Poly (glycerol-sebacate) (PGS) is a synthetic bioelastomer with a covalently crosslinked, three-dimensional network of random coils with hydroxyl groups attached to its backbone. This biodegradable polymer is biocompatible (in vitro and in vivo), tough, elastic, inexpensive, and flexible, and finds potential applications in tissue engineering and regenerative medicine. Due to the slow rate of step-growth polymerisation, the synthesis of PGS prepolymer requires 24-48 h. A batch and a continuous process, if developed, could address the inherent deficiencies (eg. long residence time, venting) associated with the large-scale synthesis of such bioelastomers. However, in order to assess whether this particular system may be adapted to continuous processes, such as reactive extrusion, studies on kinetics of controlled condensation reactions are of vital importance. FT-Raman spectroscopy was used to study the kinetics of the step-growth reactions between glycerol (G) and sebacic acid (SA) at three molar ratios (G:SA= 0.6,0.8,1.0) and three temperatures (120, 130, 140 ˚C). The rate curves followed first-order kinetics with respect to sebacic acid concentration in the kinetics regime. An increase in the molar ratio (G : SA) of the reactants decreased the average functionality of the system and the crosslinking density, resulting in the lowering of the activation energy and pre-exponential factor. The average functionality of the system had a profound effect on the crosslinking density, mechanical properties, and the reaction kinetics of the system. Three different PGS oligomers and films (PGS 0.6, PGS 0.8, PGS 1.0) were thoroughly characterised using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and contact angle measurements. FTIR spectra of PGS oligomers confirmed the formation of ester bonds (1740 cm -1). Quantification of various functional groups in PGS films using XPS was in agreement with the theoretical values of the proposed structure. WAXS results indicated that PGS system with a higher average functionality possesses a higher degree of crystallinity. Crystallisation exotherms and melting endotherms of PGS systems revealed that the average functionality influences the density of crosslinking, degree of crystallinity, and the network structure of bioelastomers. Contact angle studies confirmed that an increase in the average functionality of PGS system increases hydrophilicity, and the surface treatment through aminolysis further increases the hydrophilicity of the films. Batch studies were performed on a Brabender Plasticorder®. The samples collected over a reaction period of 5 h were characterised using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The number-average molecular weight (Mn) and the weight-average molecular weight (Mw) of the oligoesters were determined using matrix-assisted laser desroption/ionization time-of-flight spectroscopy (MALDI-TOF) and compared with the corresponding values from the benchtop synthesis. It was found that due to higher shear-mixing and better orientation of functional groups, the degree of polymerisation at any stage of the reaction was higher in the Brabender than in the benchtop process. The gel-point of the reaction was determined from the crossover point of storage and loss moduli, and the reaction rate constant was calculated using the torque vs time data of the rheometer. The kinetics rate constant and the extent of the reaction in the Brabender were found to be higher than the corresponding values obtained from the conventional benchtop process by a factor of 2. PGS was found to be thermo-mouldable and adaptable to high-shear mixing, and hence is a better candidate for making thermoplastic elastomers using reactive extrusion. The challenges and possibilities in scaling up a batch process to a continuous process were investigated. The use of a wiped film reactor or a disk reactor along with reactive extrusion and batch-mixing (as a post-extrusion operation) is a commercially viable method to synthesise PGS oligomers. Such a continuous process will boost the production of bioelastomers for tissue engineering application by addressing the constraints in step-growth polymerisation. Finally, the effect of PGS substrate stiffness and surface treatment (aminolysis, hydrolysis, layer-by-layer deposition) on the morphology and lineage of mesenchymal stem cells – which have a capacity to differentiate themselves into cartilage, adipose, tendon, and muscle tissues – was analysed using fluorescence microscopy and DNA and protein assays. Stiffness of the PGS surface and the method of treatment influenced the cell attachment and spreading on different surfaces. However, cells did not differentiate into definite phenotypes at the end of 14 d time-point, indicating that higher time-points are needed to be considered to study the effect of matrix stiffness and surface treatment on cell attachment and phenotype differentiation.

La dynamique réactionnelle est l'étude du comportement d'un système moléculaire, ou d'un ensemble de systèmes atomiques et moléculaires en réponse à une excitation externe photonique ou collisionnelle. Ces excitations localisent l'énergie déposée de manière différente, et peuvent être accompagnées du réaménagement de liaisons chimiques dans la molécule. Quelque soit le mode d'excitation choisi, ces réaménagements peuvent se réaliser selon un processus soit statistique, soit impulsionnel. Dans ce dernier cas, qui intervient dans toutes les dynamiques rapides (< 10 ps), les modifications structurales de la molécule ont lieu selon le ou les quelques degrés de libertés du système concernés par le processus d'excitation. Il s'agit donc d'une évolution directe ou l'énergie n'est pas thermodynamiquement équirépartie dans tous les modes de vibration de la molécule. Un système apriori complexe peut donc, dans le cadre d'une évolution très rapide où seules quelques coordonnées sont concernées, présenter une évolution obéissant à un modèle extrêmement simplifié. La dynamique réactionnelle a donc, en soi, pour but d'isoler les coordonnées par lesquelles se propage l'énergie déposée par le processus d'excitation.<br />L'objectif a été d'étudier des systèmes aussi proches possibles de problématiques liées à la chimie organique. Celle-ci présente certes des molécules à squelette carboné (voir chapitre « Molécules Organiques : un pas vers la photochimie organique »), mais aussi des intermédiaires réactionnels très réactifs (voir chapitre « Composés carbonés insaturés »). Plus généralement les réactions ont lieu dans un solvant, d'où l'intérêt d'en étudier l'influence de manière quantifiée. C'est la raison pour laquelle j'ai étudié des systèmes déposés sur agrégats afin de bénéficier de la puissance des techniques de la phase gazeuse tout en utilisant un solvant modèle et modifiable à volonté (voir chapitre « Solvatation des systèmes en phase gazeuse : effets de solvant»). Naturellement, cela m'a aussi conduit à étudier préalablement un certain nombre de problématiques liées à la structure électronique des agrégats (voir chapitre « Dynamique d'agrégats purs ») et à des systèmes modèles (voir chapitres « Molécules organiques : un pas vers la photochimie organique » et « Dynamique des systèmes modèles »). L'évolution de ce programme de recherche structure mon activité et détermine mes projets scientifiques.

La synthèse de nouveaux composés d'intercalation du graphite a été réalisée en phase gazeuse et en solution dans HF anhydre. Les fluorures de chrome et de rhodium s'intercalent dans le graphite pour donner lieu à des composés de stades 1 à 3. Une étude structurale sur un monocristal a montré la commensurabilité entre le sous réseau du graphite et celui de l'intercalat. L'état d'oxydation des métaux de transition a été déterminé par RPE, XPS et par mesures magnétiques. Les mesures de la réflectivité optique ont permis une estimation du transfert de charge du graphite vers l'espèce insérée. L'étude de l'effet de la fluoration d'une série d'oxydes supraconducteurs a été réalisée. Un traitement sous fluor gazeux à basse température (20°C < F < 2100°C) a mis en évidence la formation d'une fine couche d'(oxy) fluorure à la surface des matériaux. Cette couche a été caractérisée par diffraction X, TEM et par spectroscopie Auger. Dans l'oxyde YBa2Cu3O7, un phénomène de passivation de surface vis-à-vis de la dégradation atmosphérique a été observé. L'influence de la fluoration sur les propriétés supraconductrices a été étudiée par RPE, mesures magnétiques et électriques. Une étude par XPS sur un monocristal de YBa2Cu3O7 a confirmé que la surface du matériau est complétement modifiée après traitement.

<p>Quantum dynamics is the study of time-dependent phenomena in fundamental processes of atomic and molecular systems. This thesis focuses on systems where nature reveals its quantum aspect; e.g. in vibrational resonance structures, in wave packet revivals and in matter wave interferometry. Grid based numerical methods for solving the time-dependent Schrödinger equation are implemented for simulating time resolved molecular vibrations and to compute photo-electron spectra, without the necessity of diagonalizing a large matrix to find eigenvalues and eigenvectors.</p><p>Pump-probe femtosecond laser spectroscopy on the sodium potassium molecule, showing a vibrational period of 450 fs, is theoretically simulated. We find agreement with experiment by inclusion of the finite length laser pulse and finite temperature effects.</p><p>Complicated resonance structures observed experimentally in photo-electron spectra of hydrogen- and deuterium chloride is analyzed by a numerical computation of the spectra. The dramatic difference in the two spectra arises from non-adiabatic interactions, i.e. the interplay between nuclear and electron dynamics. We suggest new potential curves for the 3²Σ⁺ and 4²Σ⁺ states in HCI⁺.</p><p>It is possible to guide slow atoms along magnetic potentials like light is guided in optical fibers. Quantum mechanics dictates that matter can show wave properties. A proposal for a multi mode matter wave interferometer on an atom chip is studied by solving the time-dependent Schrödinger equation in two dimensions. The results verifies a possible route for an experimental realization.</p><p>An improved representation for wave functions using a discrete set of coherent states is presented. We develop a practical method for computing the expansion coefficients in this non-orthogonal set. It is built on the concept of frames, and introduces an iterative method for computing a representation of the identity operator. The phase-space localization property of the coherent states gives adaptability and better sampling efficiency.</p>

<p>Surface film formation at the electrode/electrolyte interface in lithium-ion batteries has a crucial impact on battery performance and safety. This thesis describes the characterisation and treatment of electrode interfaces in lithium-ion batteries. The focus is on interface modification to improve battery safety, in particular to enhance the onset temperature for thermally activated reactions, which also can have a negative influence on battery performance. </p><p>Photoelectron Spectroscopy (PES) and Differential Scanning Calorimetry (DSC) are used to investigate the surface chemistry of electrodes in relation to their electrochemical performance. Surface film formation and decomposition reactions are discussed.</p><p>The upper temperature limit for lithium-ion battery operation is restricted by exothermic reactions at the graphite anode; the onset temperature is shown to be governed by the composition of the surface film on the anode. Several electrolyte salts, additives and an anion receptor have been exploited to modify the surface film composition. The most promising thermal behaviour is found for graphite anodes cycled with the anion receptor, tris(pentafluorophenyl)borane, which reduces salt reactions and increases the onset temperature from ~80 °C to ~150 °C.</p><p>The electrochemical performance and surface chemistry of Swedish natural graphite, carbon-treated LiFePO₄ and anodes from high-power lithium-ion batteries are also investigated. Jet-milled Swedish natural graphite exhibits a high capacity and rate capability, together with a decreased susceptibility to solvent co-intercalation. Carbon-treated LiFePO₄ shows promising results: no solvent reaction products are detected. The amount of salt compounds increases, with power fade occurring for anodes from high-power lithium-ion batteries; the solvent reduction products comprise mainly Li-carboxylate type compounds.</p>

<p>This thesis is based on experimental studies in chemical physics. Titanium dioxide (TiO₂) and phthalocyanine’s (Pc’s), interesting in many future perspectives, have been deposited as thin films and studied as follows. Information has been obtained on e.g. molecular orientation, crystal structure, depth profile of the chemical composition, electrochemical properties and electronic structure. This has been achieved by means of a combination of techniques: X-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS), density functional theory calculations (DFT), UV-visible absorption spectroscopy (UVVIS) and cyclic voltammetry (CV).</p><p>Metal-free phthalcyanine (H₂Pc) has been shown to form films with different crystal structure and molecular orientation depending on deposition method, evaporation/sublimation or powder deposition, on commercial conducting glass (fluorine doped tin oxide, FTO), which is used e.g. in solar cells and organic light emitting devices (OLEDs). The unoccupied molecular orbitals are divided in x, y and z space coordinates of the molecule and also divided in inequivalent nitrogen components. </p><p>The electronic structure is also studied for a sublimated titanyl phthalocyanine (TiOPc) film and related to the metal-free phthalocyanine. The ligand field around the titanium atom in TiOPc is compared with that of TiO₂ to delineate the unoccupied levels recorded by means of x-ray absorption spectroscopy.</p><p>Nanostructured TiO₂ films were manufactured by screen printing/doctor blading on FTO. Such films were additionally covered with lutetium diphthalocyanine (LuPc₂) by means of surface assembly from solution. LuPc₂^-, LuPc₂⁺ and LuPc₂H were identified and the stability of the electrochromic reactions in this system was monitored.</p><p>Chemical vapor deposition (CVD) has been used to grow nanometer sized anatase TiO₂ crystals on pre-oxidized Si (111) without formation of interfacial carbon and with an interface layer of the size of 15- 25Å. The interface layer was found to be amorphous TiSi_xO_y with graded stoichiometry. </p>

<p>There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O₂-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO₄. A second and in some ways even more attractive material - Li₂FeSiO₄ - has emerged during the course of this work.</p><p>An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li₂FeSiO₄. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li₂FeSiO₄ and LiFeSiO₄, but with the structure of the original Li₂FeSiO₄ transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li₂FeSiO₄ and the delithiated on LiFeSiO₄ structure provide an interesting insight into the experimental result.</p><p>Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO₄ and Li₂FeSiO₄ after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling.</p><p>LiFePO₄ and Li₂FeSiO₄ should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.</p>

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 132-140).

This thesis is focused on the electronic, spin-dependent and dynamical properties of thin magnetic systems. Photoemission-related techniques are combined with synchrotron radiation to study the spin-dependent properties of these systems in the energy and time domains. In the first part of this thesis, the strength of electron correlation effects in the spin-dependent electronic structure of ferromagnetic bcc Fe(110) and hcp Co(0001) is investigated by means of spin- and angle-resolved photoemission spectroscopy. The experimental results are compared to theoretical calculations within the three-body scattering approximation and within the dynamical mean-field theory, together with one-step model calculations of the photoemission process. From this comparison it is demonstrated that the present state of the art many-body calculations, although improving the description of correlation effects in Fe and Co, give too small mass renormalizations and scattering rates thus demanding more refined many-body theories including nonlocal fluctuations. In the second part, it is shown in detail monitoring by photoelectron spectroscopy how graphene can be grown by chemical vapour deposition on the transition-metal surfaces Ni(111) and Co(0001) and intercalated by a monoatomic layer of Au. For both systems, a linear E(k) dispersion of massless Dirac fermions is observed in the graphene pi-band in the vicinity of the Fermi energy. Spin-resolved photoemission from the graphene pi-band shows that the ferromagnetic polarization of graphene/Ni(111) and graphene/Co(0001) is negligible and that graphene on Ni(111) is after intercalation of Au spin-orbit split by the Rashba effect. In the last part, a time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of a permalloy platelet comprising three cross-tie domain walls is presented. It is shown how a fast picosecond magnetic response in the precessional motion of the magnetization can be induced by means of a laser-excited photoswitch. From a comparision to micromagnetic calculations it is demonstrated that the relatively high precessional frequency observed in the experiments is directly linked to the nature of the vortex/antivortex dynamics and its response to the magnetic perturbation. This includes the time-dependent reversal of the vortex core polarization, a process which is beyond the limit of detection in the present experiments. / Diese Dissertation beschäftigt sich mit den elektronischen, spinabhängigen und dynamischen Eigenschaften dünner magnetischer Systeme. Auf dem Photoeffekt basierende Untersuchungsmethoden werden zusammen mit Synchrotronstrahlung eingesetzt, um die spinabhängigen Eigenschaften dieser Systeme im Energie- und Zeitbereich zu untersuchen. Im ersten Teil dieser Arbeit wird mit spin- und winkelaufgelöster Photoemission die Stärke von Elektronenkorrelationseffekten in der spinabhängigen elektonischen Struktur von ferromagnetischerm bcc Fe(110) und hcp Co(0001) untersucht. Die experimentellen Ergebnisse werden verglichen mit theoreteischen Berechnungen im Rahmen der Näherung der Drei-Körper-Streuung und der dynamischen Molekularfeldtheorie, zusammen mit Berechnungen des Photoemissionsprozesses im Rahmen des Ein-Stufen-Modells. Ausgehend von diesem Vergleich wird gezeigt, dass die gegenwärtig fortgeschrittensten Rechnung, obgleich sie die Beschreibung von Korrelationseffekten in Fe und Co verbessern, zu kleine Massenrenormalisierungen und Streuraten ergeben, was zu der Forderung nach verfeinerten Vielteilchentheorien unter Einbeziehung von nichtlokalen Fluktuationen führt. Im zweiten Teil wird unter Kontrolle durch die Photoelektronenspektroskopie im Detail gezeigt, wie Graphen durch chemische Gasphasenabscheidung auf den Übergangsmetall-Oberflächen Ni(111) und Co(0001) aufgebracht und mit einer Monolage Au interkaliert werden kann. Für beide Systeme wird eine lineare E(k)-Dispersion masseloser Dirac-Fermionen im Graphen-pi-Band in der Nähe der Fermi-Energie beobachtet. Spinaufgelöste Photoemission des Graphen-pi-Bandes zeigt, dass die ferromagnetische Polarisation von Graphen/Ni(111) und Graphen/Co(0001) vernachlässigbar ist und dass Graphen/Ni(111) nach Interkalation mit Au eine Spin-Bahn-Aufspaltung aufgrund des Rashba-Effekts zeigt. Im letzten Teil wird eine zeitaufgelöste Studie des Röntgenzirkulardichroismus mit Photoelektronenmikroskopie präsentiert, die an einer Permalloy-Probe durchgeführt wurde, die drei als Stachelwände ausgebildete Domänenwände enthält. Es wird gezeigt, wie eine schnelle magnetische Antwort auf der Pikosekundenskala in der Präzessionsbewegung der Magnetisierung durch einen laserangesteuerten Photoschalter erzeugt werden kann. Durch Vergleich mit einer mikromagnetischen Rechnung wird gezeigt, dass die relativ hohe Präzessionsfrequenz, die im Experiment beobachtet wird, in unmittelbarer Beziehung steht zu den Eigenschaften der Vortex/Antivortex-Dynamik und ihrer Antwort auf die magnetische Störung. Das schließt die zeitabhängige Umkehr der Vortexkernpolarisation ein, einem Vorgang der jenseits der Nachweisgrenze der gegenwärtigen Experimente liegt.

The curiosity of researchers to find novel characteristics and properties of matter constantly pushes for the development of instrumentation based on X-radiation. I present in this thesis techniques for electron spectroscopy based on developments of X-ray sources both in time structure and energy. One part describes a laser driven High-Harmonic Generation source and the application of an off-plane grating monochromator with additional beamlines and spectrometers. In initial experiments, the source is capable of producing harmonics between the 13th and 23rd of the fundamental laser 800 nm wavelength. The intensity in the 19th harmonic, after monochromatization, was measured to be above 1.2·1010 photons/second with a repetition rate of 5 kHz.  The development of a chopper system synchronized to the bunch clock of an electron storage ring is also presented. The system can be used to adjust the repetition rate of a synchrotron radiation beam to values between 10 and 120 kHz, or for the modulation of continuous sources. The application of the system to both time of flight spectroscopy and laser pump X-ray probe spectroscopy is shown. It was possible to measure triple ionization of Kr and in applied studies the valence band of a laser excited dye-sensitized solar cell interface. The combination of the latter technique with transient absorption measurements is proposed. The organic molecule maleic anhydride (MA) and its binding configuration to the three anatase TiO2 crystals (101), (100), (001) has been investigated by means of Xray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine structure Spectroscopy (NEXAFS). The results provide information on the binding configuration to the 101 crystal. High Kinetic Energy Photoelectron Spectroscopy was used to investigate multilayers of complexes of iron, ruthenium and osmium. The benefit of hard X-rays for ex-situ prepared samples is demonstrated together with the application of resonant valence band measurements to these molecules.