Filmes de polipirrol (PPy) foram eletropolimerizados potenciostáticamente sobre a liga de alumínio 1100, após ativação galvanostática, em presença de diferentes dopantes a fim de avaliar a sua utilização como revestimento protetor à corrosão. O método de síntese, o dopante e o tipo de ácido utilizado na eletropolimerização de polipirrol influenciam no desempenho do filme na proteção da liga. Os filmes de PPy sintetizados potenciostáticamente a 1,0 V, até carga de 1,0 C, em solução contendo pirrol (Py) 0,4 mol L-1, dodecilbenzenosulfonato de sódio (SDBS) 0,1 mol L-1 e ácido oxálico (H2C2O4) 0,1 mol L-1 apresentaram maior resistência de polarização. Os filmes de PPy sintetizados na mesma condição anterior e em presença das argilas montmorilonita sódica (MT-Na) ou montmorilonita modificada (MT-M), nas concentrações de 1 e 5% p/p, resultaram em material nanocompósito. Os filmes polipirrol/montmorilonita (PPy/MT) 1% em peso apresentaram melhor desempenho na proteção à corrosão da liga de alumínio Os valores de condutividade obtidos para os filmes de PPy e PPy/MT sintetizados pelo método eletroquímico utilizado são de 2-5 ordens maiores que os valores obtidos por síntese química. A partir de planejamento fatorial estatístico foi determinado que filmes de PPy sintetizados eletroquimicamente a 1 V até 1,5C em solução de Py 0,2 mol L-1, H2C2O4 0,1 mol L-1 e tungstato de sódio (Na2WO4) 0,05 mol L-1 propiciam maior resistência à corrosão da liga em meio de cloreto, devido à ação dopante e inibidora do ânion tungstato. / Polypyrrole (PPy) was deposited potentiostatically on aluminum alloy Al- 1100 after galvanostatic activation pretreatment, in the presence of different dopants, in order to obtain a protective film against corrosion. It has been shown that the corrosion resistance of the PPy recovered Al-1100 is strongly dependent on the surface pretreatment, pyrrole (Py) concentration and electropolimerization process. The higher polarization resistance of the recovered Al-1100 alloy was obtained for PPy films synthesized potentiostatically at 1.00 V, in a 0.1 mol L-1 dodecylbenzene sulfonate (SDBS) and 0.1 mol L-1 oxalic acid (H2C2O4) solution containing 0.4 mol L-1 Py. When Polypyrrole films are synthesized in the same conditions as above in the presence of 1 and 5% w/w of either Na+- Montmorillonite (MT-Na), or modified-Montmorillonite (MT-M), a nonocomposite material is obtained. It was observed that Al110 recovered with films of PPy/MTM 1% gives the higher corrosion protection. Moreover, the conductivity values obtained for the electrochemically synthesized PPy/SDBS and PPy/MT films are 2 to 5 orders of magnitude higher than those obtained by the chemical synthesis. By employing statistical factorial design it has been evidenced that the film PPy/OXA/W synthesized at 1.0 V, 5.0 C in 0.2 mol L-1 pyrrole, 0.1 mol L-1 H2C2O4 and 0.05 mol L-1 Na2WO4 solution, presents the best performance against corrosion in chloride media. Under these conditions, the tungstate anion plays the role of both dopant and inhibitor agent.

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Les polymères conducteurs sont fréquemment utilisés en génie biomédical pour la transmission de signaux électriques. Les objectifs de ce mémoire étaient d'évaluer l'électroactivité d'un composite de polymère conducteur, et d'explorer une nouvelle technique de synthèse d'une membrane mince à partir de ce polymère conducteur. L'effet de l'héparine comme dopant polyanionique sur l'électroactivité du composite a été évaluée par voltammétrie cyclique (CV) et comparée à l'effet des anions de chlore. Le composite dopé par héparine a été trouvé électriquement actif avec une stabilité améliorée de façon significative. Ces résultats confirment le potentiel de l'utilisation de ces composites conducteurs pour des applications biomédicales à long terme. Les membranes minces des polymères conducteurs sont généralement synthétisées par polymérisation électrochimique à la surface de l'électrode. Des membranes souples et autoportants de polypyrrole (PPy) et le copolymère de pyrrole et 1 -(2-carboxyéthyl)pyrrole (PPy/PPyCOOH) par électropolymérisation à l'interface air/liquide (electrolyte) ont été produites dans le cadre de ce mémoire. Ces membranes ont démontré une électroactivité stable pour un minimum de 200 balayages de CV. La membrane PPy/PPyCOOH a également démontré une importante activité d'oxydoréduction. Ces membranes peuvent être utilisées dans des biosenseurs ou des piles souples.

In this study, organo-montmorillonite (OMMT) nanocomposites containing 1%, 5%, 10% and 15% OMMT were prepared by in situ intercalative oxidative polymerization of pyrrole in the presence of OMMT. Thermal and morphological properties of the Polypyrrole(PPy)/OMMT nanocomposites were investigated by Thermal Gravimetric Analysis (TGA), X-ray Diffraction Analysis (XRD) and Scanning Electron Microscope (SEM). Electrical conductivities of composites were measured by four probe technique. Formation of PPy and its incorporation in PPy/OMMT composites were confirmed by FTIR analysis. TGA results showed that PPy/OMMT composites have outstanding thermal stability compared to that of PPy. XRD analysis revealed intercalation of PPy in the OMMT lamelles. Scanning electron micrographs demonstrated that the morphology of the PPy/OMMT nanocomposites differ slightly from that of the clay, since the modification of PPy was not significant in flaky structure of OMMT nanoparticles. Conductivity values of PPy/OMMT composites were found in the order of 10-3S/cm. Since PPy has poor processibility, Polypropylene(PP)/PPy composites were prepared in the composition range of 2-20 % PPy. Mechanical properties were investigated by tensile tests. Electrical conductivities were measured by four probe technique. Morphological characterizations were made by SEM. Young&amp / #8217 / s Modulus of PPy/PP composites increased with increasing PPy content, and addition of 2 wt % PPy to PP resulted in a dramatic decrease in the tensile strain at break of the material. Also by addition of 2 wt % PPy to PP, the tensile strength of material decreased and further increase in PPy content, tensile strength increased. Furthermore, an increase in the PPy content in PPy/PP composites resulted in an increase in conductivity. SEM micrographs revealed that as the PPy loading increases from 10% to 20% in composite system, adhered PPy particles by PP matrix were driven out of PP matrix while PP matrix oriented along the draw direction during tensile test.

La croissance de nanotubes de carbone (NTC) sur particules micrometriques d'alumine (Al2O3) permet d'obtenir une dispersion uniforme des NTC dans des matrices sans enchevêtrement de NTC. Ce type de structure hybride NTC-Al2O3 fournit également une solution prometteuse au problème de sécurité de NTC car ils intègrent NTC avec des particules micrométriques, étendant la dimension des NTC à partir de nano-échelle au micro-échelle. Cependant, l'adhérence entre les NTC et les Al2O3 particules ne permet pas de fixer efficacement les NTC. Par ailleurs, une autre préoccupation essentielle de NTC est de savoir comment créer une forte adhésion interfaciale entre les NTC et les matrices polymères pour obtenir de bonnes propriétés mécaniques et de ne pas diminuer la conductivité électrique de NTC. Motivé par ces considérations, cette thèse vise à proposer plusieurs techniques concernant le dépôt d'une nano-couche conductrice sur la surface des structures hybrides NTC-Al2O3. De plus, les impacts de la nano-couche déposée sur la fixation des NTC à la surface d’Al2O3, sur la conductivité électrique des hybrides NTC-Al2O3, et sur l'adhésion interfaciale des systèmes NTC-Al2O3/epoxy composites sont étudiés en détail. / Growth of carbon nanotubes (CNTs) on micro-sized alumina (Al2O3) particles helps to achieve a uniform dispersion of CNTs in matrices without CNT entanglement. This kind of CNT-Al2O3 hybrids also provides a promising solution to the CNT safety problem since they integrate CNTs with micrometric particles, extending dimension of CNT fillers from nano-scale to micro-scale. However, the adhesion between the CNTs and the Al2O3 particles doesn’t sufficiently enable to fix the CNTs firmly and stably. Besides, another crucial concern of CNTs is how to create a strong interfacial adhesion between CNTs and polymer matrices for good mechanical properties and meanwhile not to degrade CNTs’ electrical conductivity. Motivated by these considerations, this PhD thesis aims to establishing several techniques for deposition of an electrically conductive nano-layer on the surface of CNT-Al2O3 hybrids. And the impacts of the deposited nano-layer on the fixing the CNTs on the Al2O3 surface, on bulk electrical conductivity of the CNT-Al2O3 hybrids, and on the interfacial adhesion of CNT-Al2O3/epoxy composite systems are investigated in detail.

Ce travail de recherche porte sur l'élaboration de matériaux hybrides 3D nanotubes de TiO2/ polymère conducteur. Il est établi dans cette thèse que la nature du sel de fond de la solution de synthèse joue un rôle déterminant lors du dépôt de polymère par polarisation anodique au sein de ces nanotubes. En effet, les résultats montrent que la nature de l'électrolyte support a un impact sur la position du potentiel de bande plate du TiO2 et sur la présence ou non d'états de surface, qui tous les deux influencent la vitesse du transfert de charge. La nature de la jonction réalisée entre deux matériaux dépendant fortement de la position respective de leurs bandes énergétiques. Ainsi il est démontré que la synthèse de polypyrrole à la surface de nanotubes de TiO2 conduit à la formation d'une jonction ohmique, ce qui permet aux électrons issus de l'oxydation du polymère d'être transférés directement dans la bande de conduction du TiO2. Au contraire, la jonction formée par l'oxyde de titane et le PEDOT est de type p-n, ce qui laisse envisager que ce type de structure hybride peut trouver son application dans le domaine de l'énergie photovoltaïque. / This research work considers the realization of 3D hybrid materials TiO2 nanotubes/conducting polymer. In this thesis, it is proven that the background salt from the synthesis solution plays a decisive role during the polymer deposition through anodic polarization within TiO2 nanotube arrays. In fact, results show that the nature of the supporting electrolyte has an influence on the position of the flat band potential of the semiconductor, and on the presence of surface states, which both affect the rate of charge transfer. It is demonstrated that the nature of the junction obtained between the semiconductor and the polymer depends greatly on the respective position of their energy bands. Accordingly a TiO2 nanotubes/polypyrrole junction is shown to be of ohmic nature, allowing electrons from the polymer oxidation to be directly transferred to the conduction band of TiO2. On the contrary, the junction created between titanium dioxide and PEDOT is of p-n type, leading to potential applications in the field of photovoltaics.

Inhibitors used as dopant anions in polymer films are responsible for the anticorrosion behaviour of polypyrrole (Ppy). Ppy film doped with MoO42- and TiF62- showed the role of anions in corrosion protection of iron. Ppy doped with 3-nitro salicylate was used for zinc protection. The results of XPS revealed that molybdate exist in two types: [MoO4]2- (62%) and [Mo7O24]6- (28%). Electrochemical Impedance Spectroscopy (EIS) has indicated the change of the resistance RPM and the capacitance CPM of the Ppy film during reduction. Electrochemical Quartz Crystal Microbalance (EQCM) has shown: the mass of the Ppy film decreased in the cathodic region and increased in the anodic region. The anion flux was also observed in Scanning Kelvinprobe (SKP) and X-ray Photoelectron Spectroscopy (XPS) experiments. The release behaviour of molybdate anions depends much on the size of cations in the electrolyte. TiF62- anions has shown good inhibitor properties. However, the mechanism of this action is not yet known. 3-nitro salicylate (3-nisa) was used as inhibitor dopant for zinc in this work. Ppy film could be formed on Zn without any special pretreatment. The dissolution of Zn decreased dramatically in the presence of 3-nisa. The application of Ppy/metal inorganic composites in corrosion protection for mild steel and galvanised steel may be a better selection. Mixture of core-shell particles with matrix polymer was used as primer for protective coatings.