L'objectif de cette étude est l'élaboration de nanocomposite à base d'un élastomère de styrène et de butadiène (SBR) par l'ajout d'une dispersion aqueuse (slurry) de nanocharges lamellaires de phosphate de zirconium en phase α (α-ZrP ou ZrP). Les travaux s'attardent d'abord sur le mélange entre le SBR à l'état fondu et le slurry de ZrP en absence de traitement de surface. Différents stratégies d'élaboration sont ensuite envisagées afin d'améliorer la dispersion (intercalation exfoliation) des feuillets de ZrP dans le matériau en couplant le traitement de surface du ZrP et les paramètres de mise en œuvre. Différents traitements de surface sont abordés avec l'utilisation d'un agent intercalant métallique (Na+), de deux intercalants alkylamines (propylamine, octadécylamine) et d'un agent d'exfoliation (hydroxyde de tétrabutylammonium). En parallèle, plusieurs procédés de mise en œuvre générant des écoulements complexes sont utilisés. La complémentarité entre la diffraction des rayons X (DRX), la microscopie électronique en transmission (MET) et la spectroscopie mécanique (DTMA) permet d'obtenir une analyse multi-échelle de l'état de dispersion du ZrP et de proposer des scénarii décrivant les mécanismes de dispersion en fonction des paramètres étudiés. Un effort important est apporté pour la compréhension de la relation structure à l'échelle nanoscopique et les propriétés macroscopiques du matériau. Une étude comparative est ensuite proposée entre les valeurs expérimentales de l'effet de renforcement des matériaux et les prédictions des modèles Krieger-Dougherty et Halpi-Tsai

L'ajout de superplastifiants (SP) dans les ciments est utilisé pour améliorer la mise en œuvre du matériau. Les SP que nous étudions sont des polyélectrolytes anioniques, et plus précisément des polyméthacrylates greffés PEO. Il a été observé qu'une partie de ces SP est immobilisée dans une des premières phases résultant de l'hydratation du ciment : la phase OH-AFm, issue de l'hydratation de l'aluminate tricalcique (C3A). Ces phases appartiennent aux hydroxydes doubles lamellaires dont les feuillets sont chargés positivement et l'espace interfoliaire contient des espèces anioniques. Nous nous intéressons, à l'interaction entre les phases OH-AFm et ces SP, dont la longueur des greffons et le taux de greffage varient. Nous avons prouvé l'intercalation des SP par DRX et RMN dans la phase AFm. La conformation des SP entre les feuillets peut être décrite à partir de l'adaptation d'un modèle de conformation en solution sous forme de chaînes de blobs, élaboré par de Gennes. Des mesures de rayon de giration des polymères en solution saturée en calcium, par diffusion de neutrons aux petits angles, ont permis de valider le modèle des blobs en solution. Nous avons suivi la vitesse de sorption des SP, réalisé des isothermes et étudié la stabilité de la phase SP-AFm vis-à-vis des sulfates, présents en quantité dans les ciments. Indépendamment de leurs caractéristiques, les SP sont fixés à la même vitesse par la phase AFm. Au maximum des isothermes, un SP compense d'autant mieux les charges du feuillet que sa densité de charge est élevée. La phase SP-AFm est plus stable que la phase OH-AFm, mais la présence de sulfates entraîne une libération retardée sur plusieurs heures du SP en solution. L'hydratation du C3A en présence de polymère mène à une structure similaire à celle des phases modèles que nous avons étudiées et les interactions SP-AFm peuvent donc être considérées comme identiques.

Optical and electrical properties of electrochemically lithium ion intercalated thin films of x-ray amorphous tungsten oxide made by magnetron sputtering on glass substrates coated with a thin layer of conductive tin doped indium oxide, have been studied. The composition and the density of the films were characterized by the ion beam analysis methods Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analysis. The optical properties, transmittance and reflectance were investigated by spectophotometry in the wavelength range 300-2500 nm. The absorption coefficients were calculated at different lithium intercalation levels. It was found that the absorption coefficient in an as-deposited blue film has a similar asymmetric shape as for films intercalated to a Li/W ratio of ~0.03. It was possible to electrochemically bleach this film to transparency. Stoichiometric films show optical irreversibility between the bleached and the colored state in the first cycle. A polaron absorption model has been compared to the absorption coefficient for films of different intercalation levels. An increase in the Fermi level and in the polaron band width, and a nearly constant activation energy was found as the Li/W value increased. The radius of the polaron wavefunction for different lithium intercalation levels and film compositions has been estimated from electrical measurements. The total absorption coefficient has been compared to the site-saturation model. The model is good for films intercalated in the optically reversible region. A modified site-saturation model that could be applied also in the optically irreversible region and involves electron transitions between W6+, W5+ and W4+ sites, has also been compared to experimental values. It was found that the total absorption, optical density and the coloration efficiency is higher for the WO2.63 film than in the less oxygen deficient films and that this film is optically more durable in an electrochemically cyclic lifetime device test.

Electrochromic iridium oxide (IrOx) and iridium-tantalum oxide (IrTaOx) thin films were prepared by reactive magnetron sputtering. Composition, density, and structure were determined using Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and electron energy loss spectroscopy. The electronic density of states (DOS) and the solid phase chemical diffusion coefficient (D) were determined for hydrogen in IrOx and IrTaOx by potentiostatic intermittent titration technique (PITT), and electrochemical impedance spectroscopy (EIS). The complex refractive indices were determined for colored and bleached IrOx and IrTaOx by inverting transmission and reflectance, measured using spectrophotometry in the 300-2500 nm wavelength range. A very porous structure, with a stoichiometry of IrO2.2, was found for IrOx. It contained ~4 nm sized grains. The IrTaOx had a denser structure built up by ~4 nm sized grains. The composition of IrTaOx was found to vary on a nanometer scale, with an average composition of IrTa1.4O5.6. It was found that DOS can be measured using PITT and EIS in the presence of spontaneous side reactions, even for systems influenced by non-negligible charge transfer kinetics and Ohmic drops. It was found that the measured DOS is 30-50% of the theoretically calculated DOS and that D is in the 10-10 – 10-11 cm2/s range for both materials. The hydrogen diffusion mechanism was described by an anomalous diffusion model, possibly indicating percolation or diffusion paths described by a fractal network. The refractive indices were found to be ~1.3 and ~2 for IrOx and IrTaOx, respectively, and independent of coloration state, whereas the extinction coefficients were found to modulate by ~30% for IrOx and ~50% for IrTaOx, making IrTaOx more favorable for electrochromic applications. A modulation peak was found at ~660 nm for both IrOx and IrTaOx associated with the removal of intraband transitions within the Ir t2g band.

The RNA World hypothesis suggests that RNA, or a proto-RNA, existed in an early form of life that had not yet developed the ability to synthesize protein enzymes. This hypothesis, by some interpretations, implies that nucleic acid polymers were the first polymers of life, and must have therefore spontaneously formed from simple molecular building blocks in the "prebiotic soup." Although prebiotic chemists have searched for decades for a process by which RNA can be made from plausible prebiotic reactions, numerous problems persist that stand in the way of a chemically-sound model for the spontaneous generation of an RNA World (e.g., strand-cyclization, heterogeneous backbones, non-selective ligation of activated nucleotides). The Molecular Midwife hypothesis, proposed by Hud and Anet in 2000, provides a possible solution to several problems associated with the assembly of the first nucleic acids. In this hypothesis, nucleic acid base pairs are assembled by small, planar molecules that resemble molecules which are known today to intercalate the base pairs of nucleic acid duplexes. Thus, the validity and merits of the Molecular Midwife hypothesis can be, to some extent, explored by studying the effects of intercalation on the non-covalent assembly of nucleic acids. In this thesis, I explore the role of the sugar-phosphate backbone in dictating the structure and thermodynamics of nucleic acid intercalation by using 2′,5′-linked RNA intercalation as a model system of non-natural nucleic acid intercalation. The solution structure of an intercalator-bound 2′,5′ RNA duplex reveals structural and thermodynamic aspects of intercalation that provide insight into the origin of the nearest-neighbor exclusion principle, a principle that is uniformly obeyed upon the intercalation of natural (i.e. 3′,5′-linked) RNA and DNA. I also demonstrate the ability of intercalator-mediated assembly to circumvent the strand-cyclization problem, a problem that otherwise greatly limits the polymerization of short oligonucleotides into long polymers. Together, the data presented in this thesis illustrate the important role that the nucleic acid backbone plays in governing the thermodynamics of intercalation, and provide support for the proposed role of intercalator-mediated assembly in the prebiotic formation of nucleic acids.

Les phosphates de cuivre de type NASICON CuxM2(PO4)3 (x=0,5 pour Cu2+; x=1 pour Cu+) (M=Ti, Zr) sont des matériaux remarquables par leurs propriétés catalytiques et luminescentes. L'établissement de modèles rendant compte de ces propriétés à nécessité la localisation du cuivre et la connaissance précise de son environnement par diverses techniques complémentaires : EXAFS, diffraction de neutrons, RMN, microscopie électronique. Le caractère lacunaire de ces phosphates a permis l' enrichissement en cuivre de ces matériaux et l'intercalation notamment du lithium et de l'hydrogène au sein de ces phases.

Ce travail est consacré a l'intercalation de deux typesC d'éspèces dans des structures lamellaires : d'une part de lithium dans FeWO4C1, d'autre part des ions complexes vanadate dans des hydroxydes doubles lamellaires. La réaction du lithium dans FeWO4C1 est réversible dans le domaine de composition FeWO4C1. L'analyse structurale sur monocrstal de FeWO4C1 et de l'affinement par la methoe de rietveld une foorte modification de l'environnement du fer lors de l'intercalation.<br />Des hydroxydes doubles lamellaires dérivés de Ni(OH)2 contenant des chaînes métavanadate intercalées ont été préparés par la chimie douce. Ces matériaux ont été caractérisés par diffraction des rayons X, spectroscopie infrarouge, analyser thermogravimétrique, analyse chimique et RMN du vanadium. L'étude du processus d'intercalation montre que des ions diperoxovanadate sont insérés de prime abord pouis polycondensent spontanément pour donner des chaînes métavanadate. La RMN du vanadium met en évidence le couplage de ce comportement à un phénomène de greffage, également spontané, des entités insérées aux feuillets.

Les phases LiNi1-yCoyO2 ont été obtenues par synthèse directe. Elles sont isotypes des phases extrêmes LiNiO2 et LiCoO2. Ces matériaux ont été utilisés comme électrodes positives dans des batteries au lithium. Elles présentent des performances électrochimiques très prometteuses sur le plan appliqué. Une étude détaillée de l'évolution des propriétés structurales, physico-chimique et électrochimiques lors de la désintercalation du lithium a été effectuée en fonction de y. L'ensemble des résultats montre que le nickel est préférentiellement oxydés à l'état tétravalent que le cobalt. Par ailleurs, l'utilisation des phases homologues NaNi1-yCoyO2 dans des batteries au sodium a permis de mettre en évidence un phénomène de décomposition de l'électrolyte catalysé par le matériau d'électrode positive. Au contraire des phases au lithium, plusieurs transformations structurales ont été observées au cours de la désintercalation sodium à partir de la phase NaNi0.6Co0.4O2.

Vapor grown carbon nanofibers (VGCNFs) developed in 1980s are being widely used for reinforcing composites. Carbon nanotubes (CNTs) discovered in early 1990 can be classified as single wall carbon nanotubes (SWNTs), double wall carbon nanotube (DWNTs) and multi wall carbon nanotubes (MWNTs) depending on the number of grapheme layer forming the carbon nanotube. Polyacrylonitrile (PAN), a commercially important polymer is a predominant precursor for carbon fiber. Carbonized and activated PAN/SWNT films can find application as electrochemical supercapacitor electrodes. This study is focused on the structure, processing and properties of polyacrylonitrile/carbon nanotube (CNT) composite films. PAN/SWNT (60/40) composite film have been processed with unique combination of tensile strength, modulus, electrical conductivity, dimensional stability, low density, solvent resistance, and thermal stability. PAN molecular motion above the glass transition temperature (Tg) in the composite film is significantly suppressed, resulting in high PAN/SWNT storage modulus above Tg. The specific modulus of PAN/VGCNF composite films is consistent with the predictions of the Halpin-Tsai equation up to 20% VGCNF loading. The magnitude of modulus and other property enhancement is reduced as the nanofiber loading is increased (up to 40%). Further increase in nanofiber loading (> 40%) in composite results in modulus and tensile strength lower than those of control PAN. Electrical percolation was observed at 3.1 vol% VGCNF loading. PAN/CNT composite films were processed using SWNTs, DWNTs, MWNTs and VGCNFs to study the effect of various nanotubes on the composite properties. PAN/CNT films have been characterized by wide angle X-ray diffraction (WAXD), Raman spectroscopy, and scanning as well as transmission electron microscopy. Films have also been characterized for electrical conductivity, tensile and dynamic mechanical properties. Mechanical property results have been analyzed in terms of the nanotube surface area determined by nitrogen gas adsorption. PAN/CNT composite films and fibers are characterized using solid state 1HNMR spin lattice relaxation time (T1). With the addition of nanotubes, the T1 values for the PAN matrix generally decreased, and the reduction mechanism is discussed. The optical anisotropy of SWNT in PAN/SWNT composites was observed in their polarized infrared spectra and analyzed using the effective medium theory.

The thesis topic entitled above involves the use of small molecules as a general means to drive nucleic acid assembly and structural transitions. We have shown that coralyne, a crescent-shaped small molecule, can assemble homo-adenine DNA and RNA sequences into anti-parallel duplexes at neutral pH, a structure containing putative purine-purine (A*A) base pairs that is otherwise unstable. The importance of the structure of the small molecule in the recognition and stabilization of A*A base pairing has been established by experimental evidence. We further provide structural evidence for the putative A*A base pairing that is stabilized by coralyne and molecules of similar size and shape. Our hypothesis that planar molecules that are slightly too large to intercalate Watson-Crick base pairs might intercalate the larger purine-purine base pairs has led to the design of a new class of small molecules that tightly bind purine-purine duplexes with excellent selectively. We have demonstrated that azacyanines can exhibit strong and selective association with a human telomeric sequence that forms a unimolecular G-quadruplex in solution. The synthetic accessibility of azacyanines makes this class of molecules amenable to library preparation for high-throughput screening. Together, the findings reported in this thesis provide further evidence for the robust and versatile nature of selective small molecule recognition of nucleic acids, especially purine-purine duplexes.