Sulfur dioxide (SO2) is a gas typical of high temperature magmatic degassing, being its<p>third most abundant constituent after water vapor and carbon dioxide. SO2 flux measurements<p>are used to characterized and monitor volcanic degassing. This thesis presents advanced<p>methods for measuring the SO2 emitted in the troposphere by passive degassing volcanoes.<p>These methods are based on the absorption of infrared (IR) and ultraviolet (UV) light by SO2<p>molecules. They make use of the data acquired by satellite borne sensors (ASTER, OMI and<p>MODIS), and collected in the field using a UV camera equipped with filters<p>ASTER is a multispectral sensor observing the Earth in the thermal IR with a 90 m<p>ground resolution. The developed retrieval algorithm works with band ratios<p>(B10+B12)/2B11 and B14/B11, to avoid spectral interference from other variables than SO2.<p>With this algorithm, the impact of interferers such as atmospheric water vapor, sulfate<p>aerosols and ground emissivity is minimal, as demonstrated by radiative transfer simulations<p>by applying of the algorithm to real ASTER images and by comparing the results with ground<p>based data. ASTER is a kind of unifying thread for this thesis because its high ground<p>resolution fills the gap existing between highly localized ground based SO2 measurements and<p>the global coverage of other satellites with coarser pixels such as OMI and MODIS.<p>OMI is an imaging spectrometer operating in the UV, with a daily global coverage, a<p>high sensitivity to SO2 and a ground resolution of 13x24km. The OMI-ASTER comparison<p>shows that the SO2 columns measured on OMI pixels are two orders of magnitude smaller<p>than those of ASTER, because of the huge difference in the pixel size of the two satellites.<p>The flux measurements however are generally in good agreement. The analysis of a large<p>number of images shows that ASTER is better for cloud free scenes while OMI has an<p>optimal signal to noise ratio when the plume is lying above a low cloud cover. A practical<p>detection limit for SO2 flux measurements in tropospheric plumes has also been established:<p>5kg/s.<p>The comparison between ASTER measurements of SO2 column amounts with those of<p>MODIS (a multispectral IR imager with 1km ground resolution) shed light on systematic<p>errors in MODIS measurements. These errors were quantified and their origins were separated<p>and identified. This work demonstrates the limitations of MODIS for SO2 measurements.<p>A UV camera equipped with filters has also been developed to achieve 2D SO2 from the<p>ground at a high spatial and temporal resolution. The potential provided by this new type of<p>instruments has been demonstrated during a field campaign on Turrialba Volcano (Costa<p>Rica). The integration of measurements obtained using the camera, ASTER and OMI revealed<p>a high and sustained SO2 flux, which can be explained only by the degassing of a recently<p>intruded magma body. The slow decrease of SO2 flux since January 2010 suggests a<p>progressive exhaustion of the volatile content of the magma.<p>Finally, we applied the band ratio algorithm to a series of ASTER images of the recent<p>eruption of Eyjafjallajökull in April-May 2010. The SO2 measurements provide interesting<p>insights into the complex eruptive dynamics and into the control of hydromagmatic<p>interactions on eruptive gas release into the atmosphere. /<p><p>Le dioxyde de soufre (SO2) est un gaz typique du dégazage magmatique de haute<p>température, dont il est le troisième composant le plus abondant derrière H2O et CO2. Le flux<p>de SO2 est un excellent paramètre pour caractériser le dégazage volcanique et surveiller son<p>évolution dans le temps. Cette thèse présente de nouvelles méthodes de mesures des flux de<p>SO2 émis par l’activité volcanique. Ces méthodes se basent sur l’absorption de la molécule de<p>SO2 dans l’infrarouge (IR) et l’ultraviolet (UV). Elles utilisent les données prises par des<p>senseurs embarqués sur des satellites (ASTER, OMI et MODIS) ou opérés depuis le sol<p>(caméra UV munie de filtres).<p>Le senseur ASTER opère dans l’IR thermique avec une résolution spatiale de 90 m par<p>pixel. L’algorithme de mesure développé pour ce satellite n’est sensible qu’à la concentration<p>en SO2 et pratiquement pas aux paramètres interférents qui posaient problèmes aux méthodes<p>existantes :la vapeur d’eau atmosphérique, les aérosols de sulfate dans le panache et<p>l’émissivité de la surface sous-jacente. ASTER est un peu le fil conducteur de cette thèse, car<p>sa haute résolution spatiale lui permet de faire le lien entre des mesures au sol et les mesures<p>faites par d’autres satellites comme OMI et MODIS.<p>Le satellite OMI est un spectromètre imageant qui opère dans l’UV, avec une<p>couverture globale journalière, une haute sensitivité au SO2 et une résolution spatiale de<p>13x24km. La comparaison OMI-ASTER montre que les colonnes mesurées sur les pixels<p>d’OMI sont de deux ordres de grandeur inférieurs à celles d’ASTER, à cause de la différence<p>de résolution spatiale entre les deux satellites. Les mesures de flux, par contre, montrent une<p>très bonne concordance. L’analyse d’un grand nombre d’images a permis d’établir qu’ASTER<p>est meilleur pour des scènes sans nuages tandis qu’OMI est meilleur quand une couverture<p>nuageuse présente sous le panache augmente son rapport signal sur bruit. Une limite de<p>détection pratique a aussi été établie pour les flux de SO2 dans les panaches volcaniques dans<p>la basse troposphère :5kg/s.<p>La comparaison des mesures d’ASTER avec celle de MODIS a permis de démontrer les<p>limites de MODIS pour la mesure du SO2. Des erreurs systématiques sur les mesures de<p>MODIS on été mises en évidence et quantifiées. Ces erreurs sont dues aux interférents<p>spectraux que sont la vapeur d’eau atmosphérique et les aérosols sulfatés. L’émissivité est<p>aussi un important facteur d’erreur pour MODIS.<p>Une caméra UV équipée d’un système de filtres a également été développée pour<p>mesurer le SO2 en 2D, à haute résolution spatiale et temporelle. Le potentiel offert par ce<p>nouveau type d’instrument a été démontré lors d’une campagne de mesures sur le volcan<p>Turrialba (Costa Rica). La combinaison de mesures de SO2 réalisée avec la caméra, ASTER<p>et OMI a permis de mettre en évidence des flux très élevés (30-50kg/s) qui ne peuvent<p>s’expliquer que par une intrusion récente de magma juvénile en cours de dégazage.<p>Enfin, les mesures de SO2 ont réalisées à partir des images ASTER pendant l’éruption<p>du volcan Eyjafjallajökull en avril-mai 2010. Ces mesures fournissent des informations<p>intéressantes sur les dynamismes éruptifs qui se sont succédé et sur le contrôle des émissions<p>de SO2 dans l’atmosphère par les interactions magma-eau. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Polyethylene (PE) resins being non-polar in nature and having a high degree of crystallinity have limited miscibility and compatibility when blended with polar polymers. The miscibility and compatibility of these blends are generally worsened when they are prepared by direct injection moulding without a precompounding process. Such situations are commonly encountered in particular by polymer converters when blending colour and/or additive concentrates, commonly known as masterbatches. Typically, masterbatches are mixtures containing high loading of pigments and/or additives predispersed in a suitable solid vehicle (commonly known as carrier) such as a polyethylene resin. These masterbatches are usually used for the colouration of a wide range of polymers and the carrier used must therefore be compatible with these matrix (host) polymers. The preliminary stage of this study involved the investigation of the properties of blends based on high density polyethylene (HDPE) and a range of engineering thermoplastics (ABS, PC, PBT, PA6), prepared by injection moulding. Five different types of compatibilisers namely, ethylene-vinyl acetate (EVA) copolymer, ethylene-methyl acrylate (EMA) copolymer, ethylene-glycidyl methacrylate (E-GMA) copolymer, ethylene-methyl acrylateglycidyl methacrylate (E-MA-GMA) terpolymer and maleic anhydride grafted HDPE (HDPE-g-MAH) copolymer were evaluated with respect to their efficiencies in compatibilising HDPE with the four engineering polymers. The pre-compounded HDPE/compatibiliser binary blends at 2 different blend ratios (1:1 and 3:1) were added at 15 wt% concentration to each engineering thermoplastics and test samples were produced directly by injection moulding. Results of mechanical testing and characterisation of the blends showed that glycidyl methacrylate compatibilisers, E-MA-GMA, in particular have the most universal compatibilising effectiveness for a range of engineering thermoplastics including ABS, PC, PBT, and PA6. Blends compatibilised with E-MA-GMA compatibiliser had the best notched impact performance irrespective of matrix polymer type. The presence of an acrylic ester (methyl acrylate) comonomer in E-MA-GMA resulted in increased polarity of the ii compatibiliser leading to improved miscibility with the polar matrix polymers demonstrated by fine blend morphologies, melting point depression and reduction in crystallinity of the HDPE dispersed phase. The second stage of this study involved the reactive modification of HDPE using a low molecular weight di-functional solid diglycidyl ether of bisphenol A (DGEBA) type epoxy resin compatibilised with HDPE-g-MAH in an attempt to improve its compatibility with ABS, PBT and PA6. The maleic anhydride moieties in HDPE-g-MAH served as reactive sites for anchoring the epoxy moieties while the HDPE backbone was miscible with the HDPE resin. An excessive amount of reactive groups resulted in the formation of crosslinked gels while the addition of EVA co-compatibiliser helped in the reduction of gel content and further improved the dispersion of the epoxy. The effectiveness of epoxy grafted HDPE (with and without EVA co-compatibiliser) in compatibilising ABS/HDPE, PBT/HDPE, and PA6/HDPE was investigated by injection moulding of 5 wt% functionalised HDPE with these matrix polymers into test bars for mechanical testing, and characterisation by differential scanning calorimtery (DSC) and optical microscopy. The reactively functionalised HDPE blends, improved the mechanical properties of ABS and PA6 blends especially with EVA as co-compatibiliser. However, the mechanical properties of PBT blends were unmodified by the functionalised HDPE which was believed to be due to end-capping of the PBT chain-ends by ungrafted epoxy resins.

Biodegradabilné syntetické polyméry nesú vlastnosti, ktoré ich zvýhodňujú oproti iným materiálom používaným na poli regeneratívnej medicíny a tkanivového inžinierstva. Najdôležitejšie výhody zahŕňajú schopnosť prispôsobovať mechanické a chemické vlastnosti aj kinetiku degradácie. Obzvlášť polyestery sú zaujímavé z pohľadu na ich biodegradáciu. Podliehajú hydrolýze, počas ktorej dochádza k štiepeniu esterových väzieb a degradačné produkty sú metabolizované bez akýchkoľvek škodlivých účinkov. Diplomová práca je zameraná na syntetické biodegradabilné triblokové kopolyméry PLGA-PEG-PLGA s obsahom kyseliny polymliečnej (PLA), kyseliny polyglykolovej (PGA) a polyetylénglykolu (PEG), ktoré patria do skupiny biodegradabilných polyesterov. Obsah hydrofilnej a hydrofóbnej zložky polymérneho reťazca spôsobuje amfifilný charakter kopolyméru. Pripravené triblokové kopolyméry sú schopné tvoriť hydrogél pomocou fyzikálneho sieťovania v dôsledku ich amfifilného charakteru. Tieto materiály zaznamenali významný záujem vo vedeckej oblasti. Teoretická časť diplomovej práce všeobecne popisuje hydrogély, bližšie sa venuje fyzikálnemu sieťovaniu amfifilných blokových kopolymérov a mechanizmom degradácie. Podrobný popis triblokového kopolyméru PLGA-PEG-PLGA je rozdelený na PLGA kopolyméry, PEG a ich fyzikálno-chemické vlastnosti. Zahrnuté sú aj poznatky o chemickej funkcionalizácii anhydridom kyseliny jantárovej, anhydridom kyseliny itakonovej a kyselinou listovou. Dopamín je prezentovaný ako spájací faktor a spomenuté sú taktiež najdôležitejšie bioaktívne látky. Experimentálna časť sa zaoberá konkrétnymi metódami syntézy, ktoré viedli k funkcionalizácii a modifikácii triblokových kopolymérov PLGA-PEG-PLGA. Funkcionalizáciou anhydridom kyseliny itakonovej bol získaný kopolymér s oboma koncami obohatenými o reaktívne dvojité väzby a karboxylové funkčné skupiny. Dvojité väzby umožňujú chemické sieťovanie a koncové karboxylové skupiny ponúkajú možnosť modifikácie kopolyméru biologicky aktívnymi látkami. Modifikácia bioaktívnymi látkami L-lyzínom a butylamínom obohacuje polymérnu sieť a dopamín v roli spojovacieho faktoru poskytuje univerzálnosť v naväzovaní bioaktívnych látok, stabilizuje ich a zabezpečuje zachovanie biologickej aktivity naviazaných bioaktívnych látok predĺžením reťazca. Výsledné produkty boli charakterizované pomocou 1H NMR, FTIR a DRA analýz. Funkcionalizácia anhydridom kyseliny itakonovej bola prevádzaná v tavenine. Podarilo sa dosiahnuť vyššieho množstva naviazanej kyseliny itakovovej s hodnotou 79,4 mol % a následné modifikácie boli prevádzané vo vodnom roztoku, organickom roztoku a taktiež v tavenine. Bolo zistené, že najefektívnejšia metóda modifikácie bola syntéza v organickom roztoku s rozpúšťadlom N,N-dimetylformamidom a aktivačným systémom dicyklohexylkarbodiimid/4-(dimetylamino)pyridínom. Najvyššie množstvo naviazaného dopamínu bolo 18,6 mol %, najvyššie množstvo naviazaného butylamínu bolo 7,8 mol % a L-lyzín sa naviazať nepodarilo.

Předložená disertační práce shrnuje současné poznatky v oblasti termosenzitivních biodegradabilních kopolymerů, které ve formě vodného solu gelují při teplotě lidského těla. Tyto polymerní materiály jsou použitelné v medicíně pro injekční aplikace jako nosiče léčiv či resorbovatelné implantáty pro regeneraci tkání. V experimentální práci byly pomocí vakuové linky syntetizovány termosenzitivní amfifilní triblokové kopolymery na bázi biodegradabilního hydrofobního polylaktidu a polyglykolidu a biokompatibilního hydrofilního polyethylenglykolu (PLGA–PEG–PLGA). Připravený PLGA–PEG–PLGA kopolymer se dvěma fázovými přechody sol-gel a gel-suspenze byl následně modifikován anhydridem kyseliny itakonové. Výsledný funkcionalizovaný ITA/PLGA–PEG–PLGA/ITA kopolymer obsahuje na koncích řetězců reaktivní dvojné vazby vhodné k další polymeraci či síťování a karboxylové skupiny pro případné modifikace biologicky aktivními látkami. Fyzikální i chemické síťování bylo dále sledováno jak z hlediska poměrů hydrofilního a hydrofobního řetězce, tak i z hlediska množství navázané kyseliny itakonové. Vodné roztoky syntetizovaného ITA/PLGA–PEG–PLGA/ITA kopolymeru gelují v rozmezí teplot 33 - 43 °C. Kritická gelační koncentrace byla 6 % a kritická gelační teplota 34 °C pro kopolymer s poměrem PLGA/PEG = 2,5. Čím je kopolymer více hydrofobní, tím geluje dříve a je více hydrolyticky stabilní. Tuhost gelu stoupá se zvyšujícím se poměrem PLGA/PEG a je závislá na typu rozpouštědla použitého při přečišťování kopolymeru. Připravené ITA/PLGA–PEG–PLGA/ITA makomonomerů byly síťovány pomocí modrého světla bez dalšího síťovadla. Hydrolytická stabilita vzorků modifikovaných pomocí ITA se výrazně zlepšila a zvýšila v přímé úměře jak s rostoucí dobou síťování, tak s množstvím dvojných vazeb na koncích řetězců. Vzorek s 63 mol% ITA síťovaný 40 minut ve vodě zcela zdegradoval po 32 dnech. Protonovou NMR relaxometrií bylo zjištěno, že když vzorek ve vodě nabotnal (po cca 12 hodinách), množství nevázané vody se začalo snižovat a postupně difundovat do kavit na povrchu vzorku a pomalu se měnit na slabě a pevně vázanou vodu na polymerní řetězce. Nicméně, termální stabilita chemicky síťovaných vzorků vzrůstala pouze do 20 minut síťování. Pomocí ATR-FTIR bylo prokázáno, že se přibližně 57 % dvojných vazeb kyseliny itakonové (při vlnové délce 1640 cm-1) přeměnilo na nové jednoduché RR'C-CHR'' vazby při vlnové délce 795 cm-1. Delší čas síťování (nad 30 minut) vedl ke změnám v chemické struktuře pomocí beta-štěpení řetězců a částečné rekombinaci dvojných vazeb. Díky vzniku nových dvojných vazeb v jiných částech řetězce se snížila termální stabilita z 242 °C na 237° C a teplota skelného přechodu z -2,2 na -5.8 °C. Předložená práce popisuje, jak složení polymeru, modifikace funkčními skupinami a fyzikální podmínky ovlivňují fyzikální a chemické síťování připravených amfifilních kopolymerů. Kontrola hydrolytické a termální stability hydrogelů je zapotřebí zejména při uvolňování léčiv a regeneraci tkání.

Photoelectron Photoion Coincidence (PEPICO) Spectroscopy studies on two small oxygenated species are presented here. Diethyl Ether (Et2O) and Acetic Anhydride (AcOAc) were chosen because of their and their fragments' relevance to combustion chemistry. The Imaging PEPICO (iPEPICO) experiment at the VUV beamline of the Swiss Light Source (SLS) was utilized to provide dissociative ionization data of the two molecules of interest. In this experiment, the unimolecular fragmentation pathways of energy selected ions can be studied with high energy resolution. The iPEPICO experimental setup also allows the measurement of the dissociation rates, which is indispensable to derive accurate thermochemical information on large ions. The experimental data on the fragmentation of ions of interest are then examined through modeling the experimental ion fractional abundances (breakdown curves, BDCs) and reaction rates, in a modeling framework based on the RRKM statistical theory. In our first project, diethyl ether was studied to provide the appearance energies of its daughter ions along with the dissociation pathways of the molecular ion, leading to thermochemical data (such as heats of formation) pertinent to combustion chemistry. A revised ionization energy (IE) differing from the reviewed National Institute of Standards and Technology (NIST) was also proposed. In the second project presented, AcOAc was also measured on the iPEPICO apparatus to understand its dissociative photoionization processes. The appearance of trace amounts of acetone in the ionization spectra, discrepancies in the statistical models of the branching ratios, and the quantum chemical calculations all point to the existence of a post-transition-state bifurcation, when a single TS separates multiple products, namely a methyl-loss fragment and acetone, as well. The acetyl cation, as well as the methyl cation at higher energies, appear to be formed by both parallel and sequential dissociation processes.

Toward the next generation of nerve guidance conduits (NGCs), novel biomaterials and functionalization concepts are required to address clinical demands in peripheral nerve regeneration (PNR). As a biological polymer with bioactive motifs, gelatinous peptides are promising building blocks. In combination with an anhydride-containing oligomer, a dual-component hydrogel system (cGEL) was established. First, hollow cGEL tubes were fabricated by a continuous dosing and templating process. Conduits were characterized concerning their mechanical strength, in vitro and in vivo degradation and biocompatibility. Second, cGEL was reformulated as injectable shear thinning filler for established NGCs, here tyrosine-derived polycarbonate-based braided conduits. Thereby, the formulation contained the small molecule LM11A-31. The biofunctionalized cGEL filler was assessed regarding building block integration, mechanical properties, in vitro cytotoxicity, and growth permissive effects on human adipose tissue-derived stem cells. A positive in vitro evaluation motivated further application of the filler material in a sciatic nerve defect. Compared to the empty conduit and pristine cGEL, the functionalization performed superior, though the autologous nerve graft remains the gold standard. In conclusion, LM11A-31 functionalized cGEL filler with extracellular matrix (ECM)-like characteristics and specific biochemical cues holds great potential to support PNR.

Composites are the materials which can be used for a wide variety of applications andproducts such as sports equipment, aerospace and marine because of light and stiffnessproperties. Composites are often made from thermoset resin with glass fibers.In this study, two ways of recycling composites were evaluated, which are microwavepyrolysed composites (MGC) and mechanical composites (GC). These glass fibers weregoing to be compounded with Polypropylene (PP) or Maleic Anhydride ModifiedPolypropylene (MAPP) and then injection moulded the sample by Micro-compounder.In order to get better adhesion to the polymer, a coating was added. The Neoxil 5682-polypropylene water emulsion was evaluated.The samples were characterized by Tensile Testing, Thermogravimetric Analysis (TGA),Different Scanning Calorimetry (DSC), and Dynamic Mechanical Analysis (DMA) to find aoptimum combination of recycled glass fiber reinforced polymer.Microwave pyrolysis is a new research area. The glass fiber, polymer oil and gas can beobtained by heating the composite with microwaves to in an inert atmosphere. The polymeroil can be distillated and then evaluated with GC-MS; in order to obtain the chemicalcompositions.Keywords: Composites, grinded and microwave pyrolyse composites (MGC), grindedcomposites (GC), Polypropylene (PP), Maleic Anhydride Modified Polypropylene (MAPP),Micro-compounder, Tensile Testing, Thermogravimetric Analysis (TGA), Different ScanningCalorimetry (DSC), and Dynamic Mechanical Analysis (DMA), Microwave pyrolysis,polymer oil, distillation, GCMS Analysis. / Program: MSc in Resource Recovery - Sustainable Engineering

<p>Degradable polymers have gained an increased attention in the field of biomedical applications over the past decades, for example in tissue engineering. One way of improving the biocompatibility of these polymers is by chemical surface modification, however the risk of degradation during the modification procedure is a limiting factor. In some biomedical applications, for example in nerve guides, a patterned surface is desired to improve the cell attachment and proliferation.</p><p>In this thesis a new non-destructive, single-step, and solvent free method for surface modification of degradable polymers is described. Poly(L-lactide) (PLLA) substrates have been functionalized with one of the following vinyl monomers; N-vinylpyrrolidone (VP), acrylamide (AAm), or maleic anhydride (MAH) grafts. The substrates were subjected to a vapor phase atmosphere constituted of a mixture of a vinyl monomer and a photoinitiator (benzophenone) in a closed chamber at very low pressure and under UV irradiation. Poly(ε-caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), and poly(trimethylene carbonate) (PTMC) have been surface modified with VP using the same procedure to show the versatility of the method. The wettability of all of the four substrates increased after grafting. The surface compositions were confirmed by ATR-FTIR and XPS. The VP grafted PLLA, PTMC and PLGA substrates have been shown to be good substrates for the normal human cells i.e. keratinocytes and fibroblasts, to adhere and proliferate on. The topography of substrates with well defined nano patterns was preserved during grafting, since the grafted layer is very thin. We have also shown that the method is useful for a simultaneous chemical and topographical modification of substrates by masked vapor phase grafting. The surface topography was determined with SEM and AFM.</p> / <p>Intresset för användningen av nedbrytbara polymerer till biomedicinska applikationer som till exempel vävnads rekonstruktion har ökat avsevärt de senaste decennierna. Ett sätt att öka biokompatibiliteten hos dessa polymerer är genom kemisk ytmodifiering, men risken för nedbrytning under själva modifieringen är en begränsande faktor. I vissa biomedicinska applikationer, till exempel nervguider, är det önskvärt att ha en väldefinierad ytstruktur för att öka vidhäftningen och tillväxten av celler.</p><p>I den här avhandlingen presenteras en ny ickeförstörande, lösningsmedelsfri enstegsprocess för ytmodifiering av nedbrytbara polymerer. Substrat av poly(L-laktid) (PLLA) har ytfunktionaliserats med var och en av följande vinylmonomerer, N-vinylpyrrolidon (VP), akrylamid (AAm) eller maleinsyraanhydrid (MAH). Substraten har exponerats för en gasfasatmosfär av en blandning av en vinylmonomer och en fotoinitiator (bensofenon) i en tillsluten reaktor vid mycket lågt tryck och under UV-strålning. Metodens mångsidighet har även påvisats genom att ytmodifiera substrat av poly(ε-kaprolakton) (PCL), poly(laktid-co-glykolid) (PLGA) och poly(trimetylen karbonat) (PTMC) med VP. Vätbarheten ökade för alla fyra materialen efter ympning med en vinylmonomer. Ytsammansättningen fastställdes med ATR-FTIR och XPS. De VP ympade filmerna av PLLA, PLGA och PTMC visade sig vara bra substrat för mänskliga celler, i detta fall keratinocyter och fibroblaster, att vidhäfta och växa på. Yttopografin hos filmer med väldefinierade nanomönstrade ytor kunde bevaras efter ympning, tack vare att det ympade lagret är så tunt. Gasfas metoden har också visat sig användbar för att simultant ytmodifiera både kemiskt och topografiskt genom maskad gasfasympning. Yttopografin bestämdes med SEM och AFM.</p>

Ce travail se concentre sur le développement de systèmes catalytiques capable d’oxyder complètement le méthane à basse température. Le sujet principal concerne la conception d'une nouvelle génération de catalyseurs à base de palladium qui sont résistants aux composés soufrés et à l'eau.<p>Notre objectif a été atteint grâce à l'utilisation d'un support oxyde mixte produit par sol-gel. En effet, nos catalyseurs de palladium supporté sur un oxyde de silicium dopé au titane se sont révélés être résistants à l’empoisonnement au soufre et présentent des performances élevées pour la conversion du méthane.<p>En variant les quantités de TiO2, il a été montré que les performances atteignent un maximum pour une composition en masse de 10% TiO2. Les analyses structurelles et de surface ont montré que nos supports mixtes contiennent des liens Ti-O-Si. Nous pensons que ces liens sont responsables de l’activité accrue du catalyseur.<p>Par ailleurs, les catalyseurs contenant du titane présentent une tolérance supérieure vis-à-vis du SO2 lorsque celui-ci est ajouté aux réactifs ou que le catalyseur est exposé à une atmosphère de SO2 pur à 350°C pendant 15 heures. Nous avons mis en évidence par XPS que les sites Ti-O-Si sont également responsables de cette tolérance aux composés soufrés. Ceci est accompli par l'insertion du SO2 dans le support qui forme des liens soit Ti-O-SOx•••Si soit Si-O-SOx•••Ti. L’analyse XPS a également montré que sur le long terme, l’exposition au SO2 conduit à la formation d’une couche de PdSO4 de 18 à 20 Å. Étonnamment, les catalyseurs sont capables de récupérer entièrement leur activité initiale après ce traitement. Cette régénération se produit grâce à un mécanisme concerté avec le méthane permettant la décomposition totale du PdSO4. Par ailleurs, des études en présence d'eau ont montré que ces propriétés restent inchangées.<p>L'état du palladium a également été étudié et nous a permis de prouver qu’une activation/stabilisation du catalyseur est nécessaire. Celle-ci est réalisée en présence des réactifs par de légères modifications chimiques du support et de la phase de palladium. En effet, l'augmentation de l'activité du catalyseur a été corrélée avec une augmentation des quantités de Ti3+ et Pd0. La présence de palladium métallique dans le catalyseur semble être l'élément clé dans l'activation des liaisons C-H.<p>Enfin, nous avons étudié l'influence de la taille/la dispersion des particules de palladium sur la vitesse de réaction. L'utilisation de synthèses en phase liquide nous a permis de produire des solutions colloïdales de particules de palladium avec des tailles contrôlées. Cette étude a révélé que la combustion du méthane est une réaction sensible à la structure. Néanmoins, un meilleur contrôle de la forme des nanoparticules devrait être réalisé pour déterminer les facteurs structurels influençant la réaction./ The present work focuses on the development of highly efficient catalytic systems able to completely oxidize methane at low temperature in order to comply with modern environmental legislation. The main subject concerns the design of a new generation of palladium-based catalysts that are sulfur and water resistant. <p>Our goal was achieved through the use of a mixed oxide support produced by sol-gel. In fact, palladium-supported on titanium-doped silica catalysts have proven to be sulfur tolerant and exhibit high performances for the methane conversion. <p>Varying the amounts of TiO2 showed that the performance reached an optimum for a 10 wt.% TiO2 loading. According to the structural and surface analyses, the mixed oxides contained Ti-O-Si linkages, believed to be responsible for the better activity as compared to PdO supported on pure oxides. <p>Moreover, the titania-containing catalysts exhibited a superior tolerance towards SO2 when either adding it to the reactants or feeding it as a pure pretreatment atmosphere at 350°C (15 hour on stream). We evidenced using XPS that the Ti-O-Si sites are also responsible for the higher sulfur tolerance of the catalysts by the insertion of SO2 in the support forming either Ti-O-SOx•••Si or Si-O-SOx•••Ti. XPS analyses also evidenced that the long-term SO2-treatment leads to the formation of PdSO4 with a thickness of 18 to 20 Å. However, the catalysts can entirely recover their initial activity after this treatment. This regeneration was proven to be occurring through a concerted mechanism with methane leading to the total decomposition of PdSO4. Moreover, studies in presence of water showed that these properties remained unchanged.<p>The state of the palladium was also investigated and allowed us to evidence that an activation/stabilization of the catalyst is necessary. This is achieved in presence of the reactants by slight and subtle changes in both the support and the palladium phase. The increase of the catalyst activity was correlated with an increase of Ti3+ and Pd0 fractions. The presence of metallic palladium in the catalyst seems to be the key element in the activation of the C-H bonds. <p>Finally, we have studied the influence of the size/dispersion of the palladium particles on the reaction rate. The use of wet-chemistry synthesis allowed us to produce colloidal solutions of palladium with controlled particles sizes. This study revealed that the methane combustion is a structure sensitive or demanding reaction. Nevertheless, a better control of the shape of the nanoparticles should be achieved to determine the structural factor influencing the reaction.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Degradable polymers have gained an increased attention in the field of biomedical applications over the past decades, for example in tissue engineering. One way of improving the biocompatibility of these polymers is by chemical surface modification, however the risk of degradation during the modification procedure is a limiting factor. In some biomedical applications, for example in nerve guides, a patterned surface is desired to improve the cell attachment and proliferation. In this thesis a new non-destructive, single-step, and solvent free method for surface modification of degradable polymers is described. Poly(L-lactide) (PLLA) substrates have been functionalized with one of the following vinyl monomers; N-vinylpyrrolidone (VP), acrylamide (AAm), or maleic anhydride (MAH) grafts. The substrates were subjected to a vapor phase atmosphere constituted of a mixture of a vinyl monomer and a photoinitiator (benzophenone) in a closed chamber at very low pressure and under UV irradiation. Poly(ε-caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), and poly(trimethylene carbonate) (PTMC) have been surface modified with VP using the same procedure to show the versatility of the method. The wettability of all of the four substrates increased after grafting. The surface compositions were confirmed by ATR-FTIR and XPS. The VP grafted PLLA, PTMC and PLGA substrates have been shown to be good substrates for the normal human cells i.e. keratinocytes and fibroblasts, to adhere and proliferate on. The topography of substrates with well defined nano patterns was preserved during grafting, since the grafted layer is very thin. We have also shown that the method is useful for a simultaneous chemical and topographical modification of substrates by masked vapor phase grafting. The surface topography was determined with SEM and AFM. / Intresset för användningen av nedbrytbara polymerer till biomedicinska applikationer som till exempel vävnads rekonstruktion har ökat avsevärt de senaste decennierna. Ett sätt att öka biokompatibiliteten hos dessa polymerer är genom kemisk ytmodifiering, men risken för nedbrytning under själva modifieringen är en begränsande faktor. I vissa biomedicinska applikationer, till exempel nervguider, är det önskvärt att ha en väldefinierad ytstruktur för att öka vidhäftningen och tillväxten av celler. I den här avhandlingen presenteras en ny ickeförstörande, lösningsmedelsfri enstegsprocess för ytmodifiering av nedbrytbara polymerer. Substrat av poly(L-laktid) (PLLA) har ytfunktionaliserats med var och en av följande vinylmonomerer, N-vinylpyrrolidon (VP), akrylamid (AAm) eller maleinsyraanhydrid (MAH). Substraten har exponerats för en gasfasatmosfär av en blandning av en vinylmonomer och en fotoinitiator (bensofenon) i en tillsluten reaktor vid mycket lågt tryck och under UV-strålning. Metodens mångsidighet har även påvisats genom att ytmodifiera substrat av poly(ε-kaprolakton) (PCL), poly(laktid-co-glykolid) (PLGA) och poly(trimetylen karbonat) (PTMC) med VP. Vätbarheten ökade för alla fyra materialen efter ympning med en vinylmonomer. Ytsammansättningen fastställdes med ATR-FTIR och XPS. De VP ympade filmerna av PLLA, PLGA och PTMC visade sig vara bra substrat för mänskliga celler, i detta fall keratinocyter och fibroblaster, att vidhäfta och växa på. Yttopografin hos filmer med väldefinierade nanomönstrade ytor kunde bevaras efter ympning, tack vare att det ympade lagret är så tunt. Gasfas metoden har också visat sig användbar för att simultant ytmodifiera både kemiskt och topografiskt genom maskad gasfasympning. Yttopografin bestämdes med SEM och AFM. / QC 20101014