Nuclear magnetic resonances studies of polymer electrolytes.
Item
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Title
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Nuclear magnetic resonances studies of polymer electrolytes.
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Identifier
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AAI9108158
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identifier
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9108158
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Creator
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Pak, Yiu Sun.
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Contributor
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Adviser: Steve G. Greenbaum
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Date
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1990
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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, Condensed Matter | Engineering, Materials Science | Chemistry, Polymer
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Abstract
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{dollar}\sp{lcub}23{rcub}{dollar}Na NMR studies have been made on a variety of polymer electrolytes. Remarkably, the measurements reveal features that are common to nearly all types of material studied, including the presence of mobile and bound (aggregates) of sodium. T{dollar}\sb1{dollar}'s of the mobile and bound sodium are in the range of milliseconds and seconds respectively. The bound Na has a relatively temperature insensitive linewidth of about 5 kHz. The linewidth of mobile Na is typically 5 kHz below the glass transition temperature (T{dollar}\sb{lcub}\rm g{rcub}{dollar}), and undergoes motional narrowing above T{dollar}\sb{lcub}\rm g{rcub}{dollar} (evidence of the importance of polymer segmental motion of the ion transport process) to a minimum of about 0.5 kHz at around 45-55 K above T{dollar}\sb{lcub}\rm g{rcub}{dollar}, and then broadens somewhat. The broadening is due to the relatively fast spin-lattice relaxation time (T{dollar}\sb1{dollar} {dollar}\approx{dollar} 300 {dollar}\mu{dollar}s), i.e. lifetime-broadening.;The temperature dependence of the ratio of mobile to bound Na (M/B) indicates the process of ion dissociation and a minor role of thermal "carrier generation". A study of a series of poly(propylene-oxide)(PPO)NaI complexes of different salt concentration suggests that PPO{dollar}\sb8{dollar}NaI is the only stable amorphous phase in the complexes. Both T{dollar}\sb1{dollar} and linewidth of the bound Na measurements show that bound Na is likely to be an ion-aggregate ({dollar}\sim{dollar}10 or more ions). The drop of M/B above 353 K indicates the occurrence of salt precipitation (SP).;Ion-ion and ion-polymer interactions in polymer complexes are further investigated by measurement of a series of PPO complexes with different sodium salts. Satisfactory correlation between SP temperature and melting point of pure salt has been found. {dollar}\sp{lcub}23{rcub}{dollar}Na chemical shifts due to mobile Na{dollar}\sp+{dollar} ions exhibit a strong dependence on anion and temperature. Moreover, {dollar}\sp{13}{dollar}C NMR data show differences in ion-polymer interaction for Li- and Na- PPO complexes.;High pressure NMR of several PPO and siloxane complexes exhibit a systematic decrease in M/B with increasing pressure. In addition, the linewidth increases or decreases with the application of pressure, depending on the value of T -T{dollar}\sb{lcub}\rm g{rcub}{dollar}. The results are consistent with collaborative high pressure conductivity measurements, which also indicate that T{dollar}\sb{lcub}\rm g{rcub}{dollar} increases with increasing pressure. In multi-frequency {dollar}\sp{lcub}23{rcub}{dollar}Na NMR of PPO and siloxane-based complexes, the linewidth of the mobile Na{dollar}\sp+{dollar} ion is inversely proportional to the resonance frequency, implying second order quadrupole broadening.
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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.
