Synthesis and characterization of polyether-ester liquid crystalline polyesters and poly(arylene ether ketone)-lcp segmented copolymers

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dc.contributor.authorWaehamad, Wae-asaeen
dc.contributor.committeechairMcGrath, James E.en
dc.contributor.committeememberMcNair, Harold M.en
dc.contributor.committeememberWard, Thomas C.en
dc.contributor.committeememberBell, Harold M.en
dc.contributor.committeememberMarand, Hervé L.en
dc.contributor.departmentChemistryen
dc.date.accessioned2014-03-14T21:15:55Zen
dc.date.adate2007-07-12en
dc.date.available2014-03-14T21:15:55Zen
dc.date.issued1991en
dc.date.rdate2007-07-12en
dc.date.sdate2007-07-12en
dc.description.abstractAn A-B monomer containing an ether group, 4(4-acetoxyphenoxy) benzoic acid (PAPBA) was successfully synthesized via a new route using 4-methoxyphenol and 4-chlorobenzonitrile as starting materials. Another ether containing monomer, 4(2-acetoxy-6-naphthoxy) benzoic acid (PANBA), which appears to be a novel monomer, was also prepared in high yields from 6-methoxy-2-bromonaphthalene and ethyl-4-hydroxybenzoate via the Ullmann condensation reaction. These monomers were found to be useful for synthesizing LCP copolymers and segmented copolymers. A variety of polyarylates based on 5-tertiary butylisophthalic acid were synthesized via melt acidolysis techniques. The resulting high molecular weight polyarylates were amorphous polymers and the t-butyl groups along the polymer backbones were found to be thermoxidatively stable. Thermotropic liquid crystalline polyesters (LCPs) are well known for their thermoxidative stability, ductility, solvent resistance and the potential of generating extremely strong, stiff molecular chains. In this dissertation research, several novel liquid crystalline aromatic polyether-ester copolymers were synthesized by the incorporation of an A-B monomer, either PAPBA or PANBA, into the polymer main chain. The corresponding copolymers were thermoxidatively stable and melt processable over a wide compositional range. Novel carboxyl terminated oligomers of an amorphous engineering polymer, poly(arylene ether ketone)(PEK) were successfully synthesized. The synthetic method was somewhat similar to that of carboxyl terminated poly(arylene ether sulfone) oligomers. The PEKCOOH oligomers were quantitatively endcapped and their molecular weights could be controlled. Thermogravimetric analysis revealed that the PEKCOOH oligomers were thermoxidatively stable and therefore suitable for high temperature post-reactions. In general, thermotropic liquid crystalline polymers show excellent properties in the longitudinal direction. Nevertheless, to improve the transverse mechanical properties of liquid crystalline polymers, novel poly(arylene ether ketone)-LCP segmented copolymers were synthesized via melt acidolysis techniques. Chemically bonding an isotropic engineering thermoplastic into a potentially liquid crystalline anisotropic polyester affords segmented copolymers which may possess a balance of mechanical properties in both the longitudinal and transverse directions. In the case of PEK-poly(oxybenzoate)(PEK-POB), a limited amount of POB (~25 wt %) could be incorporated so as to produce segmented copolymers which would yield coherent films. On the other hand, when PEK-POB was modified by adding PAPBA to form PEK-POB-POPB segmented copolymers, a series of the segmented copolymers with various compositions was realized. The liquid crystalline behavior was found to be retained in the segmented copolymers, depending on the degree of the LCP content. The structural analysis of the A-B monomers mentioned earlier was performed by elemental analysis, mass spectroscopy, proton NMR and FT-IR. All the polymers synthesized were characterized by thermal analysis (DSC and TGA). The molecular weight of the carboxyl terminated PEK oligomers was determined by an automatic titration method, and indirectly, by intrinsic viscosity measurements. The latter method was also used to assess the molecular weight of the amorphous polyarylates. For liquid crystalline polyether-ester copolymers and PEK-LCP segmented copolymers, DSC and hot stage optical microscopy were utilized to investigate their thermotropic liquid crystalline behavior. DMTA was used to determine the high temperature properties of the polymers and tensile tests, i.e. stress-strain data, were employed to obtain information on their mechanical properties.en
dc.description.degreePh. D.en
dc.format.extentxix, 291 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-07122007-103934en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07122007-103934/en
dc.identifier.urihttp://hdl.handle.net/10919/38781en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1991.W345.pdfen
dc.relation.isformatofOCLC# 24073142en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1991.W345en
dc.subject.lcshCrystalline polymers -- Researchen
dc.titleSynthesis and characterization of polyether-ester liquid crystalline polyesters and poly(arylene ether ketone)-lcp segmented copolymersen
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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