Développés pour améliorer la santé et le bien-être, certains composés pharmaceutiques sont désormais sous haute surveillance car considérés comme des contaminants émergents des eaux. Pour répondre à ce nouvel enjeu, nous visons à développer un microsystème d'analyse permettant l'identification et la quantification de ces contaminants dans des échantillons d'eau. L'aspect original de ce microsystème repose sur l'intégration au sein du canal d'une zone de préconcentration dans laquelle sont immobilisés des ligands (aptamères dans notre étude), permettant l'extraction sélective de la cible et sa concentration. Pour développer ce microsystème, deux types de fonctionnalisation de surface doivent être mis en œuvre : (1) globale, sur toute la surface des canaux, pour contrôler leurs propriétés de surface et ainsi éviter l'adsorption et contrôler les écoulements de liquides, et (2) locale, pour greffer les ligands sélectifs dans une zone confinée du canal. Les polymères COC et THV, prometteurs pour la conception de puces microfluidiques grâce à leur transparence dans le domaine UV-visible et leur excellente résistance aux solvants, ont été sélectionnés pour la microfabrication du système. Cependant, leur inertie chimique rend difficile la fonctionnalisation de leur surface, et de nouvelles méthodes de traitement de surface ont été développées. Nous présentons ainsi plusieurs méthodes innovantes pour la fonctionnalisation de ces matériaux, basées sur un dépôt plasma, une modification électrochimique et/ou une réaction chimique. La possibilité d'encapsuler les ligands dans une phase monolithique à l'intérieur d'un microcanal grâce à un procédé sol-gel a également été évaluée. / Developed to promote human health and well-being, certain pharmaceuticals are now attracting attention as crucial emerging water contaminants. To deal with this concern, we aim at developing an analytical microsystem for the identification and quantitation of these contaminants in water samples. The original aspect of this lab-on-a-chip relies on the integration inside the channel of a preconcentration zone in which ligands (aptamer in our study) are immobilized, in order to concentrate the target and extract it from the rest sample matrix. Development of this microsystem requires surface treatments to modify the microchannel surface at two scales: (1) globally (on the entire channel walls) to control surface properties and thus avoid adsorption as well as control fluid flows, or (2) locally to immobilize selective ligands in restricted areas for selective target extraction and preconcentration. Polymers COC and THV, attractive for the conception of microfluidic chips thanks to their UV-visible transparency and high resistance to aggressive solvents, were selected as the microchip material. However due their chemical inertness new functionalization techniques have to be developed to modify their surface. In this work, innovative surface treatment strategies have been developed for both materials, based on plasma, electrochemical and chemical approaches. The possibility of encapsulating aptamers in a monolithic phase inside microchannel by sol-gel process was also explored.

Les récents développements dans le domaine du photovoltaïque ont permis l'apparition de cellules utilisant des technologies nouvelles. Parmi elles on trouve les cellules photovoltaïques hybrides, cependant les méthodes de fabrication utilisées actuellement présentent des défauts. Cette thèse a pour but de proposer deux nouvelles approches pour la préparation de cellules photovoltaïques hybrides sous forme d'hétérojonctions en volume d'un oxopolymère de titane et d'un polythiophène. Dans un premier temps la formation de mésostructures vermiculaires dans des couches minces de TiO2 par autoassemblage par évaporation a été étudiée, l'oxopolymère amorphe obtenu a ensuite été cristallisé en conditions douces. Ces résultats ont ensuite été utilisés afin de préparer des matériaux hybrides à partir d'homopolymères de thiophène portant des substituants hexyl et acide, ainsi qu'à partir de copolymères. Des matériaux hybrides ne présentant pas de macroségrégation ont été obtenus pour un polymère portant des fonctions acides et pour les copolymères. Dans un second temps l'électrochimie du ferrocène et du cuivre ont été étudiés dans des films de TiO2 mésostructuré et mésoporeux, puis deux dérivés thiophène : le mot et l'edot ont été électropolymérisés dans ces structures. Des cellules photovoltaïques ont été préparées en utilisant ces matériaux hybrides et caractérisées par des mesures de la courbe I/E ainsi que par l'étude du rendement quantique externe, des facteurs de forme et des rendements ont été calculés. En conclusion, deux nouvelles approches de synthèse de matériaux hybrides ont été proposées et menées à bien les propriétés photovoltaïques et ces matériaux ont été mesurées. / Recent advances in the field of photovoltaics have led to the emergence of new solar cell technologies. Among them can be found the hybrid solar cells, unfortunately the way such cells are built is still a source of problems. The aim of this phd is to develop two new approaches in the synthesis of hybrid materials as bulk heterojunctions. In first place the titanium dioxide component vas prepared by sol-gel process and its mesostructure was studied, low temperature crystallization was also investigated. Those results were used in order to prepare hybrid materials from preformed polymers. The behavior of polythiophènes with hexyl and carboxylic acid functions were used as well as copolymers bearing both functions. Hybrids without macrosegregations phenomena were obtained using acid bearing homopolymers as well as copolymers. The second approach was about investigating the electrochemical behavior of ferrocene and copper ions inside the mesoporosity, this first study was followed by a study of the electropolymerization of mot and edot inside the porosity in order to prepare hybrid materials. The obtained hybrids were studied in solar cells by measuring the I/V curve as well as the external quantum efficiency, fill factors and efficiencies were also obtained. To conclude, both approaches leaded to hybrid materials with measurable photovoltaic properties.

Master of Science / Department of Chemistry / Christopher T. Culbertson / The field of microfluidic devices has being developed quickly. It is aimed at integration of many chemical functions in a single chip, such as sample pretreatment, preconcentration, separation and detection, which provides a number of advantages including simplicity, automation, reduced analysis time, decrease in amount of samples and reduced formation of waste. Its potential applications have been conducted in the fields such as biotechnology, pharmaceuticals, life sciences, public health, agriculture and related areas. Membrane technology has been applied in analytical chemistry for many years and has won substantial growth in microfluidics over the past 10 years. Membrane is used to control transfer of some kinds of species, which can be employed for sample concentration, sample preparation, sample filtration and microreactors and so on. Sol-gel process, which usually involves catalytic hydrolysis of sol-gel precursor(s) and catalytic polycondensation of the hydrolyzed products and other sol-gel-active components present in the reaction medium to form a macromolecular network structure, is one of the most suitable methods for membrane fabrication. In this work, titanium membrane was fabricated inside glass microchips using the precursor of titanium isopropoxide. The resulted membranes demonstrated the excellent preconcentration effect. Followed separation and detection were also achieved. CE has been highly accepted as an efficient separation technique for qualitative and quantitative determination, which is performed using a narrow-bore capillary tube. It offers advantages of simplicity, high resolution separation, and minimal cost in terms of analysis time and sample consumption. In this work, protein separations were carried out by CE. Laser-induced fluorescence was used as detection. On-column fluorescence labeling using a fluorogenic labeling reagent was made. Under suitable experimental conditions, an excellent separation performance with about 1.4 million theoretical plate numbers was achieved.

L’étude présentée dans ce manuscrit porte sur la réplication de structures naturelles multi-échelles et multifonctionnelles, que sont les ailes des papillons Morpho rhetenor, Morpho menelaus et Papilio ulysse, ou celles de la cigale Cicada orni. De telles structures sont en effet constituées de sous-structures à différentes échelles, du centimètre au nanomètre, et à chacune de ces échelles est associée une propriété ou fonction. On parle alors de multifonctionnalité. Cet atout, très recherché actuellement pour nos futurs objets et matériaux, est accessible par deux voies de complexification : celle de la composition chimique du ou des matériaux constituant l’objet (matériaux composites, hybrides organique-inorganique) et/ou celle de leur géométrie (structuration). Or, si nos connaissances en chimie nous permettent de mettre en œuvre la première voie, l’élaboration de structures multi-échelles est encore difficile par nos techniques actuelles de structuration (lithographie par exemple). Ainsi, pour augmenter les propriétés d’un système possédant une géométrie multi-échelles existante dans la nature, nous avons réalisé des répliques des structures naturelles précédemment évoquées dans des matériaux inorganiques (TiO2 et SiO2), soit des matériaux très différents du complexe chitino-protéique qui constituent les ailes organiques. A cette fin, trois méthodes ont été utilisées : un dépôt de matière dans les structures naturelles par voie sol-gel, un dépôt par pulvérisation cathodique et une minéralisation directe de la structure des ailes, s’inspirant de processus de biominéralisation. / The present study deals with the replication of multiscale and multifunctional natural structures. These natural structures are wings of Morpho rhetenor, Morpho menelaus and Papilio ulysse butterflies, and those of Cicada orni cicada. Such structures are composed of smaller structures at different scales, from centimetre to nanometre, and to each of these scales is associated a property or a function. This we call multifunctionality. This multifunctionality is expected to become a property of our future objects or materials, and can be achieved by two different ways: to make the material(s) chemical composition of the object more complex (composite, hybrid organic-inorganic materials) and/or to make its architecture more complex (structuration). Although it is possible to achieve the first (chemical composition), we have so far been unable to successfully make multiscale structures with our current structuration techniques (lithography for example). Therefore, to increase the properties of a system characterised by a multiscale structure seen in nature, we have made replicas of the natural structures previously presented in inorganic materials (TiO2 and SiO2). That is to say, very different materials in comparison with the natural chitin-protein complex. To do this, three methods were used: a sol-gel solution deposition in the natural structures, a physical vapor deposition and a direct mineralization of the wings structure, which is inspired by natural biomineralization processes.

Un polymère à empreintes moléculaires (MIP) est un récepteur synthétique supramoléculaire, un matériau possédant des cavités pouvant reconnaître spécifiquement une molécule cible. Il est synthétisé en mettant en contact la molécule cible, avec un mélange de monomères fonctionnels et réticulants qui permettent d'obtenir un réseau polymérique tridimensionnel rigide. L'élimination de la molécule empreinte laissera des sites vides complémentaires de cette dernière. Ces cavités sont maintenant capables de la recapturer spécifiquement. Ces polymères sont utilisés dans les domaines tels que l’extraction en phase solide, la chromatographie d’affinité, la catalyse enzymatique, les biocapteurs et la vectorisation des médicaments. Bien que le concept des MIPs a pour origine les travaux réalisés sur des matériaux sol-gel imprimés dans les années 1930, ces derniers sont restés dans l’ombre jusqu’à l'introduction de polymères organiques imprimés plus versatiles. Par rapport aux MIPs organiques, les MIPs sol-gel présentent quelques avantages comme une plus grande stabilité thermique, une meilleure compatibilité avec l'eau et une plus grande porosité. Dans cette thèse, nous avons développé des MIPs organiques et des MIPs sol-gel pour leur application en cosmétologie et pour la vectorisation de médicaments. Dans la première partie, nous présentons des MIPs pouvant adsorber d’une façon spécifique l’acide oléique (OA), un biomarqueur de l’état pelliculaire sur le cuir chevelu. Pour la préparation des MIPs organiques, nous avons employé plusieurs monomères basiques dont l’acryloylaminobenzamidine (AB), que nous avons tout spécialement synthétisé. Tous les MIPs pouvaient lier l’OA mais beaucoup d’interaction non-spécifique était observé. D’autre part, les MIPs sol-gel présentaient une bonne reconnaissance spécifique et une capacité élevée pour OA; par exemple, un MIP de composition OA:APTES:TEOS = 1:1.6:1.7 pouvait adsorber 625 μmol.g-1 de OA dans le sébum artificiel. Des tests pour capturer l’OA sur le stratum corneum et la peau reconstruite (Episkin) ont également été effectués. La pénétration de l’OA sur les deux types de peau était plus faible en présence de MIP que de NIP. Les MIPs comme matériaux désodorisants font l’objet de la deuxième partie de cette thèse. Des MIPs pouvant adsorber les précurseurs de molécules malodorantes comme les conjugués glutamine des acides (E)-3-méthyl-2-hexénoïque (3M2H) et 3-hydroxy-3-méthyl-hexanoïque (3H3MH) ont été préparés. Le N-hexanoyl glutamine et le N-hexanoyl glutamate ont été utilisés comme template. Nous observons que le MIP synthétisé avec AB comme monomère fonctionnel possède la plus grande capacité d'adsorption pour le N-hexanoyl glutamine, ainsi que pour les précurseurs glutamines des molécules malodorantes. Des résultats préliminaires et très prometteurs ont également été obtenus dans la sueur. La dernière partie de cette thèse concerne des MIPs pour la vectorisation de médicaments. L'acide salicylique (SA) est un médicament efficace utilisé dans le traitement de l’acné. Des MIPs organiques et sol-gel contre SA ont été synthétisés. Les MIPs sol-gel ont une plus grande capacité d’adsorption, 180 μmol.g-1, que les MIPs organiques et ils lient le SA sept fois plus que le NIP. Les tests de relargage du SA ont été effectués dans plusieurs milieux, avec la plus grande efficacité dans l’eau pure. En conclusion, les applications de MIPs en cosmétologie et en vectorisation de médicaments ont étés étudiés. Nos résultats montrent que les MIPs sol-gel sont les plus appropriés pour ce type de travail. / Molecularly imprinted polymers (MIPs) are tailor-made synthetic receptors possessing specific cavities for a given target molecule. They are produced by introducing, into the polymer precursors, guest molecules that act as templates at the molecular level. Interacting and cross-linking monomers are then copolymerized to form a cast-like shell. After removal of the template, cavities complementary to the template in size, shape and position of functional groups are revealed in the polymer, which can now specifically bind the template. Thanks to these specific molecular recognition properties, MIPs have found applications in areas like bio sensors, solid phase extraction, affinity chromatography, catalysis, and drug delivery. Although the MIP concept originated from imprinted silica in the 1930s, imprinted sol-gel materials received little attention afterwards due to the introduction of the more versatile organic polymers as imprinting matrix. However, compared to organic polymers, sol-gels possess higher thermal stability, better water compatibility and larger inner surface area. There have been many applications to biomolecules in aqueous conditions with sol-gel imprinting materials. In this thesis, we have developed organic and silica sol-gel MIPs for applications in cosmetics and drug delivery. MIPs able to adsorb the dandruff-inducing molecule oleic acid (OA) were produced via both the organic and inorganic routes. In the organic MIPs synthesis, different positively charged monomers were used, one of which, acryloyl aminobenzamidine, was specifically synthesized. Although some binding of oleic acid was obtained, specificity and capacity of these polymers were not satisfying. Sol-gel MIPs, on the other hand, exhibited good specific recognition and high binding capacity for OA. A MIP of the composition OA:APTES:TEOS= 1:1.6:1.7 yielded a capacity of 625 μmol.g-1 in artificial sebum. Furthermore, tests were carried out to capture OA on stratum corneum and reconstructed skin (Episkin). Less penetration of OA was observed in the presence of a MIP than with a non-imprinted control polymer. Deodorant materials are another topic of this thesis. MIPs that are able to adsorb certain precursors of odorant molecules, the glutamine conjugates of (E)-3-methyl-2-hexenoic acid (3M2H) and 3-hydroxy-3-methyl-hexanoic acid (3H3MH) were prepared. N-hexanoyl glutamine and N-hexanoyl glutamate were used as templates. After optimization of the MIP composition, we found that MIPs synthesized with acryloyl aminobenzamidine as functional monomer had the highest adsorption capacity for N-hexanoyl glutamine, and also recognised the glutamine targets of 3M2H and 3H3MH. Some preliminary promising binding results were obtained in artificial sweat. The third part of this work concerns a drug delivery MIP. Salicylic acid (SA) is a drug used to treat acne. SA-imprinted polymers were prepared via both organic imprinting and the sol-gel process.Compared to organic MIPs, sol-gel MIPs have a higher capacity, 180 μmol.g-1, and 7 times higher binding than to a non-imprinted control polymer was observed. Release tests were carried out in different aqueous media, the most efficient drug release was observed in pure water. In conclusion, applications of molecularly imprinted polymers for cosmetics and drug delivery have been investigated. Our results demonstrate the great potential of in particular sol-gel MIPs for these purposes.

Advances in photonic materials are critical to the progress of photonic devices and optical systems. Even though a variety of materials, e.g. semiconductors, oxide based glasses, and polymers exist which are being used for numerous applications, there is a growing need to develop and find new materials in order to push the limits we are bound by with conventional materials, in pursuit of higher performance, higher levels of integration and lower cost. In this realm, new material development has had a considerable impact, as it is the material properties (optical, thermal, mechanical, electrical, ...) in addition to their processing and compatibilities with standard processes that enable us the creation of entirely new devices or improve the performance of currently available optical devices. In this dissertation, I will demonstrate the application of two new materials for novel photonic components. In the first part of the dissertation, I discuss how a hybrid approach to the silicon photonics platform can reduce thermal sensitivity using sol-gel based inorganic-organic hybrid materials. The approach is to design the optical waveguide so that it maintains its performance in a passive manner in response to environmental temperature variations and, thus, does not need external temperature control resulting in reduced electrical power consumption. Sol-gel materials are well-known, but they haven’t been exploited like polymers and titanium dioxide to be cladding layers to enable athermal silicon waveguides. In this work I show their advantages with respect to previous materials that were employed for athermal microring resonators. I studied the thermal curing parameters of the sol-gel and its effect on thermal wavelength shift of the microring resonance. With this method, I was able to achieve a thermal shift down to -6.8 pm/°C for transverse electric (TE) polarization, as well as thermal shifts below 1 pm/°C for transverse magnetic (TM) polarization in the C band under different curing conditions, all while preserving high Q resonator performance. The results and methodology described opens a new and more manufacturable approach to attain athermal silicon photonic devices. In the second part of the dissertation, I introduced a new, sulfur rich, low cost copolymer material developed by our colleagues in the chemistry department. This copolymer has unique properties that conventional optical polymers, such as polymethylmethacrylate and polycarbonate, lack, while also having low cost. I demonstrated that these polymers have very good processing capabilities, being easily moldable to make free space optical elements and solution processable for use in integrated optics. I studied their linear and nonlinear optical properties, finding them to possess high refractive indices and transparencies over a wide range from 550 nm to 6 µm, except for a small region of absorption from 3-3.3 µm. Finally, I demonstrated that these new copolymers are suitable and economical alternative for shortwave and midwave infrared optics (SWIR and MWIR, respectively).

>Magister Scientiae - MSc / In recent times, the occurrence and presence of complex recalcitrant toxic contaminants in water and wastewater is increasing and consequently contributes to the non-availability of clean and safe drinking water. Water treatment is complex, time demanding and energy intensive due to the physico-chemical structural complexity and diversity of the pollutants. Non-availability of good drinking water has negatively affected human health and the ecosystem. Over the years, numerous conventional treatment techniques were used to degrade and remove these pollutants, but investigations indicated that some of the pollutants are not susceptible to conventional treatment. Advanced oxidation technology, among which heterogeneous photocatalysis (involving the use of a semiconductor) has emerged as one of the more promising techniques to remediate contaminated water. Titanium dioxide (TiO2) semiconductor photocatalysis is considered to be a good option due to its cost effectiveness, chemical and thermal stability, and inertness in the area of wastewater reclamation and re-use. However the post separation of the titania particles poses a threat to the wastewater remediation. Hence there is a need to develop a supported high surface area photocatalyst that will resolve the post separation challenge. This present study aimed to prepare high surface area TiO2 anatase nanocrystals supported on a stainless steel mesh. These new composite materials were used to remove methylene blue (MB) from aqueous solutions. The supporting procedure involved the thermal decomposition of a sol gel solution coated upon stainless steel mesh. The nanocrystalline anatase phase was formed by thermal decomposition on a stainless steel mesh coated with 8 % PAN/DMF/TiO2 sol gel formation calcined at varying temperatures of 300 °C, 400 °C, 500 °C and 600 °C. The heating rate of 50 °C/min and independent holding time of 1 h, 2 h, 3 h and 4 h were applied to find the optimum supporting conditions. The synthesised TiO2 nanocomposites materials were characterised using the following analytical techniques: XRD, HRSEM, EDS, HRTEM, SAED, FTIR and UV-Vis absorption spectroscopy materials were characterised, and the results indicate that synthesised TiO2 nanocrystals were in the anatase form, polycrystalline in nature, and contained additional carbon-carbon bonds from the polymer used during preparation with TiO2 particle sizes range from 13.6 nm to 2285 nm.

A vehicle flying at hypersonic speeds, i.e. at speeds greater than Mach 4, needs to be able to withstand the heat arising from friction and shock waves, which can reach temperatures of up to 3000oC. The current project focuses on producing thermal protection systems based on ultra high temperature ceramic (UHTC) impregnated carbon-carbon composites. The carbon fibres offer low mass and excellent resistance to thermal shock; their vulnerability is to oxidation above 500oC. The aim of introducing HfB2, a UHTC, as a coating on the fibre tows or as particulate reinforcement into the carbon fibre preform, was to improve this property. The objectives of this project were to: i) identify a low temperature synthesis route for group IV diborides, ii) produce a powder fine enough to reduce the difficulties associated with sintering the refractory diborides, iii) develop sol-gel coating of HfB2 onto carbon fibre tows iv) improve the solid loading of the particulate reinforcement into the carbon fibre preform, which should, in turn, increase the oxidation protection. In order to achieve the above set objectives, fine HfB2 powder was synthesized through a low temperature sol gel and boro/carbothermal reduction process, using a range of different carbon sources. Study of the formation mechanism of HfB2 revealed an intermediate boron sub-oxide and/or active boron formation that yielded HfB2 formation at 1300oC. At higher temperatures the formation of HfB2 could be via intermediate HfC formation and/or B4C formation. Growth mechanism analysis showed that the nucleated particles possessed screw dislocations which indicated that the formation of HfB2 was not only through a substitution reaction, but there could have been an element of a precipitation nucleation mechanism that lead to anisotropic growth under certain conditions. The effect of carbon sources during the boro/carbothermal reduction reaction on the size of the final HfB2 powders was analysed and it was found that a direct relation existed between the size and level of agglomeration of the carbon sources and the resulting HfB2 powders. A powder phenolic resin source led to the finest powder, with particle sizes in the range 30 to 150 nm. SPS sintering of the powder revealed that 99% theoretical density could be achieved without the need for sintering aids at 2200oC. Sol-gel coatings and slurry impregnation of HfB2 on carbon fibres tows was performed using dip coating and a 'squeeze-tube' method respectively. Crack free coatings and non-porous matrix infiltration were successfully achieved. The solid loading of the fine HfB2 into the carbon fibre preform was carried out through impregnation of a HfB2 / phenolic resin/acetone slurry using vacuum impregnation. Although the sub-micron Loughborough (LU) powders were expected to improve the solid loading, compared to the commercially available micron sized powders, due to the slurry made from them having a higher viscosity because of the fine particle size, the solids loading achieved was consequently decreased. Optimisation of the rheology of the slurry with LU HfB2 still requires more work. A comparison of the oxidation and ablation resistance of the Cf-HfB2 composites prepared with both commercial micron sized HfB2 powder and Loughborough sub-micron sized HfB2 powder, each with similar level of solid loading, was carried out using oxyacetylene torch testing. It was found that the composite containing the finer, Loughborough powders suffered a larger erosion volume than the composite with the coarser commercial powders indicating that the former offered worse ablation and oxidation resistance than the latter. A full investigation of the effect of solids loading and particle size, including the option of using mixtures of fine and coarse powders, is still required.

Ce travail de thèse constitue une nouvelle approche de l’étude du comportement des bactéries immobilisées dans des matrices inorganiques centrée sur l’influence d’un champ magnétique sur le comportement cellulaire. Des nouveaux gels incorporant des nanoparticules de magnétite ont été élaborés par voie sol-gel dans des conditions cytocompatibles et caractérisés par diffraction des rayons X, sorption d’azote, microscopie électronique en transmission (MET) et mesures magnétiques. Après une étude de viabilité des bactéries modèles Escherichia coli immobilisées, le procédé d’encapsulation a été étendu aux bactéries magnétotactiques Magnetospirillum magneticum. L’effet d’un champ magnétique statique sur ces deux types de microorganismes a été étudié. Enfin, les processus de biominéralisation intracellulaire chez les bactéries magnétotactiques ont été suivis en présence et en absence d’un champ magnétique statique sur des cellules immobilisées et en suspension. Cette approche nous a permis de comprendre les phénomènes liés à l’encapsulation et à l’exposition à un environnement magnétique extérieur. Des effets originaux du champ magnétique continu sur la cinétique de production des magnétosomes et sur la dynamique collective des chaînes de magnétosomes à l’intérieur des cellules encapsulées ont pu être mis en évidence. / This work constitutes a new approach to the study of the behavior of immobilized bacteria in inorganic matrices focusing on the influence of a magnetic field on cell behavior. Novel gels incorporating magnetite nanoparticles were prepared by the sol-gel process in cytocompatible conditions and were characterized by X-ray diffraction, nitrogen sorption, transmission electron microscopy (TEM) and magnetic measurements. After studying the viability of immobilized model bacteria Escherichia coli, the encapsulation process was extended to magnetotactic bacteria Magnetospirillum magneticum. The effect of a static magnetic field on these two types of microorganisms was studied.Finally, the process of intracellular biomineralization in magnetotactic bacteria was followed in the presence and absence of a static magnetic field on the immobilized cells and suspension. This approach allowed us to understand the phenomena related to encapsulation and exposure to an external magnetic environment. New effects of the continuous magnetic field on the kinetics of magnetosome production and on the collective dynamic of magnetosome chains within the encapsulated cells are described.

Ce travail de thèse s'inscrit dans la problématique de la préparation et l'intégration des matériaux diélectriques poreux à très faible permittivité (ULK) dans les interconnexions des puces microélectroniques. Cette étude porte sur le développement de couches minces hydrophobes ULK à porosité organisée et isolée, préparées par voies sol-gel et PECVD. Elle vise une amélioration des propriétés mécaniques et une diminution de la diffusion de polluants au cœur des films. Des matériaux hydrophobes mésostructurés et ULK (k < 2,2) ont ainsi été obtenus par voie sol-gel, après retrait d'un porogène par traitement thermique, ou pour la première fois sous UV. Les caractéristiques mésostructurales et microstructurales des couches ont été reliées aux caractéristiques de porosité et aux propriétés mécaniques. Les mesures électriques et de perméation de gaz de ces matériaux sont également discutées en vue de leurs applications en tant que matériaux ULK ou comme membranes de séparation de gaz. En PECVD, des matériaux polymère plasma à base de styrène ont été synthétisés et également caractérisés en termes de propriétés mécaniques et de séparation de gaz. / This thesis is dealing with the challenging preparation and integration of porous dielectric materials with ultra low permittivity (ULK) for interconnections in microelectronic devices. This study focuses on synthesis of hydrophobic ULK thin layers with ordered and isolated porosity obtained by sol-gel. An improvement in mechanical properties and a decrease of the impurities migration in the heart of the bulk are expected. Hydrophobic and mesostructured ULK (k < 2.2) materials have been obtained by sol-gel after removal of porogen mesophases by thermal treatment and for the first time under UV irradiation. Mesostructural and microstructural properties of the layers were discussed with regard to the porosity and mechanical properties. The electrical and gas permeation measurements were also discussed in the framework of their possible applications as ULK materials and gas separation membranes, respectively. Using PECVD, styrene-based polymers, have been synthesized and also characterized in terms of mechanical and gas separation properties.