O preparo de eletrólitos sólidos poliméricos (ESPs) a partir de amidos de mandioca modificados (catiônico, eterificado e oxidado) com o objetivo de aplicação em, por exemplo, dispositivos eletrocrômicos é descrito nesse trabalho. Os materiais estudados foram obtidos a partir de amidos de mandioca modificados quimicamente (catiônico, eterificado e oxidado) plastificados com glicerol e etileno glicol e tendo como sal, o perclorato de lítio (LiClO4). Para um estudo completo foi investigada a influência do plastificante e do sal nas propriedades dos ESPs. Para o glicerol foram utilizadas concentrações em massa de 25 e 30%, e para o etileno glicol, variações de 30 a 50%. Em relação ao sal de lítio (LiClO4), as concentrações foram: 8,10,12,15,20 e 30 [O]/[Li], onde [O] é referente aos mols de oxigênio presentes no amido e plastificante (glicerol ou etileno glicol), e [Li] referente aos mols do íon Li+. A caracterização do material obtido foi feita utilizando-se as técnicas básicas de caracterização de materiais tais como: análises térmicas (DSC, TG), medidas óticas (IR), visualização da superfície das amostras através de microscopia eletrônica de varredura (MEV), ressonância magnética nuclear (RMN) e como a mais importante, medidas de condução iônica, através de espectroscopia de impedância eletroquímica (EIE), onde as amostras plastificadas com 30% de glicerol em relação à massa de amido apresentaram as melhores propriedades de condutividade, aderência e estabilidade para amostras com amido eterificado, tendo um máximo de condutividade de 3,45.10-6 S/cm para na quantidade de sal na razão 15[O]/[Li]. Em amostras contendo amido catiônico, obtiveram-se valores parecidos de condutividade quando plastificados com etileno glicol, nas razões de sal de lítio igual a 10[O]/[Li], 15[O]/[Li] e 20[O]/[Li], no entanto o melhor valor de condutividade ocorreu em filmes plastificados com 30% de etileno glicol e 08 [O]/[Li], apresentando o valor de 1,55.10-3 S/cm. Para amostras contendo amido oxidado, pode-se concluir que filmes contendo 30% de etileno glicol e sal na concentração de 8[O]/[Li] apresentam melhores resultados de condutividade iônica. Também foi observado em algumas amostras, que a condutividade em função da temperatura varia linearmente com o aumento da temperatura, mas para amostra com baixa concentração de sal, não se observa mais essa linearidade ([O]/[Li]=30). Isto significa que as espécies responsáveis pela condução estão inseridas em uma matriz que ora coopera com o deslocamento dos íons (Modelo VTF característico para amostras entrecruzadas e em concentrações altas de sal ([O]/[Li]=8) estes movimentos parecem não ter grandes influências no transporte iônico (Modelo Arrhenius); caso das amostras plastificadas. / Natural polymers are very interesting matrix to obtain solid polymeric electrolytes (SPE). The principal advantage comes from its particularly interesting biodegradation properties due to the natural precedence and also very low cost and good physical and chemical properties. These polymers contain heteroatoms in its structure and for this reason can complex protons or lithium ions leading to the ionic conduction. Among different natural polymers, starch-based SPEs show good opto-electrochemical characteristics and can be applied in electrochemical devices. This work presents the results of cassava starch derivatives-based electrolytes, which were characterized by impedance spectroscopy (EIE), thermal analysis (TGA and DSC) and scanning microscopy (SEM).. The SPEs samples were obtained from cationic, eterified and oxidated starches plasticized with glycerol and ethylene glycol and containing lithium salt LiClO4. Different compositions of SPEs i.e. salt and plasticizer quantities were investigated, where it was observed that the ionic conductivity results obtained for these SPEs varied from 10-9 S/cm to 10-4 S/cm at room temperature depending on the sample and increased following Arrhenius or VTF ionic conductivity models. The best results of ionic conductivity values of 1,55.10-3 S/cm were obtained for SPEs oxidized starch plasticized with 30% of ethylene glycol and containing 08 [O]/[Li]. Thermal analysis using thermogravimetry (TGA) was performed in order to observe the change in degradation temperature caused by the changes performed on the samples. Good conductivity results combined with transparency and good adhesion to the electrodes have shown that starch-based SPEs are very promising materials to be used as solid electrolytes in electrochromic devices.

Ischemic stroke is the leading cause of disability world-wide and affects over 800,000 people per year in the United States. The majority of these strokes are ischemic due to a blockage of blood flow to the brain. Damage to the brain occurs at the onset of stroke, neuronal cell death is irreversible and therefore, quick treatment to remove blockage is critical factor in the recovery from stroke. Mechanical thrombectomy as a treatment for ischemic stroke provides an ideal opportunity to collect blood distal and proximal to the cerebral thrombus to examine neurochemical changes occurring during stroke. The purpose of this dissertation was to explore the trajectory of neurochemical changes that occur in response to ischemic stroke during the first 72 hours and the physiological response from stroke patients to improve stroke outcomes. The specific aims were to: 1) to determine whether venous blood gases predict infarct volume and/or mortality in acute ischemic stroke in young male rats; 2) determine whether venous blood gases predict infarct and edema volume, and/or mortality in acute ischemic stroke in aged male and female rats; 3) compare the presence and relative concentrations of acid/base and electrolytes in static blood distal to thrombus and in peripheral blood drawn from adults who received thrombectomy for ischemic stroke and identify associations to postreperfusion functional outcomes. Specific Aim One was addressed by evaluation of young (three-month old) Sprague-Dawley rats that underwent permanent or transient middle cerebral artery occlusion (MCAO). Pre- and post-MCAO venous samples from permanent and transient models provided pH, carbon dioxide, oxygen, bicarbonate, glucose, hematocrit, hematocrit, and electrolyte values of ionized calcium, potassium and sodium. The analyses indicated that mean differences in the blood gas and electrolytes between pre- to post-MCAO and pH and iCa2+ were predictors of infarct volume in the permanent MCAO model. The second aim was addressed by evaluation of aged (18 month old) male and female rats pre-MCAO, post-MCAO, and at 72 hours of permanent MCAO venous blood gas samples (pH, carbon dioxide, oxygen, bicarbonate, glucose, hematocrit, hematocrit, and electrolyte concentrations of ionized calcium, potassium and sodium). Changes in pH (from pre-MCAO to post-MACO and post-MCAO to 72 hours) and changes in Na+ and iCa2+ (from post-MCAO to 72 hours) were predictors of infarct volume and edema volume, respectively in both sexes. Cox regression revealed there was a 3.25 times increased risk for mortality based on changes (cut-off range within -2.00 to - 7.00) in bicarbonate levels (pre- to post-MCAO). The third aim was addressed by evaluation of acid/base balance (pH, carbon dioxide, oxygen, bicarbonate, ionized calcium, potassium and sodium) of ischemic stroke patients who underwent mechanical thrombectomy. Our results suggests sex differences matter in ischemic stroke populations. Significant differences occur within proximal blood between the sexes. Additionally, females had approximately 2.5 hour increased time between stroke symptom onset to thrombectomy completion time (described as infarct time). Changes in bicarbonate and base deficit were predictors of infarct time, but only in our female population.

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Dans le cadre de la détection de nouveaux allergènes alimentaires, un microsystème pour la séparation bidimensionnelle de protéines par électrophorèse a été développé, ces deux dimensions étant la focalisation isoélectrique (IEF) et l'électrophorèse de zone (EZ). Ces deux modes de séparation ont été étudiées au format capillaire avant d'utiliser les résultats obtenus en microsystèmes. La séparation de protéines par IEF a d'abord été réalisée. Nous avons montré que l'utilisation d'électrolytes constitués d'ampholytes d'intervalles étroits de pH (NC) permettait d'augmenter la résolution puis réalisé la séparation de protéines du lait en microsystèmes. Des microsystèmes en verre et en PDMS et plusieurs traitements de surface ont été comparés en utilisant une méthode de mesure de flux électroosmotique développée pour cela. Nous avons ensuite étudié la séparation de protéines par EZ en microsystèmes. Des NC ont de nouveau été utilisés, pour leur faible conductivité. Nous avons montré qu'ils permettaient de diminuer fortement l'adsorption des protéines puis nous avons réalisé la séparation de ces dernières en quelques secondes après avoir optimisé leur dérivation avec un marqueur fluorescent. Enfin, différents schémas de microsystèmes ont été envisagés pour coupler les deux dimensions de séparation.

<p>The formation of surface films on electrodes in contact with non-aqueous electrolytes in lithium-ion batteries has a vital impact on battery performance. A basic understanding of such films is essential to the development of next-generation power sources. The surface chemistry, morphology and thermal stability of two typical anode and cathode materials, graphite and LiNi_0.8Co_0.2O₂, have here been evaluated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, scanning electron microscopy and differential scanning calorimetry, and placed in relation to the electrochemical performance of the electrodes. </p><p>Chemical and morphological information on electrochemically formed graphite surface films has been obtained accurately by combining XPS measurements with Ar⁺ ion etching. An improved picture of the spatial organisation, including thickness determination of the surface film and characterisation of individual component species, has been established by a novel sputtering calibration procedure. The stability of the surface films has been shown to depend strongly on temperature and choice of lithium salt. Decomposition products from elevated-temperature storage in different electrolyte systems were identified and coupled to effects such as capacity loss and increase in electrode resistance. Different decomposition mechanisms are proposed for surface films formed in electrolytes containing LiBF₄, LiPF₆, LiN(SO₂CF₃)₂ and LiCF₃SO₃ salts.</p><p>Surface film formation due to electrolyte decomposition has been confirmed on LiNi_0.8Co_0.2O₂ positive electrodes. An overall surface-layer increase with temperature has been identified and provides an explanation for the impedance increase the material experiences on elevated-temperature storage. </p><p>Surface phenomena are clearly major factors to consider in selecting materials for practical Li-ion batteries.</p>

Eine der Faustregeln der Kolloid- und Oberflächenphysik ist, dass die meisten Oberflächen geladen sind, wenn sie mit einem Lösungsmittel, normalerweise Wasser, in Kontakt treten. Dies ist zum Beispiel bei ladungsstabilisierten Kolloidalen Suspensionen der Fall, bei denen die Oberfläche der Kolloidteilchen geladen ist (gewöhnlich mit einer Ladung von mehreren Hunderttausend Elementarladungen), oder bei Monoschichten ionischer Tenside, die auf einer Luft-Wasser Grenzfläche sitzen (wobei die wasserliebenden Kopfgruppen durch die Freisetzung von Gegenionen geladen werden), sowie bei Doppelschichten, die geladene phospholipide enthalten (wie Zellmembranen). In dieser Arbeit betrachten wir einige Modellsysteme, die zwar eine vereinfachte Fassung der Realität darstellen, von denen wir aber dennoch erwarten koennen, dass wir mit ihrer Hilfe einige physikalische Eigenschaften realer geladener Systeme (Kolloide und Elektrolyte) einfangen können. / One of the rules-of-thumb of colloid and surface physics is that most surfaces are charged when in contact with a solvent, usually water. This is the case, for instance, in charge-stabilized colloidal suspensions, where the surface of the colloidal particles are charged (usually with a charge of hundreds to thousands of e, the elementary charge), monolayers of ionic surfactants sitting at an air-water interface (where the water-loving head groups become charged by releasing counterions), or bilayers containing charged phospholipids (as cell membranes). In this work, we look at some model-systems that, although being a simplified version of reality, are expected to capture some of the physical properties of real charged systems (colloids and electrolytes).<br /> <br /> We initially study the simple double layer, composed by a charged wall in the presence of its counterions. The charges at the wall are smeared out and the dielectric constant is the same everywhere. The Poisson-Boltzmann (PB) approach gives asymptotically exact counterion density profiles around charged objects in the weak-coupling limit of systems with low-valent counterions, surfaces with low charge density and high temperature (or small Bjerrum length). Using Monte Carlo simulations, we obtain the profiles around the charged wall and compare it with both Poisson-Boltzmann (in the low coupling limit) and the novel strong coupling (SC) theory in the opposite limit of high couplings. In the latter limit, the simulations show that the SC leads in fact to asymptotically correct density profiles. We also compare the Monte Carlo data with previously calculated corrections to the Poisson-Boltzmann theory. We also discuss in detail the methods used to perform the computer simulations.<br /> <br /> After studying the simple double layer in detail, we introduce a dielectric jump at the charged wall and investigate its effect on the counterion density distribution. As we will show, the Poisson-Boltzmann description of the double layer remains a good approximation at low coupling values, while the strong coupling theory is shown to lead to the correct density profiles close to the wall (and at all couplings). For very large couplings, only systems where the difference between the dielectric constants of the wall and of the solvent is small are shown to be well described by SC.<br /> <br /> Another experimentally relevant modification to the simple double layer is to make the charges at the plane discrete.<br /> The counterions are still assumed to be point-like, but we constraint the distance of approach between ions in the plane and counterions to a minimum distance D. The ratio between D and the distance between neighboring ions in the plane is, as we will see, one of the important quantities in determining the influence of the discrete nature of the charges at the wall over the density profiles. Another parameter that plays an important role, as in the previous case, is the coupling as we will demonstrate, systems with higher coupling are more subject to discretization effects than systems with low coupling parameter.<br /> <br /> After studying the isolated double layer, we look at the interaction between two double layers. The system is composed by two equally charged walls at distance d, with the counterions confined between them. The charge at the walls is smeared out and the dielectric constant is the same everywhere. Using Monte-Carlo simulations we obtain the inter-plate pressure in the global parameter space, and the pressure is shown to be negative (attraction) at certain conditions. The simulations also show that the equilibrium plate separation (where the pressure changes from attractive to repulsive) exhibits a novel unbinding transition. We compare the Monte Carlo results with the strong-coupling theory, which is shown to describe well the bound states of systems with moderate and high couplings. The regime where the two walls are very close to each other is also shown to be well described by the SC theory.<br /> <br /> Finally, Using a field-theoretic approach, we derive the exact low-density ("virial") expansion of a binary mixture of positively and negatively charged hard spheres (two-component hard-core plasma, TCPHC). The free energy obtained is valid for systems where the diameters d_+ and d_- and the charge valences q_+ and q_- of positive and negative ions are unconstrained, i.e., the same expression can be used to treat dilute salt solutions (where typically d_+ ~ d_- and q_+ ~ q_-) as well as colloidal suspensions (where the difference in size and valence between macroions and counterions can be very large). We also discuss some applications of our results.

The formation of surface films on electrodes in contact with non-aqueous electrolytes in lithium-ion batteries has a vital impact on battery performance. A basic understanding of such films is essential to the development of next-generation power sources. The surface chemistry, morphology and thermal stability of two typical anode and cathode materials, graphite and LiNi0.8Co0.2O2, have here been evaluated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, scanning electron microscopy and differential scanning calorimetry, and placed in relation to the electrochemical performance of the electrodes. Chemical and morphological information on electrochemically formed graphite surface films has been obtained accurately by combining XPS measurements with Ar+ ion etching. An improved picture of the spatial organisation, including thickness determination of the surface film and characterisation of individual component species, has been established by a novel sputtering calibration procedure. The stability of the surface films has been shown to depend strongly on temperature and choice of lithium salt. Decomposition products from elevated-temperature storage in different electrolyte systems were identified and coupled to effects such as capacity loss and increase in electrode resistance. Different decomposition mechanisms are proposed for surface films formed in electrolytes containing LiBF4, LiPF6, LiN(SO2CF3)2 and LiCF3SO3 salts. Surface film formation due to electrolyte decomposition has been confirmed on LiNi0.8Co0.2O2 positive electrodes. An overall surface-layer increase with temperature has been identified and provides an explanation for the impedance increase the material experiences on elevated-temperature storage. Surface phenomena are clearly major factors to consider in selecting materials for practical Li-ion batteries.

Les ions en solutions ont un rôle fondamental dans de nombreux processus physiques, chimiques et biologiques. Dans le cadre des applications industrielles, l'ingénieur les décrits par des modèles analytiques simples, qui sont paramétrisés et ajustés afin de reproduire des données expérimentales. Dans ce travail, nous proposons une procédure multi-échelle à gros-grains pour obtenir ces modèles simples à partir de descriptions atomiques. D'abord, les paramètres de forces classiques pour des ions en solutions sont extraits de calculs ab-initio. Des potentiels effectifs (McMillan-Mayer) ion-ion sont ensuite obtenus à partir des fonctions de distribution de paire mesurées dans des simulations de dynamique moléculaire. Avec ces potentiels effectifs, nous pouvons établir une description à solvant continu des électrolytes. Finalement, nous mettons en œuvre un calcul de perturbation, pour définir la meilleure représentation possible pour ces systèmes, en termes de sphères dures chargées (éventuellement associées). Le modèle final ainsi obtenu est analytique et il ne contient pas de paramètres ajustables. On montre qu'il est en bon accord avec les résultats exacts obtenus par des simulations Monte-Carlo pour la structure et la thermodynamique. La thèse se termine en proposant la mise au point d'une analyse similaire pour la viscosité des électrolytes, obtenue à partir d'une base moléculaire