation of 100-150nm thick crystals, which corresponds to a nearly extended-chain conformation. By contrast, when crystallized from a dilute solution, folded-chain crystals result. The mechanisms of chain unfolding was studied by variable temperature atomic force microscopy on PDPS single crystals. It was found that crystals rapidly thicken above the initial melting point, up to 80 nm.

Orientador: Watson Loh / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T09:05:41Z (GMT). No. of bitstreams: 1 Ferreira_MairaSilva_D.pdf: 4524526 bytes, checksum: 98c8f3d75444a9697c4d47cc2b82c519 (MD5) Previous issue date: 2011 / Resumo: Surfatantes à base de silicona possuem propriedades diferentes e especiais e são amplamente empregados na indústria de produtos farmacêuticos e cosméticos. Neste trabalho o emprego deste tipo de surfatante é utilizado para o estudo de incorporação de água em solventes que exibem comportamento diferenciado daquele apresentado por solventes hidrocarbonetos, devido à sua baixa energia coesiva, como o óleo de silicona. Siliconas fazem parte de uma classe de materiais industrialmente importante que apresentam uma excelente estabilidade química e inúmeras aplicações, tais como, cosméticos, agente de controle de espumas, antiaderente, entre outras. Embora importante, existem poucas pesquisas relatando o equilíbrio de fases e a caracterização de sistemas com estes constituintes. Dado este fato, iniciou-se a primeira etapa deste trabalho que é um estudo com o objetivo de caracterizar sistemas que contém óleos e surfatantes à base de silicona em água, investigando as estruturas dos agregados formados utilizando a técnica de espalhamento de raios-X a baixo ângulo (SAXS). Observações importantes como a presença de estados de agregação (microemulsões e mesofases) foram identificadas e caracterizadas a partir da construção do diagrama de fases dos sistemas. A identificação das fases formadas por estes constituintes, em especial as microemulsões bicontínuas e fase lamelar, impulsionaram o desenvolvimento da outra etapa deste trabalho, o estudo de nanoemulsões utilizando um método de baixa energia. Este método faz uso de propriedades físico químicas do sistema e utiliza a inversão espontânea da curvatura do surfatante para obtenção de gotas com tamanho diminuto. As nanoemulsões com surfatantes e óleos à base de silicona obtidas neste trabalho apresentaram raio hidrodinâmico (rh) entre 26 e 40 nm, baixo índice de polidispersidade (< 0,1), uma boa estabilidade cinética (semanas) e podem ser utilizadas em aplicações que não requerem sua formação por longos períodos como dispersões na área agroquímica. A presença do SDS nessa formulação aumentou o rh para 150 a 300 nm, mas melhorou consideravelmente a sua estabilidade cinética, estendendo-a a meses. O desenvolvimento de tais sistemas nos mostra uma nova classe de dispersões que podem competir ou superar sistemas semelhantes e assumir um grande papel no setor científico e industrial / Abstract: Silicone surfactants display unusual properties and are widely employed in industries, in which they are used as basic material in pharmaceutical and cosmetic products. In this work, these types of surfactants have been employed to study the water incorporation into solvents that exhibit behavior different from that presented by hydrocarbon solvents due to their low cohesive energy, such as silicone oil. Silicone oils are important industrial substances that present an excellent chemical stability and numerous applications, for instance in cosmetics, foam control and nonstick agents, among others. Despite their importance, there are few studies reporting phase equilibrium and characterization of these systems. Given this fact, the first step of this work is to characterize systems containing oils and silicone surfactants using small angle x-ray scattering (SAXS). Important aggregates (microemulsions and mesophases) were identified and characterized through their phase diagrams. Thus, identification of phases formed, in particular, by surfactant aggregation in bicontinuous microemulsions and lamellar phases has driven the next stage of this work that consists of preparing nanoemulsions using a low energy method. This method uses physical and chemical properties of the system and exploits the reversal of spontaneous curvature of surfactant structures to obtain droplets with diminutive size. The nanoemulsions formed by silicone surfactants and silicone oils in this work displayed hydrodynamic radii (rh) between 26 and 40 nm, low polydispersion index (< 0.1), a good kinetic stability (weeks) and may be used in applications allow for shorter shelf-life periods, such as in agrochemical area. The presence of SDS in its formulation increased the rh to around for 150-300 nm, but improved considerably its kinetic stability from weeks to months. The development of such systems reveals us a new class of dispersions that can compete or exceed similar systems and assume a significant role in the scientific and industrial sector / Doutorado / Físico-Química / Doutor em Ciências

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Le développement des nanotechnologies a permis à la médecine de progresser là où lesméthodes traditionnelles de diagnostic et de thérapie connaissaient certaines limites. La manipulationet le contrôle de l’infiniment petit permet aujourd’hui de créer des systèmes adaptés à l’environnementcellulaire.Dans ce travail, nous nous sommes intéressés au potentiel des nanoparticules magnétiques d’oxydede fer en nanomédecine et notamment à l’utilisation de leurs propriétés magnétiques particulièrespour la mise au point de nouveaux matériaux pour la délivrance de principe actif par activationthermomagnétique. Notre système est constitué d’un hydrogel physique biocompatible, denanoparticules magnétiques et d’émulsions de mésophases lipidiques (Isasomes). Les Isasomes sontdes dispersions de systèmes auto assemblés qui selon la température peuvent changer de structure(phases hexagonales, cubiques,…). L’ajout d’un principe actif aux Isasomes peut aussi modifier leurstructure interne ; des mesures de SAXS ont permis de confirmer cet effet. Ces émulsionsnanostructurées ont servi de réservoir aux molécules modèles de principe actif (le radical TEMPO).Après activation magnétique, la diffusion contrôlée du principe actif hors de l’hydrogel a été suivie parRPE. Enfin, les nanoparticules ont été fonctionnalisées de façon à concevoir un hydrogel réticulé parles nanoparticules magnétiques. Les diverses étapes de la fonctionnalisation ont été validées pardifférentes techniques expérimentales (Diffraction de rayons X, MET, Raman, IRTF, Zétamétrie, ATG,XPS). / The development of nanotechnology led to significant progress in medicine especially wheretraditional methods of diagnosis and therapy showed limits. The manipulation and control of thephysics at the nanoscale offered new opportunities for creating systems tailored to the cellularenvironment. In this work, we were interested in the high potential of magnetic nanoparticles of ironoxide in medicine. In particular, we would like to use their peculiar magnetic properties for developingnew materials for the delivery of active compounds through thermomagnetic activation. Our systemconsists of a biocompatible hydrogel with confined magnetic nanoparticles and lipid-based emulsions,called Isasomes. Those are dispersions of lipid mesophases (hexagonal, cubic,…) that can be tunedby temperature or composition. The incorporation of an active compound into the Isasomes canequally modify their internal structure as confirmed by SAXS measurements. These nanostructuredemulsions are used here as reservoirs for model molecules (radical TEMPO), which are trapped intothe hydrogel. After magnetic activation, the controlled release of TEMPO outside the hydrogel hasbeen followed by Electron Paramagnetic Resonance (EPR). Finally, magnetic nanoparticles havebeen functionalized and connected to hyaluronic acid in order to design a crosslinked hydrogel. Thevarious steps of functionalization have been checked by various experimental techniques (Xrays,Raman spectroscopy, TEM, FTIR, zetametry, TGA, XPS).

L’idée directrice de ce travail de thèse était d’introduire au sein de mésophases lipidiques des molécules de β-cyclodextrine (βCD) amphiphiles obtenue par bio-estérification afin d’obtenir des nano-assemblages plurimoléculaires et multi-compartimentés combinant trois fonctions essentielles pour le transport ou la vectorisation de molécules thérapeutiques : (i) la capacité d’incorporer une substance d’intérêt par formation de complexe d’inclusion avec la cyclodextrine ; (ii) être biocompatibles et aptes à passer facilement les barrières biologiques ; (iii) pouvoir co-incorporer une seconde substance d’intérêt, hydrophile ou hydrophobe, dont l’action biologique soit différente de celle assurée par la première substance. L’ensemble des travaux ont porté sur le dérivé βCD-C10 polysubstitué en face secondaire par des chaînes hydrocarbonées en C10 avec un degré moyen de substitution de 7,5. L’association de ce dérivé avec trois catégories de lipides a été envisagée : des tensioactifs micellaires non-ioniques (Brij 98, Polysorbate 80, n-dodécyl-β-D-maltoside), un lipide lyotrope non lamellaire formant des mésophases de type cubique bicontinue (monooléine), un phospholipide s’auto-organisant en bicouches propices à l’obtention de vésicules (dimyristoyl phosphatidylcholine). Selon une démarche principalement physico-chimique, différentes techniques ont été mises en œuvre pour caractériser les systèmes mixtes lipide/βCD-C10 aux échelles moléculaire et supramoléculaire : diffusion-diffraction des rayons X, calorimétrie différentielle, spectrophotométrie d’absorption UV-visible, spectroscopie de fluorescence, diffusion de la lumière statique (turbidimétrie) ou quasi-élastique, microscopie optique et microscopie électronique par cryo-transmission. L’ensemble des résultats démontrent que le dérivé βCD-C10 forme spontanément ou selon un protocole très simple, des assemblages plurimoléculaires mixtes avec les trois catégories de lipides, assemblages dont la topologie dépend de la structure chimique du lipide et du taux de cyclodextrine amphiphile incorporé (tubules, vésicules uni- ou oligolamellaires, cubosomes). Ces assemblages sont stables et capables d’incorporer une substance hôte hydrophobe, notamment les vésicules mixtes tensioactif non-ionique/ βCD-C10 et les cubosomes mixtes monooléine/P80/ βCD-C10. / The key idea of this Ph.D. thesis is to introduce amphiphilic β-cyclodextrin molecules (βCD), obtained by bio-transesterification, within lipid mesophases in order to obtain multi-compartment plurimolecular nano-assemblies, which combine three essential functions for transport or delivery of therapeutic molecules: (i) capacity to incorporate a substance of interest through formation of inclusion complexes with the modified cyclodextrin; (i) biocompatibility and ability to easily pass the biological barriers; and (iii) possibility for co-encapsulation of a second substance of interest, a hydrophilic or a hydrophobic one, whose biological action is different from that provided by the first substance. The performed Ph. D. work focused on the β-cyclodextrin derivative βCD-C10 with an average degree of substitution of 7.5 of the secondary face of the macrocycle by hydrocarbon chains C10. The association of this derivative with three classes of amphiphiles was studied: (i) nonionic micellar surfactants (Brij 98, Polysorbate 80, n-dodecyl β-D-maltoside), (ii) a lyotropic nonlamellar lipid forming bicontinuous cubic mesophases (monoolein), and (iii) a phospholipid (dimyristoyl phosphatidylcholine), which self-ssembles into bilayer membranes permitting the production of vesicles.The employed physical-chemical approach involved different techniques for characterization of the mixed βCD-C10/lipid systems at molecular and supramolecular levels: cryo-transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, UV-visible absorption spectroscopy, fluorescence spectroscopy, turbidimetry, and quasi-elastic light scattering.The obtained results indicated that the βCD-C10 derivative forms spontaneously (or via a very simple preparation protocol) plurimolecular mixed nano-assemblies with the three types of lipids. The topologies of the resulting nano-assemblies essentially depend on the chemical structures of the lipids and the degree of incorporation of the amphiphilic cyclodextrin (tubules, unilamellar or oligolamellar vesicles, and cubosomes). These assemblies, namely the mixed vesicles of nonionic surfactant/βCD-C10 and the cubosomes of mixed monoolein/P80/βCD-C10 compositions, are stable and capable of incorporation of hydrophobic guest substances.

La microscopie à l'angle de Brewster est une nouvelle et tres puissante technique d'étude des films monomoléculaires à la surface de l'eau. Son principe est basé sur les propriétés de réflectivité des interfaces. Elle est sensible à l'épaisseur, la densité et l'anisotropie optique des films. Cette technique a été appliquée à l'étude de couches adsorbées à la surface de solutions aqueuses d'acides gras (acides palmitiques et myristiques). Ces couches traversent pendant leur formation des transitions de phases. Le nombre, la nature et la morphologie de ces phases dépendent de nombreux paramètres dont le pH. Nous avons entre autres observé des phases optiquement anisotropes, contituées de molécules inclinées par rapport à la normale à la solution.Ces phases sont sans doute des mésophases "verrouillées", c'est à dire que la direction des molécules est fixée par rapport aux directions intermoléculaires. Elles présentent différents types de défauts d'orientation, dont des structures en étoile. L'existence de telles structures est expliquée par application d'un modèle d'élasticité continue développé pour l'étude des films minces de cristaux liquides smectiques. Des structures en zig-zag, en spirales et en bandes de largeur déterminée ont également été observées. Nous avons également étudié les couches d'un polymère (le PDMS) à la surface de l'eau. Nous y avons observé la séparation latérale en domaines de densités de surface différentes, à la fois dans le régime monocouche et le régime multicouches.

Surfactants are amphiphilic molecules which self-assemble at the interface in oil-water-surfactant mixtures such that the hydrophobic part, called tail, stays in oil and the remaining part, called head, resides in hydrophilic en-vironment. Depending upon concentration of individual components, these mixtures form several microphases, such as bilayers, micelles, columnar and lamellar phases. A lamellar phase, at equilibrium, is made up of alternat-ing layers of water and oil separated by surfactants, or of alternate layers of water and surfactant bilayers such that the hydrophilic heads are in contact with water. This equilibrium state is rarely achieved in macroscopic samples due to thermodynamic and kinetic constraints; instead, a lamellar fluid is usually disordered with a large number of defects. These defects have significant effect on the flow behaviour of the lamellar mesophase systems. They are known to alter the flow field, resulting stresses and in turn could get distorted or annihilated by the flow. In present work, we analyse this two way coupling between lamellar structure and flow field. The structural and rheological evolution of an initially disordered lamellar phase system under a shear flow is examined using a mesoscale model based on a free energy functional for the concentration field, which is the scaled difference in the concentration between the hydrophilic and hydrophobic components. Two distinct modes of structural evolution are observed depending only on Peclet number, which ratio of inertial forces to mass diffusivity, in-dependent of system size. At low Peclet number, local domains are formed which are then rotated and stretched by shear. A balance between defect creation and annihilation is reached due to which the system never reaches the equilibrium layer configuration. In the opposite limit, partially formed layers break and reform so as to form a nearly aligned lamellar phase con-figuration with residual defects. Viscosity of lamellar phase system increases with layer moduli, differences in viscosity of individual components, fluidity of the lamellae due to shear banding and defect pinning. These factors however, do not have any effect on alignment mechanism.