An investigation was carried out on a three stage method (extrusion/annealing/uniaxial-stretching) (MEAUS) utilized to produce semicrystalline polymeric microporous membranes. The two semicrystalline polymers studied were selected based on a set-of-prerequisites proposed for the formation of highly porous membranes via the method in question. The prerequisites included "fast" crystallization kinetics, presence of an ac relaxation, ability to form a planar stacked lamellar morphology with a "good" crystalline orientation upon melt-extrusion, and rapid heat transfer of the film during extrusion. The first polymer was isotactic poly(4-methyl-1-pentene) (PMP), and the second was polyoxymethylene (POM). Three PMP resins were studied, which differed in weight average molecular weight. Three POM resins were also investigated where two of resins were characterized by relatively narrow molecular weight distributions (MWD) ca 2 while the third POM resin possessed a MWD ca 5.9. The melt-extruded film morphologies and orientation values were a consequence of the melt-relaxation times as a result of the resin characteristics and/or the melt-extrusion conditions. Following the extrusion stage, the effect of annealing (second stage) on film properties was investigated. The annealing variables investigated included the temperature, time, and level of extension applied during annealing. The annealed films were then subjected to the uniaxially stretching stage (third stage) consisting of a cold and hot step, respectively, where deformation was along the extrusion direction. The variables of interest included the cold and hot stretch temperature and extension level. It was found that starting precursor morphology and orientation, annealing conditions, and stretching variables impact the final film microporous morphology and permeability. Additionally, the proposed prerequisites were verified in both the PMP and POM film series. In addition to the MEAUS study, a comprehensive investigation was conducted of the optical properties of blown and cast films made from conventional Ziegler-Natta catalyzed linear low density polyethylene (LLDPE) as well as metallocene-catalyzed LLDPE resins. From this work, it was determined that in PE blown and cast films made using conventional processing conditions, the optical haze properties are adversely affected due to enhanced surface roughness caused by the formation of spherulitic-like superstructures in polymer melts that possess fast relaxing and low melt elasticity rheological characteristics. This optical property study was also published in J. Appl. Polym. Sci., 77(13), 2845, (2000). / Ph. D.

O presente trabalho teve como finalidade estudar os efeitos das variações do vento resultantes de ocorrências do fenômeno El Niño-Southern Oscillation (ENSO) nos padrões da circulação superficial ao longo da costa peruana, através da análise de dados observados e de modelagem numérica. É enfocado o período 1991-2000, quando ocorreram fortes eventos La Niña (1996-97, 1998-2000) e El Niño (1997- 98). Esses eventos tiveram fortes impactos em escala global mas muito pouco se sabe sobre os impactos locais na estrutura da termoclina e no ciclo da dinâmica de Ekman ao longo da costa peruana. Os dados analisados no presente estudo foram dados coletados em duas radiais ao longo das latitudes 5 S e 15 S. O modelo oceânico utilizado foi o Modelo da Universidade de Princeton (Princeton Ocean Model-POM). As simulações numéricas foram forçadas com produtos de vento relativos ao período 1991-2000. Essas simulações reproduziram satisfatoriamente os padrões médios da circulação na região de estudo, confirmando que nas áreas próximas da costa o vento é o principal mecanismo gerador de ressurgência ou subsidência. Os resultados mostraram que durante a ocorrência do forte evento El Niño 1997-1998, nas radiais de 5 S e 15 S, houve uma drástica alteração do sistema de ressurgência costeira em resposta às variações do vento. / The objective of the present work was to study the effects of variability in the wind due to the El Niño-Southern Oscillation events in the surface circulation patterns of the Peruvian coast, by means of data analysis and numerical modeling. It is focused the period 1991-2000, when it was observed strong La Niña (1996-1997, 1998-2000) and El Niño events (1997-98). These events had strong effects worlwide but very little is known on the local impacts on the circulation, thermocline structure and the Ekman dynamics of the Peruvian coast. The data analysed in the present study were collected on transects along 5 S and 15 S. The model used was an implementation of the Princeton Ocean Model (POM). The numerical simulations were forced with wind products relative to the period of interest (1991-2000). The simulations reproduced satisfactorily the mean circulation patterns in the study area, confirming that the in the nearshore region the wind is the main driving mechanism for coastal upwelling/downwelling. The results show that during the strong 1997-1998 El Niño, a drastic alteration of the coastal upwelling system ocurred in response to the changes in the wind.

Ziele dieser Dissertation sind die Aufklärung der Strömungsverhältnisse und Untersuchungen zum Verhalten von Arzneimittelrückständen im Tegeler See, die Entwicklung eines Simulationsmodells für Szenarioberechnungen sowie die Ableitung neuer Bewirtschaftungskonzepte unter Zuhilfenahme der gewonnenen Erkenntnisse und Modellergebnisse. Das zweidimensionale Strömungsmodell 2D-POM kann die Mischungsverhältnisse der beiden Zuflüsse zum Tegeler See, insbesondere den Einstrom der Oberhavel, ausreichend genau abbilden. Der Oberhaveleinstrom ist sowohl windinduziert als auch vom Abfluss der Oberhavel abhängig. Der Wind wirkt je nach Windrichtung verstärkend oder abschwächend auf den Oberhaveleinstrom. Der Tegeler See weist im Vergleich zu anderen Oberflächengewässern, die als Trinkwasserressource dienen, die höchsten bisher berichteten Gehalte an Arzneimittelrückständen auf. Die räumliche Verteilung von Carbamazepin (CBZ) und Sulfamethoxazol (SMX) wird hauptsächlich durch die Verdünnung mit Oberhavelwasser bestimmt. Nur ein geringer Teil des CBZ (40%) wird im Tegeler See eliminiert. Für SMX konnte keine Elimination festgestellt werden. Im Gegensatz dazu wird Diclofenac (DCF) im Oberflächenwasser photolytisch abgebaut (50% in den Wintermonaten, mehr als 95% im Sommer). Die Konzentrationen von DCF im Tegeler See zeigen deshalb eine hohe saisonale Variabilität. Durch Simulation von sieben Bewirtschaftungsszenarien wurde untersucht, ob mithilfe der existierenden Seeleitung und Phosphateliminierungsanlage die Konzentrationen der Arzneimittelrückstände im Tegeler See verringert werden können, ohne die erfolgreiche Seerestaurierung zu gefährden. In keinem Szenario konnten die Gehalte an Arzneimittelrückständen und Phosphor gleichzeitig auf einem akzeptablen Niveau gehalten werden. Aus diesem Grund sind ergänzende Maßnahmen notwendig, z.B. eine zusätzliche Spurenstoffentfernung im Zulauf des Sees oder eine weitere Phosphorreduzierung in der Oberhavel. / This cumulative thesis aims at (i) understanding the hydrodynamic characteristics of Lake Tegel, (ii) examining the occurrence and fate of pharmaceutical micro-pollutants in the lake, (iii) developing a modeling tool for scenario prediction, and (iv) utilizing the above findings and applying the above modeling tool to create new management strategies for Lake Tegel. The free-surface two-dimensional circulation model 2D-POM serves as an adequate tool for representing the intrusion of River Havel and the mixing intensity of both inflows, as validated by measured data. The calculations indicated that the intrusion of River Havel into Lake Tegel fluctuates with river discharge and wind, both of which can amplify or neutralize the other. Compared to other surface waters also used as drinking water resources, Lake Tegel seams to feature the highest ever reported pharmaceutical concentrations worldwide. The spatial distribution of carbamazepine (CBZ) and sulfamethoxazole (SMX) in the lake was shown to be primarily affected by dilution with water from River Havel rather than by degradation within the lake. By contrast, concentrations of diclofenac (DCL) are affected by both dilution and photodegradation. DCF showed the strongest elimination of all three pharmaceuticals and revealed significant seasonality with 50% elimination in winter and more than 95% in summer. Elimination of CBZ was 40%, while SMX did not degrade at determinable rates. Seven different management scenarios were tested to answer the question of whether the existing lake pipeline could be used to reduce the amount of pharmaceuticals in Lake Tegel without deteriorating the current phosphorus level. No scenario provided a strategy optimal for both pharmaceuticals and phosphorus. Consequently, additional efforts need to be made, such as supplementary pharmaceutical treatment of the inflow originating from the wastewater treatment plant, or phosphorus reduction in the River Havel catchment.

O presente trabalho teve como finalidade estudar os efeitos das variações do vento resultantes de ocorrências do fenômeno El Niño-Southern Oscillation (ENSO) nos padrões da circulação superficial ao longo da costa peruana, através da análise de dados observados e de modelagem numérica. É enfocado o período 1991-2000, quando ocorreram fortes eventos La Niña (1996-97, 1998-2000) e El Niño (1997- 98). Esses eventos tiveram fortes impactos em escala global mas muito pouco se sabe sobre os impactos locais na estrutura da termoclina e no ciclo da dinâmica de Ekman ao longo da costa peruana. Os dados analisados no presente estudo foram dados coletados em duas radiais ao longo das latitudes 5 S e 15 S. O modelo oceânico utilizado foi o Modelo da Universidade de Princeton (Princeton Ocean Model-POM). As simulações numéricas foram forçadas com produtos de vento relativos ao período 1991-2000. Essas simulações reproduziram satisfatoriamente os padrões médios da circulação na região de estudo, confirmando que nas áreas próximas da costa o vento é o principal mecanismo gerador de ressurgência ou subsidência. Os resultados mostraram que durante a ocorrência do forte evento El Niño 1997-1998, nas radiais de 5 S e 15 S, houve uma drástica alteração do sistema de ressurgência costeira em resposta às variações do vento. / The objective of the present work was to study the effects of variability in the wind due to the El Niño-Southern Oscillation events in the surface circulation patterns of the Peruvian coast, by means of data analysis and numerical modeling. It is focused the period 1991-2000, when it was observed strong La Niña (1996-1997, 1998-2000) and El Niño events (1997-98). These events had strong effects worlwide but very little is known on the local impacts on the circulation, thermocline structure and the Ekman dynamics of the Peruvian coast. The data analysed in the present study were collected on transects along 5 S and 15 S. The model used was an implementation of the Princeton Ocean Model (POM). The numerical simulations were forced with wind products relative to the period of interest (1991-2000). The simulations reproduced satisfactorily the mean circulation patterns in the study area, confirming that the in the nearshore region the wind is the main driving mechanism for coastal upwelling/downwelling. The results show that during the strong 1997-1998 El Niño, a drastic alteration of the coastal upwelling system ocurred in response to the changes in the wind.

O presente trabalho tem como objetivo estudar o efeito da carga normal aplicada, da velocidade de deslizamento, do acabamento superficial e do tipo de contra-corpo, na degradação dos materiais poliméricos POM e UHMWPE, resultante do contato deslizante contra corpos rígidos. Para tanto, foram realizados ensaios de desgaste em um tribômetro do tipo pino-contra-disco, com os pinos de materiais poliméricos e os discos de alumina e aço inoxidável. Nos ensaios de desgaste, utilizou-se 3 valores de carga, 3 velocidades de deslizamento e 3 níveis de acabamento superficial do contra-corpo. Para cada condição de ensaio, foram realizadas 3 repetições. Durante os ensaios, foram monitoradas a temperatura na interface dos materiais, a força de atrito e a posição vertical do pino. O deslocamento vertical do pino devido ao desgaste foi utilizado para a determinação da taxa de desgaste do polímero. A distância percorrida pelos pinos sobre o disco foi de 3.500 metros. Os ensaios foram realizados em ambiente com umidade relativa controlada em 50 ± 5 %. As análises por microscopia eletrônica de varredura das superfícies de desgaste dos pinos e dos discos indicaram a ocorrência de três tipos de mecanismos de desgaste: a abrasão, a fadiga e a transferência de filme (adesão). Para analisar o comportamento do desgaste mediante as influências estudadas, um parâmetro de severidade global (PVR/DD) é proposto. No parâmetro PVR/DD, considerou-se a relação entre um fator mecânico (condição de pressão e velocidade, PV), um fator topográfico (rugosidade do contra-corpo, R) e um fator térmico (difusividade térmica dos materiais em contato, DD). Verificou-se que os níveis de desgaste dos materiais poliméricos são influenciados pela condição de severidade global do contato; entretanto, o efeito preponderante foi devido ao tipo de material do contracorpo. Como foi observado que o deslocamento vertical ocorre devido não somente ao desgaste, mas também à fluência do polímero, à atuação de diferentes mecanismos de desgaste e ao fenômeno da fusão, os resultados de cada material de polímero estudado foram organizados na forma de mapas em função da severidade global, salientando as regiões de atuação de cada fenômeno. / The present investigation aims to study the degradation of polymeric materials resulting from the sliding contact against rigid bodies. The effect of some tribological influences, such as the applied load, the sliding velocity, the surface roughness and the counter-face material, were investigated. Experimental sliding wear tests were performed through a pin-on-disc tribometer, with the pins of polymeric material and the discs of alumina and stainless steel. The testing conditions of the wear tests encompassed three values of load (normal pressure) and three values of sliding velocity, or PV values, and three ranges of disc surface roughness. Three tests were performed in each condition. The interface temperature between the specimens, the friction force and the vertical position of the pin were monitored along the tests. The vertical displacement of the pin, resulting from the wear, was used for the determination of the polymer wear rate. The total sliding distance was of 3,500 meters. During the tests, the relative humidity of the environment was controlled to 50 ± 5 %. Analyses on the worn surfaces of pins and discs performed through scanning electronic microscopy indicated the occurrence of three wear mechanisms: abrasion (scratches), fatigue (waves) and adhesion (transfer film). In order to analyze the wear behavior of the polymer, a parameter of global severity of the contact (PVR/DD) was proposed. This parameter comprised a mechanical factor (the PV values), a topographic factor (the disc roughness) and a thermal factor (the thermal diffusivity of the materials in contact). It was possible to verify that the polymer wear depended on the level of global severity of the contact, where the major effect was due to the counterface material. It was also observed that the vertical displacement of the pin occurred not only due to the wear phenomena, but also due to the creep and the melting of the polymer, both depending on the testing condition. The creep and the melting phenomena were considered in the polymer degradation behavior, organizing the results of polymeric pin displacement in degradation maps, showing the boundaries of each observed phenomena, in function of the contact global severity.

Este trabalho tem como meta investigar a relação entre o fluxo vertical de matéria orgânica particulada (MOP) e a biomassa de foraminíferos bentônicos vivos na região do talude da Bacia de Campos/RJ (400 a 3000m). O fluxo vertical de MOP para o assoalho oceânico foi inferido através de modelos que utilizam dados de sensoriamento remoto, como estimativas da concentração de clorofila a, valores de temperatura da superfície do mar e produtos derivados destes (i.e. produção primária e determinação de classes de tamanho do fitoplâncton), enquanto que a biomassa de foraminíferos bentônicos foi estimada através da técnica de biovolume. Os resultados indicam que as estimativas de fluxo se correlacionaram com os conteúdos de carbono orgânico total (COT) no sedimento, com a biomassa total de 19 espécies de foraminíferos bentônicos e com a biomassa, sendo que a distribuição de biomassa dessas espécies evidencia além da quantidade de MOP, a qualidade da MOP (labilidade). A distribuição dos valores de fluxo vertical e biomassa total de foraminíferos bentônicos estão atreladas às feições de mesoescala (meandros e vórtices de Cabo Frio e Cabo de São Tomé), que propiciam o aumento de produtividade primária e o crescimento do microplâncton, aumentando o fluxo vertical e consequentemente o suplemento alimentar para os foraminíferos bentônicos, estimulando o aumento de biomassa destes. / This study aims to investigate the relationship between the particulate organic matter (POM) vertical flux and living benthic foraminifera biomass in the slope of Campos Basin region (between 400 and 3000). The POM vertical flux to the seafloor was inferred through models using remote sensing data, such as estimates of chlorophyll a concentration, sea surface temperature and derivatives of these (i.e. primary production and determination of classes phytoplankton size), whereas the biomass of benthic foraminifera was estimated using the biovolume technique . The fluxes estimates were correlated with total organic carbon (TOC) contents in the sediments, with benthic foraminifera total biomass and with 19 species biomass. The spatial distribution of these species biomass reveals both POM quantity and quality (i.e. lability). The distribution of the values of POM vertical flux and foraminifera total biomass are linked to mesoscale features (eddies and meanders in Cape Frio and Cape São Tomé), which provide increased primary productivity and microplankton growth increasing the POM vertical flux and consequently the food supplement for benthic foraminifera community, stimulating biomass increase.

Este trabalho tem como meta investigar a relação entre o fluxo vertical de matéria orgânica particulada (MOP) e a biomassa de foraminíferos bentônicos vivos na região do talude da Bacia de Campos/RJ (400 a 3000m). O fluxo vertical de MOP para o assoalho oceânico foi inferido através de modelos que utilizam dados de sensoriamento remoto, como estimativas da concentração de clorofila a, valores de temperatura da superfície do mar e produtos derivados destes (i.e. produção primária e determinação de classes de tamanho do fitoplâncton), enquanto que a biomassa de foraminíferos bentônicos foi estimada através da técnica de biovolume. Os resultados indicam que as estimativas de fluxo se correlacionaram com os conteúdos de carbono orgânico total (COT) no sedimento, com a biomassa total de 19 espécies de foraminíferos bentônicos e com a biomassa, sendo que a distribuição de biomassa dessas espécies evidencia além da quantidade de MOP, a qualidade da MOP (labilidade). A distribuição dos valores de fluxo vertical e biomassa total de foraminíferos bentônicos estão atreladas às feições de mesoescala (meandros e vórtices de Cabo Frio e Cabo de São Tomé), que propiciam o aumento de produtividade primária e o crescimento do microplâncton, aumentando o fluxo vertical e consequentemente o suplemento alimentar para os foraminíferos bentônicos, estimulando o aumento de biomassa destes. / This study aims to investigate the relationship between the particulate organic matter (POM) vertical flux and living benthic foraminifera biomass in the slope of Campos Basin region (between 400 and 3000). The POM vertical flux to the seafloor was inferred through models using remote sensing data, such as estimates of chlorophyll a concentration, sea surface temperature and derivatives of these (i.e. primary production and determination of classes phytoplankton size), whereas the biomass of benthic foraminifera was estimated using the biovolume technique . The fluxes estimates were correlated with total organic carbon (TOC) contents in the sediments, with benthic foraminifera total biomass and with 19 species biomass. The spatial distribution of these species biomass reveals both POM quantity and quality (i.e. lability). The distribution of the values of POM vertical flux and foraminifera total biomass are linked to mesoscale features (eddies and meanders in Cape Frio and Cape São Tomé), which provide increased primary productivity and microplankton growth increasing the POM vertical flux and consequently the food supplement for benthic foraminifera community, stimulating biomass increase.

O presente trabalho tem como objetivo estudar o efeito da carga normal aplicada, da velocidade de deslizamento, do acabamento superficial e do tipo de contra-corpo, na degradação dos materiais poliméricos POM e UHMWPE, resultante do contato deslizante contra corpos rígidos. Para tanto, foram realizados ensaios de desgaste em um tribômetro do tipo pino-contra-disco, com os pinos de materiais poliméricos e os discos de alumina e aço inoxidável. Nos ensaios de desgaste, utilizou-se 3 valores de carga, 3 velocidades de deslizamento e 3 níveis de acabamento superficial do contra-corpo. Para cada condição de ensaio, foram realizadas 3 repetições. Durante os ensaios, foram monitoradas a temperatura na interface dos materiais, a força de atrito e a posição vertical do pino. O deslocamento vertical do pino devido ao desgaste foi utilizado para a determinação da taxa de desgaste do polímero. A distância percorrida pelos pinos sobre o disco foi de 3.500 metros. Os ensaios foram realizados em ambiente com umidade relativa controlada em 50 ± 5 %. As análises por microscopia eletrônica de varredura das superfícies de desgaste dos pinos e dos discos indicaram a ocorrência de três tipos de mecanismos de desgaste: a abrasão, a fadiga e a transferência de filme (adesão). Para analisar o comportamento do desgaste mediante as influências estudadas, um parâmetro de severidade global (PVR/DD) é proposto. No parâmetro PVR/DD, considerou-se a relação entre um fator mecânico (condição de pressão e velocidade, PV), um fator topográfico (rugosidade do contra-corpo, R) e um fator térmico (difusividade térmica dos materiais em contato, DD). Verificou-se que os níveis de desgaste dos materiais poliméricos são influenciados pela condição de severidade global do contato; entretanto, o efeito preponderante foi devido ao tipo de material do contracorpo. Como foi observado que o deslocamento vertical ocorre devido não somente ao desgaste, mas também à fluência do polímero, à atuação de diferentes mecanismos de desgaste e ao fenômeno da fusão, os resultados de cada material de polímero estudado foram organizados na forma de mapas em função da severidade global, salientando as regiões de atuação de cada fenômeno. / The present investigation aims to study the degradation of polymeric materials resulting from the sliding contact against rigid bodies. The effect of some tribological influences, such as the applied load, the sliding velocity, the surface roughness and the counter-face material, were investigated. Experimental sliding wear tests were performed through a pin-on-disc tribometer, with the pins of polymeric material and the discs of alumina and stainless steel. The testing conditions of the wear tests encompassed three values of load (normal pressure) and three values of sliding velocity, or PV values, and three ranges of disc surface roughness. Three tests were performed in each condition. The interface temperature between the specimens, the friction force and the vertical position of the pin were monitored along the tests. The vertical displacement of the pin, resulting from the wear, was used for the determination of the polymer wear rate. The total sliding distance was of 3,500 meters. During the tests, the relative humidity of the environment was controlled to 50 ± 5 %. Analyses on the worn surfaces of pins and discs performed through scanning electronic microscopy indicated the occurrence of three wear mechanisms: abrasion (scratches), fatigue (waves) and adhesion (transfer film). In order to analyze the wear behavior of the polymer, a parameter of global severity of the contact (PVR/DD) was proposed. This parameter comprised a mechanical factor (the PV values), a topographic factor (the disc roughness) and a thermal factor (the thermal diffusivity of the materials in contact). It was possible to verify that the polymer wear depended on the level of global severity of the contact, where the major effect was due to the counterface material. It was also observed that the vertical displacement of the pin occurred not only due to the wear phenomena, but also due to the creep and the melting of the polymer, both depending on the testing condition. The creep and the melting phenomena were considered in the polymer degradation behavior, organizing the results of polymeric pin displacement in degradation maps, showing the boundaries of each observed phenomena, in function of the contact global severity.

Les polyoxométallates (POMs) de type Keggin [XM12O40]n- (avec X=P… et M= W, Mo …) sont des oxydes moléculaires de métaux de transition à haut degré d’oxydation qui présentent des réductions successives et réversibles dans une gamme étroite de potentiel. Leur incorporation dans des dispositifs de mémoire moléculaire semble alors prometteuse. Nous avons développé leur intégration comme briques élémentaires via une approche “bottom-up” qui surmonte les limites de l’approche “top-down” plus commune. Cela nécessite un contrôle fin de leur greffage et de leur densité surfacique pour l’obtention de dispositifs performants. Nous avons donc développé le greffage covalent de POMs sur des surfaces à base de silicium et d’or. Des hybrides de POMs à terminaison diazonium BA3[PM11O39{SnC6H4C≡CC6H4N2}] (avec M=W or Mo) ont formé des monocouches complètes greffées sur des surfaces de silicium hydrogénées qui mettent en évidence l’influence du métal constitutif du fragment polyoxométallate sur les propriétés de transport de charges de la jonction. Le greffage d’hybrides de POM à terminaison acide carboxylique sur des substrats d’oxyde de silicium a aussi été développée. Un hybride de POM à terminaison aniline TBA4[PW11O39{SnC6H4C≡CC6H4NH2}] a été greffé en deux étapes via un couplage peptidique sur une monocouche à terminaison acide carboxylique sur surface d’or. Des monocouches compactes ont été obtenues mais pas de façon totalement reproductible et les premiers essais de dilution sont encourageants. Une nouvelle famille d’hybrides de POMs mixtes a été synthétisée : TBA4[PMoxW11-xO39{SnR}]. Cela permettra de combiner les propriétés redox du molybdène et la robustesse due au tungstène. / Keggin type polyoxometalates (POMs) [XM12O40]n- (with X=P… and M= W, Mo…) are molecular oxides of early transition metals with a high oxidation state. They present electrochemical successive reversible reduction waves in a narrow range of potential. This makes them good candidates to be incorporated into molecular memory devices. We chose a “bottom-up” approach where the POMs are the building blocks to overcome the limitation of the “top-down” process commonly used. A fine control of the POM grafting and of the surface density is essential to get better erase/writing time of the device. So, we developed POM hybrids for grafting them covalently onto silicon based and gold substrates. Diazonium-terminated POM hybrids (with M=W or Mo) lead to compact homogeneous monolayers onto hydrogenated silicon surfaces. Electrical measurements of the two analogous modified surfaces show different behaviour highlighting the role of the constituting POM metal into the charge transport. Carboxylic-terminated POM hybrids have also been grafted in a one-step process onto silicon oxide surface resulting in a smooth and dense monolayer. Then, an aniline-terminated POM hybrid has been grafted onto a carboxylic-terminated SAM of thiols onto gold thanks to a peptide coupling. Compact monolayers have been obtained without complete reproducibility and the first attempts of dilution are encouraging. A new family of POM hybrids have been synthesized: mixed-metal POM hybrids TBA4[PMoxW11-xO39{SnR}]. This will permit to combine the electrochemical properties of molybdenum and the robustness of tungsten.

Ce travail de thèse est une étude expérimentale et théorique de la contribution de la composante organique réfractaire des comètes à leur phase gazeuse.<br /> Certaines espèces gazeuses observées dans la coma, telles que le formaldéhyde (H2CO) et les radicaux cyanogènes (CN), ne sont pas produites uniquement par la sublimation du noyau ou par la photodissociation d'autres molécules gazeuses. Elles pourraient provenir de la dégradation de la composante organique réfractaire présente dans les grains cométaires.<br /> L'objectif de cette thèse est de tester cette hypothèse. Dans un premier temps, les rendements quantiques et les paramètres cinétiques de production d'espèces gazeuses par irradiation dans l'UV lointain et dégradation thermique de composés organiques solides sont déterminés expérimentalement. Dans un deuxième temps, un modèle physico-chimique de la coma, prenant en compte ces processus de dégradation, a été développé.<br /> Les polymères de HCN et l'hexaméthylènetétramine (ou HMT, C6H12N4) ayant été proposés afin d'expliquer l'origine des radicaux cyanogènes, j'ai irradié et chauffé ces composés solides dans des conditions représentatives de l'environnement cométaire. Je montre ainsi que l'hexaméthylènetétramine est particulièrement stable par irradiation dans l'UV lointain et que ce composé ne se dégrade pas mais se sublime lorsqu'il est chauffé sous vide. Le HMT ne semble donc pas être un bon candidat pour une source de radicaux CN dans l'environnement cométaire. Je me suis ensuite concentré sur l'étude de la dégradation des polymères de HCN. J'ai mis en évidence, par spectroscopie infrarouge à transformée de Fourier (IRTF), la production de HCN, CO, CH4 et C2H2 par irradiation à 122 et 147 nm de ces polymères et celles de NH3, HCN, HNCO et CO par chauffage entre 430 et 580 K. La vitesse de production de l'ensemble de ces espèces gazeuses a été quantifiée grâce à l'analyse de l'évolution temporelle des spectres infrarouge. D'autre part, la mesure par spectroscopie de fluorescence induite par laser (LIF) n'a pas permis d'atteindre la limite de détection nécessaire pour détecter le radical CN à partir de la dégradation des polymères de HCN. J'ai donc modélisé la production des radicaux CN dans la coma en supposant que leur production est égale à celle mesurée pour l'acide cyanhydrique (HCN). Bien que la densité de colonne des radicaux CN ne puisse pas être fidèlement reproduite en prenant en compte la dégradation des polymères de HCN, cette hypothèse ne peut pas être infirmée. Sa confirmation nécessite des études expérimentales supplémentaires. <br /> En parallèle à ce travail sur la production des radicaux CN, j'ai poursuivi une étude précédemment menée au laboratoire afin d'expliquer la production de H2CO dans C/1995 O1 (Hale-Bopp). Dans cette comète, les taux de production de H2CO présentent une évolution héliocentrique plus rapide que celle d'autres composés gazeux similaires, tels que HCN ou H2S. J'ai tout d'abord obtenu de nouvelles données expérimentales concernant la dégradation thermique du polyoxyméthylène (polymère de H2CO, -(CH2-O)n-) dans une large gamme de température et pour deux types de polymères. Ceci me permet alors de reproduire les mesures des taux de production de H2CO dans cette comète et de montrer que l'évolution héliocentrique peut être expliquée par la prédominance de la production de H2CO par dégradation thermique du POM jusqu'à des distances de 3,5 UA. Ce travail confirme donc que la dégradation du POM permet d'expliquer l'origine du H2CO et que, quelle que soit la distance héliocentrique, la contribution de la phase organique réfractaire à la phase gazeuse des comètes doit être prise en compte.