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Molecular weight control and endgroup functionalization in poly(arylene ether sulfones) has been achieved by two synthetic routes. The first utilizes DMSO/sodium hydroxide and aminophenol to introduce the amine functionality. This route, though synthetically useful, suffers from serious limitations, such as hydrolytic side reactions and oxidation of the end capping reagent. An alternative route utilized K₂CO₃/NMP as base and solvent respectively. This approach has been used with great success in the preparation of both high molecular weight polymers and functionalized oligomers. We have extended this method to include amine terminated oligomers through the use of a novel aminophenolic compound 2-p-aminophenyl-2-p-hydroxyphenylpropane or MBA. The use of MBA to introduce terminal amine functionality allowed a simpler, 1-step synthesis of controlled molecular weight oligomers to be realized. Our investigations focused on bisphenol-A based systems, but this technique may be also utilized with other bisphenols. The synthesis and characterization of a wide variety of derivatives of these functionally terminated oligomers was demonstrated. A number of potential post reactions involving these oligomeric diamines were investigated and synthetic techniques to prepare novel block and segmented copolymers were defined. As the molecular weight of the sulfone oligomer was varied, the percent sulfone character in a given polymeric material could be systematically changed. The effect was studied in block copolymers with poly(arnide sulfones) and in novel modified epoxy and bismaleimide thermosetting systems. / Ph. D.

Formation of the diaryl ether moiety remains a challenging target for organic synthesis despite modern technologies, however, better understanding of older techniques often leads to improvements. The copper-catalysed Ullmann ether synthesis, whilst attractive in many ways, is frequently problematic due to the inherent irreproducibility of the reaction on scale up. Little is yet known about the mechanism of the reaction and conflicting views are rife within the scientific community. In a well-studied example, we show that the potassium iodide formed during the reaction slows catalysis. Additionally, the deprotonation of phenol is complicated by the insolubility of the inorganic base. This results in a beneficial outcome, providing a rate enhancement and reduction of by-products, which can be further exploited to provide lower stoichiometries, improved selectivity and greater functional group tolerance. The development of an improved, more reproducible procedure in combination with reaction calorimetry has allowed the mechanism to be studied in intricate detail. Excellent agreement with a mechanistic model has led to further insight into the enigmatic aryl halide activation and provides good evidence for a single electron transfer mechanism. In addition, evidence for a dynamic catalyst resting state has been observed which adds to the complexity of the mechanism. This, in turn, leads to a fine balance of concentration and electronic effects that prove vital to the rate of reaction.

In this research that we design in the polymer structure containing the core monomer into benzene ring structure for appied on the flexible substrate and the optoelectronic components .Three novel bisphenol monomers have been synthesised successfully and converted to a series of poly(arylene ether)s by nucleophilic displacement reaction with Bis(4-fluorophenyl) sulfone, then we called them:P1, P2 and P3.We can see from the material structure that the steric hindrance of the group connected to the side of the main chain (M2) is larger than the group in the main chain(M1,M3),and the steric hindrance of the longer length of main chain (M3) is smaller than the shorter one(M1) in the polymerization Thermal analysis physics studies with these polymers confirmed by Thermogravimetric analyzer(TGA) and differential scanning calorimetry (DSC).It is indicated that Td5% of these polymers were 476¢XC~577¢XC in TGA and Tg of these polymers were 264¢XC~290¢XC in DSC. Besides, these polymers were not observed apparent crystallizing point, so we consider that they are not crystallized easily. The transmission spectra of thin film in the visible light region were up to 87%~93%. In drop shape analysis system, the contact angles of them are 85¢X~87¢X, show that they have good hyrophobicity.By above material properties of these polymers, they have high thermal stabilities, high optical transparency and good hydrophobicity.

Fast depletion of oil reserves necessitates the development of novel alternative motor vehicle fuels. Global warming problems also initiated new research to develop new fuels creating less CO2 emission. Nowadays, dimethyl ether (DME) and diethyl ether (DEE) are considered as important alternative clean energy sources. These valuable ethers are produced by the dehydration reaction of methanol and ethanol, respectively, in the presence of acidic catalysts. Besides DEE, ethylene which is very important in petrochemical industry, can also be produced by ethanol dehydration reaction. In the first part of this study, the catalytic activity of tungstophosphoric acid (TPA), silicotungstic acid (STA) and molybdophosphoric acid (MPA), which are well-known heteropolyacids were tested in ethanol dehydration reaction. The activities of other solid acid catalysts, such as Nafion and mesoporous aluminosilicate, were also tested in the dehydration reaction of ethanol. In the case of DME production by dehydration of methanol, activities of STA, TPA and aluminosilicate catalysts were tested. Among the heteropolyacid catalysts, STA showed the highest activity in both ethanol and methanol dehydration reactions. With an increase of temperature from 180oC to 250oC, Ethylene selectivities increased while DEE selectivities decreased. Ethylene yield values over 0.70 were obtained at 250oC. The presence of water in the feed stream caused some reduction in the activity of TPA catalyst. Very high DME yields were obtained using mesoporous aluminosilicate catalyst at about 450oC. The surface area of heteropolyacids are very low and they are soluble in polar solvents such as water and alcohols. Considering these drawbacks of heteropolyacid catalysts, novel mesoporous STA based high surface area catalysts were synthesized following a hydrothermal synthesis route. These novel catalysts were highly stable and they did not dissolve in polar solvents. The catalysts containing W/Si ratios of 0.19 (STA62(550)) and 0.34 (STA82(550)) have BJH surface area values of 481 m2/g and 210 m2/g, respectively, with pore size distributions ranging in between 2-15 nm. These catalysts were characterized by XRD, EDS, SEM, TGA, DTA, DSC, FTIR and Nitrogen Adsorption techniques and their activities were tested in ethanol dehydration reaction. Calcination temperature of the catalysts was shown to be a very important parameter for the activities of these catalysts. Considering the partial decomposition and proton lost of the catalysts over 375oC, they are calcined at 350oC and 550oC before testing them in ethanol dehydration reaction. The catalysts calcined at 350oC showed much higher activity at temperature as low as 180oC. However, the catalysts calcined at 550oC showed activity over 280oC. Ethylene yield values approaching to 0.90 were obtained at about 350oC with catalysts calcined at 350oC. DEE yield past through a maximum with an increase in temperature indicating its decomposition to Ethylene at higher temperatures. However, at lower temperatures (&lt / 300oC) Ethylene and DEE were concluded to be formed through parallel routes. Formation of some acetaldehyde at lower temperatures indicated a possible reaction path through acetaldehyde in the formation of DEE. DRIFTS results also proved the presence of ethoxy, acetate and ethyl like species in addition to adsorbed ethanol molecules on the catalyst surface and gave additional information related to the mechanism.

Litter-decay fungi have recently been shown to secrete heme-thiolate peroxygenases that oxidize various organic chemicals, but little is known about the physiological role or the mechanism of these enzymes. The aromatic peroxygenase of Agrocybe aegerita (AaeAPO) was purified and catalytically characterized. An overall reaction mechanism was proposed. The results show that AaeAPO catalyzed diverse H2O2-dependent monooxygenations (two-electron oxidations) including (a) the cleavage of aliphatic and aromatic ethers, (b) the regio- and enantioselective hydroxylation of aromatic compounds, (c) the stepwise oxygenation of benzylic compounds, (d) the N-dealkylation of secondary amines and (e) the dehalogenation of halogenated aliphatic compounds as well as typical peroxidase reactions (suggested to involve one-electron oxidation) such as (f) oxidation and polymerization of phenols and (g) halogenations. The enzyme failed to oxidize polymers such as polyethylene glycol (PEG). Mechanistic studies with several model substrates provided information about the reaction cycle of AaeAPO: (1) stoichiometry of tetrahydrofuran cleavage showed that the reaction was a two-electron oxidation that generated one aldehyde group and one alcohol group, yielding the ring-opened product 4-hydroxybutanal, (2) steady-state kinetics results with methyl 3,4-dimethoxybenzyl ether, which was oxidized to 3,4-dimethoxybenzaldehyde, gave parallel double reciprocal plots suggestive of a ping-pong mechanism, (3) the cleavage of methyl 4-nitrobenzyl ether, the hydroxylation of aromatics such as diclofenac and nitrophenol and the oxygenation of benzylic compounds, resulted in incorporation of 18O into the reaction product in the presence of H218O2, and (4) the demethylation of 1-methoxy-4-trideuteromethoxybenzene showed an distinct observed intramolecular deuterium isotope effect. These results support a mechanism similar to that envisaged for the peroxygenase activity of P450s in which the enzyme heme is oxidized by H2O2 to give an iron species that carries one of the peroxide oxygen. This intermediate then abstracts a hydrogen from the substrate, which is followed by rebound of an •OH equivalent to produce the monooxygenated reaction product (hydrogen abstraction and oxygen rebound mechanism). AaeAPO may accordingly have a role in the biodegradation of natural and anthropogenic low molecular weight compounds in soils and plant litter. Moreover, the results raise the possibility that fungal peroxygenases may be useful for versatile, cost-effective, and scalable syntheses of drug metabolites and herbicide precursors. / Die Peroxygenase des Südlichen Ackerling (Agrocybe aegerita, AaeAPO) wurde gereinigt, ihr Katalysepotential ermittelt und ein allgemeiner Reaktionsmechanismus postuliert. Die AaeAPO katalysiert sowohl H2O2-abhängige Monooxygenierungen (Zwei-Elektron Oxidationen) wie (a) die Spaltung aliphatischer und aromatischer Ether, (b) die regio- und enantioselektive Hydroxylierung von Aromaten, (c) die schrittweise Monooxygenierung von Toluolderivaten, (d) die N-Dealkylierung sekundärer Amine und (e) die Dehalogenierung chlorierter Aliphaten als auch typische Reaktionen bekannter Peroxidasen (vermutlich Ein-Elektron-Oxidation) unter anderem (f) die Oxidation/ Polymerisierung von Phenolen und (g) die Halogenierung von Aromaten. Polymere Verbindungen wie Polyethylenglycol (PEG) werden nicht oxidiert. Mechanistische Untersuchungen zur Etherspaltung am Beispiel der AaeAPO haben Einblick in den generellen Reaktionsmechanismus dieses neuen Enzymtyps ermöglicht: (1) die Stöchiometrie der Spaltung von Tetrahydrofuran entspricht der einer zwei-Elektron-Oxidation, (2) die Spaltung von Methyl-3,4-Dimethoxybenzylether zu 4-Dimethoxybenzaldehyd und Methanol ergaben parallele Verläufe für die ermittelten Ausgleichsgeraden in der doppelt reziproken Darstellung, was einem „Ping-Pong“-Reaktionsmechanismus entspricht (3) die Monooxygenierungen haben stets den Einbau eines aus dem Peroxid (H2O2) stammenden Sauerstoffatoms in das Produkt zur Folge, (4) die O-Dealkylierung von 1-Methoxy-4-Trideuterummethoxybenzol zeigt einen ausgeprägten Deuterium Isotopen Effekt, was auf die primäre Abspaltung eines Wasserstoffatoms vom Substratmolekül hindeutet. Demnach verläuft die Peroxygenase-katalysierte Monooxygenierung über Wasserstoffabstraktion und eine unmittelbar anschließende Sauerstoffrückbindung (hydrogen abstraction - oxygen rebound mechanism). Diese Reaktionsabfolge ähnelt dem sogenannten peroxide "shunt" pathway, der von einer Reihe Cytochrom-P450-abhängiger Monooxygenasen her bekannt ist. Die physiologische Funktion der AaeAPO besteht möglicherweise in der extrazellulären Transformation und Detoxifikation niedermolekularer Pflanzeninhaltsstoffe, mikrobieller Metabolite und anthropogener Xenobiotika. Aufgrund der Stabilität und Unabhängigkeit der AaeAPO von teuren Kofaktoren ergeben sich vielversprechende biotechnologische Möglichkeiten zum Einsatz isolierter Biokatalysatoren in selektiven (bio)chemischen Synthesen monooxygenierter Metabolite.

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There has been a great interest in preparing polymeric reflective surfaces in the last few years. The application of supercritical fluid technology in this area is beginning to receive a great deal of attention. Poly ether ether ketone (PEEK) is well known for its excellent thermal, chemical, mechanical and electrical properties. These properties make it ideal for use in aerospace, electrical, fluid handling and coating industries. Supercritical infusion of a silver-containing additive (1,5-cyclooctadiene- 1,1,1,5,5,5-hexafluoroacetylacetonato)silver(I) into a PEEK film was achieved with moderately high density CO2 at various temperatures, pressures, and times. During the infusion process: 1) polymer sample was exposed to both supercritical CO2 and the additive under pressure for a brief time, 2) depressurization of the system caused the CO2 to rapidly diffuse out of the polymer; while the remaining additive in the polymer desorbed at a much slower rate governed by its diffusivity in the CO2-free polymer. Following this process the infused film was heated for a short time period to thermally reduce the infused metal and to form a reflective surface. In this research the effect of different additive concentrations, infusion conditions (e.g. temperature, pressure, time), and curing conditions (e.g. air flow rate, temperature, time) on the nature of the PEEK surface will be presented. / Master of Science

No description available.

This dissertation describes the past and recent progress in proton exchange membranes (PEM) for fuel cells. In particular the synthesis and characterization of materials for advanced alternative PEM were studied with an emphasis on structure-property and structure-property-performance relationships. The focus has included firstly a one-step synthesis and characterization of 3,3'-disulfonated 4,4'-dichlorodiphenyl sulfone comonomer. The procedure developed is adaptable for industrial-scale commercialization efforts. Secondly, the synthesis of aromatic nitrile containing poly (arylene ether sulfone) random copolymers was demonstrated. Various levels of disulfonation allowed the membrane characteristics to be investigated as a function of the membrane ion exchange capacity. The results favorably compare with the current state-of-the-art (Nafion™), particularly for direct methanol systems (DMFC). Thirdly, the mechanically and thermooxidatively stable copolymer membranes were blended with heteropolyacids producing nanocomposites which have potential in higher temperature fuel cell applications. Lastly, the basic PEM parameters such as water uptake, proton conductivity, and methanol permeabilities were controlled and presented as tunable properties as a function of molecular structure. This was achieved by in-situ control of chemical composition. The direct methanol fuel cell performance (DMFC) was much better than Nafion™. Hydrophobic surface properties of the membranes were improved by partial fluorination which made the Nafion™ bonded electrodes more compatible with the partially fluorinated copolymer membranes. The influence of surface enrichment had two important roles in increasing both initial and long term performance tests. The surface fluorine provided lower contact resistance and lower water uptake. The former was important for the initial tests and the latter provides for better long term performances. A delamination failure mechanism was proposed for the hydrocarbon membrane electrode assemblies (MEA) due to the large difference between water uptake of the catalyst layer and membrane and this was verified by a reduction in high frequency resistance (HFR) for the partially fluorinated systems. This thesis has generated the structure-property and structure-property-performance relationships which will provide direction for the development of next generation (PEM) materials. / Ph. D.