La membrane échangeuse de protons est un élément essentiel des piles à combustible. Elle permet le transfert des protons d’une électrode à l’autre pour produire de l’électricité. La conduction protonique des membranes actuelles est optimale vers 80°C et très sensible à l’eau. La conception de nouvelles membranes permettant le fonctionnement des piles à combustible à température ambiante et moins sensibles à l’eau est nécessaire. La solution proposée pendant ma thèse est de concevoir des microémulsions solidifiées conductrices de protons. Les microémulsions sont des mélanges liquides nanostructurés d’eau, d’huile et de tensioactifs à l’équilibre thermodynamique. Des microémulsions bicontinues, constituée de canaux d’eau et d’huile séparés par une monocouche de tensioactifs, formulées avec des tensioactifs conducteurs protoniques devraient avoir des propriétés intéressantes de conduction protonique. Il est ensuite nécessaire de solidifier les microémulsions obtenues pour pouvoir les utiliser comme membrane échangeuse de protons. Dans ce travail, la voie explorée consiste à utiliser une huile solide à température ambiante pour résoudre ce problème. Deux systèmes, contenant une huile solide à température ambiante et des tensioactifs conducteurs protoniques, ont été étudiés. Des microémulsions bicontinues sont ainsi préparées au-dessus du point de fusion de l’huile. Il s’agit ensuite de maîtriser comment un simple refroidissement permet d’obtenir des microémulsions solidifiées, matériaux solides avec la même structure que le liquide de départ. Cette étude a permis de mettre en évidence l’influence de la cristallisation sur la structure du matériau obtenu. / Proton-exchange membrane is an important part of fuel cells. It allows protons to move from one electrode to the other while producing energy. Proton conduction in current membranes is optimum at 80°C and very sensitive to water. It is therefore necessary to build new proton-exchange membranes to design fuel cells that are effective at ambient temperature and less water-sensitive.During my PhD, we intend to prepare solidified microemulsions as proton-exchange membranes. Microemulsions are nanostructured liquids composed of water, oil and surfactants at thermodynamic equilibrium. Bicontinuous microemulsions, made of water and oil channels separated by surfactants, obtained using proton conducting surfactants should have interesting proton conductivity. It is then necessary to solidify the obtained liquid to be able to use them as proton-exchange membrane. In this study, we use oil that is solid at room temperature to overcome this trouble. Two systems, with an oil solid at room temperature and proton-conducting surfactants, were studied. Bicontinuous microemulsions are prepared above the melting point of the oil. The point is then to understand how cooling down the liquid microemulsion allow to prepare a solidified microemulsion which is a solid with the same nanostructure as the initial liquid. This study highlights the influence of crystallization on nanostructure during cooling.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19957号 / 理博第4224号 / 新制||理||1607(附属図書館) / 33053 / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 島川 祐一, 教授 竹腰 清乃理 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

As células a combustível a etanol direto (DEFCs) são consideradas geradores de energia eficientes e de baixo impacto ambiental. O foco deste trabalho é avançar o entendimento sobre eletrólitos compósitos híbridos do tipo Nafion-cerâmica visando o aumento do desempenho das DEFCs operando em T ~ 130 °C. Partículas inorgânicas foram crescidas na matriz polimérica formando os compósitos Nafion-Sílica (NS), Nafion-Fosfato de Zircônio (NZ) e Nafion-Titânia (NT). Este último (NT) serviu como material precursor para a conversão in situ da titânia em nanotubos de titanato de hidrogênio por uma rota hidrotérmica alcalina assistida por micro-ondas (NNTH). A relação microestrutura-propriedades elétricas foi estudada por meio de medidas de espectroscopia dielétrica, análise dinâmico-mecânica, calorimetria diferencial exploratória e espalhamento de raios X em baixo ângulo. Estas técnicas contribuíram, por exemplo, para inferir a localização das partículas inorgânicas na estrutura multifásica do Nafion e estabelecer a sua influência nas propriedades gerais dos compósitos. Os resultados indicaram que as interações de repulsão eletrostática de longo alcance entre os grupos sulfônicos do Nafion hidratado provocam a transição conformacional das cadeias principais do estado enovelado para a conformação tipo bastão. Tal transição promove a redução da condutividade protônica e da estabilidade mecânica do Nafion para temperaturas acima da temperatura da relaxação (Tα ~ 110 °C), a qual pode ser deslocada para maiores temperaturas (T > 160 °C) nos compósitos híbridos. A interação das partículas de sílica e de titânia com a fase condutora do Nafion é maximizada, enquanto que as partículas de fosfato de zircônio estão localizadas majoritariamente nos domínios apolares. As interações entre os grupos sulfônicos do Nafion e as partículas de titânia contribuíram para a melhora das propriedades mecânicas em altas temperaturas e para a redução da permeabilidade ao etanol, as quais promoveram o aumento do desempenho da DEFC em altas temperaturas. A baixa permeabilidade ao etanol e as melhores propriedades termomecânicas e de transporte protônico dos compósitos NNTH refletiram em um elevado desempenho das DEFCs a 130 °C, evidenciando que estes eletrólitos compósitos são promissores para a aplicação pretendida. / Direct Ethanol Fuel Cells (DEFCs) are considered a clean and high efficient power source. The focus of this thesis is to contribute to advance the understanding of Nafion-based hybrid composites aiming at high-performance DEFCs operating at elevated temperatures (T ~ 130 °C). Three inorganic particles were grown in the polymer matrix forming the electrolyte composites Nafion-Silica (NS), Nafion-Zirconium Phosphate (NZ), and Nafion-Titania (NT). The latter (NT) served as a precursor composite for the in situ conversion of titania into hydrogen titanate nanotubes by a microwave-assisted alkaline hydrothermal reaction (NNTH). The relation microstructure-eletrical property was studied by dielectric spectroscopy, dynamic-mechanical analysis, differential scanning calorimetry, and small angle X-ray scattering. Such techniques contributed, for example, to infer the localization of the inorganic particles in the Nafion multiphase structure and to establish its influence in the general properties of the composites. The results indicated that long range electrostatic repulsion occurring within Nafion ionic groups promotes a conformational transition of the polymer main chains from entangled to rodlike. Such transition reduces both the proton conductivity and the mechanical stability at temperatures higher than relaxation temperature (Tα ~ 110 °C), which was found to be shifted to higher T > 160 ºC in the hybrid composites. The interaction between silica and titania particles with Nafion conducting phase is maximized, while the zirconium phosphate particles occupy preferably the hydrophobic domains. The interactions between Nafion sulfonic acid groups and titania particles contributed to the improvement of the mechanical properties at high temperature and to the lowering of ethanol permeability that increased DEFC performance at high temperature. The low ethanol permeability, high mechanical and electrical properties of NNTH reflected in the high DEFC performance at 130 °C, evidencing this composite as a promising electrolyte for the intended application.

As células a combustível a etanol direto (DEFCs) são consideradas geradores de energia eficientes e de baixo impacto ambiental. O foco deste trabalho é avançar o entendimento sobre eletrólitos compósitos híbridos do tipo Nafion-cerâmica visando o aumento do desempenho das DEFCs operando em T ~ 130 °C. Partículas inorgânicas foram crescidas na matriz polimérica formando os compósitos Nafion-Sílica (NS), Nafion-Fosfato de Zircônio (NZ) e Nafion-Titânia (NT). Este último (NT) serviu como material precursor para a conversão in situ da titânia em nanotubos de titanato de hidrogênio por uma rota hidrotérmica alcalina assistida por micro-ondas (NNTH). A relação microestrutura-propriedades elétricas foi estudada por meio de medidas de espectroscopia dielétrica, análise dinâmico-mecânica, calorimetria diferencial exploratória e espalhamento de raios X em baixo ângulo. Estas técnicas contribuíram, por exemplo, para inferir a localização das partículas inorgânicas na estrutura multifásica do Nafion e estabelecer a sua influência nas propriedades gerais dos compósitos. Os resultados indicaram que as interações de repulsão eletrostática de longo alcance entre os grupos sulfônicos do Nafion hidratado provocam a transição conformacional das cadeias principais do estado enovelado para a conformação tipo bastão. Tal transição promove a redução da condutividade protônica e da estabilidade mecânica do Nafion para temperaturas acima da temperatura da relaxação (Tα ~ 110 °C), a qual pode ser deslocada para maiores temperaturas (T > 160 °C) nos compósitos híbridos. A interação das partículas de sílica e de titânia com a fase condutora do Nafion é maximizada, enquanto que as partículas de fosfato de zircônio estão localizadas majoritariamente nos domínios apolares. As interações entre os grupos sulfônicos do Nafion e as partículas de titânia contribuíram para a melhora das propriedades mecânicas em altas temperaturas e para a redução da permeabilidade ao etanol, as quais promoveram o aumento do desempenho da DEFC em altas temperaturas. A baixa permeabilidade ao etanol e as melhores propriedades termomecânicas e de transporte protônico dos compósitos NNTH refletiram em um elevado desempenho das DEFCs a 130 °C, evidenciando que estes eletrólitos compósitos são promissores para a aplicação pretendida. / Direct Ethanol Fuel Cells (DEFCs) are considered a clean and high efficient power source. The focus of this thesis is to contribute to advance the understanding of Nafion-based hybrid composites aiming at high-performance DEFCs operating at elevated temperatures (T ~ 130 °C). Three inorganic particles were grown in the polymer matrix forming the electrolyte composites Nafion-Silica (NS), Nafion-Zirconium Phosphate (NZ), and Nafion-Titania (NT). The latter (NT) served as a precursor composite for the in situ conversion of titania into hydrogen titanate nanotubes by a microwave-assisted alkaline hydrothermal reaction (NNTH). The relation microstructure-eletrical property was studied by dielectric spectroscopy, dynamic-mechanical analysis, differential scanning calorimetry, and small angle X-ray scattering. Such techniques contributed, for example, to infer the localization of the inorganic particles in the Nafion multiphase structure and to establish its influence in the general properties of the composites. The results indicated that long range electrostatic repulsion occurring within Nafion ionic groups promotes a conformational transition of the polymer main chains from entangled to rodlike. Such transition reduces both the proton conductivity and the mechanical stability at temperatures higher than relaxation temperature (Tα ~ 110 °C), which was found to be shifted to higher T > 160 ºC in the hybrid composites. The interaction between silica and titania particles with Nafion conducting phase is maximized, while the zirconium phosphate particles occupy preferably the hydrophobic domains. The interactions between Nafion sulfonic acid groups and titania particles contributed to the improvement of the mechanical properties at high temperature and to the lowering of ethanol permeability that increased DEFC performance at high temperature. The low ethanol permeability, high mechanical and electrical properties of NNTH reflected in the high DEFC performance at 130 °C, evidencing this composite as a promising electrolyte for the intended application.

Nitrogen-rich porous organic frameworks show great promise for use as acid-doped proton conducting membranes, due to their high porosity, excellent chemical and thermal stability, ease of synthesis, and high nitrogen content. Aided by very high surface area and pore volume, the material has the ability to adsorb high amounts of H3PO4 into its network, which creates a proton rich environment, capable of facile proton conduction. The morphology and chemical environment, doping behavior, and proton conduction of these materials were investigated. With such high acid-doping, ex-situ studies revealed that under anhydrous conditions, PA@BILP-16 (AC) produced a proton conductivity value of 5.8 x 10-2 S cm-1 at 60 °C and PA@ALP-6 showed a slightly higher value of 5.91 x 10-2 S cm-1 at 60 °C. With such promising results, in-situ experiments with various analogues are scheduled to be conducted in the near future.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23715号 / 理博第4805号 / 新制||理||1688(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 吉村 一良, 教授 竹腰 清乃理 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18951号 / 工博第3993号 / 新制||工||1615(附属図書館) / 31902 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 北川 進, 教授 松田 建児, 教授 安部 武志 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13071号 / 論工博第4148号 / 新制||工||1659(附属図書館) / 33222 / (主査)教授 北川 進, 教授 松田 建児, 教授 阿部 竜 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24177号 / 理博第4868号 / 新制||理||1697(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 有賀 哲也, 教授 吉村 一良 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The majority of this dissertation focuses on proton conducting materials that could be used at high operating temperatures. Higher operating temperatures are desirable as they will increase fuel cell efficiency, reduce cost, and simplify the heat management system. The factors governing proton conduction including segmental mobility, protogenic group identity, and charge carrier density were investigated on a variety of polymers containing 1H-1,2,3-triazole moieties. Proton conductivity measurements were made using AC impedance spectroscopy. Random copolymers and terpolymers of triazole-containing acrylates and poly(ethylene glycol)methyl ether acrylate (PEGMEA) have been synthesized. Conductivity increased with increasing degree of PEG incorporation until reaching a maximum at 30% mole PEGMEA. In comparison to benzimidazole-functionalized polyacrylate with 35% mole PEGMEA, the triazole analog showed a higher proton conductivity, and a less pronounced conductivity temperature dependence. Further increases in conductivity was achieved through the addition of trifluoroacetic acid. To study the effect of charge carrier density on proton conduction, polyacrylates containing a different number of triazole groups per repeat unit were synthesized. The result showed that introduction of more than one triazole per repeat unit did not result in an increase in conductivity as there was an accompanying increase in Tg. To improve the thermal and mechanical properties, triazole groups were tethered to a higher Tg backbone polymer, polynorbornene. Introduction of polyhedral oligomeric silsesquioxane (POSS) into triazole-functionalized polynorbornene was also investigated. In a parallel set of investigations, poly(2-(dimethylamino)ethyl methacrylate), PDMAEMA, and copolymers of DMAEMA and methyl methacrylate (PDMAEMA-co-PMMA) were synthesized via atom transfer radical polymerization (ATRP). Fluorescently-labeled PDMAEMAs were synthesized using fluorescent ATRP initiators to ensure the presence of one dye molecule on every polymer chain. PDMAEMAs and PDMAEMA-co-PMMA with different molecular weights have been deposited onto a negatively-charged silica surface via controlled flow deposition. The results show that the polymer deposition rate depends on molecular weight, and is inversely proportional to molecular weight. A preliminary adhesion study of 1-μm negatively charged silica spheres onto these functionalized surfaces indicates that by varying the molecular weight, the adhesion threshold can be changed. System modeling is being conducted to support experimental observations.