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Este trabalho busca avaliar a ductilidade de ligas metálicas utilizando como ferramenta a teoria da mecânica do dano proposta por Kachanov e desenvolvida por Lemaitre, a qual é apresentada desde as hipóteses básicas até as equações que modelam a deterioração de um material em regime de fratura dúctil. Como o enfoque do trabalho é a predição de trincas em processos de conformação mecânica, em especial estampagem de chapas, o mecanismo de formação destes defeitos é revisado, buscando na literatura o entendimento de como os parâmetros microestruturais influenciam na fratura dúctil. Ensaios de tração foram efetuados em corpos de prova retirados de chapas de aço SAE 1050 em duas condições microestruturais, cementita esferoidizada em matriz ferrítica e ferritaperlita, e em duas direções em relação à laminação da chapa original, paralelo e transversal. A evolução do dano foi medida de maneira indireta por meio da variação do módulo elástico e as propriedades mecânicas necessárias para utilização do modelo de Lemaitre foram calculadas. Por meio de difração de raios X, efetuamos o estudo da evolução da textura cristalográfica, apresentado na forma de figuras de distribuição de orientação e análise da intensidade das principais fibras encontradas em aços laminados a quente. Não foi observada influência significativa do tipo de microestrutura e da direção de deformação na evolução da textura. Por fim, o modelo de evolução de dano de Lemaitre foi transformado em um algoritmo numérico e implementado no código comercial Abaqus, em sua versão explícita, por meio do uso da subrotina VUMAT. Resultados foram obtidos e comparados com os experimentos, validando a aplicação do modelo. A evolução do dano para o aço SAE 1050 também foi comparada com resultados para outros aços ao manganês encontrados na literatura. Relações empíricas entre o teor de carbono e parâmetros como a deformação limite para início do dano, resistência à evolução do dano e dano máximo suportado foram desenvolvidas e apresentadas, com o intuito de funcionar como guias gerais para cálculo sem a necessidade de uma bateria de ensaios dedicados, facilitando a utilização da teoria da mecânica do dano em condições industriais. / The aim of the present work is to evaluate the ductility of metallic alloys employing the theory of damage mechanics as suggested by Kachanov and developed by Lemaitre, which is presented since its basic hypothesis until the equation that model the material deterioration under a regime of ductile fracture. As the focus of the work is the fracture prediction during mechanical working processes (mainly sheet metal stamping), the mechanism of formation of these defects is revised, based upon literature data, aiming at the understanding of how the material microstructural parameters influence ductile fracture. Tensile tests have been performed on samples obtained from SAE 1050 steel sheets for two microstructural conditions namely spheroidized cementite and regular ferrite-perlite for two rolling directions (rolling and transverse directions). In those tests, damage evolution has been measured indirectly through the materials variation in the Young modulus with strain, obtaining the mechanical properties, needed to be used in the calculation of Lemaitres model. Through X-ray diffraction measurements, the crystallographic texture evolution, presented in the form of orientation distribution functions and the associated fiber intensities observed for both microstructural conditions, has been evaluated. No major influence has been observed in this texture evolution, for the tested conditions. Finally, the Lemaitre damage evolution model has been transformed into a numerical algorithm and implemented in the Abaqus commercial code, in its explicit form, through the VUMAT sub-routine. Results have been obtained and compared with the experimental values, validating the suggested model. Damage evolution for the SAE 1050 steel has been also compared with results from literature for other C-Mn steels. Empirical relationships between C level and damage parameters such as limit strain for damage initiation, resistance to damage evolution and maximum allowable damage, have been developed and presented, envisaging their application as general guidelines, without requiring a sequence of dedicated tests, making easier the usage of damage mechanics under industrial conditions.

Traditional solution and solid state approaches (Nuclear Magnetic Resonance, X-Ray Crystallography) are methods of choice when analysing both biological and inorganic analytes. However, the characterisation of transient species, often encountered in self-assembling systems, is difficult. Such systems rarely produce crystals of high quality and due to their dynamic nature; their structures are difficult to study with NMR. Hyphenated gas phase methods which rely on mass spectrometry detection offer simultaneous structural analysis and direct stoichiometry measurement. As a consequence, it is possible to investigate specific, non-interacting molecules and molecular complexes in an isolated environment. This thesis focuses on the development and applications of two such methods - ion mobility mass spectrometry (IM-MS) and cold ion spectroscopy. IM-MS measurements yield a so called collisional cross sectional area (CCS). This parameter can be pictured as a rotationally averaged, shadow projection of a molecule structure. When correlated with the ion abundance, a CCS distribution yields intuitively interpretable information about the conformational preferences of an isolated molecule. Although indispensable in describing a "global" geometrical structure, the CCS parameter itself provides a limited insight into the local structural features of the assembly. Ion spectroscopy, both in the UV and IR regions, can provide an extra layer of highly descriptive information. Here, we present several cases where the above techniques have been applied. With the aid of IM-MS, we have analysed the geometry of inorganic supramolecular assemblies, highlighting the stability of particular metal-ligand interactions. Using cold ion spectroscopy, we have assessed the fine structural information of self-assembled oligomers of an amyloidogenic peptide. We correlated spectral features of isolated oligomers to features observed in the mature fibrils; therefore attempting to delineate the events in early stages of amyloidogenic aggregation. A major part of this report focusses on technological aspects of the design and development of a high resolution, variable temperature ion mobility mass spectrometer (VT-IM-MS). The thermal stability of molecules is a vital aspect in industrial process development and formulation science. Solution phase Differential Scanning Calorimetry (DSC) is a widely applied technique, allowing to monitor reversibility of thermally induced conformational transitions, a key aspect in protein folding analysis. The instrument reported here aims to provide parallel information about gaseous ions, with a particular focus on protein ions. Capabilities of the newly built instrument have been tested using small, rigid molecules, a small protein and a large multiprotein complex.

HU est une protéine bactérienne de type histone impliquée dans de nombreuses fonctions biologiques telles que la compaction, la transcription, la réplication et la réparation de l'ADN. Chez E. coli, il existe trois espèces dimériques de HU (HUα2, HUβ2 et HUαβ) ayant des rôles biologiques distincts. La formation de l'hétérodimère repose sur un échange de chaines peptidiques entre les homodimères. Un mécanisme modèle a été proposé par Ramstein et collaborateurs (J.M.B. 331, 101-121 2003) et a servi de point de départ a ce travail. Dans ce modèle, les homodimères transitent d'une conformation native (N2) vers une conformation intermédiaire (I2). Les homodimères sous forme I2 s'associent ensuite dans un hétérotetramère transitoire qui se redissocie en formant des hétérodimères. L'objectif principal de ce travail de thèse a été de caractériser chaque étape du mécanisme d'échange du point de vue structural et cinétique. Parmi les principaux résultats de ce travail, deux structures originales, HUβ2 de E. coli et HU de L. lactis, ont été obtenues par diffraction des rayons X et complètent la caractérisation structurale des protéines HU sous leur forme N2. Un modèle de la conformation I2, partiellement désordonnée, a été élaboré à partir des résultats obtenus en RMN et en simulation de dynamique moléculaire. De plus, l'existence de la conformation tétramérique a été mise en évidence en faible concentration par spectrométrie de masse en conditions natives. Des protocoles de production/purification/oxydation ont été mis au point pour l'introduction de ponts disulfure afin de stabiliser la conformation tétramérique en vue de sa caractérisation structurale. L'ensemble des données acquises par ces différentes méthodes biophysiques affine la compréhension du mécanisme d'échange de chaines d'un point de vue structural et cinétique et met en lumière le rôle clef de la conformation I2 dans le contrôle de la composition des dimères de HU. / HU is a histone like protein of bacteria involved in numerous biological functions such as DNA compaction, transcription, replication and repair. In E. coli, three HU dimers types are present (HUα2, HUβ2 et HUαβ) and show distinct biological roles. The heterodimer is formed from homodimers through a peptidic chain exchange. A model of this mechanism has been proposed by Ramstein and coworkers (J.M.B. 331, 101-121 2003) and was used as a starting point for this study. In this model, homodimers undergo a conformationnal change from a native state (N2) toward an intermediate state (I2). Then, I2 homodimers associate to form a transient heterotetramer which then dissociate into heterodimers. The main aim of this work was to characterize the structure and kinetic of each step of this mechanism. Major results of this work include the elucidation of two original crystal structures : HUβ2 from E. coli and HU from L. lactis in N2 states. A model of the partially disordered I2 state has also been proposed for HUβ2 and HUα2, and is consistent with results obtained from both NMR and molecular dynamics experiments. In addition, the existence of a low concentration tetrameric conformation has been evidenced by native mass spectrometry experiments. A protocol of production/purification/oxydation as been developped for the introduction of disulfide bridges in order to stabilize this conformation and characterize its structure. Together, results obtained from these different biophysical means refine our understanding of the chain exchange mechanism at the molecular level and highlight the role of the I2 conformation in controlling HU dimers composition.

L'organisation de la chromatine eucaryote ainsi que les mécanismes qui régulent sa compaction restent discutés. Nous proposons de comprendre le rôle de variations locales de charges et de concentrations ioniques dans l'organisation supramoléculaire de la chromatine. Nous utilisons un système modèle, la particule cœur de nucléosome (NCP) constituée de 146pb d'ADN qui s'enroulent autour d'un octamère d'histones sur un 1.75 tours. Les extensions terminales des histones, les queues, sont mobiles et positivement chargées. A l'aide de NCPs reconstituées à partir d'ADN et d'histones intactes ou globulaires recombinants, nous montrons que les queues des histones H3 et H4 sont essentielles pour l'établissement d'interactions attractives entre NCPs, en solution diluée. Le rôle d'ions multivalents dans les interactions entre NCPs et la formation de précipités ont été étudiés. Le rôle des queues d'histones est également abordé pour la formation de phases denses obtenues sous stress osmotique.

Les propriétés mécaniques de films polymériques peuvent être considérablement améliorées par l'inclusion de nanoparticules au sein de la matrice du fait de deux effets majeurs : (i) la structure locale de la dispersion des charges et (ii) la modification potentielle de la dynamique et de la conformation des chaînes à l'interface charge/polymère. Néanmoins, les mécanismes précis qui permettent de relier ces contributions à l'échelle nanométrique aux propriétés macroscopiques des matériaux, et en particulier aux propriétés mécaniques, sont actuellement mal décrits. Dans ce contexte, nous avons synthétisé des nanocomposites modèles à base de nanoparticules magnétiques de maghémite γ-Fe2O3 (nues ou greffées d'une couronne de polystyrène (PS) par polymérisation radicalaire contrôlée) dispersées dans une matrice de PS, que nous avons caractérisé en couplant la diffusion de rayonnement (Rayons X et neutrons) et la microscopie électronique à transmission. En jouant sur différents paramètres tels que la taille des particules, la concentration, ou le rapport de taille entre les chaînes greffées et celles de la matrice pour les charges greffées, nous avons obtenu des nanocomposites présentant un éventail de dispersions de charges variées, contrôlées, parfaitement reproductibles, allant de particules individuelles ou d'agrégats ramifiés jusqu'à la formation d'un réseau de charges connecté. En appliquant un champ magnétique externe durant la synthèse des nanocomposites, nous sommes parvenus à aligner les différentes structures le long de la direction du champ et ainsi former des matériaux présentant des propriétés remarquables de renforcement anisotropes. La conformation des chaînes au sein des nanocomposites, déterminée expérimentalement grâce aux propriétés spécifiques de contraste neutronique du système, n'est pas affectée par la présence des charges, quels que soient le degré de confinement des chaînes, l'orientation, la dispersion ou l'état de surface des charges. L'alignement des charges sous champ magnétique a permis de décrire précisément l'évolution du module de renforcement des matériaux avec la réorganisation structurale locale des charges et des chaînes sous étirement, et de finalement mettre en évidence le rôle majeur joué par la réorganisation des charges sous déformation dans les mécanismes de renforcement.

The thesis constitutes investigations from two distinct areas of research. One part deals with controlling and modulating the conformation of linear polymer in solution. Folding of a polymer chain has been achieved by utilising weak non-covalent interactions interaction like metal ion binding, charge-transfer complex formation and solvophobic effect in tandem. The second part of the thesis deals with synthesis and characterization of end-functionalized polymers prepared by melt-transesterification. The thesis is divided into five chapters. Chapter 1 provides a general introduction on foldamers – a class of polymers that adopts an ordered conformation in solution and various approaches to obtain end-functionalized polymers. Chapter 2 describe the attempts to improve the association constant (based on earlier works reported by Ghosh and Ramakrishnan) between the external folding agent and the polymer repeat unit. The polymer used in this study constitutes an electron deficient pyromellitic dimide units (PDI) linked with a flexible oxyethylene glycol spacer. An electron rich dialkoxy naphthalene (DAN) serves as the folding agent which forms a charge-transfer (C-T) complexation with the electron deficient aromatic units (PDI) in the polymer backbone and effects the folding. The folding agent has the metal ion as its integral part and this aids the interaction between electron-deficient and electron-rich aromatic units by complexing with oxyethylene glycol spacer. Thus folding is due to the synergistic effect of C-T complex formation and metal ion binding. Further a new polymer with larger -surface area of electron acceptor units was prepared with naphthalene dimide (NDI) unit instead of PDI unit which is expected to show higher folding propensity. Chapter 3 explores the possibility of modulating the folding of the donor acceptor (D-A) polymer. A D-A polymer consist of adjacently placed DAN and PDI units linked by an oxyethylene glycol spacer. Folding of the D-A polymer is effected in the presence of suitable metal ion that binds to the oxyethyleneglycol spacer. Random copolymers with segments of alternately placed D-A pairs and segments that is devoid of D-A pairs were prepared. Depending on composition of the random copolymer, the stack length was shown to be modulated as evident from UV-visible and NMR titration experiments. Following a similar approach, a two step folding of the synthetic polymer was demonstrated. The synthesis and characterization of end functionalized polyesters by melt transesterification is discussed in chapter 4. Well defined linear polymer with propargyl group as the end functionalizable group is prepared by the polycondensation of AB type monomer whereas polycondensation of AB2 type monomer leads to peripherally functionalized hyperbranched polymer. Azide-alkyne ‘click’ reactions carried out at the chain end of linear polyester with fluorophores allowed the estimation of the molecular weight by UV-visible and fluorescence spectroscopic method which is compared with estimation from 1H-NMR. Similarly the glass-transistion temperature of hyperbranched polyester is modulated by the peripheral functionalization with various organic azides by ‘click’ reaction. Chapter 5 gives the conclusion and future directions based on the findings from the thesis work.

Aquesta tesi és una continuació dels estudis iniciats en l'equip en el camp de les relacions estructura-activitat (SAR i QSAR) dels brassinoesteroides (BRs) mitjançant mètodes computacionals. L'objectiu general és centrar l'atenció en la cadena lateral, ja que la influència dels hidroxils depenia del tipus d'estudi (quantitatiu o qualitatiu) i la influència de l'extrem final de la cadena lateral era molt genèrica. El desenvolupament d'aquest objectiu principal ha portat a: 1. Estudiar les cadenes laterals d'anàlegs BRs androstànics: Basant-se en l'aproximació a l'anàleg actiu (AAA) prenent com a referència l'estructura de la brassinolida, s'ha vist que els anàlegs α-hidroxiester i α-aminoester són computacionalment bons candidats per presentar activitat brassinoesteroide. Un cop sintetitzats (en una tesi paral·lela), tres anàlegs amb la funcionalitat lliure han donat inactius mentre que quatre anàlegs amb la funcionalitat protegida han donat actius o moderadament actius. Basant-se novament en l'AAA, no ha estat possible explicar computacionalment i de forma inequívoca l'activitat i/o inactivitat d'aquests anàlegs. 2. Revisar i redefinir la conformació activa dels BRs: S'ha conclòs que la conformació activa in silico és l'anomenada HIP. Aquesta és la que explica amb més coherència la distribució tridimensional tan dels hidroxils com de l'extrem final de la cadena lateral de cara a explicar la unió de les cinc cadenes laterals tipus dels BRs amb el receptor. La raó per la qual s'han trobat diverses conformacions actives es troba en l'anàlisi conformacional dels BRs i no pas en els processos de selecció de la conformació activa. 3. Estudiar la influència de la conformació activa dels BRs sobre els models de QSAR: Conformacions actives estructuralment diferents han donat lloc a models quantitati-vament similars, però qualitativament diferents. Quantitativament similars perquè les parts dels BRs que correlacionen amb l'activitat són les mateixes. Qualitativament diferents perquè la contribució a l'activitat d'aquestes parts, especialment de cadena lateral, i la variació de la predictibilitat en funció de l'estructura són diferents en cada cas. Els models reduïts i el model HOMO han posat de manifest que no es pot extreure més informació dels models degut als desequilibris estructurals del conjunt de BRs que formen part del data set. El model a 1 μg/planta explica els requeriments estructurals que fan que un BR sigui actiu o inactiu. El model HIP explica els requeriments estructurals que determinen el grau d'activitat dels BRs actius. Fora de l'objectiu principal, però íntimament relacionat amb els estudis de QSAR s'ha volgut: 4. Determinar l'error experimental de la resposta i de les dades d'activitat: Comparant-los amb els errors dels models, s'observa que el model a 1 μg/planta està força ben ajustat i no té gaire marge de millora. En canvi, que el model HIP pot millorar considerablement sobretot en la predictibilitat, sempre i quan s'arreglin els desequilibris estructurals. D'altre banda, s'ha vist que els diferents tractaments estadístics realitzats en el bioassaig no afecten significativament al valor d'activitat. / Esta Tesis es una continuación de los estudios iniciados por el equipo en el campo de las relaciones estructura-actividad (SAR y QSAR) de los brasinoesteroides (BRs) mediante métodos computacionales. El objetivo general es centrar la atención en la cadena lateral, ya que la influencia de los hidroxilos dependía del tipo de estudio (cuantitativo o cualitativo) y la influencia del extremo final de la cadena lateral era muy genérica. El desarrollo de este objetivo principal ha llevado a: 1. Estudiar las cadenas laterales de los análogos BRs androstánicos: Basándose en la apro-ximación al análogo activo tomando como referencia la estructura de la brasinolida, se ha observado que los análogos α-hidroxiester i α-aminoester son computacionalmente buenos candidatos para presentar actividad brassinoesteroide. Una vez sintetizados (en una tesis paralela), tres análogos con la funcionalidad libre han resultado inactivos mientras que cuatro análogos con la funcionalidad protegida han resultado activos o moderadamente activos. Basándose nuevamente en la AAA, no ha sido posible explicar computacionalmente y de forma inequívoca la actividad o inactividad de estos análogos. 2. Revisar y redefinir la conformación activa de los BRs: Se ha llegado a la conclusión que la conformación activa in silico es la llamada HIP. Esta es la que explica con más coherencia la distribución tridimensional tanto de los hidroxilos como del extremo final de la cadena lateral a fin de explicar la unión de las cinco cadenas laterales tipo de los BRs con el receptor. La razón por la cual se han encontrado diversas conformaciones activas se encuentra en el análisis conformacional y no en los procesos de selección de la conformación activa. 3. Estudiar la influencia de la conformación activa de los BRs en los modelos de QSAR: Conformaciones activas estructuralmente diferentes han dado lugar a modelos cuantita-tivamente similares, pero cualitativamente diferentes. Cuantitativamente similares porque las partes de los BRs que correlacionan con la actividad son las mismas. Cualitativamente diferentes porque la contribución a la actividad de dichas partes, especialmente de la cadena lateral, y la variación de la predictibilidad en función de la estructura son diferentes en cada caso. Los modelos reducidos y el modelo HOMO han puesto de manifiesto que no se puede extraer más información de los modelos debido a los desequilibrios estructurales del conjunto de BRs que conforman el "data set". El modelo a 1 μg/planta explica los requisitos estructurales que hacen que un BR sea activo o inactivo. El modelo HIP explica los requisitos estructurales que determinan el grado de actividad de los BRs activos. Fuera del objetivo principal, pero íntimamente relacionado con los estudios de QSAR se ha querido: 4. Determinar el error experimental de la respuesta y de los datos de actividad: Compa-rándolos con los errores de los modelos, se observa que el modelo a 1 μg/planta está bastante bien ajustado y tiene poco margen de mejora. En cambio, el modelo HIP puede mejorar considerablemente sobretodo en la predictibilidad, siempre y cuando se solucionen los desequilibrios estructurales. Por otro lado, se ha observado que los diferentes tratamientos estadísticos realizados en el bioensayo no afectan significativamente al valor de actividad. / This Thesis is the continuation of the studies started by our laboratory in the field of brassinosteroids (BRs) structure activity relationships (SAR and QSAR) using computational methods. The main aim is to focus the study on the side chain, due to the influence of hydroxyl groups depends on the study (quantitative or qualitative) and the influence of the side chain end is very generic. The development of this goal has leaded to: 1. Study the side chain of androstanic BRs analogues: Based on active analogue approach (AAA) taking brassinolide as the reference structure, it has been shown that α-hydroxyester and α-aminoester analogues are computationally good candidates to elicit brassinosteroid activity. Once synthesized (in a parallel thesis), three analogues with free functionality have result inactive but four analogues with protected functionality have result active or mild active. Based once again on AAA it has not been possible explain computationally and unequivocally the activity and/or inactivity of these analogues. 2. Revise and redefine the active conformation of BRs: It has been concluded that in silico active conformation is the named as HIP. This explains more consistently the tridimensional distribution of both the hydroxyls and the end of the side chain in order to explain the union of the five side chain types with BRs receptor. The reason for having found several active conformations is in BRs conformational analysis not in the active conformation selection procedures. 3. Study the influence of BRs active conformation in QSAR models: Active conformations structurally different has lead to models which are quantitatively similar but qualitatively different. Quantitatively similar due to the parts of BRs that correlate with activity are the same. Qualitatively different due to this parts contribution, especially the side chain, and the structure depending variation of predictability are different on each model. Reduced models and HOMO model has shown that get more information from the models is not possible due to a structural imbalance in BRs data set. The 1 μg/plant model explains the structural requirements that make BRs active or inactive. The HIP model explains the structural requirements that determine the activity degree of active BRs. Out of the main aim, but close related to QSAR studies I wanted to: 4. Determine the experimental error of both the response and the activity data: Compared with models error, it is observed that the 1 μg/plant model is really well adjusted and has little improvement margin, but the HIP model can be considerably improved, overall in predictability. On the other hand, it has been shown that the different statistical treatments done in bioassay do not affect in a significant way the activity value.

<p>Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer.</p><p>Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt.</p><p>Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion.</p><p>I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa visade att PAE adsorberade i större mängd än CMC, både i hänseende av massa och laddning. Adsorptionen av PAE var signifikant långsammare än CMC och adsorptionstiden till 90% av mättnadsadsorptionen bestämdes till 3 respektive 1 minut. Zetapotentialen för kryll bestämdes för adsorption av de två första polyelektrolytskikten och resultaten tydde på att kryllmaterialet omladdade inom en minut efter tillsatserna av polyelektrolyt. Reflektometriförsök inom sekventiell adsorption av PAE och CMC på kiseloxid antydde att den låga molekylviktsfraktionen av PAE störde uppbyggnaden av polyelektrolyt-multiskikten.</p> / <p>This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres.</p><p>The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte.</p><p>Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations.</p><p>In the second part of the thesis, the sequential adsorption of PAE and CMC on pulp fibres was determined using the polyelectrolyte titration technique. Layer-by-layer adsorption isotherms derived on fractionated pulp showed that PAE adsorbed in higher amounts than CMC did, both in terms of adsorbed mass and adsorbed charge. The adsorption of PAE was significantly slower compared to CMC, and the adsorption times required to reach 90% of the saturation adsorption were 3 and 1 min, respectively. The zeta potential of pulp fines was determined for the adsorption of the two first polyelectrolyte layers, and data indicated that the fines recharge within one minute after the polyelectrolyte additions. Reflectometry experiments regarding the sequential adsorption of PAE and CMC on silica indicated that the low-molecular-weight fraction of PAE disturbed the formation of polyelectrolyte multilayers.</p>

The important roles of fluid dynamics in immersion lithography (IL) and step-and-flash imprint lithography (S FIL) are analyzed experimentally and theoretically. In IL there are many challenges with managing a fluid droplet between the lens and the wafer, including preventing separation of the fluid droplet from the lens and deposition of small droplets behind the lens. Fluid management is also critical in S FIL because the imprint fluid creates capillary and lubrication forces, both of which are primarily responsible for the dynamics of the template and fluid motion. The fluid flow and shape of the wafer determine how uniform the gap height between the wafer and the template is, and they affect the resistance during the alignment phase. IL was investigated as a methodology to improve laser lithography for making photomasks. The fluid flow in IL was investigated by building a test apparatus to simulate the motion of the fluid droplet during microlithographic production, and using this apparatus to conduct experiments on various immersion fluids and wafer topcoats to determine what instabilities would occur. A theoretical model was used to predict the fluid separation instabilities. Finite element simulations were also used to model the fluid droplet, and these simulations accurately predict the fluid instabilities and quantitatively agreed with the model and experiments. It is shown that the process is viable: capillary forces are sufficient to keep the fluid droplet stable, heating effects due to the laser are negligible, and other concerns such as evaporation and dissolution are manageable. Euler beam theory and the lubrication equation were used to model the bending of an S FIL template and the flow of the fluid between the template and a non-flat wafer. The template filling time, conformance of the template to the wafer, and the alignment phase are investigated with an analytical model and finite element simulations. Analysis and simulations show that uniformity of the residual film thickness and ease of proper alignment depend greatly on the planarity of the wafer, the properties of the template, and the surface tension of the fluid. / text