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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Phase selectively soluble polymer supports to facilitate homogeneous catalysis

Ortiz-Acosta, Denisse 15 May 2009 (has links)
Soluble polymers that have phase selective solubility are useful in synthesis because they simplify purification and separation. Such selectively soluble polymers simplify catalyst, reagent, and product recovery and enable the use of Green chemistry principles in homogeneous catalysis. However, while homopolymers have been reported that have excellent thermal and phase-dependent solubility, less is known about copolymers. Also, less is known about the phase selective solubility of polar aprotic N,N-dialkyl polyacrylamides. This work describes a library synthesis of dye-labeled poly(N-n-octadecylacrylamide-co-N-n-butylacrylamide) copolymers and study of the effects of polymer composition in phase selective solubility of these copolymers. To study the relative importance of n-octadecyl versus n-butyl groups, copolymers with different ratios of n-octadecylacrylamide and n-butylacrylamide but with similar degrees of polymerization and polydispersity were prepared by a split-pool synthesis using a highly soluble poly(N-acryloxy-2-dodecylsuccinimide) as the precursor. Polymer sequestrants were used to remove excess amines and the byproduct N-hydroxyl-2- dodecylsuccinimide without fractionation of the polyacrylamides. Results demonstrated that poly(N-n-octadecylacrylamide-co-N-n-butylacrylamide) copolymers’ phase selective solubility is equally dependant of the polar n-butyl and nonpolar n-octadecyl groups on the copolymers. Dye-labeled poly(N,N-dialkylacrylamide)s prepared by the polymerization of N,N-dialkylacrylamides monomers with methyl, ethyl, propyl, butyl, hexyl, and dodecyl N-alkyl groups in a variety of thermomorphic or latent biphasic polar/nonpolar solvent mixtures were also prepared. Studies showed that poly(N,N-dialkylacrylamide)s have phase selective solubility that is highly dependent of the size of the N-alkyl group. Soluble polymers are known to be useful supports for catalysts. This thesis also describes approaches to immobilization of a variety of catalysts on polyisobutylene (PIB). The most effective of these catalysts were analogs of pyridyl N-oxides that have been used as organocatalysts for the catalytic allylation of a variety of aromatic aldehydes. PIB-supported N-oxide promoted the allylation of aldehydes in up to 99% isolated yield. The products were isolated in the polar phase of a thermomorphic system and the catalyst was recycled through five cycles.
2

Studies of phase separable soluble polymers

Furyk, Steven Michael 16 August 2006 (has links)
The technique of phase labeling has the ability to greatly enhance synthetic protocol by simplifying purification and increasing efficiency. Traditional insoluble supports offer efficient and simple recovery of the “phase tagged” material but suffer from problems inherent to their heterogeneous nature. A solution to these problems has been to utilize phase separable soluble polymers in the design of “smart” responsive systems that offer the option of homogenous reaction conditions with heterogeneous separation conditions. The subject of this dissertation focuses on the application of soluble polymeric phase tags in systems where the miscibility between solid-liquid and liquid-liquid systems is thermally induced. Low molecular weight poly(ethylene glycol) (PEG) oligomers were investigated as phase anchors for SCS palladacycle catalysts. The oligomeric PEG chains were sufficient to engender polar phase solubility in a heptane-DMA thermomorphic system. Microwave irradiation of these thermomorphic mixtures of palladium complexes and substrates was a viable scheme to recycle and significantly shorten reaction times for simple Heck reactions of aryl iodides. Soluble polymeric supports possessing a lower critical solution temperature (LCST) were utilized in the sequestration of the S-triazine herbicide, atrazine, from contaminated water samples. The ability of poly(N-isopropylacrylamide) to sequester hydrophobic guests like atrazine was examined. A functionalized PNIPAM derivative containing secondary cyclic amines exhibited superior sequestration ability that was credited to the covalent binding of the atrazine. In order to facilitate the design of tailored, thermally responsive, smart polymers, a high throughput temperature gradient microfluidic device was used to obtain LCST data in a fast, accurate manner. The specific ion effects of various alkali metal halide salts on the LCST of PNIPAM were investigated. The high precision in the measurements enabled more subtle effects such as changes in solvent isotope, polymer microstructure, molecular weight, and importance of end group effects on the LCST of poly(N-alkylacrylamide)s to be evaluated.

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