Dans le contenu de l’amélioration des performances des piles à combustible, des catalyseurs Pt/Vulcan ont été greffés soit avec du polystyrène sulfonate (PSSA) soit avec de l'acide 4-phenysulfonique (PSA). L'influence du ratio du greffage, de la couche de diffusion de gaz et de la qualité de Nafion, sur les performances électrochimiques ont été étudiées en demi-pile et en assemblage membrane-électrodes (AME). La surface électrochimique du catalyseur a été améliorée en présence de la couche microporeuse sur le papier carboné en tant que couche de diffusion de gaz, aussi une densité de courant supérieure et une résistance de transfert de charge inférieure ont été observées. Pt/Vulcan catalyseurs ont été greffés des chaines PSSA avec 5, 10 et 20 wt.% 4-styrènesulfonate de sodium. Les résultats en demi-pile et en pile ont montré que des taux de sulfonation de 5 à 10 wt.% étaient optimaux. La sulfonation des catalyseurs a aussi été effectuée avec 5.8, 11.6, 18.0 et 23.3 wt.% PSA. Des résultats meilleurs ont été obtenus par la sulfonation. L'AME ayant 18.0 wt.% PSA a présenté une excellente stabilité pendant 3000 cycles de test de vieillissement accéléré. Moins de Nafion a entraîné une plus faible performance des demi-piles, aussi des AMEs ayant catalyseurs des greffé de 5 wt.% PSSA ou PSA. Cependant, celles contenant 10 et 20 wt.% de PSSA, ont montré un une densité de puissance élevé lors que la quantité de Nafion a diminué de 0.50 à 0.25 mg•cm-2 / In the development of the performances of PEM fuel cell, sulfonated Pt/Vulcan catalysts were prepared by grafting with either polystyrene sulfonate (PSSA) or with 4-phenysulfonic acid (PSA). The influences of the graft ratio, the amount of Nafion and the gas diffusion layer, on the electrochemical performances were studied in a half-cell and membrane electrode assembage (MEA). Larger electrochemical surface area of the catalyst was obtained in the presence of microporous layer on the carbon paper, as well as higher ORR current and lower charge transfer resistance. PSSA was grafted onto Pt/Vulcan catalysts by in-situ radical polymerization with 5, 10 and 20 wt.% sodium styrene sulfonate. It was presented in the half-cell tests and fuel cell tests that the catalysts grafted with 5 and 10 wt.% sulfonated groups performed improved properties. Pt/Vulcan catalysts were also grafted with 5.8, 11.6 18.0 and 23.3 wt.% PSA. Compared with non-functionalized catalysts, significant developments were achieved because of the sulfonation. The MEA with 18.0 wt.% PSA was studied in accelerated durability tests and showed excellent durability after 3000 cycles. For half-cells and MEAs with catalysts grafted with 5wt.% PSSA or PSA groups, low Nafion addition resulted in to lower performances. However, the MEAs with 10 and 20 wt.% PSSA exhibited an enhanced performance than the counterparts with 0.50 mg•cm-2 Nafion

A new material for use as a proton exchange membrane in fuel cells has been developed: a blend of a perfluorocyclobutane-based block ionomer (S-PFCB) and Poly (vinylidene-co-hexafluoropropylene) (Kynar Flex, KF). This thesis details the work done thus far to characterize the morphology of this material, using small angle x-ray scattering, differential scanning calorimetry, atomic force micrscopy, and some other techniques to a lesser extent. Small angle x-ray scattering (SAXS) of pure S-PFCB showed a strong block copolymer- associated phase separation, on the order of 25 nm. Differential scanning Calorimetry (DSC) confirmed this finding. SAXS also revealed the presence of a peak representing individual ionic aggregates on the order of 3 nm. Finally, it was shown with DSC that no crystallinity develops in the S-PFCB block copolymer, while one of the blocks, known as 6F, crystallizes extensively. SAXS of incremental blend compositions of KF and S-PFCB revealed a steady increase in size of the block copolymer phase separation peak in SAXS, demonstrative of the miscibility of KF and the non-sulfonated 6F block of S-PFCB. Furthermore, this incremental study determined the scattering vector range relevant for comparing amounts of KF crystallinity. DSC of incremental blend compositions revealed two phases of KF crystallinity develops upon cooling a membrane, independent of cooling rate. Atomic force microscopy (AFM), small angle x-ray scattering (SAXS), and differential scanning calorimetry (DSC) corroborate to suggest a nonuniform morphology through the thickness of solution cast membranes. Also, the effect of different casting temperatures and after-casting anneals on morphology was assessed. Future work on this project involves morphological studies at various relative humidities and temperatures, as well as following up on discoveries already made. Finally, transmission electron micrscopy (TEM) should be performed to provide a visual analog, which will greatly help in developing an accurate morphological model. / Master of Science

This dissertation focuses on the synthesis and characterization of high performance polymers, specifically polybenzimidazoles (PBIs) for gas separation applications and polyimides (PI) for water purification and as interfacial agents for thermoplastic carbon fiber composites. Two methods for improving the gas transport properties (for H2/CO2 separation) of a tetraaminodiphenylsulfone (TADPS)-based polybenzimidazole were investigated. Low molecular weight poly(propylene carbonate) (PPC) and poly(ethylene oxide) (PEO) were incorporated as sacrificial additives that could be removed via a controlled heat treatment protocol. PBI films containing 7 and 11 wt% PPC (blend) and 13 wt% PEO (graft) were fabricated and the gas transport properties and mechanical properties after heat treatment were measured and compared to the PBI homopolymer. After heat treatment, the 7 wt% PPC blend exhibited the highest performance while retaining the toughness exhibited by the PBI homopolymer. Novel sulfonated polyimides and their monomers were synthesized for use as interfacial agents and water purification membranes. Polyimides are high performance polymers that have high thermal, mechanical, and chemical stability. The objective was to assess structure-property relationships of novel sulfonated polyimides prepared by direct polymerization of the diamine monomers. A series of sulfonated polyimides was synthesized using an ester-acid polymerization method with varying degrees of sulfonation (20%, 30%, and 50% disulfonated and 50% and 100% monosulfonated polyimides). The results showed that the toughness of the polyimides in the fully hydrated state was much better than current commercial cation exchange membranes. A 100% disulfonated polyimide (sPI) and poly(amic acid) salt (PAAS) using the same monomers used for the synthesis of Ultem® were utilized as suspending agents for the fabrication of coated sub-micron polyetherimide (PEI) particles. Sub-micron particles were obtained using 1 wt% PAAS and 4 wt% sPI to coat the PEI. The PEI particles were coupled onto ozone treated carbon fibers using a silane coupling agent. SEM images showed a significant amount of particle coating on the treated carbon fibers compared to the non-silane treated carbon fibers. / PHD / This dissertation describes synthetic and processing techniques used to fabricate materials for applications such as, water purification and gas separation. The polymers included in this dissertation include polybenzimidazoles and polyimides, which are materials that have exceptional mechanical and thermal properties. The polybenzimidazoles were specifically used for gas separation, while the polyimides were synthesized for use as water purification membranes and surfactants for coating polyimides and carbon fibers. Gas separation membranes are effective tools for purifying gas mixtures (e.g. H₂/N₂, O₂/N₂, CO₂/CH₄). Additionally, they offer the advantage of being economical and environmentally-friendly compared to other methods of separation (e.g. cryogenic distillation). Many synthetic membranes made from polymers are used commercially, however, very few polymers can be used for elevated temperature separations. Because polybenzimidazoles exhibit high thermal stability, they are excellent candidates for high temperature gas separations (specifically H₂/CO₂ gas mixture). However, polybenzimidazoles have inherently low gas permeabilities. Thus, the focus of this research was to develop a simple method to introduce “pores” into the polymer membrane to improve gas permeability. Water purification is a very important process as the demand for clean water increases with the growing global population. Currently, one-third of the global population experience water scarcity, and by 2025, two-thirds of the world’s population may face water shortages. Multi-stage flash distillation is the most widely used method for water desalination from sea water but it is also the most energy intensive process. Water desalination using polymer membranes (e.g. reverse osmosis, nanofiltration, electrodialysis) has been developed as low energy and environmentally-friendly alternatives for producing clean water. The current state-of-the-art membranes used for water purification lack mechanical integrity and chemical resistance, which complicate and reduce the overall efficiency of the separation process. Thus, the focus of the research was to synthesize polyimide membranes with improved toughness and chemical stability.

The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems. / QC 20100922

Novel on-line methods are presented for the extraction, preconcentration and analysis of zwitterionic biomolecules using sol-gel-coated columns coupled to a conventional UV/visible detector. The presented approaches do not require any additional modification of the commercially available standard CE instrument. Extraction, stacking, and focusing techniques were used in the preconcentration procedures. The positively charged sol-gel coatings were created using N-octadecyldimethyl[3-(trimethoxysilyl) proply]ammonium chloride (C18-TMS) in the coating sol solutions. Due to the presence of a positively charged quaternary ammonium moiety in C18-TMS, the resulting sol-gel coating carried a positive charge. The negatively charged sol-gel coatings were due to the presence of sulfonate groups, which was formed from the oxidation of thiol groups in precursor mercaptopropyltrimethoxysilane (MPTMS) by hydrogen peroxide. Besides MPTMS, tetramethoxysilane (TMOS) and n-octadecyltriethoxysilane (C18-TEOS) were also used to prepare the sol solution for the creation of the negatively charged coatings. For extraction, the pH of the samples was properly adjusted to impart a net charge opposite to the sol-gel coatings. When a long plug of the sample was passed through the sol-gel-coated capillary, extraction was achieved via electrostatic interaction between the charged sol-gel coating and the charged sample molecules. The extracted analytes were then desorbed and focused via local pH change and stacking. The local pH change was accomplished by passing buffer solutions with proper pH values, while a dynamic pH junction between the sample solution and the background electrolyte was utilized to facilitate solute focusing. The developed methods showed excellent extraction and preconcentration effects on both positively and negatively charged sol-gel-coated columns. On-line preconcentration and analysis results obtained on the sol-gel coated columns were compared with those obtained on an uncoated fused silica capillary of identical dimensions using conventional sample injections. The described procedure provided a 150 000-fold enrichment effect for alanine on the positively charged sol-gel-coated column. On the negatively charged sol-gel-coated column, the presented sample preconcentration technique provided a sensitivity enhancement factor (SEF) on the order of 3 x 103 for myoglobin, and 7 x 103 for asparagines. The developed methods provided acceptable repeatability in terms of both peak height and migration time.

Incorporation of monoacetylferrocene to the sulfonated polystyrene ionomers imparted some changes in the properties of sulfonated polystyrene. Sulfonation was carried out by acetic anhydride and concentrated sulphuric acid. The sulfonation reaction and the degree of sulfonation were determined by analytical titration and adiabatic bomb calorimeter . For this purpose, sulfonated polystyrene (SPS) samples with varying percentages of sulfonation were prepared between 0.85% and 6.51%. Monoacetyl ferrocene was used in equivalent amount of sulfonation through addition procedure. FTIR Spectroscopy was one of the major techniques used to support the successful addition of AcFe to the SPS samples. Altering the sulfonation degree did not change the characteristic peak positions, but increased the peak intensities with increasing the degrees of sulfonation. Mechanical properties of resultant polymers were investigated. As a result, elastic modulus of polymers decreased by the amount of monoacetylferrocene. Thermal characteristic were found by Differential Scanning Calorimeter (DSC). Thermal analysis revealed that sulfonated polystyrene samples after addition of monoacetylferrocene displayed lower values of Tg. Microscopic analysis were made by Scanning Electron Microscopy (SEM) and single phase for each sample was observed. Besides, energy dispersed micro analysis showed an increase in the intensity of the iron (II) peaks that is related to the amount of monoacetylferrocene added to the SPS samples. Flame retardancy for each polymer was also examined and found that addition of monoacetylferrocene to sulfonated polystyrene does not change the Limiting Oxygen Index value (LOI)(17). However, LOI value for polystyrene is 18.

La pile à combustible comme moyen de production d'énergie propre et durable participera à la protection de l'écosystème en permettant à la filière hydrogène d'offrir une alternative aux énergies fossiles avant leur total épuisement. Cependant une baisse des coûts et une plus grande durabilité sont indispensables pour ces systèmes et notamment le cœur de pile, constitué d'un assemblage membrane-électrodes (AME). Cette étude a été menée sur une membrane alternative poly-aromatique sulfonée : le PolyEtherEtherCétone sulfoné, ou sPEEK. Cette membrane, qui n'offre qu'une stabilité chimique médiocre, a l'avantage d'offrir une bien meilleure tenue thermomécanique que la membrane de référence Nafion®. Le but de cette étude fut donc d'évaluer l'influence des conditions de fonctionnement sur les performances de la pile utilisant une membrane sPEEK, dans le but de les améliorer, mais aussi de mieux comprendre l'impact du vieillissement chimique de cette membrane sur ses propriétés physicochimiques et sur ses performances en pile. Ce travail fut réalisé en deux temps. Tout d'abord l'étude du comportement de la membrane sPEEK en pile pour différentes conditions d'utilisation a montré que le transport de l'eau dans l'AME est un point déterminant des performances de la pile. En effet une très forte hétérogénéité de fonctionnement imputable à la mauvaise répartition de l'eau dans la membrane sPEEK a été observé, aboutissant à des performances fortement dégradées par rapport à celles du Nafion®. Le diagnostic in situ de la dégradation de la membrane étant difficile et le système particulièrement complexe, il fut ensuite décidé d'étudier « ex situ » le vieillissement chimique de la membrane (dans des conditions de laboratoire). Les membranes vieillies sous l'action de H2O2 (oxydant responsable du vieillissement chimique des membranes en pile) ont ensuite été caractérisées et enfin testées en pile. Il apparaît que le vieillissement chimique résulte en des coupures des chaînes polymère, qui induisent une augmentation du gonflement de la membrane. Pour de forts vieillissements, ces coupures de chaînes entraînent une perte de la tenue mécanique de la membrane, incompatible avec une utilisation en pile. Cependant, pour des vieillissements contrôlés (très faible degré d'avancement), les modifications chimiques induites permettent un meilleur gonflement de la membrane qui résulte en une augmentation de sa conductivité ainsi qu'un meilleur transport de l'eau en pile, permettant d'obtenir des performances comparables à celles du Nafion®. / Fuel cells as production system of clean and sustainable energy will help to protect our ecosystem by providing an alternative to fossil fuels before their total exhaustion. However, lower costs and a greater durability are needed for these systems and more particularly the center of the cell, naming the membrane-electrodes assembly (MEA). This study was performed on a sulfonated poly-aromatic membrane: sulfonated polyetheretherketone, or sPEEK. This alternative membrane, which possesses only poor chemical stability, offers a much better thermomechanical behavior than Nafion®, the reference membrane. Aim of this study was first to understand the impact of operating conditions on fuel cell performance, for a sPEEK membrane, in order to improve performance, but also to better understand the impact of the membrane chemical aging onto its physicochemical properties and the resulting fuel cell performance. First the behavior of sPEEK in fuel cell for different operating conditions showed that water transport in the MEA is critical for fuel cell performance. Indeed a very high heterogeneity of operation due to slow water transport in the sPEEK membrane was observed, resulting in a major drop of fuel cell performance compared with what observed using Nafion®. As in situ diagnosis of membrane degradation is difficult and the system particularly complex, it was then decided to study "ex situ" the chemical aging of the membrane (laboratory conditions). Aged membranes under the action of H2O2 (oxidative responsible for the in situ chemical aging of the membranes) were characterized and finally tested in fuel cell. It appears that the chemical aging results in chains scissions, which induce an increase of the membrane swelling. For too much aging, these chains scissions result in the membrane loss of mechanical strength, incompatible with their use in fuel cell. However, for controlled aging (very low degradation), the induced chemical changes allow better swelling of the membrane resulting in an increase of the conductivity and better water transport in the MEA, making it possible to reach, with sPEEK, as good performance as with the use of Nafion®.

The presents study results of the addition of sulfonated polystyrene, derived from discarded plastic cups as additive in mortars. The mortar were studied with polystyrene content of 0.0, 0.2, 0.6, 1.0 and 1.4% (relative to the mass of cement). CPV - ARI Portland cement and sand washed were used at rate 1:4 by weight. It was determined consistency index, water retention, water absorption, void index, static modulus of elasticity, compressive strength, tensile strength in bending and adhesion. The mortar modified with the additive showed increase in the porosity, tensile strength in bending, adhesion, plastic capacity and water retention. Furthermore the use of polystyrene leads to decrease in the density, the modulus of elasticity and in the capillary water absorption with increasing content of sulfonated polystyrene, which may indicate that even by increasing the number pores in the mortar, the pores are not communicated among themselves and the polymeric film had contributed for the mechanical properties. / O trabalho apresenta resultados do estudo da adição de poliestireno sulfonado, oriundo de copos plásticos descartados, como aditivo em argamassas. Foram analisadas argamassas com os teores de poliestireno de 0,0; 0,2; 0,6; 1,0 e 1,4% em relação à massa de cimento. Foi utilizado o cimento Portland CPV - ARI e areia lavada no traço 1:4 em massa. Para se avaliar a influência da adição de poliestireno nas propriedades das argamassas determinouse índice de consistência, retenção de água, absorção de água, índice de vazios, módulo estático de elasticidade, resistência à compressão, resistência à tração na flexão e resistência potencial de aderência à tração. Em relação à argamassa sem aditivo a argamassa modificada demonstrou aumento na resistência de aderência à tração, resistência a tração na flexão, porosidade, absorção de água, retenção de água e consistência. No entanto, o aumento do teor de poliestireno sulfonado leva à uma redução do módulo de elasticidade, da massa específica e da absorção de água por capilaridade, o que pode indicar que mesmo aumentando o número de poros na argamassa, estes poros não são intercomunicáveis e o filme polimérico contribui para o incremento das propriedades mecânicas, especialmente à tração. / Mestre em Engenharia Civil