Modification of chemical reactivity using soluble polymeric supports /
The effects of polymer size, solvent and solubility on the reactivity of soluble polymer-bound substrates in various catalyzed hydrogenation reactions have been examined. Heterogeneous hydrogenations of nitroarenes terminally bound to poly(ethylene glycol) supported substrates illustrate the potenti...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739667341&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The effects of polymer size, solvent and solubility on the reactivity of soluble polymer-bound substrates in various catalyzed hydrogenation reactions have been examined. Heterogeneous hydrogenations of nitroarenes terminally bound to poly(ethylene glycol) supported substrates illustrate the potential useful effects of soluble PEG ligands on substrate reactivity. Hydrogenation of such terminal groups was completely suppressed by virtue of the polymer's size or immiscibility with some catalysts. In other cases, changing(, solvents significantly perturbed reactivity of such soluble polymer-bound substrates. In these latter cases, the effects of solvents were magnified by the type and size of the soluble polymer supporting group. These effects together show that a polymer can be used to control reactivity of a substrate by virtue of the polymer's solubility. Further demonstration of reactivity control was seen with polymers which exhibit temperature dependent solubility properties. Substrate groups such as nitroaryl, benzyloxy, or vinyl groups that could react with a heterogeneous or homogeneous hydrogenation catalyst were bound to the termini of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer or to the carboxyl groups of a copolymer of poly(N-isopropylacrylamide) and acrylic acid (PNIPAM/PAA). These polymer derivatives have inverse temperature dependent solubility in water with the precipitation temperature depending on the copolymer composition and microstructure of the derivative. These solubility properties can be used to advantage in both synthetic and catalytic chemistry. Substrates bound to such copolymers have activity toward heterogenous and homogeneoustransition metal catalysts that turns on and off as a function of temperature. In the case of supported reducible substrates like these, catalytic hydrogenation had an inverse temperature dependence with a sharp change in reactivity at the polymer's lower critical solution temperature. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiii, 156 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 149-155. |