Os polissabões são polímeros constituídos de unidades monoméricas anfifílicas. Em meio aquoso, os polissabões formam microdomínios intra- ou inter-poliméricos capazes de mimetizar muitas das propriedades de micelas, como solubilizar moléculas orgânicas, trocar contraíons e catalisar reações químicas. Os polissabões utilizados em nossos estudos foram os [n,m]-Ionenos, cuja estrutura química consiste de grupos dimetilamônio interligados por segmentos de cadeia alifática. [-(CH2)n-+N(CH3)2-(CH2)m-+N(CH3)2-]x Br- Br-[n,m]-Ioneno. Em solução aquosa, os [n,m]-Ionenos com segmentos metilênicos curtos, como por exemplo o [3,10]-Ioneno, adotam uma conformação extendida tipo \"bastão\". Por outro lado, ionenos com segmentos mais compridos, como o [3,22]-Ioneno, preferem conformações globulares, formando microdomínios através de um processo de agregação intra-polimérica dos segmentos compridos. Pelo fato de ionenos serem polímeros, podem ser imobilizados em suportes sólidos, tanto covalentemente como por adsorção eletrostática. O objetivo desse trabalho foi desenvolver novas estratégias para a eficiente imobilização covalente de ionenos sobre suportes sólidos. Os ionenos podem ser seletiva e quantitativamente desquaternizados (desmetilados), formando a poli(amina terciária) correspondente: [-(CH2)n-+N(CH3)2-(CH2)m-+N(CH3)2-]x → [-(CH2)n-N(CH3)-(CH2)m-N(CH3)-]x. Ao contrário do ioneno, a poli(amina terciária) é solúvel em meio orgânico, não apresenta forte tendência de adsorver em superfícies e possui numerosos grupos reativos (as aminas terciárias) distribuídos ao longo de toda cadeia polimérica, adequados para a imobilização da poli(amina terciária) em sílica funcionalizada com grupos cloropropil. A requaternização foi feita com vários reagentes, incluindo haletos de alquila com comprimentos de cadeia distintos (e.g., brometo de etila ou brometo de dodecila) e com 1,3-propanosultona (que fornece ionenos zwitteriônicos com grupos amôniopropano-sulfonato). A fluorescência (comprimento de onda máximo e emissão) do ácido 4-amino-1-naftaleno sulfônico (AMS) mostrou-se útil para a detecção da presença de microdomínios formados pelos ionenos imobilizados na sílica. A relação de intensidades das bandas vibracionais I/III do espectro de fluorescência do pireno dissolvido nos microdomínios permitiu inferir o grau residual de contato entre pireno e a água na superfície dos microdomínios. As propriedades \"catalíticas\" dos ionenos imobilizados foram averiguadas por meio de medidas da velocidade da hidrólise alcalina do octanoato de p-nitrofenila (NPO) e do brometo de N-dodecil-4-cianopiridíneo (DCP). A espessura da camada formada pelos ionenos imobilizados na presença de água foi medida experimentalmente ex-situ e in-situ por elipsometria. Finalmente, alguns ensaios de HPLC utilizando a sílica funcionalizada com ionenos como fase estacionária foram feitos de modo a avaliar sua aplicabilidade real. / Polysoaps are polymers consisting of amphiphilic monomeric units. In aqueous medium, the polysoaps form intra- or inter-polymeric microdomains capable to mimicking many of the properties of micelles, such as solubilization of organic molecules, exchanging counter-ions and catalyzing chemical reactions. The polysoaps used in our studies were [n, m]-ionenes, whose chemical structure consists of dimethylammoniun groups interconnected by aliphatic chain segments. [-(CH2)n-+N(CH3)2-(CH2)m-+N(CH3)2-]x Br- Br-[n,m]-Ioneno. In aqueous solution, [n, m]-ionenes with short methylenic segments, for example [3,10]-ionene, adopt an extended or rodlike conformations. In contrast, ionenes with longer segments, as the [3,22]-ionene, prefer globular conformations, forming microdomains through a process of intra-polymeric aggregation of the long segments. Because the ionenes are polymers, they can be immobilized on solid supports by covalent or electrostatic adsorption. The objective of this work was to develop new strategies for the efficient covalent immobilization of ionenes on solid supports. Ionenes can be selectively and quantitatively dequaternized (demethylated), forming the corresponding poly(tertiary amine): [-(CH2)n-+N(CH3)2-(CH2)m-+N(CH3)2-]x → [-(CH2)n-N(CH3)-(CH2)m-N(CH3)-]x. Unlike the ionene, the poly(tertiary amine) is soluble in organic medium, does not adsorb onto surfaces and possesses numerous reactive groups (the tertiary amines) distributed throughout the polymer chain. Suitable for immobilization of poly(tertiary amine) on silica funcionalizada with chloropropyl groups. The requaternization was performed with alkyl halides with distinct chain lengths (e.g., ethyl bromide or dodecyl bromide) and with 1,3-propanosultone (yielding zwitterionic ionenes with amoniopropane-sulfonate groups). The fluorescence (maximum wavelength and emission) of 4-amino-1-naphthalene sulfonic acid (AMS) was useful for the detection of the presence of microdomains formed by the immobilized ionenes on silica. The intensity ratio of the I/III vibrational bands of the fluorescence of pyrene dissolved in the microdomains was used to infer the residual degree of contact between pyrene and water at surface of the microdomains. \"The catalytic\" properties of the immobilized ionenes was invetigated by measuring the rate of alkaline hydrolysis of p-nitrophenyl octanoate (NPO) and of the N-dodecyl-4-cyanopyridinium ion (DCP). The thickness of the layer formed by the immobilized ionenes in the presence of water was measured experimentally ex-situ and in-situ by ellipsometry. Finally, some HPLC tests using silica functionalized with ionenes as the stationary phase were made in order to evaluate thesis applicability.

Proton exchange membrane (PEM) fuel cells are one of the most promising clean energy technologies under development. The major advantages include electrical efficiencies of up to 55 %, high energy densities (relative to batteries), and low emissions. However, the main obstacles to commercialization of PEM fuel cells are related to the limitations of the proton conducting solid polymer electrolytes such as Nafion. These membranes are expensive, mechanically unfavorable at higher temperatures, and conduct protons only in the presence of water, which limits the fuel cell operating temperature to about 80 C. This in turn, results in low fuel cell performance due to slow electrode kinetics and virtually no CO tolerance. The potential operation of PEM fuel cells at higher temperature (above 100 C) can provide many advantages such as improved kinetics at the surface of electrode, which is especially important in methanol and CO-containing reformate feeds, and efficient heat rejection and water management. Another issue above 100 C is the reduction of electrochemical surface area of the electrodes due to shrinkage of electrolyte (Nafion phase) within the catalyst layers. This research work is thus focused on the development of nanocomposite proton exchange membranes (NCPEMs) which are chemically and mechanically more stable at higher temperatures and electrodes which can result into better fuel cell performance. These are composite materials with inorganic acidic nanoparticles incorporated within a host polymer electrolyte membrane such as Nafion. The target operating fuel cell temperature in this work is above 100 oC with relative humidity around 30 to 40 %. To achieve these targets, both theoretical and experimental investigations were undertaken to systematically develop these NCPEMs. Various experimental techniques, namely, TEOM (Tapered Element Oscillating Microbalance), Impedance Spectroscopy, MEA (membrane electrode assembly) testing, Ion Exchange Capacity, Scanning Electron Microscope (SEM), Optical Electronic Holography (OEH), Thermal Gravimetric Analysis (TGA), and Dynamic Mechanical Analysis (DMA) were employed to characterize the NCPEMs. A thermodynamic model was developed to describe sorption in proton-exchange membranes (PEMs), which can predict the complete sorption isotherm. A comprehensive proton transport model was also developed to describe proton diffusion in Nafion/(ZrO2/SO42-) nanocomposite membranes. The conductivity of the in situ sol-gel prepared Nafion/ (ZrO2/SO42-) nanocomposite membranes was accurately predicted by the model as a function of relative humidity (RH) without any fitted parameters. This transport model developed offers a theoretical framework for understanding the proton transfer in nanocomposite membranes and is an insightful guide in systematically developing high proton-conducting nanocomposite. Nafion-MO2(M = Zr, Si, Ti) nanocomposite membranes were synthesized with the goal to increase the proton conductivity and water retention by the membrane at higher temperatures and lower relative humidity (120 C, 40% RH) and also to improve the thermo-mechanical properties. The results obtained are promising and indicate that this is a potentially useful approach for developing PEMs with desirable properties. Finally, commercially available high temperature PBI (polybenzimidazole)-H3PO4 (phosphoric acid) gel membrane fuel cell was investigated in the temperature range of 160-180 C. This system exhibited very good and stable performance in this temperature range.

The search for environmentally benign energy sources is becoming increasingly urgent. One such technology is fuel cells, e.g., the polymer electrolyte membrane (PEM) fuel cell which uses hydrogen as a fuel and emits only H2O. However, reforming hydrocarbon fuels to produce the needed hydrogen yields reformate streams containing CO2 as well as CO, which is toxic to the PEM fuel cell at concentrations above 100ppm. As the amount of CO permitted to reach the fuel cell increases, the performance of the PEM fuel cell decreases until it ultimately stops functioning. The water-gas-shift (WGS) reaction, CO + H2O <-> H2 + CO2, provides a method for extracting the energy from the toxic CO by converting it into usable H2 along with CO2 which can be tolerated by the fuel cell. Although a well established industrial process, alternate catalysts are sought for fuel cell application. Catalyst selection for the WGS reaction has, until recently, been based on trial-and-error screening of potential catalysts due to a lack of fundamental understanding of the catalyst's functioning. For this reason, we embarked on a deeper understanding of the molecular events involved in the WGS reaction such that a more systematic and theory-guided approach may be used to design and select catalysts more efficiently, i.e., rational catalyst design. The goal of this research was to develop a comprehensive predictive microkinetic model for the WGS reaction which is based solely on a detailed mechanism as well as theories of surface-molecule interactions (i.e., the transition-state theory) with energetic parameters determined a priori. This was followed by a comparison of the experimental results of sample catalysts to validate the model for various metal-based catalysts of interest including Cu, Fe, Ni, Pd, Pt, Rh, and Ru. A comprehensive mechanism of the plausible elementary reaction steps was compiled from existing mechanisms in the literature. These were supplemented with other likely candidates which are derivatives of those identified in the literature. Using established theories, we predicted the kinetics of each of the elementary reaction steps on metal catalysts of interest. The Unity Bond Index-Quadratic Exponential Potential Method (UBI-QEP) was used to predict the activation energies in both the forward and reverse direction of each step based solely on heats of chemisorption and bond dissociation energies of the species involved. The Transition State Theory (TST) was used to predict the pre-exponential factors for each step assuming an immobile transition state; however, the pre-exponential factors were adjusted slightly to ensure thermodynamic consistency with the overall WGS reaction. In addition, we have developed a new and powerful theoretical tool to gain further insight into the dominant pathways on a catalytic surface as reactants become products. Reaction Route (RR) Graph Theory incorporates fundamental elements of graph theory and electrical network theory to graphically depict and analyze reaction mechanisms. The stoichiometry of a mechanism determines the connectivity of the elementary reaction steps. Each elementary reaction step is viewed as a single branch with an assumed direction corresponding to the assumed forward direction of the elementary reaction step. The steps become interconnected via nodes which reflect the quasi-steady state conditions of the species represented by the node. A complete RR graph intertwines a series of routes by which the reactants may be converted to products. Once constructed, the RR graph may be converted into an electrical network by replacing, in the steady-state case, each elementary reaction step branch with a resistor and including the overall reaction as a power source where rate and affinity correspond to current and voltage, respectively. A simplification and reduction of the mechanism may be performed based on results from a rigorous De Donder affinity analysis as it correlates to Kirchhoff's Voltage Law (KVL), akin to thermodynamic consistency, coupled with quasi-steady state conditions, i.e., conservation of mass, analyzed using Kirchhoff's Current Law (KCL). Hence, given the elementary reaction step resistances, in conjunction with Kirchhoff's Laws, a systematic reduction of the network identifies the dominant routes, e.g., the routes with the lowest resistance, along with slow and quasi-equilibrium elementary reaction steps, yielding a simplified mechanism from which a predictive rate expression may possibly be derived. Here, we have applied RR Graph Theory to the WGS reaction. An 18-step mechanism was employed to understand and predict the kinetics of the WGS reaction. From the stoichiometric matrix for this mechanism, the topological features necessary to assemble the RR graph, namely the intermediate nodes, terminal nodes, empty reaction routes and full reaction routes, were enumerated and the graph constructed. The assembly of the RR graph provides a comprehensive overview of the mechanism. After reduction of the network, the simplified mechanism, comprising the dominant pathways, identified the quasi-equilibrium and rate-determining steps, which were used to determine the simplified rate expression which predicts the rate of the complete mechanism for different catalysts. Experimental investigations were conducted on the catalysts of interest to validate the microkinetic model derived. Comparison of the experimental results from the industrially employed catalysts (e.g., Cu, Ni, Fe, etc.) shows that the simplified microkinetic model sufficiently predicts the behavior of the WGS reaction for this series of catalysts with very good agreement. Other catalysis tested (Pt, Pd, Rh and Ru), however, had sufficient methanation activity that a direct comparison with WGS kinetics could not be made. In summary, we have developed a comprehensive approach to unravel the mechanism and kinetics of a catalytic reaction. The methodology described provides a more fundamental depiction of events on the surface of a catalyst paving the way for rational analysis and catalyst design. Illustrated here with the WGS reaction as an example, we show that the dominant RRs may be systematically determined through the application of rigorous fundamental constraints (e.g. thermodynamic consistency and mass conservation) yielding a corresponding explicit a priori rate expression which illustrates very good agreement not only with the complete microkinetic mechanism, but also the experimental data. Overall, RR graph theory is a powerful new tool that may become invaluable for unraveling the mechanism and kinetics of complex catalytic reactions via a common-sense approach based on fundamentals.

Made available in DSpace on 2017-07-24T19:38:13Z (GMT). No. of bitstreams: 1 Alan Fernando Matsushita.pdf: 4074465 bytes, checksum: 5a6766b6dfd2ff1e7de5f241b872a175 (MD5) Previous issue date: 2014-03-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The fabrics are used for various applications in our daily life, and particularly natural fabrics such as cotton are susceptible to bacterial growth due to moisture that it can accumulate which facilitates this process and also the fibers themselves may serve as nutrients for the growth of microorganisms. In this work, the synthesis of silver and zinc oxide particles was carried out for their and corporation into cotton fibers by the Layer-by-layer method. The silver nanoparticles provide high biocidal activity when incorporated into fabrics textiles and zinc oxide particles promote a block against ultraviolet radiation and also provide the self-cleaning properties for the fabric by the oxidation of compounds on its surface. Therefore the aim of this work was to promote these characteristics in a cotton fabric. The synthesis of silver nanoparticles and zinc oxide were performed using polyelectrolytes as suspension stabilizers. The syntheses were carried out using four ratios related to the metal concentration and polyelectrolyte (1, 2, 5 and 10%). For silver nanoparticles, the 3-n-propylpyridinium silsesquioxane chloride (SiPy+Cl-) was used as stabilizer obtaining nanoparticles of 5 nm in diameter and for ZnO nanoparticles it was used the poly(dialildimethylamonium chloride) PDDA, obtaining in this case particles with sizes larger than 400 nm. These nanocomposites were used to obtain a thin coating on the cotton fibers. For the construction of the films on the cotton fibers, it was used the LbL technique, where it was necessary to perform a prior chemical treatment on the fabric in order to provide an interaction between the cotton fabric surface and the polyelectrolytes. The bilayers were grown in fabrics with the use of polystyrenesulfonate (PSS) as polyanion. Characterization of the fabrics coated with Ag/SiPy+Cl- nanocomposites was performed by varying the number of bilayers. From the SEM images, it was observed the LbL coating on the fabric surface and EDS analysis enabled to estimate the amount of AgNps adsorbed on fabrics. The antibacterial tests for these fabrics showed good results for E. coli and S. aureus bacteria indicating a bactericidal and bacteriostatic character. From the color analysis and UV- Vis spectra of cotton fabrics, it was possible to estimate its homogeneity. Studies of the release of silver nanoparticles were performed by atomic absorption analysis of the washing solution up to 15 washing cycles of the fabric, indicating a high stability of the nanocomposite coating. SEM characterization of the fabrics coated with the nanocomposite ZnO/PDDA showed the growth of the bilayers as well as increase of the ZnO amount on the cotton fiber by the EDS analysis. Through TEM images observed nanoparticles with sizes between 2-10 nm. The analysis of the UV protection factor of these fabrics showed a 60% blockage of UVA and UVB radiations. Studies of photocatalytic degradation of methylene blue dye showed good results degradando totalmente o corante em 8 horas para tecidos revestidos com poucas bicamadas, which increased with the number of bilayers in the fabric. It was observed that in presence of silver nanoparticles, the degradation of the dye becomes more pronounced. The analysis of the shedding of particles of zinc oxide was also performed by atomic absorption analysis of the wash solution until 15 washing cycles. The results for this nanocomposite coated on the fabric also showed satisfactory results. / Os tecidos são utilizados para várias aplicações em nosso dia a dia, e principalmente os tecidos naturais como o algodão são suscetíveis ao crescimento bacteriano devido ao fato de acumularem umidade o que facilita esse processo, além das próprias fibras servirem como nutrientes para o crescimento de microorganismos. Neste trabalho foi realizada a síntese de nanopartículas de prata e óxido de zinco para incorporação em fibras de algodão através do método Layer-by-layer. As nanopartículas de prata conferem alta atividade biocida quando incorporada em tecidos e as nanopartículas de óxido de zinco promovem um bloqueio contra radiação ultra-violeta e também pode tornar o tecido auto limpante através da oxidação de compostos na sua superfície. Portanto o objetivo deste trabalho foi promover essas características em um tecido de algodão. A síntese das nanopartículas de prata e óxido de zinco foram realizadas utilizando-se polieletrólitos como estabilizantes da suspensão. As sínteses foram realizadas em 4 proporções (1, 2, 5 e 10%) do metal em relação a concentração do polieletrólito. Para as nanopartículas de prata utilizou-se o cloreto de 3-n-propilpiridínio silsesquioxano (SiPy+Cl-) como estabilizante obtendo-se nanopartículas de 5 nm de diâmetro enquanto que para o ZnO utilizou-se o Poli(cloreto de dialildimetilamônio) PDDA, obtendo-se neste caso nanopartículas com tamanhos maiores que 400 nm. Esses nanocompósitos foram utilizados para realizar um revestimento sobre fibras de algodão. Para isto utilizou-se a técnica LbL, onde se foi necessário realizar um tratamento químico prévio no tecido para haver uma interação entre a superfície do tecido e os polieletrólitos. As bicamadas foram crescidas no tecido com a utilização do poliestireno sulfonado (PSS) como poliânion. A caracterização dos tecidos revestidos com os nanocompósitos Ag/SiPy+Cl- foi realizada variando-se o número de bicamadas. A partir de imagens de MEV observou-se o revestimento crescido sobre a superfície do tecido e a análise de EDS foi utilizada como tentativa de estimar a quantidade de prata adsorvida nos tecidos. Através de imagens de TEM observou-se nanopartículas com tamanhos entre 2 – 10 nm. Os testes antibacterianos para estes tecidos apresentaram bons resultados para as bactérias E. coli e S. aureus indicando um caráter bactericida e bacteriostático. Também realizou-se a análise de cor através do método CieLab e espectros UV-Vis dos tecidos para estimar a sua homogeneidade. A análise de desprendimento de partículas de prata foi realizada através da análise de absorção atômica da solução de lavagem até um ciclo de 15 lavagens do tecido, resultado que indicou uma alta estabilidade do nanocompósito revestido sobre o tecido. A caracterização dos tecidos revestidos com o nanocompósito ZnO/PDDA foi realizada através das imagens de MEV, onde observou-se o crescimento das bicamadas bem como o aumento da quantidade de ZnO nos tecidos visto pela análise de EDS. A análise do fator de proteção UV destes tecidos apresentou um resultado de até 60% do bloqueio das radiações UVA e UVB. Os testes de degradação fotocatalítica do corante azul de metileno apresentaram bons resultados degradando totalmente o corante em 8 horas para tecidos revestidos com poucas bicamadas, aumentando esse efeito à medida que aumentou-se o número de bicamadas no tecido e na presença de nanopartículas de prata a degradação do corante apresentou-se mais acentuada. A análise de desprendimento de partículas de zinco também foi realizada através da análise de absorção atômica da solução de lavagem até um ciclo de 15 lavagens do tecido, o resultado para este nanocompósito revestido sobre o tecido também apresentou resultados satisfatórios.

De nos jours, de nombreuses maladies chroniques telles que le cancer ou l’arthrose nécessitent encore de nouvelles modalités de traitement. Des biomatériaux naturels capables de véhiculer des substances actives font partie des solutions à cette problématique. Récemment, des travaux ont été menés sur un nouveau type de biomatériau, les Complexes de Polyélectrolytes Compacts (CoPEC). Dans le cadre de cette thèse, des CoPEC à base de polyélectrolytes biosourcés, le chitosan et l’alginate, fonctionnalisés avec la β-cyclodextrine (βCD) ont été formulés. Le CoPEC βCD-chitosan/alginate, non-cytotoxique, a présenté des propriétés anti-inflammatoires intrinsèques dans le cadre d’un modèle in vitro d’inflammation. De plus, ce CoPEC a présenté une capacité à contenir et relarguer deux substances actives hydrophobes modèles, le piroxicam et la prednisolone. Enfin, une stratégie d’inclusion de substances actives hydrophiles au sein du matériau a été mise en œuvre. Le nouveau CoPEC est prometteur car il peut exposer un effet anti-inflammatoire intrinsèque et d’autres effets thérapeutiques via l’inclusion de substances actives au sein des cyclodextrines. / Nowadays, many chronic diseases, such as cancer or osteoarthritis, still need new modalities of treatment. Natural biomaterials able to convey active substances represent a solution to this problematic. Lately, several research works have been conducted on a new type of biomaterial named Compact Polyelectrolyte Complexes (CoPEC). As part of this thesis, CoPEC have been prepared from two biosourced polyelectrolytes, chitosan and alginate, functionalized with β-cyclodextrin (βCD). Through an in vitro inflammation model, the non-cytotoxic βCD-chitosan/alginate CoPEC has displayed intrinsic anti-inflammatory properties. Moreover, this CoPEC has demonstrated a capacity to host and release piroxicam and prednisolone, two model hydrophobic active substances. Finally, a strategy to include hydrophilic active substances into the material has been implemented.Thus, the newly CoPEC is promising because it can exhibit an intrinsic anti-inflammatory effect as well as other therapeutic effects through the inclusion of active substances into the cyclodextrins.

Polyacrylamides (PAMs) are a class of polymers formed from acrylamide alone or copolymerized with other monomers. PAMs have been used in drinking water treatment as flocculants or coagulants in the highest volume among all the polymer types. In potable water treatment processes, polyacrylamides are often exposed to oxidants (e.g. chlorine and permanganate) and UV irradiation from sunlight or artificial sources. The purpose of this study is to evaluate the possible degradation of PAMs caused by chemical oxidation and/or UV irradiation. Three types of PAM products (nonionic, cationic and anionic) were studied under free chlorine and permanganate oxidation, UV irradiation, and their combined effects. It has been found that the cationic PAM was the most unstable polymer among the three types of polymer sample studies, however, only partial degradation was observed. Acrylamide residual in the cationic PAM C-3280 was higher than the U.S. guideline value, and exposure to either chlorine or permanganate resulted in decline of acrylamide level to some extent. UV irradiation did not cause reduction of total polymer contents and acrylamide residuals, but did accelerate chemically induced degradation. Exposure to chlorine or permanganate for one hour resulted in about 20-35% loss in flocculation performance for each polymer sample. Short time exposure (5 minutes) did not result in loss of flocculation performance for the nonionic and anionic PAMs. However, for the cationic PAM, even short time exposure to chlorine led to loss of flocculation performance of 25-35 %, which indicated that the cationic PAM was more susceptible to oxidation.

L'arsenic, existe dans l'environnement sous une grande variété de formes et à divers degrés d'oxydation. Aux pH naturels, l'arsenic libre se rencontre essentiellement sous forme inorganique aux degrés d'oxydation +III (arsénite) et +V (arséniate). Il est reconnu que l'efficacité des processus d'élimination de l'arsenic dépend fortement de la possibilité de convertir les espèces de l'arsenic (III) en celle de l'arsenic (V), plus faciles à extraire. La recherche développée au cours de cette thèse démontre d'abord qu'il est possible d'éliminer l'arséniate de solutions aqueuses par extraction par des polymères solubles (LPR : liquid-phase polymer-based retention). La technique LPR utilise l'ultrafiltration sur membrane pour la séparation, basée sur des effets de taille, d'espèces ioniques suite à leur complexation par des polyélectrolytes solubles. Les espèces oxo-anioniques de l'arsenic(V), associés à des polyélectolytes du type polyalkyammonium, ne passent pas à travers la membrane et peuvent être ainsi séparés des espèces non-complexées de plus petite taille. Nous avons aussi montré la grande activité catalytique des matériaux composites du type nanoparticules de Pt0 et Pd0 dispersées dans des matrices de poly(pyrrole-alkylammonium), pour l'oxydation électrochimique de l'arsénite en arséniate. En particulier, des microélectrodes de carbone modifiées par des films de ces nanocomposites ont été appliquées à l'analyse de l'arsenic(III). Enfin, l'oxydation exhaustive de solutions d'arsénite a été réalisée sur des électrodes de carbone modifiées de grande surface. L'utilisation de sels poly(alkyl-ammonium) jouant le rôle à la d'électrolyte support et d'agent d'extraction des espèces de l'arsenic(V) a permis de combiner les processus d'électrocatalyse et d'extraction par LPR, permettant ainsi d'extraire efficacement des traces d'arsenic de solutions aqueuses.

In the course of this thesis gold nanoparticle/polyelectrolyte multilayer structures were prepared, characterized, and investigated according to their static and ultrafast optical properties. Using the dip-coating or spin-coating layer-by-layer deposition method, gold-nanoparticle layers were embedded in a polyelectrolyte environment with high structural perfection. Typical structures exhibit four repetition units, each consisting of one gold-particle layer and ten double layers of polyelectrolyte (cationic+anionic polyelectrolyte). The structures were characterized by X-ray reflectivity measurements, which reveal Bragg peaks up to the seventh order, evidencing the high stratication of the particle layers. In the same measurements pronounced Kiessig fringes were observed, which indicate a low global roughness of the samples. Atomic force microscopy (AFM) images veried this low roughness, which results from the high smoothing capabilities of polyelectrolyte layers. This smoothing effect facilitates the fabrication of stratified nanoparticle/polyelectrolyte multilayer structures, which were nicely illustrated in a transmission electron microscopy image. The samples' optical properties were investigated by static spectroscopic measurements in the visible and UV range. The measurements revealed a frequency shift of the reflectance and of the plasmon absorption band, depending on the thickness of the polyelectrolyte layers that cover a nanoparticle layer. When the covering layer becomes thicker than the particle interaction range, the absorption spectrum becomes independent of the polymer thickness. However, the reflectance spectrum continues shifting to lower frequencies (even for large thicknesses). The range of plasmon interaction was determined to be in the order of the particle diameter for 10 nm, 20 nm, and 150 nm particles. The transient broadband complex dielectric function of a multilayer structure was determined experimentally by ultrafast pump-probe spectroscopy. This was achieved by simultaneous measurements of the changes in the reflectance and transmittance of the excited sample over a broad spectral range. The changes in the real and imaginary parts of the dielectric function were directly deduced from the measured data by using a recursive formalism based on the Fresnel equations. This method can be applied to a broad range of nanoparticle systems where experimental data on the transient dielectric response are rare. This complete experimental approach serves as a test ground for modeling the dielectric function of a nanoparticle compound structure upon laser excitation. / Im Rahmen dieser Arbeit wurden Gold-Nanopartikel/Polyelektrolyt Multischichtstrukturen hergestellt, strukturell charakterisiert und bezüglich ihrer optischen Eigenschaften sowohl statisch als auch zeitaufgelöst analysiert. Die Strukturen wurden mithilfe der Dip-coating oder der Spin-coating Methode hergestellt. Beide Methoden ermöglichen das Einbetten einzelner Partikellagen in eine Polyelektrolytumgebung. Typische Strukturen in dieser Arbeit bestehen aus vier Wiederholeinheiten, wobei jede aus einer Nanopartikelschicht und zehn Polyelektrolyt-Doppellagen (kationisches und anionisches Polyelektrolyt) zusammengesetzt ist. Die Stratizierung der Gold-Nanopartikellagen wurde mittels Röntgenreflektometrie-Messungen im Kleinwinkelbereich nachgewiesen, welche Bragg Reflexionen bis zur siebten Ordnung aufzeigen. Das ausgeprägte Kiessig Interferenzmuster dieser Messungen weist zudem auf eine geringe globale Rauheit hin, die durch Oberflächenanalysen mit einem Rasterkraftmikroskop bestätigt werden konnte. Diese geringe Rauheit resultiert aus den glättenden Eigenschaften der Polyelektrolyte, die die Herstellung von Multilagensystemen mit mehreren Partikellagen erst ermöglichen. Die Aufnahme eines Transmissionselektronenmikroskops veranschaulicht eindrucksvoll die Anordnung der Partikel in einzelne Schichten. Durch photospektroskopische Messungen wurden die optischen Eigenschaften der Strukturen im UV- und sichtbaren Bereich untersucht. Beispielsweise wird eine Verschiebung und Verstärkung der Plasmonenresonanz beobachtet, wenn eine Goldnanopartikellage mit transparenten Polyelektrolyten beschichtet wird. Erst wenn die bedeckende Schicht dicker als die Reichweite der Plasmonen wird, bleibt die Absorption konstant. Die spektrale Reflektivität jedoch ändert sich auch mit jeder weiteren adsorbierten Polyelektrolytschicht. Die Reichweite der Plasmonenresonanz konnte auf diese Art für Partikel der Größe 10 nm, 20 nm und 150 nm bestimmt werden. Die Ergebnisse wurden im Kontext einer Effektiven Mediums Theorie diskutiert. Die komplexe dielektrische Funktion einer Multilagenstruktur wurde zeitabhängig nach Laserpulsanregung für einen breiten spektralen Bereich bestimmt. Dazu wurden zuerst die Änderungen der Reflektivität und Transmittivität simultan mittels der Pump-Probe (Anrege-Abtast) Spektroskopie gemessen. Anschließend wurden aus diesen Daten, mithilfe eines Formalismus, der auf den Fresnelschen Formeln basiert, die Änderungen im Real- und Imaginärteil der dielektrischen Funktion ermittelt. Diese Methode eignet sich zur Bestimmung der transienten dielektrischen Funktion einer Vielzahl von Nanopartikelsystemen. Der rein experimentelle Ansatz ermöglicht es, effektive Medien Theorien und Simulationen der dielektrischen Funktion nach Laserpulsanregung zu überprüfen.

Within this work, three physicochemical methods for the hydrophobization of initially hydrophilic solid particles are investigated. The modified particles are then used for the stabilization of oil-in-water (o/w) emulsions. For all introduced methods electrostatic interactions between strongly or weakly charged groups in the system are es-sential. (i) Short chain alkylammonium bromides (C4 – C12) adsorb on oppositely charged solid particles. Macroscopic contact angle measurements of water droplets under air and hexane on flat silica surfaces in dependency of the surface charge density and alkylchain-length allow the calculation of the surface energy and give insights into the emulsification properties of solid particles modified with alkyltrimethylammonium bromides. The measure-ments show an increase of the contact angle with increasing surface charge density, due to the enhanced adsorp-tion of the oppositely charged alkylammonium bromides. Contact angles are higher for longer alkylchain lengths. The surface energy calculations show that in particular the surface-hexane or surface-air interfacial en-ergy is being lowered upon alkylammonium adsorption, while a significant increase of the surface-water interfa-cial energy occurs only at long alkyl chain lengths and high surface charge densities. (ii) The thickness and the charge density of an adsorbed weak polyelectrolyte layer (e.g. PMAA, PAH) influence the wettability of nanoparticles (e.g. alumina, silica, see Scheme 1(b)). Furthermore, the isoelectric point and the pH range of colloidal stability of particle-polyelectrolyte composites depend on the thickness of the weak polye-lectrolyte layer. Silica nanoparticles with adsorbed PAH and alumina nanoparticles with adsorbed PMAA be-come interfacially active and thus able to stabilize o/w emulsions when the degree of dissociation of the polye-lectrolyte layer is below 80 %. The average droplet size after emulsification of dodecane in water depends on the thickness and the degree of dissociation of the adsorbed PE-layer. The visualization of the particle-stabilized o/w emulsions by cryogenic SEM shows that for colloidally stable alumina-PMAA composites the oil-water interface is covered with a closely packed monolayer of particles, while for the colloidally unstable case closely packed aggregated particles deposit on the interface. (iii) By emulsifying a mixture of the corrosion inhibitor 8-hydroxyquinoline (8-HQ) and styrene with silica nanoparticles a highly stable o/w emulsion can be obtained in a narrow pH window. The amphoteric character of 8-HQ enables a pH dependent electrostatic interaction with silica nanoparticles, which can render them interfa-cially active. Depending on the concentration and the degree of dissociation of 8-HQ the adsorption onto silica results from electrostatic or aromatic interactions between 8-HQ and the particle-surface. At intermediate amounts of adsorbed 8-HQ the oil wettability of the particles becomes sufficient for stabilizing o/w emulsions. Cryogenic SEM visualization shows that the particles arrange then in a closely packed shell consisting of partly of aggregated domains on the droplet interface. For further increasing amounts of adsorbed 8-HQ the oil wet-tability is reduced again and the particles ability to stabilize emulsions decreases. By the addition of hexadecane to the oil phase the size of the droplets can be reduced down to 200 nm by in-creasing the silica mass fraction. Subsequent polymerization produces corrosion inhibitor filled (20 wt-%) poly-styrene-silica composite particles. The measurement of the release of 8-hydroxyquinoline shows a rapid increase of 8-hydroxyquinoline in a stirred aqueous solution indicating the release of the total content in less than 5 min-utes. The method is extended for the encapsulation of other organic corrosion inhibitors. The silica-polymer-inhibitor composite particles are then dispersed in a water based alkyd emulsion, and the dispersion is used to coat flat aluminium substrates. After drying and cross-linking the polmer-film Confocal Laser Scanning Micros-copy is employed revealing a homogeneous distribution of the particles in the film. Electrochemical Impedance Spectroscopy in aqueous electrolyte solutions shows that films with aggregated particle domains degrade with time and don’t provide long-term corrosion protection of the substrate. However, films with highly dispersed particles have high barrier properties for corrosive species. The comparison of films containing silica-polystyrene composite particles with and without 8-hydroxyquinoline shows higher electrochemical impedances when the inhibitor is present in the film. By applying the Scanning Vibrating Electrode Technique the localized corrosion rate in the fractured area of scratched polymer films containing the silica-polymer-inhibitor composite particles is studied. Electrochemical corrosion cannot be suppressed but the rate is lowered when inhibitor filled composite particles are present in the film. By depositing six polyelectrolyte layers on particle stabilized emulsion droplets their surface morphology changes significantly as shown by SEM visualization. When the oil wettability of the outer polyelectrolyte layer increases, the polyelectrolyte coated droplets can act as emulsion stabilizers themselves by attaching onto bigger oil droplets in a closely packed arrangement. In the presence of 3 mM LaCl3 8-HQ hydrophobized silica particles aggregate strongly on the oil-water inter-face. The application of an ultrasonic field can remove two dimensional shell-compartments from the droplet surface, which are then found in the aqueous bulk phase. Their size ranges up to 1/4th of the spherical particle shell. / Im Rahmen dieser Arbeit wurden drei Oberflächenmodifikationen zur Hydrophobierung von ursprünglich hydrophilen Feststoffpartikeln entwickelt. Die so modifizierten Partikel werden dann zur Stabilisierung von Öl-in-Wasser Emulsionen verwendet. Für sämtliche entwickelte Methoden sind elektrostatische Wechselwirkungen zwischen stark oder schwach dissoziierten chemischen Gruppen essentiell. (i) Kurzkettige Alkyltrimethylammonium Bromide (C4-C12) adsorbieren auf entgegengesetzt geladenen Partikeln. Makroskopische Kontaktwinkelmessungen von Wasser Tropfen in Luft und Hexan auf flachen Siliziumoxid Oberflächen mit variabler Oberflächenladungsdichte und Alkylkettenlänge ermöglichen die Berechnung der Oberflächenenergie und geben Einblicke in die Emulgationseigenschaften von so modifizierten Feststoffpartikeln. Die Messungen zeigen einen Anstieg des Kontakwinkels mit steigender Oberflächenladungsdichte, bedingt durch die verstärkte Adsorption von entgegengesetzt geladenen Alkyltrimethylammonium Bromiden. Die Kontaktwinkel sind zudem größer für längerkettige Alkyltrimethylammonium Bromide. Die Berechnungen der Oberflächenenergie zeigen, dass besonders die Feststoff-Hexan oder Feststoff-Luft Grenzflächenenergie durch die Adsorption verringert wird, wohingegen die Feststoff-Wasser Oberflächenenergie nur bei längeren Alkylkettenlängen und hohen Oberflächenladungsdichten signifikant ansteigt. (ii) Die Schichtdicke und Ladungsdichte von adsorbierten schwachen Polyelektrolyten (z.B. PMAA, PAH) beeinflusst die Benetzbarkeit von Nanopartikeln (z.B. Aluminiumoxid, Siliziumoxid). Der isoelektrische Punkt und der pH Bereich für kolloidale Stabilität solcher Polyelektrolyt modifizierter Partikel hängt von der Dicke der Polyelektrolytschicht ab. Siliziumoxid und Aluminiumoxid Nanopartikel mit adsorbierten PAH bzw. PMAA werden Grenzflächenaktiv und dadurch befähigt Öl-in-Wasser Emulsionen zu stabilisieren, wenn der Dissoziationsgrad der Polyelektrolytschicht geringer als 80 % ist. Die durchschnittliche Tropfengröße von Dodecan-in-Wasser Emulsionen ist abhängig von der Polyelektrolytschichtdicke und dem Dissoziationsgrad. Die Visualisierung von Partikel stabilisierten Öl-in-Wasser Emulsionen durch kryogene REM zeigt, dass im Falle von kolloidal stabilen Aluminiumoxid-PMAA Partikeln die Öl-Tröpfchen mit einer dichtgepackten Partikelhülle belegt sind, während für kolloidal destabilisierte Partikel eine Hülle aus aggregierten Partikeln gefunden wird. (iii) Durch das Emulgieren einer Lösung des Korrosionsinhibitors 8-Hydroxychinolins (8HQ) in Styrol mit Siliziumoxid Nanopartikeln können stabile Öl-in-Wasser Emulsionen in einem pH Fenster von 4 - 6 hergestellt werden. Der amphoterische Charakter von 8HQ ermöglicht eine pH abhängige elektrostatische Wechselwirkung mit den Siliziumdioxid Nanopartikeln, welche diese Grenzflächenaktiv werden lässt. In Abhängigkeit der Konzentration und des Dissoziationsgrads von 8HQ folgt die Adsorption auf Siliziumdioxid aus elektrostatischen oder aromatischen Wechselwirkungen zwischen 8HQ und der Partikeloberfläche. Bei mittleren adsorbierten Mengen wird die Öl Benetzbarkeit der Partikel ausreichend erhöht um Öl-in-Wasser Emulsionen zu stabilisieren. Kryogene REM zeigt, dass die Partikel dann in dicht gepackte Hüllen, mit teilweise aggregierten Domänen auf der Öltröpfchenoberfläche vorliegen. Durch weiter ansteigende adsorbierte 8HQ Mengen wird die Öl-Benetzbarkeit wieder zurückgesetzt und die Emulgationsfähigkeit der Partikel aufgehoben. Durch die Zugabe von Hexadecan zur Öl Phase kann die Tropfengröße durch Erhöhung des Siliziumdioxid Anteils auf 200 nm herabgesetzt werden. Anschließende Polymerisation des Styrols generiert Korrosionsinhibitor gefüllte (20 Gew-%) Polystyrol-Silizumoxid Komposite. Die Messung der Freisetzungsrate von 8HQ zeigt einen schnellen Anstieg der 8HQ Konzentration in einer gerührten wässrigen Lösung innerhalb von 5 Minuten. Die Verkapselungsmethode wird auch für andere organische Korrosionsinhibitoren erweitert. Die Komposite werden dann in einer wasserbasierten Alkydpräpolymeremulsion dispergiert und diese Mischung wird zur Beschichtung von flachen Aluminiumplatten genutzt. Nach Trocknung und Quervernetzung des Films wird Konfokale Laser Mikroskopie dazu verwendet um die räumliche Verteilung der Composite im Film zu visualisieren. Elektrochemische Impedanzspektroskopie zeigt, dass die Barriereeigenschaften des Films durch die Anwesenheit der Komposite verbessert sind. Raster Vibrationselektroden Messungen zeigen, dass die Korrosionsrate in einem Kratzer des Films durch die Anwesenheit der Inhibitor efüllten Komposite reduziert ist. Durch die Ablagerung von 6 Polyelektroytschichten auf Feststoffstabilisierten Emulsionströpfchen verändert sich deren Oberflächenmorphologie deutlich (gezeigt durch REM). Wenn die Ölbenetzbarkeit der äußeren Polyelektrolytschicht ansteigt, dann können solche Polyelektolytbeschichteten Feststoffstabilisierte Emulsionströpfchen selber als Emulsionsstabilisatoren verwendet werden. Diese lagern sich dann in einer dicht gepackten Schicht auf der Oberfläche von größeren Emulsionstropfen ab. In der Gegenwart von 3 mM LaCl3 aggregieren 8HQ modifizierte Siliziumoxid Partikel stark auf der Öl-Wasser Grenzfläche. Der Einsatz von Ultraschall kann aggregierte Schalenbestandteile von der Tropfenoberfläche wegreißen. Diese Wracks können bis zu einem Viertel der Kugelhülle ausmachen und liegen dann als kolloidale Schalen im Wasser vor.

Biomaterial surface energy, chemical composition, charge, wettability and roughness all play an important role in determining the degree of the direct bone-to-implant interface, termed osseointegration. Surface chemistry, which is influenced by surface energy, wettability, and composition, is another factor that determines osteoblast phenotype and regulates osteoblast maturation. Increased surface energy is desirable for bone implants due to enhanced interaction between the implant surface and the biological environment. The extent of bone formation in vivo is also increased with increasing water wettability of implants. The physiological role of implant surface chemistry is important in determining the success of implant osseointegration because of molecular rearrangements, surface reactions, contamination, and release of toxic or biologically active ions that are determined by the starting chemistry. However, the role of surface chemistry on osteoblast response is not fully studied. Therefore, the overall goal of this dissertation is to understand how the surface chemistry, including wettability, chemical composition, and charge density, of titanium biomaterials impacts osteoblast maturation (in vitro). This study focuses on the general hypothesis that modifications of surface chemistry of titanium surfaces with sterilization or polyelectrolyte coating on titanium surfaces regulate osteoblast response.