Investigou-se o efeito do \"caráter iônico\" de interfaces zwitteriônicas, formalmente neutras, representadas por micelas e vesículas obtidas de monômeros com cabeça hidrofílica dipolar, nas propriedades de acumulação e troca de espécies iônicas. Os sistemas estudados incluíram, micelas de 1-(N-hexadecil-N,N-dimetilamônio) propanossulfonato (HPS), Hexadecil fosforil colina (C16PN), 3-hexadecil glicerofostidil colina (lisoPC) e vesículas de fosfatidil colina (PC). O estudo da ligação e troca iônica nestas interfaces foi monitorado a partir de efeitos sobre reações prototrópicas de sondas como a 8-hidroxi-1,3,6-pirenotrisulfonato de sódio (piranina). Observou-se a ligação crescente da piranina na seguinte ordem lisoPC < C16PN < HPS e troca iônica com sais adicionados (função do ânion) na ordem inversa, isto é, lisoPC &gt; C16PN &gt; HPS. Estudos de reprotonação de 1 e 2 naftóis incluídos nestes agregados, via salto de pH induzido por laser, revelaram um perfil de concentração de prótons inverso àquele das cargas do dipolo, isto é, concentração nos polos negativos e exclusão nos positivos. Este resultados foram ainda reforçados por estudos de excitação de volume, via espalhamento de luz, com micelas de HPS em função de sal adicionado. A partir destes resultados propôs-se um modelo de capacitor esférico imerso em meio eletrolítico para estas interfaces, o qual se mostrou bastante versátil na análise e previsão de resultados experimentais. Em suma, estabeleceu-se no presente trabalho a visão de que interfaces dipolares são geradoras de assimetria iônica na circunvizinhança da interface, assimetria esta de polaridade invertida àquela do dipolo radialmente disposto à interface. A generalidade deste modelo pode ser extrapolado para outras interfaces e colaborar na compreensão de diversos processos que dependem da acumulação e troca iônica. / The effect of ionic domains of formally neutral zwitterionic interfaces, represented by micelles and vesicles obtained with dipolar headgroups amphiphiles, on the binding and exchange of ionic species were investigated. The systems studied included: aqueous micelles of 1-(N-hexadecyl-N,N-dimethylammonio) Propane Sulfonate (HPS), Hexadecyl Phosphoryl Choline (C16PN), and 1-hexadecylglycerophostidyl Choline (lisoPC) and vesicles of Phosphatidylcholine (PC). Binding and ion-exchange processes were assessed from the effect of these agreggates on prototropic reactions of probes such as 8-hydroxy-1,3,6-pyrenetrisulfonate pyranine). Binding of pyranine increased in the following order lisoPC < C16PN < HPS. The effectiveness of anion dependent salt displacement of the probe from the aggregates was opposite to that of affinities, i.e. lisoPC &gt; C16PN &gt; HPS. Laser pH jump studies with 1 and 2 naphtols incorporated in these aggregates revealed a proton concentration profile inverse to that of the charged dipole, that is, accumulation in the region vicinal to the negatively charged group and exclusion from the positive end of the dipole. This finding were substantiated by HPS micelle excluded volume data, obtained from light scattering studies as function of added salt. A model of a spherical capacitor immersed in an electrolyte media for these interfaces was proposed. This model accounts for satisfactorily the observed characteristics of these interfaces. The model establishes that dipolar interfaces generate ionic asymmetries in the neighborhood of the interface that opposes the radially extended monomer dipole. The generality of the model can be very helpful in the analysis and understanding of several processes occurring in/at zwitterionic interfaces.

Micelas e agregados de cloreto de dimetildialquilamônio (Herquat) foram utilizados como modelos de interfaces para o estudo de reações químicas. As reações de tiólise de acetato de p-nitrofenila (NPA) e octanoato de p-nitrofenila (NPO) por n-heptilmercaptana (HM) foram estudadas na presença de concentrações variáveis de brometo de hexadeciltrimetilamônio(CTAB), dodecilsulfato de sódio (SDS) e 3-(N,N dimetildodecilamônio) propano-l-sulfohato(SDP). O detergente positivo (CTAB) provoca uma alteração máxima da reação de tiólise de NPA de 6.103 vezes e da reação de tiólise de NPO por um fator máximo de 1,6.104 vezes. O efeito da concentração de CTAB na constante de pseudo-primeira-ordem das reações de tiólise (k&#968;) e no pK aparente (pKap) da HM foi analisado segundo o modelo de Troca Iônica (Quina, F.H. e Chaimovich, H. (1979). Os parâmetros necessários para a análise dos resultados descritos acima foram determinados por métodos independentes dos experimentos cinéticos. Um ajuste excelente das curvas teóricas aos dados experimentais foi obtido utilizando-se uma relação entre as constantes de velocidade de segunda ordem nas fases micelar (km2) e aquosa (ko2) de 1 e 5 para as reações de tiólise de NPA e NP0, respectivamente. Assim, o efeito de CTAB sobre a k&#968; das reações de tiólise de NPA e NPO pode ser atribuído a uma concentração de substratos na fase micelar, desvio do pKap da HM e concentração do íon hidróxido na interface. A velocidade da reação de tiólise de NPO por HM diminui cerca de 70 vezes em 0,1 M de SDS e, na presença de SDP, aumenta por um fator máximo de 270 vezes, O pKap da HM aumenta com a concentração de ambos os detergentes. O efeito da concentração de SDS e SDP no pKap da HM e na k&#968; da reação de tiólise de NPO foi analizado segundo o modelo de pseudo-fase (Yatsimirski, A.K., Martinek, K. e Berezin, I.V., (1971). Um ajuste muito bom das curvas teóricas aos dados experimentais foi obtido utilizando-se um valor de 0,085 para a relação km2/ko2 em SDS e 1 para a relação em SDP. Assim, a inibição da tiólise de NPO por SDS é devida a um aumento do pKap do substrato, uma km2 menor que ko2 e uma pequena constante de associação entre o SDS e a forma aniônica da mercaptana. A aceleração da reação de tiólise de NPO por SDP pode ser atribuída unicamente a concentração de reagentes na pseudo-fase. A reação de hidrólise de 2-Feniliminotetrahidrofurano (FI) foi estudada em presença de SDS observando-se que o detergente aumenta o pKap do substrato e a velocidade da reação de hidrólise (a pHs maiores que 4). A análise destes resultados empregando-se equações derivadas a partir do modelo de Troca-Iônica mostrou que a relação km/ko é praticamente 1 a todos os pHs estudados. Desde que a reação é inibida a alta força iônica em fase aquosa, podemos inferir que, no microambiente no qual o FI é solubilizado (camada de Stern do SDS), a reação ocorre com uma constante de velocidade similar à observada em baixa força iônica. Poi feita uma caracterização parcial dos agregados de Herquat (vesículas) por filtração em Sephadex G-25. Demonstrou-se que as vesículas incorporam substratos hidrofóbicos (4-(-1-pireno) butanoato de metila) e hidrofílicos ((14C) glicose) e que o contraíon do anfifílico (cloreto) pode ser deslocado do Herquat pelo ânion do tampão. Estes agregados aceleram a reação de tiólise de NPA por HM por um fator máximo de 5.104 vezes e a reação de tiólise de NPO por HM por um fator de 7.106 vezes. O efeito mais impressionante destes agregados é que a reação de tiólise de NPO por HM em Herquat pode ser estudada a pH 4, portanto, cerca de 6,7 unidades de pH abaixo do pK da mercaptana em água. Após a análise deste sistema de reações utilizando-se o modelo de Troca-Iônica obteve-se uma relação km2/ko2 da ordem de 5 para a reação de HM e NPA e da ordem de 13 para a reação de tiólise de NPO. A aceleração provocada pelos agregados de Herquat pode ser atribuída a concentração de reagentes nas vesículas, efeito dos agregados sobre o pKap da HM e uma constante de segunda ordem na pseudo-fase maior que na fase aquosa. / Micelles and dialkyldimethylammonium chloride aggregates (Herquat) were employed as model interfaces for the study of interfacial effects on chemical reactions. The thiolyses of p-nitrophenyl acetate (NPA) and p-nitrophenyloctanoate (NPO) by n-heptylmercaptan (HM) were investigated as a function of concentration of added hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and 3- (N,N-dimethyl-N-dodecyl ammonium) - propane-l-sulfonate (SDP). In the presence of the cationic detergent (CTAB), maximum rate acceleration of 6x103 and 1.6xl04 were observed for the thiolyses of NPA and NPO, respectively. The CTAB concentration dependences of the pseudo first-order rate constants (k&#968;) for these reactions and of the apparent pK (pKap) of HM were analyzed within the framework of the conceptual Model for Ion Exchange (Quina, F.H. and Chaimovich, H., 1979), the requisite parameters for the analysis being determined independently of the kinetic results. Excellent simulations of the experimental results were obtained using ratios of second order rate constants in the micellar (km2) and aqueous (ko2) phases of 1 and 5 for thiolysis of NPA and NPO, respectively. Thus, in this case, the effect of CTAB on k&#968; may be attributed to the interplay of concentration of the substrate in the micellar phase, changes in the pKap of HM and concentration of the hydroxide ion at the interfaces. The rate of thiolysis of NPO by HM diminishes by roughly a factor of 70 upon addition of O.1M SDS (anionic detergent) and increases by a factor of 270 at the maximum in the presence of SDP (zwitterionic detergent). The pKap of HM increases in the presence of both detergents. The effect of detergent concentration on the pKap of HM and on k&#968; for thiolysis of NPO were analyzed in terms of the pseudo-phade model (Yatsimirski, Martinek, Berezin, 1971). Ressonable simulation of the experimental data were obtained using values of 0.085 for the ratio km2/ko2 in SDS and 1 for this some ratio in SDP. Thus, the inhibition of the thiolysis of NPO by SDS may be ascribed to an increase in the pKap of HM, coupled with a small value of the constant for association of the mercaptide ion of HM with the micellar phase and an apparent decrease in km2 relative to ko2. The acceleration of this same reaction by SDP can be attibuted exclusively to extrinsic factors, concentration of the reagents in the micellar phase predominating over the increase in the pKap of HM. The hydrolysis of 2-Phenyliminotetrahydrofuran (FI) was studied in the presence of SDS, it being verified that both the pKap of the substrate and the velocity of hydrolysis (at pH values higher than 4) increase in the presence of the detergente Analysis of these results, using equations derived from the conceptual Model for Exchange, demonstrates that the ratio km/ko is essentially 1 over the entire pH vange investigated. Since this reaction is inhibited at high ionic strength in aqueous solution, one may infer that, in the micro environment in which FI is solubilized (Stern layer of SDS), the reaction occurs with a rate constant similar to that observed in aqueous medium at low ionic strength. A partial characterization of the aggregates (vesicles) formed by Herquat in aqueous dispersion was performed by gel filtration on Sephadex G-25. In this manner, it was demonstrated that the vesicles incorporate hydrophobic(methyl 4-(1-pireno)butanoate) and hydrophilic (14C-glucose) substrates and that the chloride counterion of Herquat can be exehanged with anionic buffer components. These aggregates accelerate the thiolysis of NPA by HM by up to a factor of 5x104 and that of NPO by up to a fator of 7x106. The most impressive aspeet of these Herquat agregates is the fact that the thiolysis of NPO by HM can be studied at pH 4, some 6.7 pH units below the pKa of HM in water. Applying an ion-exchange formalism analogous to that amployed for reactions in CTAB to the analysis of these thiolyses, km2/ko2 ratios of about 5 for the reaction between NPA and HM and of roughly 13 for the reaction between NPO and HM were obtained. The acceleration observed in the presence of these aggregates may thus be attributed to concentration of the reagents in the vesicle phase, effects on the pKap of HM and a somewhat larger second-order rate constant in the vesicle phase relative to the aqueous phase.

Certains fluides complexes présentent un plateau horizontal de la contrainte en fonction du cisaillement dans leur courbe d'écoulement. Sur ce plateau une structuration de l'écoulement en bandes de cisaillement est parfois observée. Trois fluides complexes sont étudiés, qui possèdent tous trois un plateau horizontal dans leur courbe d'écoulement. Les techniques expérimentales utilisées : la rhéologie, la mesure de profils de vitesse par IRM, et des expériences de biréfringence ont permis de mettre en évidence trois origines à ce plateau. Une première solution de micelles géantes dans le régime semi-dilué montre le développement d'une bande biréfringente et fortement cisaillée sur le plateau, qui croît avec le cisaillement. Un deuxième système, une phase lamellaire avec une texture oignon présente une structuration en bande de vorticité sur le plateau horizontal. Enfin pour une troisième solution de micelles géantes dans le régime dilué, le plateau est expliqué par du glissement à la paroi. La diminution de la traînée turbulente, observée pour ce système, semble également due à du glissement.

L'objet de cette étude est d'utiliser la technique des micelles inverses pour synthétiser des nanoparticules à transition de spin, de taille et de forme contrôlées afin d'en permettre l'utilisation en électronique moléculaire. Dans la première partie, nous avons déterminé les paramètres de synthèse influençant la taille et la forme des particules d'un complexe à transition de spin à fort potentiel d'application. Dans un deuxième temps, nous avons utilisé ces paramètres sur trois autres complexes afin de comprendre la relation entre les paramètres de la synthèse et la morphologie des particules. Les nanoparticules ainsi synthétisées constituent la base d'une discussion sur l'existence d'un lien entre la taille/forme des particules et les propriétés de transition de spin. Enfin, la dernière partie de ce travail est consacrée à l'utilisation de ces matériaux en électronique moléculaire, et l'observation des propriétés de photoconductivité et photovoltaïque à l'échelle des nanoparticules.

Les chromophores classiques ne sont pas toujours efficaces en absorption à deux photons. Leur faible efficacité nécessite l'utilisation de fortes puissances laser et de grandes concentrations en colorants. Dans ce sens, la microscopie à deux photons in vivo requière le développement de nouvelles stratégies de marquage utilisant des chromophores spécialement dédiés à la microscopie à deux photons. Dans le cadre de collaborations avec des chimistes spécialisés dans la synthèse de molécules à forte section efficace d'absorption à deux photons, différents chromophores ont été synthétisés. Ces molécules organiques sont souvent hydrophobes et ne sont pas utilisables directement pour les applications en biologie. Le travail effectuer ici a consisté à encapsuler ces molécules dans des micelles de copolymères biocompatibles, les Pluronic. Les Pluronic sont des matériaux pouvant s'auto assembler en milieu aqueux sous forme de micelles et permettent de solubiliser des composés hydrophobes. Cette stratégie est déjà utilisé pour permettre de transporter différents composés hydrophobes dans les organismes vivants et a été utilisée ici pour transporter des chromophores ultrasensibles à deux photons dans le sang de manière à imager la vascularisation in vivo.

Des mesures optiques en microcanaux permettent d'obtenir de nouvelles informations sur différents fluides complexes, en lien avec des procédés de récupération assistée du pétrole. Nos expériences reposent sur une méthode de microfabrication innovante en colle photoréticulable résistante en pression. Nous concevons un laboratoire sur puce pour l'étude de la dégradation des polymères sous écoulement. Intégrant une zone d'écoulement violent et un viscosimètre dans un même microsystème, nous caractérisons l'influence de la masse, de la concentration, de la chimie et de la géométrie. Par ailleurs, un système de vélocimétrie en microcanal nous permet de caractériser la rhéologie d'une phase hors équilibre de solutions semi-diluées de micelles géantes sur plus d'une décade de taux de cisaillements, mesurant indépendamment le glissement. Par des cartographies tridimensionnelles de cet écoulement, nous étudions ensuite l'apparition de structurations spécifiques à ces fluides à bandes de cisaillement: un effet de confinement amplifié et une instabilité d'interface, confrontés à un modèle théorique avec un accord quantitatif.

Nous étudions des solutions semi-diluées de micelles géantes en géométrie Couette présentant une transition vers un état en bandes de cisaillement au-delà d'une sollicitation seuil. La signature mécanique de cette transition se traduit par la présence d'un plateau en contrainte dans la courbe d'écoulement de ces solutions, associé à la formation de bandes supportant différents cisaillements. Nous nous sommes intéressés au comportement de l'interface entre ces bandes de cisaillement. L'étude aux temps courts est motivée par la proposition de modélisation de la courbe d'écoulement de ces solutions par le modèle diffusif Johnson-Segalman. Dans ce modèle, le terme de diffusion de la contrainte viscoélastique est relié à la migration de l'interface, que nous estimons expérimentalement. Aux temps longs, nous avons observé la déstabilisation de l'interface entre ces bandes de cisaillement, dans le plan d'observation vorticité–gradient de vitesse, pour plusieurs solutions. La réponse mécanico-optique est similaire pour des solutions composées de différents tensioactifs. D'autre part, nous avons montré que la déstabilisation de l'interface est associée à la formation d'un écoulement secondaire sous la forme de cellules de convection empilées suivant la vorticité. Le scénario de base, supposant un écoulement unidirectionnel, est remis en cause par l'observation directe d'un écoulement tri-dimensionnel. L'ensemble de ces résultats suggèrent le développement de la même instabilité dans différentes solutions et nous ont amenés à envisager deux mécanismes de type « élastique » pouvant être à l'origine de l'instabilité : un mécanisme interfacial et un mécanisme en volume.

The present work is dealing with the first synthesis and characterisation of amphiphilic diblock copolymers bearing b-dicarbonyl (acetoacetoxy) chelating residues. Polymers were obtained by Group Transfer Polymerisation (GTP)/acetoacetylation and controlled radical polymerisation techniques (RAFT).<br><br>Different micellar morphologies of poly(n-butyl methacrylate)-block-poly[2-(acetoacetoxy)ethyl methacrylate] (pBuMA-b-pAEMA) were observed in cyclohexane as a selective solvent. Depending on the block length ratio, either spherical, elliptical, or cylindrical micelles were formed. The density of the polymer chains at the core/corona interface is considerably higher as compared to any other strongly segregating system reported in the literature. It is demonstrated that there are H-bond interactions existing between acetoacetoxy groups, which increase the incompatibility between block segments. In addition, such interactions lead to the formation of secondary structures (such as b-sheets or globular structures) and larger superstructures in the micrometer length scale.<br><br>Block copolymers were also used to solubilise metal ion salts of different geometries and oxidation states in organic media, in which are otherwise insoluble. Sterically stabilised colloidal hybrid materials are formed, i.e. monodisperse micelles having the metal ion salt incorporated in their core upon complexation with the ligating pAEMA block, whereas pBuMA forms the solvating corona responsible for stabilisation in solution. Systematic studies show that the aggregation behaviour is dependent on different factors, such as the tautomeric form of the beta-dicarbonyl ligand (keto/enol) as well as the nature and amount of added metal ion salt.

This Thesis is a characterization study on substances having potency as drugs as well as on a lipid based drug-delivery matrix. The optical properties of newly synthesized molecules with proven pilicide properties have been characterized with several spectroscopic methods. These methods include optical absorption and fluorescence as well as time-resolved fluorescence. Upon covalently linking compounds with high quantum yields of fluorescence to specific parts of the pilicide, the biological impact was found to increase for some of the derivatives. Furthermore, by expanding the aromatic part of the pilicide molecule, a significant increase in the inherent fluorescence was obtained. The S0-S1 absorption band for these molecules was found to originate from an impure electronic transition, vibronically promoted by intensity borrowing from higher electronic states. Included in this Thesis is the measurement of how deeply some in this class of newly synthesized molecules become situated when placed inside ganglioside GM1 micelles, and how the molecules’ reorientation is affected. By means of radiation-less energy transfer, it was shown that the molecules place themselves close to the hydrophobic-hydrophilic interface inside the GM1 micelles. As a consequence they are exposed to a densely packed environment, which inhibits the free tumbling of the molecule. This restricted tumbling could be measured by means of time-resolved depolarization experiments. The release of drug-like fluorescent molecules is investigated from a lipid mixture, which upon equilibrium with water forms a mixture of inverted hexagonal and cubic phases. The lipid matrix displayed an extended release over the course of weeks, in vitro, for molecules having a large variation in hydrophobicity.

L'intestin assure l'absorption des lipides alimentaires et doit faire face aux variations d'apport en lipides, entre les périodes inter-prandiales et post-prandiales. J'ai donc étudié dans les cellules Caco-2/TC7, la réponse des entérocytes à différents modes d'apports en lipides. Par une approche transcriptomique, j'ai montré que les lipides modulent l'expression de nombreux gènes entérocytaires. Les profils géniques obtenus diffèrent entre l'apport luminal ou sérique en lipides. La comparaison des apports apicaux de micelles inter- ou post-prandiales (MPP) a montré que les MPP modulent spécifiquement l'expression de 46 gènes majoritairement impliqués dans la transduction de signaux, le métabolisme lipidique, et l'architecture cellulaire. Ces résultats, s'ajoutant aux effets spécifiques des MPP obtenus dans l'équipe, suggéraient une détection entérocytaire des lipides alimentaires apportés par ces MPP. J'ai alors montré que les MPP se lient à une protéine dont le poids moléculaire correspond à celui du récepteur SR-BI, induisant sa clusterisation à la membrane apicale et son adressage vers les rafts. Seules les MPP induisent, le trafic de l'apoB, de la membrane apicale vers les compartiments sécrétoires et l'activation de kinases. Ces effets sont abolis quand SR-BI est bloqué par un de ses ligands ou invalidé par ARN interférence. Ces travaux montrent pour la première fois que les entérocytes sont capables de détecter spécifiquement les lipides alimentaires sous forme micellaire. Cette détection implique SR-BI et induit des voies de signalisation aboutissant à la mise en place de paramètres morphologiques et fonctionnels nécessaires au transfert des lipides alimentaires.