Dissertations / Theses on the topic 'Multilayered membranes'

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 153-157).
In this thesis, I developed a novel methodology for characterizing interfacial delamination of thermal barrier coatings. The proposed methodology involves novel experiments-plus numerical simulations in order to determine the material parameters describing such failure when the interface is modeled using traction-separation constitutive laws. Furthermore, a coupled fluid-permeation and large deformation theory is proposed for crosslinked polymers with a view towards application to reverse-osmosis. A systematic simulation plus experiment-based methodology is proposed in order to calibrate the material parameters of the theory. Finally, the process of reverse osmosis is studied in the context of water desalination. An experimental set-up is proposed in order to characterize the thin-film composite membranes widely used in the industry, and a preliminary set of experiments are performed.
by Jacques Luk-Cyr.
Part 1. Thermal barrier coatings -- part 2. Reverse osmosis membranes -- part 3. Thin-film-composite membranes: application to reverse osmosis in water desalination.
S.M.

Thesis (Ph. D.)--University of Oregon, 2003.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 205-212). Also available for download via the World Wide Web; free to University of Oregon users.

IT-­PEFC operating at 120°C and not the usual 80°C has many advantages, such as faster chemical reactions. If the gas humidification is reduced, simpler and lighter humidifiers can be used, leading to a reduction in the fuel cell total cost. However, at this condition the current commercial membrane Nafion is not able to hold water and perform satisfactorily. Therefore, in this study the application of multilayer membranes for IT-PEFC was investigated. These membranes were divided into two groups, a first with external layers of Nafion and an inner layer of sulphonated polyindene, and a second with external layers of Nafion and an inner layer of graphene oxide. The membrane preparation method was also investigated. The multilayer membranes were prepared by hot pressing and solution casting. As a result, cast multilayer membranes showed better performance and proton conductivity than hot pressed. Delamination and low interface interaction were the main drawbacks for hot pressed membranes. Cast multilayer sulphonated polyindene membranes showed higher performance than Nafion at 120°C and 20% of relative humidity. In the meantime, cast graphene oxide multilayer membranes showed higher water uptake and open circuit voltage than Nafion.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
O 17Þ - etinilestradiol (EE2) é um hormônio esteróide sintético com baixa solubilidade em água. A contaminação por esse estrogênio tem sua origem na contínua introdução em ambientes através do descarte inadequado de esgoto sanitário e industrial, como também pelo uso do lodo ativado de estações de tratamento de esgoto na agricultura. A exposição a esse composto vem sendo associada a causas de câncer de mama, infertilidade masculina e mutações em pequenos seres vivos, como peixes, cujos efeitos podem estar associados à interação do hormônio com a membrana celular. Assim, o estudo de modelos de membrana biológica na forma de filmes de Langmuir expostos ao EE2 na subfase foi realizado com o objetivo de avaliar a interação membrana/EE2 e gerar subsídios para o desenvolvimento de sensores para detectar tais substâncias em meio aquoso (língua eletrônica). Monocamadas compostas por moléculas antifilicas de diferentes cargas foram espalhadas sobre bubfase de ágau ultrapura contendo o EE2, sendo a interação membrana/hormônio estudada por meio das isotermas de pressão de superfície vs. área molecular média (isotermas л - A). Neste estudo foram utilizados os fosfolipídios dipalmitoil fosfatidil colina (DPPC), que é zwiteriônico, dipalmitoil fosfatidil glicerol (DPPG), que é aniônico, e o surfactante brometo de dioctadecil dimetil amônio (DODAB), que é catiônico. O ácido esteárico (AE) foi utilizado como estudo complementar para se obter um melhor entendimento sobre a interação de DPPC com EE2. Todas as moléculas utilizadas como modelos de membranas apresentam interações com o EE2, de acordo com as isotermas л - A, o que foi confirmado por espectroscopia de reflexão e absorção no infravermelho com modulação da polarização (PM-IRRAS). Os estudos mostraram que as interações ocorrem através de interações eletrostáticas, principalmente na região polar dos lipídios, envolvendo não somente...
The 17 Þ - ethinyl estradiol (EE 2) is a synthetic steroid hormone with poor water solbility. Contamination by that estrogen has the origin in continuous introduction into aquatic environments through the improper disposal of domestic and industrial sewage, as well as the use of activated sludge wastewater treatment plants in agriculture. Exposure to this compound has been linked to breast cancer causes, male infertility and small mutations in living organisms such as fish, whose effects can be associated with the interaction of the hormone with the cell membrane. Thus, the study of membrane models in the form of Langmuir films exposed to EE2 in subphase was carried out to evaluate the interaction membrane/hormone. Monolayers composed of amphiphilic molecules with different charges were spread on ultrapure water subphase containing EE2, and the interaction membrane/hormone studied by surface pressure vs. mean molecular area isotherms (л - A isotherms). This study used the phospholipids dipalmitoyl phosphatidyl choline (DPPC), which is zwitterionic, dipalmitoyl phosphatidyl glycerol (DPPG), which is anionic, and the surfactant dimethyl dioctadecyl ammonium bromide (DODAB), which is cationic. The stearic acid (SA) was used to obtain a better understanding of the interaction of EE2 with DPPC and DPPG. All molecules used as membrane models presented interactions with EE2, according to л - A isotherms, which was confirmed by spectroscopic reflection and absorption in the infrared polarization modulation (PM-IRRAS). The studies have shown that interactions occur through electrostatic interations, especially in the polar region of lipids, involving not only cationic and anionic group but also the groups C=O and P=O the lipids with OH group of EE2

Orientador: Carlos José Leopoldo Constantino
Banca: Luciano Caseli
Banca: Eloi da Silva Feitosa
O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: O 17Þ - etinilestradiol (EE2) é um hormônio esteróide sintético com baixa solubilidade em água. A contaminação por esse estrogênio tem sua origem na contínua introdução em ambientes através do descarte inadequado de esgoto sanitário e industrial, como também pelo uso do lodo ativado de estações de tratamento de esgoto na agricultura. A exposição a esse composto vem sendo associada a causas de câncer de mama, infertilidade masculina e mutações em pequenos seres vivos, como peixes, cujos efeitos podem estar associados à interação do hormônio com a membrana celular. Assim, o estudo de modelos de membrana biológica na forma de filmes de Langmuir expostos ao EE2 na subfase foi realizado com o objetivo de avaliar a interação membrana/EE2 e gerar subsídios para o desenvolvimento de sensores para detectar tais substâncias em meio aquoso (língua eletrônica). Monocamadas compostas por moléculas antifilicas de diferentes cargas foram espalhadas sobre bubfase de ágau ultrapura contendo o EE2, sendo a interação membrana/hormônio estudada por meio das isotermas de pressão de superfície vs. área molecular média (isotermas л - A). Neste estudo foram utilizados os fosfolipídios dipalmitoil fosfatidil colina (DPPC), que é zwiteriônico, dipalmitoil fosfatidil glicerol (DPPG), que é aniônico, e o surfactante brometo de dioctadecil dimetil amônio (DODAB), que é catiônico. O ácido esteárico (AE) foi utilizado como estudo complementar para se obter um melhor entendimento sobre a interação de DPPC com EE2. Todas as moléculas utilizadas como modelos de membranas apresentam interações com o EE2, de acordo com as isotermas л - A, o que foi confirmado por espectroscopia de reflexão e absorção no infravermelho com modulação da polarização (PM-IRRAS). Os estudos mostraram que as interações ocorrem através de interações eletrostáticas, principalmente na região polar dos lipídios, envolvendo não somente...
Abstract: The 17 Þ - ethinyl estradiol (EE 2) is a synthetic steroid hormone with poor water solbility. Contamination by that estrogen has the origin in continuous introduction into aquatic environments through the improper disposal of domestic and industrial sewage, as well as the use of activated sludge wastewater treatment plants in agriculture. Exposure to this compound has been linked to breast cancer causes, male infertility and small mutations in living organisms such as fish, whose effects can be associated with the interaction of the hormone with the cell membrane. Thus, the study of membrane models in the form of Langmuir films exposed to EE2 in subphase was carried out to evaluate the interaction membrane/hormone. Monolayers composed of amphiphilic molecules with different charges were spread on ultrapure water subphase containing EE2, and the interaction membrane/hormone studied by surface pressure vs. mean molecular area isotherms (л - A isotherms). This study used the phospholipids dipalmitoyl phosphatidyl choline (DPPC), which is zwitterionic, dipalmitoyl phosphatidyl glycerol (DPPG), which is anionic, and the surfactant dimethyl dioctadecyl ammonium bromide (DODAB), which is cationic. The stearic acid (SA) was used to obtain a better understanding of the interaction of EE2 with DPPC and DPPG. All molecules used as membrane models presented interactions with EE2, according to л - A isotherms, which was confirmed by spectroscopic reflection and absorption in the infrared polarization modulation (PM-IRRAS). The studies have shown that interactions occur through electrostatic interations, especially in the polar region of lipids, involving not only cationic and anionic group but also the groups C=O and P=O the lipids with OH group of EE2
Mestre

This dissertation investigates the three-stage method MEAUS (melt-extrusion, annealing, and uniaxial stretching) for producing microporous membranes. This method for membrane preparation is a solvent-free process based on the stretching of semicrystalline polymer films containing a row-nucleated lamellar structure. In this regard, the first section of this thesis is dedicated to establishing an initial set of requirements based on the ability of different polyolefin materials for the formation of microporous membranes. The influence of the polymer matrix composition and the architecture structure on the flow-induced crystallization was studied. This was done using two linear polypropylenes having different molecular weights, and blending them with branched and very fluid PP resins. Lower porosity and permeability values were observed when low molecular weight polypropylenes were employed. Under the same processing conditions, the more prolonged relaxation time behavior of high molecular weight resins constituted the main factor in maintaining the macromolecular alignment for the generation of a row-lamellar crystalline structure. In the second part of this research work, heterophasic and random copolymers of polypropylene–ethylene were selected to study the influence of ethylene comonomer and its distribution along the polymer backbone. Most of these polymers can form a planar stacked lamellar morphology with a high crystalline orientation by selecting appropriate processing conditions. From a process engineering standpoint, the influence of the extrusion draw ratio was analysed, and in-depth study concerning the annealing and uniaxial strain stages was performed. After annealing, the films were subjected to a uniaxially stretching step where the films are deformed along the machine direction. First, to generate pores at room temperature and subsequently stretched at a high temperature to enlarge the pore size by increasing lamellar separation. This thesis was also conducted as part of a comprehensive study aimed at evaluating the effect of temperature in the stages of extrusion, annealing, and uniaxial strain, as well as the use in some cases of extreme strain rates and strain extents. High levels of molecular orientation can be obtained with high extrusion draw ratios and fast cooling. Regarding the annealing process, an increment in temperature gave rise to a greater molecular orientation and a rearrangement of polymer chains in both the crystalline and amorphous phases, which led to an increase in crystallinity and molecular orientation. A close relationship was found between the starting crystalline characteristics and annealing and stretching conditions that affected the final porous morphology, and the trends registered for permeability. The last section of this thesis is devoted to ascertaining the effects of mineral fillers (CaCO3 and talc) on the crystallization and mechanical behavior of multilayer polypropylene/high density polyethylene microporous membranes. Celgard initially developed PP/PE/PP trilayer separators. This multilayer system can be produced by various processes such as lamination and co-extrusion, which allows combining the lower melting temperature of PE with the high-temperature strength of PP. The crystallization and crystalline orientation were affected by both the flow-induced crystallization and the nucleating mechanism of the fillers. A synergistic effect was observed in the filled samples due to the generation of pores during the uniaxial stretching stages (MEAUS method) along with the debonding mechanisms of mineral fillers from the polymeric matrix, which promoted the formation of larger pores giving rise to a change in membrane permeability. The agglomeration of fillers in the composites affected the mechanical properties, the average membrane pore size, and pore size distribution.
En esta tesis doctoral se investiga el método extrusión en fundido, recocido y estiramiento uniaxial (MEAUS, por sus siglas en inglés) para el desarrollo de membranas microporosas. Este método para la preparación de muestras porosas no parte de ninguna solución líquida de polímero, si no que un proceso basado en el estiramiento de películas hechas a partir de termoplásticos semicristalinos que contienen una estructura no esferulítica denominada estructura "row-nucleated" (estructura nucleada en fila o de lamelas apiladas). La primera parte de esta tesis está dedicada a establecer un conjunto de requisitos iniciales basados en la capacidad de diferentes poliolefinas para la formación de membranas microporosas. Se estudió la influencia de la composición y estructura del polímero en su proceso de cristalización seleccionando distintos grados comerciales de polipropileno homopolímero, con diferentes promedios de peso molecular, así como un polipropileno con ramificación de cadena larga. En las membranas hechas a partir de polipropilenos de menor peso molecular se obtuvieron valores más bajos tanto de porosidad como de permeabilidad. Bajo las mismas condiciones de procesamiento, el mayor tiempo de relajación de las resinas con mayor peso molecular constituyó un factor clave a la hora de mantener la orientación molecular deseada. En la segunda parte de este trabajo de investigación se seleccionaron dos tipos de copolimero de propileno-etileno (copolimero heterofásico y copolimero al azar), con el objetivo de estudiar la influencia de esta segunda fase y su distribución a lo largo de la cadena principal del material. La mayoría de los polímeros investigados han tenido la capacidad de desarrollar la estructura de lamelas apiladas "row-nucleated" aplicando las condiciones óptimas de procesado. Teniendo en cuenta las diferentes etapas de fabricación de las que consta este método, se ha realizado un estudio en profundidad sobre la influencia que tiene tanto la relación de estirado aplicada durante el proceso de extrusión, como la de las etapas de recocido y estiramiento uniaxial en el desarrollo de la estructura porosa. Tras el recocido de las muestras, los films son sometidos a una etapa de estiramiento a dos temperaturas diferentes. En primer lugar, el film recocido es estirado uniaxialmente a baja temperatura con el fin de nuclear poros en el interior de la estructura cristalina. Posteriormente, la misma muestra es estirada uniaxialmente a mayor temperatura con el objetivo de agrandar el tamaño promedio de poro. En esta tesis también se ha evaluado el efecto que tiene la variable de temperatura en las etapas de extrusión, recocido y estiramiento. La última sección de esta tesis está dedicada a determinar el efecto de la incorporación de distintas cargas minerales (CaCO3 y talco) en la cristalización y el comportamiento mecánico de membranas multicapa polipropileno / polietileno de alta densidad. Este sistema multicapa se puede obtener mediante diferentes métodos de procesado tales como la laminación y la coextrusión, los cuales permiten combinar la temperatura de fusión más baja del PE con la resistencia a la alta temperatura del PP. El proceso de cristalización y orientación de las muestras se vio afectado tanto por las variables descritas anteriormente, como por los mecanismos de nucleación y cristalización producidas por la presencia de las cargas minerales. En estas muestras compuestas se observó la presencia de poros de mayor tamaño fruto de la combinación de dos fenómenos distintos. Por un lado, la separación lamelar producida durante las etapas de estiramiento uniaxial y por otro, la separación producida entre las cargas inorgánicas y la matriz de polímero tras ser sometidos ambos a esfuerzos externos. La presencia de aglomerados en estos materiales compuestos influyó tanto en las propiedades mecánicas, como en el tamaño promedio y distribución de poros

L'oxydation spontanée de la dopamine en solution légèrement basique a été étudiée sur la base de la publication de Lee [Science, 318:426-430, 2007], et le produit de la réaction a été identifié comme de la mélanine. La capacité de la mélanine de lier des groupements amines de façon covalente a été confirmée par la quantification des sites de liaison correspondants. En outre il est possible de rédisperser des agrégats de mélanine dans des solutions fortement basiques. Les grains de mélanine ainsi obtenus ont été utilisés pour construire des films multicouches avec le poly(diallyldimethyl ammonium) (PDADMA). Différentes méthodes d'oxydation de la dopamine pour former des films de mélanine à l'interface solide-liquide ont été développées. Toutes les méthodes mènent à la formation de films continus de mélanine ayant des morphologies de surface similaires. Elles deviennent imperméables à des sondes électrochimiques à partir d'une épaisseur de l'ordre de 10 nm. Une plus grande perméabilité à des sondes chargées positivement ou neutres qu'à des sondes négatives a été confirmée. L'adsorption de protéines à des revêtements de mélanine a été expliquée par une combinaison d'interactions électrostatiques et covalentes. Pour arriver à cette explication le potentiel zêta de dépôts de mélanine a été mesuré en fonction du pH. La formation de la mélanine dans des films multicouches de poly(L-lysine) (PLL) et de hyaluronate (HA) a été étudiée: la mélanine est capable de remplir des films (PLL-HA)_n de manière homogène, et les composés ainsi obtenus peuvent être détachés de leurs substrats comme membranes autosupportées préparées par une méthode biomimétique sous conditions douces
The spontaneous oxidation of dopamine in slightly alkaline solutions was investigated on the basis of the work of Lee and others [Science, 318:426-430, 2007], and the reaction product was identified as dopamine-melanin. The ability of melanin to covalently bind amine functional groups was confirmed by quantification of the corresponding binding sites on dopamine-melanin aggregates. Furthermore it is possible to redissolve dopamine-melanin aggregates in strongly alkaline solutions. The obtained small melanin grains were used to build layer-by-layer deposits with poly(diallyldimethylammonium). Different methods of dopamine oxidation to grow melanin films at solid--liquid interfaces were developed. All examined methods lead to continuous dopamine-melanin films with very similar surface morphologies. The dopamine-melanin films become impermeable to electrochemical probes at a thickness in the 10 nm range. In this context a higher permeability for positively charged and neutral probes than for negatively charged ones was confirmed for one preparation method. The adsorption of proteins on dopamine-melanin coatings was explained as combination of electrostatic and strong, most probably covalent, interactions. To obtain this explanation, the zeta-potential of dopamine-melanin deposits has been measured as a function of pH. The formation of melanin by dopamine oxidation in layer-by-layer films of poly(L-lysine) (PLL) and hyaluronate (HA) was studied: Melanin is able to homogeneously fill (PLL-HA)_n films and the obtained polyelectrolyte-melanin composites can be detached from their substrate as free-standing membranes prepared by a biomimetic method in mild conditions

Orientador: Carlos José Leopoldo Constantino
Banca: Luis Vicente de Andrade Scalvi
Banca: Eloi da Silva Feitosa
Banca: Paola Corio
O programa de Pós graduação em Ciência e Tecnologia de Materiais, POSMAT, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da UNESP
Resumo: A presente dissertação de mestrado trata da fabricação de filmes ultrafinos (nanômetros de espessura) de fosfolipídios aniônicos (DPPG e CLP) e zwiteriônicos (DPPC e DOPC) utilizando as técnicas layer-by-layer (LbL) e Langmuir-Blodgett (LB), possibilitando assim a obtenção de filmes com diferentes arquiteturas moleculares. O objetivo principal foi explorar a aplicação destas diferentes arquiteturas moleculares na detecção do fármaco fenotiazínico azul de metileno (AM) em soluções diluídas. O crescimento linear, camada por camada, desses filmes foi verificado e monitorado por espectroscopia de absorção no UV-Vis. Verificou-se por FTIR que o crescimento dos filmes LbL e LB é determinado por interações eletrostáticas entre os fosfolipídios e o polieletrólito catiônico PAH utilizado como camada de suporte, favorecendo o crescimento dos filmes com fosfolipídios aniônicos. A morfologia foi analisada através de microscopias ópticas, AFM e MEV, revelando que os fosfolipídios estruturam-se como vesículas nos filmes LbL e monocamadas nos filmes LB. Filmes LbL e LB de fosfolipídios com diferentes espessuras foram então depositados sobre eletrodos interdigitados de Pt formando unidades sensoriais que foram aplicadas na detecção de AM via espectroscopia de impedância. Os resultados mostraram que as diferentes arquiteturas moleculares dos filmes LbL e LB levam a respostas elétricas distintas e permitem a detecção de AM em concentrações de nanomolar. A técnica SERS foi utilizada para obter informações estruturais do sistema AM/fosfolipídios nos níveis de diluição alcançados via espectroscopia de impedância. Para tanto, monocamadas LB foram depositados sobre filmes evaporados com 6 nm de Ag e nanopartículas de Ag foram dispersas no interior dos filmes LbL. A presença da Ag na forma de nanopartículas em ambos os casos permitiu a obtenção... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Thin films of anionic (DPPG and CLP) and zwiterionic (DPPC and DOPC) phospholipids with different molecular architectures were fabricated using the layer-by-layer (LbL) and Langmuir-Blodgett (LB) techniques. The main goal of this work was to explore the Application of these distinct molecular architectures in the detection of high diluted solutions of methylene blue (MB), a phenothiazine derivative drug. The linear growth, layer by layer, of these films was verified and monitored by UV-Vis absorption spectroscopy. It was found by FTIR that electrostatic interactions among the phosholipids and the supporting layer of PAH (cationic electrolyte) are the main driving force allowing the growth of the LbL and LB films, which favors the growth of the cationic phospholipids. The morphology was analyzed through optical microscopy, AFM and SEM, revealing that the phospholipids are structured as vesicles in the LbL films and as monolayers in the LB films. Different thickness of LbL and as monolayers in the LB filma containing phospholipids were deposited onto Pt interdigitated electrodes forming sensingn units applied in the detection of MB using impedance spectroscopy. The results showed that the different molecular architectures of the LbL and LB films take to different eletrical responses and allow the MP detection in concentrations of nanomolar. The SERS technique was applied to obtain structural information of the system MP/phospholipids at the dilution levels reached via impedance spectroscopy at the dilution levels reached via impedance spectroscopy. Then, LB monolayers were deposited onto 6nm of Ag evaporated films with and Ag evaporated films with and Ag nanoparticles were dispersed within the LbL films. The presence of Ag forming nanoparticles in both cases played a key role in achieving the MB SERRS signal allowing obtaining the detection in high dilution levels, approaching... (Complete abstract click electronic access below)
Mestre

Le manque croissant en eau potable dans le monde est un problème d’envergure pour la population. La filtration par des membranes des eaux usées, insalubres ou la désalination apparaît comme une alternative viable pour le futur. La modification de membranes d’ultrafiltration par l’assemblage couche-par-couche permet d’obtenir des propriétés de nanofiltration en contrôlant avec une précision nanométrique l’épaisseur de la couche active de séparation déposée. Lors de cette thèse, nous avons étudié la construction de la couche de séparation ainsi que sa régénérabilité. Pour ce faire, nous avons développé des surfaces « membrane-like » pour étudier la construction sur des surfaces possédant des fonctions chimiques similaires à l’applicative. Par ailleurs, le temps de déposition a aussi été investigué afin de déterminer si les propriétés de séparation des membranes modifiées dépendaient du nombre de couches déposé ou du temps de dépôt. Les membranes ainsi développées présentent une couche de séparation régénérable et des propriétés de nanofiltration
The increasing lack of drinking water in the world is of major concern for the population. Membrane filtration of brackish water, seawater appears to be a viable alternative for the future. Nanofiltration membranes can be obtained by modifying ultrafiltration membranes by the Layer-by-Layer (LbL) technique. This method also the deposition of an ultra-thin separation layer with a nanoscale precision and with tunable properties. During this PhD thesis, the build-up and the regenerability of the separation layer was investigated. For this purpose, mimicry surfaces were developed in order to study the LbL-assembly on surfaces presenting similar chemical functions as the applicative one. In addition, the deposition time was also investigated in order to determine if the separation properties of the membrane depend on the number of deposited layers or on the coating time. The developed membranes possessed a regenerable separation layer presenting nanofiltration properties

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

L'oxydation spontanée de la dopamine en solution légèrement basique a été étudiée sur la base de la publication de Lee [Science, 318:426-430, 2007], et le produit de la réaction a été identifié comme de la mélanine. La capacité de la mélanine de lier des groupements amines de façon covalente a été confirmée par la quantification des sites de liaison correspondants. En outre il est possible de rédisperser des agrégats de mélanine dans des solutions fortement basiques. Les grains de mélanine ainsi obtenus ont été utilisés pour construire des films multicouches avec le poly(diallyldimethyl ammonium) (PDADMA). Différentes méthodes d'oxydation de la dopamine pour former des films de mélanine à l'interface solide-liquide ont été développées. Toutes les méthodes mènent à la formation de films continus de mélanine ayant des morphologies de surface similaires. Elles deviennent imperméables à des sondes électrochimiques à partir d'une épaisseur de l'ordre de 10 nm. Une plus grande perméabilité à des sondes chargées positivement ou neutres qu'à des sondes négatives a été confirmée. L'adsorption de protéines à des revêtements de mélanine a été expliquée par une combinaison d'interactions électrostatiques et covalentes. Pour arriver à cette explication le potentiel zêta de dépôts de mélanine a été mesuré en fonction du pH. La formation de la mélanine dans des films multicouches de poly(L-lysine) (PLL) et de hyaluronate (HA) a été étudiée: la mélanine est capable de remplir des films (PLL-HA)n de manière homogène, et les composés ainsi obtenus peuvent être détachés de leurs substrats comme membranes autosupportées préparées par une méthode biomimétique sous conditions douces.

La thèse est décomposée en trois parties. Dans la première partie, les modèles de la CUF sont présentés. La CUF permet d’obtenir, dans un formalisme générale, de nombreux modèles qui diffèrent 1) selon l’ordre d’expansion dans l'épaisseur choisie pour les variables primaires; 2) selon le type de modèle: modèles couche équivalente (ESL) ou couche discrète (LW); 3) selon le principe variationnel : “Principle of Virtual Displacements” (raffinée) ou “Reissner’s Mixed Variational Theorem” (avancée). Des géométries cylindrique et à double courbure sont traités. La deuxième partie de la thèse est consacrée à l'obtention des équations fondamentales en utilisant différentes méthodes: la méthode analytique de Navier et deux méthodes numériques approchées; la “Finite Element Method” (FEM) et la “Radial Basis Functions” (RBF). La méthode RBF est une méthode sans maillage “meshless” et peut être considérée comme une méthode alternative à la FEM. La FEM est la plus utilisée dans la littérature et le sujet principal de cette thèse.Dans la dernière partie, différents problèmes sont proposés. Navier est utilisé pour l’analyse thermomécanique de coques FGM, l’analyse de coques piézo-électrique et l’analyse dynamique de nanotubes de carbone. Un élément fini coque, présenté dans cette thèse, est utilisé pour l’analyse de coques composites et FGM. Les résultats obtenus démontrent la supériorité de cet élément par rapport aux éléments finis basés sur les théories classiques pour l’analyse des matériaux avancés. Enfin, la méthode RBF est utilisée pour l’analyse de coques composites, permettant d'illustrer l'avantage des méthodes sans maillage
The dissertation is organized in three main parts. In the first part, the shell models contained in the CUF are presented. The CUF permits to obtain, in a general and unified manner, several models that can differ by 1) the chosen order of expansion in the thickness direction, 2) the equivalent single layer or layer wise approach and 3) the variational statement used: “Principle of Virtual Displacements” (refined models) or “Reissner’s Mixed Variational Theorem” (advanced models). Both the cylindrical and the double-curvature geometries are considered. The second part is devoted to the derivation of the governing equations by means of different methods: an analytical method, that is the Navier method, and two approximated numerical methods, that are the Finite Element Method (FEM) and the Radial Basis Functions (RBF) method. The RBF method is based on a meshless approach and it can be considered a good alternative to the FEM. The finite element method is the most common method used in literature and it is the main topic of this thesis. In the last part, different problems are analyzed. The thermo-mechanical analysis of FGM shells, the electromechanical analysis of piezoelectric shells and the dynamic analysis of carbon nanotubes are performed by means of the Navier method. Then, the CUF shell finite element, presented in this thesis, is tested and used for the analysis of composite and FGM shells. The superiority of this element in respect to finite elements based on classical theories is shown. Finally, the RBF method is combined with the CUF for the analysis of composite and FGM shells in order to overcome the numerical problems relative to the mesh that usually affect the finite elements

Structural colours arise from the interaction of visible light with nano-structured materials. The occurrence of such structures in nature has been known for over a century, but it is only in the last few decades that the study of natural photonic structures has fully matured due to the advances in imagining techniques and computational modelling. Even though a plethora of different colour-producing architectures in a variety of species has been investigated, a few significant questions are still open: how do these structures develop in living organisms? Does disorder play a functional role in biological photonics? If so, is it possible to say that the optical response of natural disordered photonics has been optimised under evolutionary pressure? And, finally, can we exploit the well-adapted photonic design principles that we observe in Nature to fabricate functional materials with optimised scattering response? In my thesis I try to answer the questions above: I microscopically investigate $\textit{in vivo}$ the growth of a cuticular multilayer, one of the most common colour-producing strategies in nature, in the green beetles $\textit{Gastrophysa viridula}$ showing how the interplay between different materials varies during the various life stages of the beetles; I further investigate two types of disordered photonic structures and their biological role, the random array of spherical air inclusions in the eggshells of the honeyguide $\textit{Prodotiscus regulus}$, a species under unique evolutionary pressure to produce blue eggs, and the anisotropic chitinous network of fibres in the white beetle $\textit{Cyphochilus}$, the whitest low-refractive index material; finally, inspired by these natural designs, I fabricate and study light transport in biocompatible highly-scattering materials.

This dissertation discusses, in brief, the production and transport property characterization of films made from the extrusion and biaxial stretching of [beta] nucleated isotactic polypropylene and the extrusion of PEBAX block copolymers. Multilayered films for modified atmosphere packaging applications were also produced by coextrusion and biaxial stretching of these two materials and similarly characterized. Current membranes for packaging applications are generally produced by coating a porous support with a polymeric solution to deposit an active layer for separation. The goal of this project is to displace membranes produced by solvent-based processes, which are environmentally hazardous and thus costly, with equivalent or superior materials produced using melt extrusion.
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Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Biomateriais, Reabilitação e Biomecânica)
In several biomedical applications, one of the major disadvantages of natural polymers is their low mechanical performances. Such drawback has led scientists to search for new materials capable to improve their mechanical properties. In the last few years, graphene and graphene oxide (GO) nanocomposite materials have been proposed to be used in different applications due their outstanding mechanical and electrical properties. We hypothesized that the incorporation of such materials could be useful for biomedical applications. To achieve this goal, we transpose the layerby- layer technology for the production of nanostructured free-standing (FS) polymeric membranes that have such nanofillers in their composition. To this end, chitosan (CHI, polycation) and alginate (ALG, polyanion) were used as a biopolymeric matrix and GO (polyanion) as a reinforcement nanofiller. Prior to FS membranes production, different GO were synthetized, using a modified Hummers' method, from two diferente materials: exfoliated graphite and multi-walled carbon nanotubes, resulting in oxidized graphene flakes (o-GF) and graphene nanoribbons (o-GNR), respectively. Such oxidation process provided oxygen functional groups that among other features improve the bonding with biopolymers. Three membranes were developed, (CHI/ALG/CHI/ALG)100 that acted as controls, while (CHI/ALG/CHI/o-GF)100 and (CHI/ALG/CHI/o-GNR)100 were built up as proof of concept. The morphological analysis was performed by scanning electron microscopy, atomic force microcopy and Raman mapping. The physical properties were assessed by thermogravimetric analysis, water contact angle measurements, water uptake and weight loss. Tensile tests and dynamic mechanical analysis were employed to test the mechanical behavior of the FS membranes. Moreover, biological assays using L929 mouse fibroblasts line were executed to investigate their cytocompablity. Our results showed that the addition of both o-GF and o-GNR forms improved the mechanical properties however with no significant changes on the thermal properties. At the same time, the FS membranes presented a rough surface and an hydrophilic behavior. Concerning the cellular assays, the FS membranes with o-GF revealed a better promotion of cell adhesion and proliferation than both controls and o-GNR FS membranes. The outcomes of this thesis suggests that o-GF membranes may have potential for wound healing, cardiac and bone applications.
Em diferentes aplicações biomédicas, uma das maiores desvantagens apresentadas pelos polímeros naturais são as baixas propriedades mecânicas. Tais desvantagens têm levado a uma maior procura de soluções, nomeadamente através do desenvolvimento de nanocompósitos de grafeno e de grafeno oxidado. Neste trabalho, foi estudado os benefícios que o uso destes materiais podem trazer para aplicações biomédicas. Para tal, foi usada a técnica de camada-a-camada para a produção de membranas poliméricas free-standing, onde, quitosano (CHI, policatião) e alginato (ALG, polianião) foram usados como matriz biopolimérica e o grafeno oxidado (GO) como um nanomaterial de reforço. Antes da deposição das diversas camadas foi necessário proceder à síntese do GO através do método de Hummer modificado, usando para isso dois materiais: a grafite e os nanotubos de carbono de paredes múltiplas (MWNTs), resultando em flocos (o-GF) e nanofitas (o-GNR) de grafeno oxidados, respetivamente. De modo a alcançar os objetivos propostos foram desenvolvidos 3 tipos de membranas, (CHI/ALG/CHI/ALG)100 como controlos, (CHI/ALG/CHI/o-GF)100 e (CHI/ALG/CHI/o-GNR)100 como prova do conceito. A sua caracterização morfológica foi realizada através do recurso a técnicas como: microscopia eletrónica de varrimento, microscopia de força atómica e mapeamento de Raman. Já as propriedades físicas foram avaliadas através termogravimetria, medição dos ângulos de contacto, pela capacidade de absorção de água e pela perda de massa. Testes de tração e análise mecânica dinâmica foram usados para analisar as propriedades mecânicas. Para além disso, a aplicabilidade das membranas foi ainda testada através de ensaios celulares, usando-se para tal linhas celulares L929. Os resultados demonstraram que a adição de o-GF e o-GNR resultam num melhoramento mecânico das membranas sem que exista alteração das propriedades térmicas. Ao mesmo tempo foi também registada uma maior rugosidade e hidrofilicidade das membranas. No que diz respeito aos testes celulares, as membranas onde o-GF estava presente obtiveram uma maior adesão e proliferação celular. Sendo assim, as membranas com o-GF poderão encontrar várias aplicações biomédicas, nomeadamente em aplicações para a cicatrização de tecidos ou ainda para aplicações cardíacas ou ósseas.

Desde a sua introdução, em meados dos anos 90, a técnica de Layer-by-Layer tem sido muito utilizada para a produção hierárquica de filmes com múltiplas camadas. É um método versátil e económico que consiste na deposição alternada de diversos materiais sobre um substrato através de forças eletrostáticas e/ou não eletrostáticas. Quando o substrato utilizado possui baixa tensão superficial, este facilita a remoção do filme sem recorrer a qualquer tipo de ajuda externa, permitindo assim a obtenção de membranas autossustentadas. Este tipo de biomaterial pode ser utilizado para mimetizar microestruturas encontradas na natureza ou para aplicação em medicina regenerativa. A inspiração em fenómenos naturais ou até mesmo em organismos é uma forma promissora de obter biomateriais com características únicas, uma área conhecida como biomimetismo. Tendo em conta tudo isto, a alforreca é um animal marinho que possui na sua estrutura uma matriz particularmente dura, porém gelatinosa chamada de mesogleia. Tendo isso em conta, o trabalho aqui apresentado visa a produção de um novo tipo de membranas estratificadas através de biopolímeros de origem marinha como é o caso do quitosano (CHT) e do alginato (ALG). Para simular a estrutura porosa da mesogleia, estes polissacarídeos foram quimicamente modificados com grupos metacrilados (MA) e a sua modificação foi confirmada através da caracterização espectroscópica por RMN e ATR-FTIR. Posteriormente, dois tipos de membranas intercaladas (CHT/ALG/CHT-MA/ALG-MA) foram produzidas e posteriormente fotorreticuladas. Relativamente às condições de deposição dos polímeros, na análise do potencial zeta verificaram-se as cargas de cada composto, enquanto que a microbalança de quartzo (QCM-D) evidenciou a boa interação eletrostática entre o CHT e ALG, bem como entre os polissacarídeos modificados. Uma vez que a alforreca apresenta boas propriedades mecânicas mesmo sendo constituída por quase 99% de água, todas as membranas foram caracterizadas quanto à capacidade de absorção de água, bem como ensaios mecânicos de tração. Assim como a mesogleia da alforreca, as membranas, quando imersas numa solução aquosa mostram alta capacidade de absorção. Por outro lado, enquanto que as membranas de (CHT/ALG)200 apresentam um modulo de Young superior, as membranas intercaladas alcançam uma maior extensão. Finalmente, as imagens de SEM mostram que as membranas intercaladas (10/10)200 apresentam uma estrutura mais porosa quando comparadas com as membranas (CHT/ALG)200, evidenciando, portanto, mais semelhanças com a estrutura da mesogleia presente na alforreca
Methods for producing multilayered thin films have garnered a powerful scientific interest due to their potential for reinventing multifunctional materials in emerging research fields, like optics, energy, membranes and also biomedicine. Since its introduction in the early 90’s, layer-by-layer (LbL) assembly is a versatile method based on the sequential deposition of multivalent materials over an underlying substrate, coordinated by electrostatic and/or non-electrostatic forces. Also, when the substrate possesses low surface energy, it allows for easy film removal without resorting to any postprocessing steps, thus allowing the production of free-standing (FS) membranes. Such membranes can be used across several research fields with different applications such as biomimetic membranes and regenerative medicine. Taking inspiration from natural phenomena and living organisms is a promising way of designing and rethinking novel materials with unique features, a thriving research area known as biomimetics. Regarding this, jellyfish is a free-swimming marine organism with a particularly tough, yet gelatinous matrix called mesoglea. Inspired by this, the thesis work here presented envisions the design of novel multilayered FS membranes resorting to marine-derived biopolymers. In order to mimic the jellyfish´s mesoglea porous structure, chitosan (CHT), a polycation derived from marine crustaceans, and alginate (ALG), a polyanion derived from brown-algae, were initially modified with pendant methacrylic groups (MA). The successful synthesis of both modified polymers was confirmed by means of 1H NMR and ATR-FTIR characterization. Afterwards, aiming to recapitulate the jellyfish structure, two types of intercalated (CHT/ALG/CHT-MA/ALG-MA) membranes were produced by selective photocrosslinking. As for the deposition conditions of the natural polymers, zeta potential analysis assured the positive and negative charge of the biopolymers, whereas quartz crystal microbalance with dissipation monitoring (QCM-D) demonstrated effective layer deposition of CHT/ALG, as well as among modified polysaccharides. Moreover, jellyfish is able to maintain great mechanical properties even though it is constituted of nearly 99% wt. of water. Thus, water uptake ability and tensile tests were performed in all of the produced membranes. The FS biomimetic membranes, just like jellyfish’s mesoglea, when immersed in a water-like solution show a high-water uptake ability. In addition, (CHT/ALG)200 membranes appear to have a higher Young's modulus when compared to the intercalated ones, however, these last ones achieved a greater elongation profile. Finally, scanning electron microscopy images indicate that the bioinspired intercalated membranes (10/10)200 appear to have a more porous structure than unmodified control ones, therefore resembling the jellyfish’s mesoglea anisotropic structure
Mestrado em Materiais e Dispositivos Biomédicos

Access to safe drinking water is one of the greatest challenges that have afflicted people across the globe. Approximately 1.2 billion people do not have access to safe drinking water while 2.6 billion have no access to sanitation. Around 4,000 children die per day due to communicable diseases transmitted through contaminated drinking water. Rising population, the burden on agriculture and technological growth has triggered rapid industrialization leading to overexploitation and contamination of freshwater aquifers that have declined the groundwater table. Energy efficient, low cost and effective methodology for water purification has to be devised in order to address this challenge and reutilize the available resources. To address this challenge, researchers have turned towards membrane-based separation technology. Various membrane-based separation processes like microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) have been extensively used in water purification. Although these membranes are highly efficient, they lose their performance due to bacterial and protein fouling i.e. undesirable deposition or accumulation of contaminants such as bacteria and protein on the membrane surface and/or inside the pores of the membrane. This thesis entitled “Porous polymeric membranes with engineered surfaces for water remediation” addresses these key issues using surface engineering of polymeric surfaces and by the fabrication of new biocidal and foul release materials using polymerization techniques. Like MF and UF based membranes, RO membranes are also susceptible to fouling and have limited salt rejection and heavy metal removal capabilities. To address these concerns, the concept of multilayered membranes was used wherein an antibacterial polymer will be the active layer, mixed metal organic framework (MMOF) is the interlayer and RO membrane will be the support layer. This is discussed in Chapter 5. To optimize the best antibacterial polymer, different polymer tool boxes were tailored by reversible addition-fragmentation chain-transfer (RAFT) polymerization from quaternary ammonium compound, hyperbranched amine and phosphonium-based homo/copolymers. The result reflected that one specific polymer was exemplary in terms of its overall performance but there was a scope of improvement of the rejection capabilities. This was achievable by changing the interlayer material prudently. Hence, in Chapter 6 and Chapter 7, the polymer active layer was kept as is and the interlayer was varied from MMOF to molybdenum disulfide tethered magnetospheres and graphene oxide anchored MOF, respectively. This mitigated fouling and yielded efficient and excellent performance for desalination and heavy metal removal. Finally, Chapter 8 sums up the major conclusions from each chapter and highlights the outcome of the works. It also discusses the future work that can be undertaken in this research area and new strategies that can be devised for novel antibacterial and antifouling membranes that can yield unimpeded flow to water

Membrane processes are considered energy-efficient for water desalination and treatment. However most membranes are based on polymers prepared from fossil petrochemical sources. The development of multilayer membranes for nanofiltration and ultrafiltration, with thin selective layers of naturally available cellulose, has been hampered by the availability of non-aggressive solvents. We propose the manufacture of cellulose membranes based on two approaches: (i) silylation, coating from solutions in tetrahydrofuran, followed by solvent evaporation and cellulose regeneration by acid treatment; (ii) casting from solution in 1-ethyl-3-methylimidazolum acetate ([C2mim]OAc), an ionic liquid, followed by phase inversion in water. In the search for less harsh, greener membrane manufacture, the combination of cellulose and ionic liquid is of high interest. Due to the abundance of OH groups and hydrophilicity, cellulose-based membranes have high permeability and low fouling tendency. Membrane fouling is one of the biggest challenges in membrane industry and technology. Accumulation and deposition of foulants onto the surface reduce membrane efficiency and requires harsh chemical cleaning, therefore increasing the cost of maintenance and replacement. In this work the resistance of cellulose 5 membranes towards model organic foulants such as Suwanee River Humic Acid (SRHA) and crude oil have been investigated. Cellulose membrane was tested in this work for oil-water (o/w) separation and exhibited practically 100 % oil rejection with good flux recovery ratio and membrane resistivity. The influence of anionic, cationic and ionic surfactant as well as pH and crude oil concentration on oil separation was investigated, giving a valuable insight in experimental and operational planning.

碩士
元智大學
化學工程與材料科學學系
94
In this study, Nafion-117 membranes were modified by layer-by-layer electrostatic self assembly (LBLESA) technique and tested for their application as proton exchange membranes in direct methanol fuel cells (DMFCs). Polyelectrolyte multilayered (PEM) membranes were constructed by electrostatic absorbed polycation poly(allylamine hydrochloride) (PAH) and polyanion poly(acrylic acid) (PAA). A series of standard methods were used to characterize the membrane properties, such as ATR-FTIR analysis, contact angle experiment, XPS analysis, TEM observation, AFM observation, water uptake test, pervaporation test of aqueous methanol solution, AC impedance analysis. The properties of modified membranes were compared with those of pristine Nafion-117 with an aim to be used for the fabrication of membrane electrode assembly (MEA). Polycation and polyanion layer showed difference in water contact angle；therefore monolayer adsorption of polyelectrolytes could be confirmed. The averaged thickness of each layer in the multilayer was about 30-45 nm by TEM observation. ATR-FTIR confirmed the presence of polyelectrolyte element group in the modified membranes. After absorbed four double layer, membranes surface have a non-homogeneous layer growth by AFM observation. XPS analysis suggests the sulfonate group through polyelectrolyte layer as a path to permit easy proton transport. In pervaporation experiment, Six double layers were sufficient to minimize the methanol crossover ( 9.6 wt % in feed, methanol conc. of permeate 0.33 wt% ). The proton conductivity of LBL6 (σ = 2.4×10-1 S/cm) was higher than Nafion-117 membrane (σ = 3.2×10-2 S/cm) at 80℃, relatively humidity of 95 %. Base on all tested results, LBL6 membranes have potential to be used for DMFC.

碩士
國立臺灣科技大學
機械工程系
107
Bile duct obstruction is the main problem caused by cholangiocarcinoma. Currently, placing biliary stent in the body is the main solution to biliary occlusion. However, the obstruction could happen again after several months. The secondary endoscopic surgery is a method to solve biliary reocclusion, but it may cause life risk and financial burden. This study is trying to develop a multilayer self-cleaning membrane to postpone stent reocclusion. This multilayer self-cleaning membrane consists of biodegradable PLA (Polylactic Acid) films and PVA (Polyvinyl Alcohol) films. In order to achieve the functions that the structural membrane can not only degrade into PLA fragments periodically but also clean the attached contaminant away smoothly. The experiments of this study focus on different kinds of designed patterns and intervals. Based on the limitation of nanosecond laser machine, the minimum interval can be downsized to 0.3 mm. The experimental results show the structural film with narrower intervals between the structures can disintegrate more effectively. Also, the structural film can disintegrate effectively with comparatively large ratio of pattern size and connection interval width. If the PLA structural film is thinner, it would disintegrate rapidly after the solution permeates the film and degrade the under PVA film. In addition, our experiments have proved the structural membrane can clean the attached contaminant during degradation process periodically.

碩士
雲林科技大學
化學工程與材料工程研究所
98
The sulfonated polyimide/Nafion multilayer membrane (SPI-NF) was successfully prepared by immersing the sulfonated poly(amic acid) (SPAA) into the Nafion coating solution. SPAA was prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 2,2 –benzidinedisulfonic acid (BDSA) as sulfonated diamines, and non-sulfonated diamines 4,4’-Oxydianiline (ODA). The SPAA-NF membrane was thermally imidized via evaporation of the solvent and formation SPI-NF membrane. The SPI-NF membrane properties were investigated including water uptake, proton conductivity, methanol permeability, oxidative and hydrolytic stability, thermal properties and morphology. Finally, we fabricated the MEA with the SPI-NF membrane to process PEFCs performance test, used commercial Nafion 212 as a reference standard, we estimated the possibility of Nafion/SPI/Nafion multilayer membrane for PEFCs application. The thermal properties analysis showed that both SPI and SPI-NF had good thermal stability up to 300℃. The proton conductivity of the SPI-NF membrane exceeded that of the SPI membrane under the same condition, and was compared to Nafion 212 at 80℃. The methanol permeability of SPI and SPI-NF membranes were lower than Nafion 212 at different concentration of feed methanol. Through immersing both membranes into the Fenton’s reagent at room temperature for an oxidative stability test and the durability test of a single PEFCs, the result showed the stability of the SPI-NF has been greatly improved by adding Nafion layer compared with the SPI. From the cross-section morphology, the Nafion layers were with good adhesion to the native SPI membrane. With the Nafion layer coated on the SPI membrane could improved the interfacial adhesion between the electrode and the membrane, new MEA with the SPI-NF could maintain the stable interface after long-term operation compared to the MEA with the SPI. The PEFCs performance with the SPI-NF was similar to the performance with the commercial product Nafion 212 at 70℃.

Polymers films and membranes with immobile and irreversible reactive sites can provide significant barrier properties for packaging materials. There is a need to develop mathematical models to understand the behavior of these reactive materials and to confidently extrapolate experimental data. Due to mechanical and optical requirements, barrier films may consist of composites, such as polymer blends and multilayer films with alternating reactive and inert layers. The reactive term that consumes the mobile species in the governing transport equations for such materials is a function of both the mobile species and the immobilized reactive sites, leading to non-linear partial differential equations that typically have to be solved numerically. Composite structures add to the complexity of the model. For the polymer blend, a multiscale model was developed, incorporating the reactive details within the particle into the bulk transport equation. For the multilayer film, initial conditions and diffusion coefficients were assigned independently for reactive or inert layers. The models developed for the three configurations were solved numerically over a wide parameter space. Three regimes were identified, namely early times characterized by an initial flux plateau, and intermediate regime, and long times, characterized by the time lag. Asymptotic analysis of the homogeneous model was used to develop analytical predictions for the three regimes, obviating the need to numerically solve the model’s non-linear equations. These predictions were generalized to polymer blends. For multilayer films, predictions for early and long times were developed. Results for polymer blends and multilayer composites were compared and discussions of the most suitable configuration for different scenarios were presented. The reactive barrier configurations studied require the knowledge of parameters such as reaction rates and coefficients of diffusion and solubility of the reactive polymer. Model and predictive equations have been developed to describe the transient mass uptake in reactive homogeneous films, enabling the extraction of these parameters from sorption experiments.
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The development of a suitable coating or material, which physico-chemical, mechanical or biological properties, that can be tailored according the features of the target tissue, has been gaining increased importance in biomedical and tissue engineering and regenerative medicine (TERM) fields. Biomimetic strategies have contributed significantly for the progress of biomedical field during the last years. This is possible to be achieved at different levels: imitating Nature form or function and mimicking natural processes and systems are the most used biomimetic approaches. In this thesis, Layer-by-Layer (LbL) methodology was used as a hierarchical biomimetic tool to modify surfaces and to produce freestanding membranes based on polyelectrolyte multilayers (PEMs). The possibility to functionalize or engineer biomaterials combined with the ability to incorporate a wide range of building blocks, makes LbL a powerful processing technique in the biomedical field. Synthetic polymers have been used to construct PEMs for biomedical and TERM applications; however, they lack often on adhesive cues for cell attachment and tissue growth. To overcome such issue, biomimetic synthetic polymers have been developed. Elastin-like polypeptides (ELPs) are a class of nature-inspired polymers, nonimmunogenic, genetically encodable and biocompatible. These materials are based on the repetition of short peptides considered to be building blocks in natural elastin and can include specific bioactive sequences, as the tripeptide Arginine-Glycine-Aspartame (RGD) known by promoting cell adhesion. For the first work of this thesis, ELPs were functionalized with azide and alkyne groups to introduce the reactivity required to carry out the 1,3-dipolar cycloaddition under mild biocompatible conditions, with no toxic by-products and in short reaction times. This reaction was done by means of a LbL assembly, driven by covalent interactions instead of being driven by electrostatic interactions, obtaining a bioactive and biomimetic multilayer coating. Moreover, these polymers are characterized by a critical temperature, known as the transition temperature in aqueous solution (Tt), which is related with a conformational reorganization. Thus, below Tt the polymer chains were soluble in water and above Tt they formed nano- and micro-aggregates becoming insoluble in a reversible process, making these coatings stimuli-responsive. In the following chapters, several polysaccharides as chitosan (CHT), alginate (ALG), hyaluronic acid (HA) or chondroitin sulfate (CS) were used to produce freestanding structured membranes through LbL processes, mainly driven by electrostatic interactions. The use of PEMs containing biopolymers are particularly appealing to coat and develop multilayered structures with biochemical functionalities, biocompatibility, and to mimic the interactions observed in native extracellular matrix (ECM). CHI/CS multilayers were used throughout the thesis, revealing some unique properties, when compared with other polysaccharide-based multilayers, such as their elasticity and degradation rate. However, natural origin polymer-based multilayers present low stiffness and higher hydration rates, which hinder cell adhesion. To overcome this, the CHT/CS multilayers were crosslinked with genipin. This is also a natural product, that is extracted from gardenia fruits and presents the ability to improve the mechanical properties, while preserves the biocompatibility and even enhances the cell adhesive properties. The ability to tailor the multilayers properties can be applied during their assembly or postassembly. Upon adjusting cross-linking parameters (e.g., cross-linker concentration and reaction time) the morphology, thickness, water uptake, rate of biodegradation, mechanical properties and cell adhesive properties can be tuned. Studies of shape-memory of these multilayered films, presented promising results regarding their use in biomedical applications. The mechanical properties of the multilayers can be further improved combining covalent and ionic crosslinking, which gives rise to a full interpenetrating polymer network. More interesting, it was possible to create a well-organized patterned topography at the surface of the freestanding multilayered membrane, just by using a different underlying substrate. This strategy envisaged to mimic the topography of the ECM of some tissues, as bone, skin or nerves, creating grooves on the material’s surface at nanoscale. Using this approach, it was possible to control some cellular functions and behavior as alignment and differentiation. Further in this thesis and inspired by the composition of the adhesive proteins in mussels, freestanding multilayered membranes containing dopamine-modified hyaluronic acid (HA-DN) were produced. The presence of DN along with the thickness of the membranes presented better lap-shear adhesion strength than the control membranes (hyaluronic acid and alginate films – two polysaccharides often regarded as good natural adhesives – were assembled together). Moreover, in vitro tests showed an enhanced cell adhesion for the membranes containing HA-DN and ability to use such kind of membranes for different biomedical and TERM applications, particularly for bone regeneration and skin wound healing. Combining different biomimetic concepts, it was also possible to recreate the complex environment of osteoarthritic articular cartilage by preparing human circular discs of superficially damaged articular cartilage from human samples. Herein, the adhesive freestanding multilayered membranes were used as a vehicle to deliver human adipose stem cells (hASCs) to help to repair the damaged cartilage. hASCs temporarily adhered to the adhesive LbL-based membranes, and were transported to the cartilage discs, creating a bridge of cells between the membranes and the surface of the cartilage. The cells started to migrate into the defects of the cartilage, proliferating and secreting factors capable of repairing the cartilage. Overall, the developed work in this thesis shows that LbL is a very versatile technique that provides the means to develop a wide range of solutions to be useful in biomedical and TERM applications.
O desenvolvimento de um revestimento ou material cujas propriedades físicoquímica, mecânicas ou biológicas podem ser modificadas de acordo com as propriedades do tecido alvo, tem ganho cada vez mais importância, nomeadamente para fins biomédicos e de engenharia de tecidos e medicina regenerativa. Durante os últimos anos, diferentes estratégias biomiméticas têm contribuído significativamente para o progresso destas áreas. Estas são possíveis de implementar a diferentes níveis: imitar formas e funções existentes na natureza ou mimetizar processos e sistemas naturais. Na presente tese, a técnica camada-a-camada (LbL) foi usada como uma ferramenta biomimética para modificar superfícies ou produzir membranas com base em múltiplas camadas de polieletrólitos. A crescente utilização desta técnica, concretamente na área biomédica, prende-se com a possibilidade de funcionalizar ou produzir biomateriais aliada à capacidade de incorporar uma gama alargada de blocos de construção. Aqui, diferentes polímeros sintéticos e naturais têm sido usados para construir estruturas multicamada; no entanto, a generalidade dos polímeros sintéticos não apresenta naturalmente locais de ligação e adesão celular. Para contornar este obstáculo, algumas modificações químicas aos polímeros sintéticos têm sido sugeridas e novos compostos têm sido desenvolvidos, inspirados na composição de sistemas naturais. Por exemplo, polipéptidos tipo-elastina (ELPs) são uma classe de polímeros inspirados na natureza, que apresentam propriedades não-imunogénicas e biocompatíveis, podendo ser geneticamente programados conforme desejado. A sua composição baseia-se na repetição de pequenos péptidos também presentes na elastina humana, com a possibilidade também de incorporar outras sequências bioativas especificas, como o tripéptido Arginina-GlicinaÁcido Aspártico (RGD), reconhecido por promover a adesão celular. Para esta tese foram produzidos ELPs, que mais tarde foram funcionalizados com grupos azida e alquino para introduzir a reatividade necessária para uma reação 1,3-dipolar de ciclo-adição se realizar em condições biocompatíveis, sem produtos tóxicos resultantes e em curtos tempos de reação. Esta reação foi realizada sob a técnica LbL, mas conduzida por interações covalentes ao invés de electroestáticas, para atuar como revestimento biomédico. Estes polímeros são ainda reconhecidos pela sua temperatura de transição (Tt) em solução aquosa, relacionada com uma reorganização conformacional da cadeia polimérica. Abaixo da Tt as suas cadeias poliméricas são solúveis, mas acima de Tt formam-se micro-agregados; este é um processo reversível que confere propriedades responsivas aos revestimentos. Nos seguintes capítulos, diferentes polissacarídeos como quitosano (CHT), alginato (ALG), sulfato de condroitina (CS) ou ácido hialurónico (HA), foram usados para produzir membranas multicamadas conduzidas maioritariamente via interações electroestáticas. Esta abordagem tem ganho cada vez mais importância para desenvolver materiais com funcionalidade bioquímica, biocompatibilidade e para mimetizar algumas interações observadas na matriz extracelular (ECM). Ao longo desta tese foram usadas membranas multicamada de CHT/CS; estes materiais revelaram algumas propriedades muito particulares, quando comparadas com outros sistemas de multicamada, como a sua elasticidade e taxas de degradação mais rápidas. No entanto, a baixa rigidez e maiores taxas de hidratação, que muitas vezes impedem a adesão celular, surgem frequentemente associados a sistemas multicamada compostos somente por polissacarídeos. Para contornar este obstáculo, as membranas multicamada de CHT/CS foram reticuladas com genipina. De notar que este composto é de origem natural, sendo extraído da fruta da gardénia; a pós-modificação das membranas com genipina resultou na melhoria das propriedades mecânicas e biocompatibilidade, e ainda, no aumentando das propriedades bio-adesivas. Na realidade, a possibilidade de modular as propriedades destes sistemas multicamada por reticulação química pode ser conseguida logo durante a adsorção de cada camada ou no fim do processo. Características dos biomateriais como a morfologia, espessura, taxas de adsorção de água ou biodegradação, propriedades mecânicas e biológicas podem ser moduladas ajustando certos parâmetros de reticulação (por exemplo, agente de reticulação, concentração ou tempo de reação). Para além do mais, estudos de memória de forma destas membranas multicamada mostraram resultados promissores, considerando o seu uso para fins biomédicos. As propriedades mecânicas destes sistemas foram melhoradas combinando as ligações electroestáticas já existentes com ligações covalentes conferidas pela reticulação química, dando origem a uma rede polimérica multicamada, mas interpenetrada. Na continuação deste trabalho foi possível criar uma topografia com padrão bem organizado na superfície das membranas, alterando somente o material onde efetuamos a deposição das multicamadas. Esta estratégia visou mimetizar a topografia da ECM de diferentes tecidos, como o osso, a pele ou os nervos, criando canais alinhados na superfície do material. Usando este tipo de materiais multicamada padronizados foi possível modular funções e comportamentos celulares como o alinhamento ou a diferenciação. Em seguida, inspirados pela composição das proteínas que conferem adesividade aos mexilhões, foram produzidas membranas multicamada contendo HA modificado com dopamina (DN). A presença de DN ao longo da espessura das membranas multicamada parece ter contribuído para uma melhor e maior força de adesão, quando comparadas com as membranas controlo (membranas multicamada CHT/HA e CHT/ALG). Para além do mais, os testes in vitro resultaram em uma significante melhoria da adesão celular às membranas contendo DN. Esta estratégia mostrou ser promissora para diferentes aplicações biomédicas e de engenharia de tecidos, particularmente para a regeneração de tecido ósseo e a cicatrização de feridas da pele. Combinando diferentes estratégias e conceitos biomiméticos, foi também possível recriar um sistema complexo associado à cartilagem articular e concretamente a doenças como a osteoartrite. Assim sendo, na última parte desta tese, estas membranas multicamada com propriedades adesivas foram utilizadas como veículo para transportar células estaminais humanas do tecido adiposo (hASCs) para o local onde a cartilagem se encontra danificada. A presença deste tipo de células tem sido utilizada como tratamento para cartilagem danificada. Aqui, hASCs aderiram temporariamente às membranas multicamada, e foram assim transportadas diretamente para discos de cartilagem humana danificada, permitindo a criação de uma ponte celular entre as membranas e a superfície da cartilagem. Desta forma, estas células começaram a proliferar na superfície da cartilagem começando a migrar para os defeitos (em profundidade), segregando fatores capazes de ajudar na reparação da cartilagem. No geral, o trabalho desenvolvido para a presente tese mostra a grande versatilidade da técnica LbL, que proporciona os meios necessários para desenvolver uma gama alargada de materiais, estratégias e soluções muito necessárias e promissoras para aplicações biomédicas e de engenharia de tecidos e medicina regenerativa.
Programa Doutoral em Química