Nuclear magnetic resonance studies of water in polyimide films.
Item
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Title
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Nuclear magnetic resonance studies of water in polyimide films.
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Identifier
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AAI9218248
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identifier
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9218248
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Creator
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Li, Shizhe.
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Contributor
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Adviser: Steve G. Greenbaum
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Date
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1992
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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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Chemistry, Polymer | Physics, Condensed Matter
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Abstract
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Polyimide films containing water (H{dollar}\sb2{dollar}O, D{dollar}\sb2{dollar}O and H{dollar}\sb2\sp{17}{dollar}O), methanol and acetic acid have been studied by dielectric relaxation (DR) and nuclear magnetic resonance (NMR) spectroscopies. Two types polyimides, Kapton (PMDA-ODA) and Upilex-S (BPDA-PDA) are investigated.;The morphology of dry polyimide films has been investigated by X-ray and proton NMR. The polymer backbones of thin Kapton films are slightly more rigid and more oriented than those of thick films. However compared to Upilex films, the polymer structure of Kapton is much more flexible.;Both DR and NMR measurements of Kapton show that water exists in two configurations called {dollar}\gamma\sb1{dollar} and {dollar}\gamma\sb2{dollar}. The {dollar}\gamma\sb1{dollar} water corresponds to the high temperature DR loss peak and broad NMR lineshape component, the {dollar}\gamma\sb2{dollar} water corresponds to the low temperature DR peak and narrow NMR lineshape component. The {dollar}\gamma\sb1{dollar} water molecules are distributed uniformly throughout the volume of the film and bound to the host polymer through hydrogen bonds. The {dollar}\gamma\sb2{dollar} configuration corresponds to small clusters of water molecules where one or more water molecules are linked to the {dollar}\gamma\sb1{dollar} water molecules and form a chain-like structure through weak hydrogen bonds. Therefore, the water molecules in {dollar}\gamma\sb2{dollar} clusters are more mobile than the {dollar}\gamma\sb1{dollar} bound water molecules. The greater degree of anisotropic configuration and molecular motion of {dollar}\gamma\sb2{dollar} water molecules lead to a strong orientation effect while the {dollar}\gamma\sb1{dollar} water display only a weak orientation effect.;The DR spectra of methanol and acetic acid consist primarily of one loss peak, methanol peak is at low temperature while acetic acid peak is at high temperature. Both CH{dollar}\sb3{dollar}OD and CH{dollar}\sb3{dollar}COOD exhibit a stronger orientation effect compared to D{dollar}\sb2{dollar}O water. It was found that the O-D bond directions of D{dollar}\sb2{dollar}O, CH{dollar}\sb3{dollar}OD and CH{dollar}\sb3{dollar}COOD are averaged by molecular motion about an axis perpendicular to the film plane.;The measurements of water absorbed in Upilex films are also reported.
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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.
