New polymer architectures: synthesis and characterization of polyurethane-crown ether based polyrotaxanes

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dc.contributor.authorShen, Ya Xien
dc.contributor.committeechairGibson, Harry W.en
dc.contributor.committeememberMcGrath, James E.en
dc.contributor.committeememberRiffle, Judyen
dc.contributor.committeememberWard, Thomas C.en
dc.contributor.committeememberWilkes, Garth L.en
dc.contributor.departmentChemistryen
dc.date.accessioned2014-03-14T21:09:22Zen
dc.date.adate2007-02-05en
dc.date.available2014-03-14T21:09:22Zen
dc.date.issued1992en
dc.date.rdate2007-02-05en
dc.date.sdate2007-02-05en
dc.description.abstractRotaxane chemistry provides a new direction of research in polymer architectures. Unlike conventional polymers, polyrotaxanes are molecular composites comprised of macrocycles threaded by linear polymer backbones with no covalent bonds between the two components. This novel class of materials displays unusual chemical and physical properties due to their unique architectures. The studies include crown ether and blocking group syntheses, synthetic methodologies leading to rotaxanes and polyrotaxanes and structure-property relationships of polyrotaxanes. Crown ethers (30-crown-10, 36-crown-12, 42-crown-14, 48-crown-16 and 60-crown-20) were systematically synthesized from low molecular weight glycols with 30 - 60% yields. Bis(p-phenylene)-32-crown-4 and bis(p-phenylene)-34-crown-10 (BPP34C10) were also synthesized in 8 - 13% yields; the latter was synthesized with four different synthetic routes. All crown ethers were prepared in large quantities. A series of monofunctionalized triaryl derivatives were also synthesized as rotaxane blocking groups. A series of polyrotaxanes comprised of a polyurethane backbone and crown ethers with ring size ranging from 36 - 60 membered were synthesized via the statistical threading method. The polyrotaxane formation was proven by multiple reprecipitations, ¹H-NMR and GPC analyses. The threading efficiency (rings per repeat unit) increases from 0.16 to 0.87 with an increase in ring size of crown ethers from 36 to 60 membered at 1.5 molar ratio of crown ether to linear glycol. Host-guest complexation of paraquat dication and BPP34C10 has been studied. A series of difunctionalized paraquat dication derivatives was synthesized and used to prepare host-guest complexes (pseudorotaxanes) with BPP34C10. X-Ray crystal structures of the complexes were determined. Furthermore, a class of viologen-containing polyurethane elastomeric polyrotaxanes was synthesized via this host guest complexation. The threading efficiencies from this method were quantitative. Through rotaxane formation, polymer solubilities increase and glass transition temperatures decrease. Evidenced by DSC and WAXS analyses, the crown ether forms crystalline domains without dethreading from the amorphous polyurethane backbone. This process is kinetically "retarded". It is time and temperature dependent and reversible. It can only be observed for polyrotaxanes with large rings and high ring contents, which provide high mobilities of rings along the backbone and also wide T<sub>m</sub> - T<sub>g</sub> windows. The study of recrystallization kinetics has also shown that 60-crown-20 recrystallizes much slower in a polyrotaxane than in its physical blend with the model polymer.en
dc.description.degreePh. D.en
dc.format.extentxv, 383 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-02052007-081239en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-02052007-081239/en
dc.identifier.urihttp://hdl.handle.net/10919/37321en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1992.S534.pdfen
dc.relation.isformatofOCLC# 26121372en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1992.S534en
dc.subject.lcshCrown ethersen
dc.subject.lcshPolymerizationen
dc.subject.lcshPolymers -- Structureen
dc.subject.lcshPolyurethanesen
dc.titleNew polymer architectures: synthesis and characterization of polyurethane-crown ether based polyrotaxanesen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineChemistryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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