Nuclear quadrupole resonance studies of the SORC sequence and nuclear magnetic resonance studies of polymers.
Item
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Title
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Nuclear quadrupole resonance studies of the SORC sequence and nuclear magnetic resonance studies of polymers.
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Identifier
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AAI9405535
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identifier
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9405535
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Creator
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Jayakody, Jayakody R. Pemadasa.
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Contributor
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Adviser: Robert A. Marino
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Nuclear | Chemistry, Polymer | Physics, Condensed Matter
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Abstract
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The behavior of induction signals during steady-state pulse irradiation in {dollar}\sp{14}{dollar}N NQR was investigated experimentally. Because Strong Off-resonance Comb (SORC) signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these steady-state SORC signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method.;Also as part of the NQR work, Cocaine base has been detected using conventional NQR techniques. The experimental results show that SORC detection can be of sufficient sensitivity to form the basis of narcotics screening devices for both mail and airline baggage.;A new NMR technique, to obtain the correlation time of the random thermal motion of a polymer at temperatures near the glass transition has been introduced. The temperature dependence is a result of thermal motion. For slow-motion of a polymer chain near the glass transition, the CSA parameter begins to decrease. This motional narrowing can be interpreted to yield the correlation time of the thermal motion. In this work Nitrocellulose isotopically highly enriched with {dollar}\sp{15}{dollar}N was studied at four different temperatures between 27{dollar}\sp\circ{dollar} and 120{dollar}\sp\circ{dollar} Celsius and the correlation times for polymer backbone motions were obtained.;Nafion films containing, water (D{dollar}\sb2{dollar}O and H{dollar}\sb2\sp{17}{dollar}O) and methanol (CH{dollar}\sb3{dollar}OD, CH{dollar}\sb3\sp{17}{dollar}OH), have been studied using Deuteron and Oxygen-17 NMR spectroscopy. Glassy behavior of the water domains at low temperature is evidenced by the specific nature of the {dollar}\sp2{dollar}H NMR lineshapes. Activation energies extracted from {dollar}\sp2{dollar}H spin-lattice relaxation data on the high temperature side of the T{dollar}\sb1{dollar} minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra of both unstretched and stretched samples reflect considerable anisotropy of the host polymer. Activation volumes corresponding to a specific dynamical process were obtained from measurements of spin-lattice relaxation vs. pressure. From the NMR measurements of Nafion films containing methanol, it was found that the molecular motion is much more rapid than the molecular motion of water in Nafion membranes.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
