Medidas eletroquímicas, incluindo voltametria cíclica com e sem rotação do eletrodo, cronoamperometria, deconvolução experimental, aplicação de procedimentos eletroquímicos de envelhecimento e programas de perturbação de potencial foram empregadas no estudo eletroquímico da interface estanho/solução de bicarbonato de sódio 0,5 mol L-1. Os estudos preliminares evidenciaram a natureza complexa dos processos que ocorrem no sistema e várias séries de ensaios foram propostos a partir desses resultados. Observou-se o deslocamento do principal pico catódico, devido à mudanças das configurações de energia do filme, que foram analisadas mediante a aplicação de procedimentos de envelhecimento potenciostático e potenciodinâmico. A ocorrência de reativação em condições de baixa velocidade de varredura e a razão entre as cargas anódica e catódica sempre superior à unidade foram atribuídas à dissolução. O emprego de eletrodo de disco rotativo permitiu acompanhar a presença de espécies solúveis de Sn(II) envolvidas nos primeiros estágios de formação de filme. Foi observado que há contribuição difusional no controle da cinética dos dois primeiros processos anódicos. A variação da corrente com a rotação deve-se à difusão de uma mesma espécie nos dois processos anódicos. A presença de óxidos formados em diferentes condições experimentais com características e propriedades elétricas diferentes, evidenciada nos ensaios preliminares, foi analisada sob uma abordagem modelística. A ocorrência de processos de nucleação na redução, sugerida pela presença de histerese de corrente e pela dependência da corrente do pico de redução com a velocidade de varredura, foi confirmada com o emprego de medidas cronoamperométricas. Programas de perturbação de potencial, com o objetivo de eletromodificar a superfície do estanho, foram aplicados. A influência das variáveis de interesse (velocidade da perturbação, tempo de duração, limites de potencial, catodização e número de catodizações) no aparecimento de mudanças no perfil padrão foi estudada. A cinética de desprendimento de oxigênio foi analisada mediante curvas de Tafel, para avaliar as mudanças das propriedades eletrocatalíticas das superfícies resultantes da aplicação dos programas de perturbação. / Electrochemical measurements including cyclic voltammetry with and without electrode rotation, chronoamperometry, experimental deconvolution, electrochemical ageing procedures, and perturbing potential programmes, were carried out in order to study the tin/0,5 mol L-1 sodium bicarbonate solution interface. Preliminary studies evidence the complex nature of the processes and enable the proposal of various series of experiments. The potential shift of the main cathodic current peak was assigned to changes in the energetic configuration of the species formed during the positive scan. That effect was studied by means of potenciostatic and potentiodynamic ageing procedures. Reactivation occurrence at low sweep rates and the anodic to cathodic charges ratio always higher than one, were attributed to dissolution. Rotating disc measurements evidence the presence of soluble species, probably Sn(II) species, involved in the first steps of film formation. It was observed that a diffusional contribution has to be taken into account into the global control that involves the first two anodic processes. The same current-rotation dependence observed suggests the diffusion of the same species for both the anodic processes. The films formed under different experimental conditions, which exhibit differences in nature and electric properties, were studied under a modelistic approach. Current hysteresis presence as well as the dependence of peak current with sweep rate observed at the preliminary studies, suggest cathodic nucleation processes. Nucleation was confirmed by means of chronoamperometric measurements. In order to electromodify tin surface, the electrode was subjected to perturbing potential programmes. The influence of experimental variables (as perturbation sweep rate, perturbation time, potential limits, cathodic polarization and number of cathodic polarization applied) on the cathodic profile was studied. Oxygen evolution reaction, in terms of Tafel plots, was used in order to evaluate changes in the electrocatalytic properties of the modified surfaces.

Made available in DSpace on 2017-07-21T20:43:46Z (GMT). No. of bitstreams: 1 Sabrina Marinho Kaplun.pdf: 2639962 bytes, checksum: a9f7e8225e77abb24e8a18b7dd472300 (MD5) Previous issue date: 2015-04-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The purpose of this study was to obtain, characterize and evaluate the photocatalytic activity of the surface modified titanium dioxide in relation to the unmodified titanium dioxide. Titanium dioxide (TiO2) anatase (commercial) was introduced into an oven made, with the function of modifying the external surface of the oxide by the effect of pressure, temperature and time. The modified titanium (TM) oxides and unmodified (TN) were characterized by the techniques of X-ray diffraction (XRD)and refinement by the Rietveld method, transmission electron microscopy (TEM) and determination of specific surface area. In heterogeneous photodegradation tests, degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was accompanied by UV/vis, high performance liquid chromatography efficiency (HPLC) and determination of total organic carbon (TOC). The influence of pressure on the surface of titanium dioxide resulted in a change in the external surface of titanium dioxide, surface irregularities increases, without changes in unit cell parameters and increases the surface area. The photocatalytic activity of the modified titanium dioxide (TM) was higher to the unmodified titanium dioxide (TN).The modified titanium dioxide had a higher percentage of degradation of the herbicide 2,4-dichlorophenoxyacetic acid and a higher mineralization making it more efficient. / A proposta desse trabalho consistiu em obter, caracterizar e avaliar a atividade fotocatalítica do dióxido de titânio modificado superficialmente em relação ao dióxido de titânio não modificado. O dióxido de titânio (TiO2) anatase (comercial) foi introduzido em um forno confeccionado, com a finalidade de modificar a superfície externa do óxido de titânio pelo efeito da pressão, temperatura e tempo. Os óxidos de titânio modificados (TM) e não modificados (TN) foram caracterizados pelas técnicas de difração de raios X (DRX) e refinamento pelo método de Rietveld, microscopia eletrônica de transmissão (MET) e determinação da área superficial específica. Nos ensaios de fotodegradação heterogênea, a degradação do herbicida 2,4-diclorofenoxiacético (2,4-D) foi acompanhada pelas técnicas de UV/vis, cromatografia líquida de alta eficiência (HPLC) e determinação de carbono orgânico total (COT). A influência da pressão na superfície do dióxido de titânio resultou em uma modificação na superfície externa do dióxido de titânio aumentando irregularidades na superfície, sem alterações nos parâmetros da célula unitária e com elevação da área superficial. A atividade fotocatalítica do dióxido de titânio modificado (TM) foi superior ao dióxido de titânio não modificado (TN). O dióxido de titânio modificado apresentou maior porcentagem de degradação do herbicida 2,4-diclorofenoxacético e uma maior mineralização o que o torna mais eficiente.

Orientador: Heloisa Andréa Acciari / Resumo: Nas últimas décadas houve um enorme crescimento do uso titânio comercialmente puro nos mais variados setores da economia como por exemplo na indústria petrolífera, aeroespacial e biomédica. Na indústria biomédica o uso desse metal se caracteriza por ter propriedades mecânicas semelhantes às do osso do corpo humano, por apresentar excelente resistência à corrosão quando comparado com outros metais, e também por ser biocompatível. A biocompatibilidade do titânio ocorre em função da camada de óxido que é formada sobre a superfície deste metal quando exposto a uma atmosfera em que há a presença de oxigênio. Esta camada pode ser amorfa ou cristalina, geralmente quando formada espontaneamente os filmes são amorfos, porém para o uso biomédico é interessante que a fase cristalina anatase se forme sobre a superfície do titânio, pois de acordo com a literatura esta fase favorece a osseointegração. Sendo assim várias técnicas de modificação de superfície, como por exemplo, anodização, tratamento térmico, eletrodeposição, são estudadas para melhorar as propriedades da camada de TiO2. Por tanto, o objetivo desse trabalho foi investigar como os parâmetros de anodização e características de filmes anódicos estão relacionados. Os filmes foram obtidos por anodização em soluções de 0,25 e 2,5 mol L-1 de H3PO4 em três tempos de anodização (3, 6 e 12 horas), comparando dois tipos de substratos: superfícies de titânio eletropolidas e polidas com alumina, com a finalidade de obter uma superfície m... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the last decades, there has been a great growth in the use of commercially pure titanium in the most varied sectors of the economy, such as in the aerospace and biomedical industries. In the biomedical industry the use of this metal is due to its properties, such as mechanical strength, which is similar to human bone, as well as its excellent corrosion resistance compared to other metals, and also because of it is a biocompatible element. The biocompatibility of titanium occurs as a function of the oxide layer formed on the surface of this metal when it is exposed to an atmosphere where there is the presence of oxygen. This layer can be amorphous or crystalline, usually when it is formed spontaneously the films are amorphous, but for biomedical use it is interesting that the morphology of the anodic film is composed by the Crystalline phase of the anatase, because according to the literature this phase favors osseointegration. In order to improve the properties of the titanium oxide layer, various surface modification techniques have been studied, such as anodizing, heat treatment and electrodeposition. Thus, the proposal of this work was to investigate how the anodization parameters and the characteristics of anodic films are related. The films were obtained by anodization in 0.25 and 2.5 mol L-1 H3PO4 solutions in three anodization times (3, 6 and 12 hours), comparing two types of substrates: electropolished and non-electropolished titanium surfaces, aimed to create a mo... (Complete abstract click electronic access below) / Mestre

Maîtriser la biocontamination surfacique et les risques susceptibles d’y être associés demeure un challenge majeur. Cette maîtrise passe par la préparation de nouveaux matériaux polymères possédant des propriétés de surface adaptées. Dans cette optique le LCOM développe depuis quelques années une thématique consistant à mettre au point des méthodes de modifications de surfaces de matériaux polymères par greffage de biomolecules. [ ] [ ] [ ] Dans ce contexte, l’objectif de cette étude est de fonctionnaliser des films polymères de type poly (téréphtalate d’éthylène) (PET) avec des dérivés sucrés et/ou polysaccharides dans le but d’étudier le caractère bactériostatique, biocide et pro ou anti-adhésion. [ ] La préparation des matériaux se fait en plusieurs étapes :Etape 1 : Fonctionnalisation de surfaces polymères (films) par traitement plasma N2/H2 et NH3 pour introduire à la surface des fonctions amines. Cette technique modifie la surface sans changer les propriétés intrinsèques des matériaux.Etape 2 : Greffage d’un amorceur de polymérisation radicalaire par transfert d’atome (ATRP)Etape 3 : Polymérisation en surface d’un monomère sucré par ATRP (contrôle de la longueur des chaînes greffées). La mise au point des paramètres de polymérisation ATRP de ces monomères est d’abord menée en solution avant d’étudier la polymérisation en surface.Etape 4 : Etudes microbiologiques des surfaces modifiées.Après chaque étape de modification de surface, les matériaux sont caractérisés par différentes méthodes d’analyses telles que : la spectroscopie de photoélectrons X (XPS), la microscopie à force atomique, la chromatographie d’exclusion stérique. Des glycopolymères protégés et déprotégés issus du galactose et de la glucosamine ont été synthétisés. Ceux issus de la glucosamine ont été synthétisés afin de mimer les propriétés antibactériennes du chitosane. Le glycomonomère issu du galactose est polymérisé par ATRP par voie « grafting from » sur des surfaces de PET. Ces surfaces modifiées présentent des propriétés anti-adhésives intéressantes contre les bactéries du type Bacillus subtilis. En effet, après greffage du glycomonomère déprotégé, il n’ ya plus d’adhésion de bactéries. Des polymères contenant des fonctions ammonium quaternaire et fluor ont aussi été greffés avec succès sur les films de PET par la même méthode. / Control surface contamination by microorganism is of great concern in a variety of areas such as food packaging, medical devices, hospitals and so on. To reduce or prevent microbial adhesion, new polymer surfaces must be developed. In this context, we investigate a new theme which deals with the modification of polymer materials containing carbohydrate molecules. , , The aim of the study is to attach covalently glycopolymers or potential antimicrobial polymers on films of polyethylene terephthalate (PET) in order to study the biocidal or anti-fooling properties. Indeed, grafting glycopolymers on PP fibers have brought anti-fooling properties. The surfaces are prepared in several steps:Step 1: Incorporation of primary amino groups by N2/H2 or NH3 plasma treatment. The pretreatment by plasma exhibits many benefits for the surface modification, which enables to introduce functional groups at the surface without any modification of the chemical and mechanical properties of the material during the process.Step 2: Insertion of Atom Transfer Radical Polymerization (ATRP) initiatorStep 3: Grafting from surface polymerization method of a monomer in order to control the molecular weight distribution on the surfaces. ATRP parameters of glycomonomers are studied in solution before carrying polymerization on surfaces.Step 4: Microbial adhesion tests of modified surfaces with Bacillus Subtilis and Lactoccocus Lactis as bacterial strains. Several analytical techniques such as X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy, size exclusion chromatography of polymers obtained in solution have been used to characterize the modified surfaces. The first step was to optimize plasma parameters in order to have a high density of primary amino group on the surfaces. Then several monomers have been studied especially glycomonomers from galactose and glucosamine to mimic antimicrobial properties of chitosan. Protected and deprotected glycopolymers from galactose polymerized on PET surfaces exhibit anti-fooling properties toward Bacillus Subtilis. Polymers containing quaternary ammonium salt or fluor have also been successfully polymerized by a grafting from method on PET films.

La prise de conscience sociétale vis-à-vis des problèmes environnementaux augmente et conduit à une forte demande en matériaux issus de ressources renouvelables, comme les biocomposites. La sensibilité thermique et le comportement au feu restreint leur utilisation pour certaines applications comme le bâtiment. La réglementation en matière de sécurité incendie est très importante et nécessite donc de trouver des solutions adaptées pour améliorer le comportement au feu de ces matériaux. Dans ce contexte, nous avons dans un premier temps étudié la dégradation thermique et le comportement au feu des fibres naturelles seules et particulièrement l'impact de ses composants sur le comportement au feu. Ensuite, nous avons étudié la réactivité de quatre fonctions (amine, acide carboxylique, alcoxysilane et acide phosphonique) sur la fibre de lin et ses composants (cellulose, hemicellulose, lignine). La caractérisation des greffages a été réalisée de manière originale par des techniques de dégradation thermique.Ensuite, nous nous sommes intéressés à la dégradation thermique et au comportement au feu de biocomposites. Nous avons étudié le comportement au feu de biocomposite à base de PBS et de fibres naturelles en faisant varier différents paramètres comme le taux de fibres, la nature des fibres et l'influence d'un retardateur de flamme phosphoné. Deux stratégies d'ignifugation ont été testées : l'ajout en masse dans la matrice et le greffage sur les fibres naturelles de retardateur de flamme. Pour aller plus loin dans les stratégies d'ignifugation par greffage de retardateur de flamme, nous avons comparé l'influence du greffage d'une molécule et d'une macromolécule sur le comportement au feu du lin et du biocomposite PBS/lin. / The environmental awareness in the society is increasing and leads to a strong demand in material from renewable resources, such as biocomposites. The thermal sensitivity and the flammability restrict their use for certain applications such as building. The fire safety regulation is of prime importance and requires adaptive solutions to be found to improve the fire behavior of these materials.In this context, we have studied the thermal degradation and the fire behavior of natural fibers and particularly the effect of its components on the fire behavior. Then, we studied the reactivity of four moieties (amine, carboxylic acid, alkoxisilane and phosphonic acid) on the natural fibers. The grafting characterization was carried out with original techniques based on thermal degradation.Then, we are interested on the thermal degradation and the fire behaviour of biocomposites. We studied the fire behaviour of biocomposite based on PBS and natural fibers varying different parameters such as the amount of fibers, the type of natural fibers and the influence of a phosphonated fire retardant. Two fireproofing strategies have been tested: the addition in polymer matrix and the grafting on natural fibers of fire retardant. To go further in the fireproofing strategy by fire retardant grafting, we have compared the influence of the molecule or macromolecule grafting on the fire behaviour of flax and PBS/flax biocomposite.

Organic semiconductors have wide applications in organic-based light-emitting diodes, field-effect transistors, and thermoelectrics due to the easily modified electrical and optical properties, excellent mechanical flexibility, and solution processability. To fabricate high performance devices, it is important to understand charge transport mechanisms, which are mainly affected by material energetics and material morphology. Currently it is difficult to control the charge transport properties of new organic semiconductors and organic-inorganic nanocomposites due to our incomplete understanding of the large number of influential variables. Molecular doping of π-conjugated polymers and surface modification of nanowires are two means through which charge transport can be manipulated. In molecular doping, both the energetics and microstructures of polymer films can be changed by controlling the degree of oxidation of the conjugated polymer backbone. For surface modification of inorganic nanowires, the energetics and morphology can be influenced by the properties of the surface modifiers. Meanwhile, the energy band alignment, which can be controlled by surface modification and molecular doping, may also alter the charge transport due to the variation in energetic barriers between the transport states in the organic and inorganic components. To reveal the effects of morphology and energetics on charge transport in conjugated polymers and organic-inorganic nanocomposites, the influence of surface modifier on the electrical and morphological properties of nanocomposites was first probed. Silver nanowires modified with different thiols were blended with poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS) to fabricate thin films. The modified nanowires provided a means of controllably altering the nanowire dispersability and compatibility with solvents and polymers. The results also demonstrated that charge transport between the nanowires was facilitated due to low wire-to-wire junction resistance. To further figure out the charge transport mechanism in organic-inorganic nanocomposites and the potential applications, tellurium nanowires and ferric chloride doped poly (3-hexylthiophene-2,5-diyl)(P3HT) were used to characterize energy band alignment effects on charge transport, electrical conductivity, and thermoelectric properties. The results showed that charge transfer between nanowires can be mediated by the polymer and may potentially increase the electrical conductivity as compared to the pure polymer or pure nanowires; while the observed enhancement of power factor (equal to electrical conductivity times the square of Seebeck coefficient) may not be affected by the energy band alignment. It is important to investigate the change of polymer morphology caused by molecular doping and processing method to determine how the morphology will influence the electrical and thermoelectric properties. Various p-type dopants, including ferric chloride and molybdenum tris(1,2-bis(trifluoromethyl)ethane-1,2-dithiolene) (Motfd3), were examined for us in P3HT and other polymers. The results showed that: i) At light doping levels, the electrical conductivity and power factor of polymers doped with the large electron affinity (EA) dopants were larger than small EA dopants; ii) At heavy doping levels, the large size dopants cannot effectively dope polymers even for the dopants with large EAs; iii) For the same dopant, as the IE of the polymer increased, the doping efficiency gradually decreased.

L’objectif de cette étude était d’améliorer les performances de séparation OSN de membranes commerciales en vue d’applications en métathèse dans laquelle des catalyseurs hautement dilués sont utilisés. Dans ce travail, des membranes polymères commerciales ont d'abord été étudiée pour caractériser leurs performances dans des milieux organiques en utilisant des mélanges binaires très dilués solute-solvant. Sur la base d'une revue de la littérature, il a été montré que la membrane PERVAP4060, dont le PDMS est la couche active dense était un candidat prometteur pour la nanofiltration milieu organique (OSN). En tant que membrane poreuse, les supports commerciaux AMS et PAN ont également été pris en compte. Dans cette étude, nous avons considéré la modification sur la surface pour conserver les propriétés de matrice polymère. Les multicouches de plasma Ar/O2 et/ou de polyélectrolytes ont été utilisées pour la préparation de membranes prototypes. Les membranes non modifiées et modifiées ont été testées dans des conditions OSN en utilisant des mélanges d'alimentation biniares. Plusieurs solutés très dilués, le ligand organophosphoré R-BINAP, un catalyseur de transfert de phase (ToABR) et des alcanes linéaires ont été étudiés. Le R-BINAP et le ToABR ont tous deux été utilisés dans la plage de 0,0001 à 0,5% en masse et la plupart des expériences ont été réalisées ensuite avec des concentrations de 0,05% en masse de soluté dans le toluène. Il a été montré que le PDMS était capable de retenir 80% de R-BINAP et environ 93% de ToABr dans du toluène. Après modification par les dépôt LBL, le taux de rejet est amélioré avec les membranes modifiées PERVAP4060, conduisant à une rétention de 88% du R-BINAP avec un dépôt de 10 bicouches de polyélectrolytes PAH / PSS en surface, ce taux de rejet pouvant atteindre 95% lorsque le nombre de bicouches est de 20. Le taux de rejet de ToABr augmente à 97%. Les performances de la membrane ont été étudiées sous différentes pressions comprises entre 1 et 40 bars; le haut rejet, encore observé dans ces conditions OSN, plaide résolument en faveur d'un mécanisme de transfert de type solution-diffusion à travers le PDMS. On a également étudié le traitement des mélanges ternaires mimant le mélange catalyseur / solutés / solvant, correspondant à l'hydroformylation ; aucun signe de couplage n’a été détectée et le taux rejet du soluté de masse molaire la plus forte est resté inchangé. D'autre part, l'amélioration du taux de rejet a également observée à partir des membranes poreuses après modification. Le taux de rétention du C44 dans l'AMS a été atteint 75% après modification par 10 bicouches de PDDA / PSS, alors qu’il n'était que de 25% avant modification. Dans le PAN modifié, le taux de rejet des solutés obtenus est dans la plage de 37 à 50%, alors qu’il n'était que de 3 à 7% en masse avant modification. L'inconvénient de la membrane poreuse est toutefois la forte diminution du flux après le dépôt des couches multiples. / The objective of this study was to improve the OSN separation performance of commercial membranes for metathesis applications in which highly diluted catalysts are used. In this work, commercial polymeric membranes were first studied to characterize their performance in organic media using very dilute solute-solvent binary mixtures. Based on a literature review, it was shown that the PERVAP4060 membrane, of which PDMS is the dense active layer, was a promising candidate for organic solvent nanofiltration (OSN). As a porous membrane, the AMS and PAN commercial supports have also been taken into account. In this study, we considered the modification on the surface to improve the separation properties of polymeric OSN membranes. Ar/O2 plasma and/or polyelectrolytes multilayers were used for the preparation of new prototype membranes. Unmodified and modified membranes were tested under OSN conditions using binary feed mixtures. Several highly dilute solutes, organophosphorus ligand R-BINAP, phase transfer catalyst ToABR, and linear alkanes have been studied. Both R-BINAP and ToABR were used in the range of 0.0001 to 0.5% by weight, and most experiments were subsequently performed with 0.05% solute concentrations in toluene. It has been shown that PDMS can retain 80% R-BINAP and about 93% ToABr in toluene. After modification by the LBL deposition, the rejection is improved with the modified PERVAP4060 membranes, leading to an 88% rejection of R-BINAP with a deposit of 10 PAH / PSS polyelectrolyte bilayers at the surface and this rejection being able to reach 95% when the number of bilayers is 20. ToABr rejection increases to 97% with the ten bilayered membranes. The performance of the membrane was studied under different pressures of between 1 and 40 bar; the high rejection, still observed in these OSN conditions, strongly supports a solution-diffusion transfer mechanism through the PDMS. The treatment of ternary mixtures mimicking the catalyst/solute/ solvent mixture corresponding to the hydroformylation has also been studied; no evidence of coupling was detected, and the highest retention remained unchanged. On the other hand, the improvement of the rejection also observed from the porous membranes after modification. The rejection of C44 in the AMS was reached 75% after modification by tention10 bilayers of PDDA / PSS, whereas it was only 25% before modification. In the modified PAN, the rejection of the solutes obtained is in the range of 37 to 50%, whereas it was only 3 to 7% by weight before modification. The disadvantage of the porous membrane, however, is the sharp decrease in flux after the deposition of the multiple layers.

In this study, dendronization and grafting via controlled polymerization techniques, atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP), have been explored. Modification of surfaces and cellulose using these techniques, which enable grafting of well-defined polymer architectures, has been investigated. The interest in using cellulose stems from its renewability, biocompatibility, high molecular weight, and versatile functionalization possibilities. Dendronization was performed using disulfide-cored didendrons of 2,2-bis(methylol)propionic acid (bis-MPA) on gold surfaces, for the formation of self-assembled monolayers. It was found that the height of the monolayer increased with increasing dendron generation and that the end-group functionality controlled the wettability of the modified surface. Superhydrophobic cellulose surfaces could be obtained when a ‘graft-on-graft’ architecture was obtained using ATRP from filter paper after subsequent post-functionalized using a perfluorinated compound. The low wettability could be explained by a combination of a high surface roughness and the chemical composition. Biobased dendronized polymers were synthesized through the ‘attach to’ route employing dendronization of soluble cellulose, in the form of hydroxypropyl cellulose (HPC). The dendronized polymers were studied as nanosized objects using atomic force microscopy (AFM) and it was found that the dendron end-group functionality had a large effect on the molecular conformation on surfaces of spun cast molecules. ATRP of vinyl monomers was conducted from an initiator-functionalized HPC and an initiator-functionalized first generation dendron, which was attached to HPC. The produced comb polymers showed high molecular weight and their sizes could be estimated via AFM of spun cast molecules on mica and from dynamic light scattering in solution, to around 100-200 nm. The comb polymers formed isoporous membranes, exhibiting pores of a few micrometers, when drop cast from a volatile solvent in a humid environment. HPC was also used to initiate ROP of ε-caprolactone, which was chain extended using ATRP to achieve amphiphilic comb block copolymers. These polymers could be suspended in water, cross-linked and were able to solubilize a hydrophobic compound. / QC 20100826

Nanostructured materials are the next generation of high-performance materials, harnessing the novel properties of their nanosized constituents. The controlled assembly of nanosized particles and the design of the optimal nanostructure require a detailed understanding of particle interactions and robust methods to tune them. This thesis describes innovative approaches to these challenges, relating to the determination of Hamaker constants for iron oxide nanoparticles, the packaging of nanopowders into redispersible granules, the tuning of the wetting behavior of nanocrystals and the simulation of collective magnetic properties in arrays of superparamagnetic nanoparticles. The non-retarded Hamaker constants for iron oxides have been calculated from their optical properties based on Lifshitz theory. The results show that the magnitude of vdW interactions in non-polar solvents has previously been overestimated up to 10 times. Our calculations support the experimental observations that oleate-capped nanoparticles smaller than 15 nm in diameter can indeed form colloidally-stable dispersions in hydrocarbons. In addition, a simple procedure has been devised to remove the oleate-capping on the iron oxide nanoparticles, enabling their use in fluorometric assays for water remediation, with a sensitivity more than 100 times below the critical micelle concentration for non-ionic surfactants. Nanosized particles are inherently more difficult to handle in the dry state than larger micron-sized powders, e.g. because of poor flowability, agglomeration and potential toxicity. The rheology of concentrated slurries of TiO2 powder was optimized by the addition of sodium polyacrylate, and spray-dried into fully redispersible micron-sized granules. The polymer was embedded into the granules, where it could serve as a re-dispersing aid. Monte Carlo (MC) simulations have been applied to the collective magnetic behavior of nanoparticle arrays of various thicknesses. The decrease in magnetic susceptibility with the thickness observed experimentally was reproduced by the simulations. Ferromagnetic couplings in the arrays are enhanced by the finite thickness, and decrease in strength with increasing thickness. The simulations indicate the formation of vortex states with increasing thickness, along with a change in their orientation, which becomes more and more isotropic as the thickness increases. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

Paper and cellulosic materials hold a good promise of being candidates for flexible packaging materials provided suitable barrier properties such as water repellence and grease resistance are imparted to them. One of the methods to achieve these objectives is to surface modify paper/cellulose by applying thin fluorocarbon coatings on the surface. Fluorocarbon thin films produced by plasma enhanced chemical vapor deposition (PECVD) offer several advantages over the films produced by conventional polymerization means. Plasma deposited films are pinhole-free, chemically inert, insoluble, mechanically tough, thermally stable and highly coherent and adherent to variety of substrates. In this work, we investigate the use of PECVD technique to produce barrier films on paper and cellulosic materials. These films, with composition and properties not much different from PTFE, repel water and act as a good barrier to lipophilic materials. Two different monomers, pentafluoroethane (PFE; CF3CHF2) and octafluorocyclobutane (OFCB; C4F8), were investigated and compared in terms of deposition rates and final film properties. Various analytical techniques (XPS, FT-IR, SEM, Ellipsometry, Contact Angle Goniometry, etc.) were used to characterize the fluorocarbon films. The fluorocarbon coated paper exhibited hydrophobic character as evidenced by high water contact angles. Although the films allow water vapor diffusion, the films are hydrophobic and are not wetted when liquid water contacts these layers. Based on various thickness of these films deposited on surface of cellulose, there was a minimum PFE film thickness required to achieve a stable hydrophobic behavior. The fluorocarbon films investigated in this work also exhibited good resistance to lipophilic materials (e.g. oils, fatty acids, etc.). While techniques such as oleic acid penetration and TAPPI "oil-kit" test are commonly used in paper industry to qualitatively test the grease barrier properties of paper/cellulose, this work attempts to quantify the grease barrier properties of fluorocarbon coated paper using techniques such as magnetic resonance imaging (MRI) and quartz crystal microbalance (QCM). Finally, the feasibility of deposition of dual layer films by PECVD was investigated using PFE and n-isopropylacrylamide (NIPAAM) as precursors for applications in barrier packaging and printing.