EPOXIDATION OF TRANS-1,4-POLYISOPRENE LAMELLAS CRYSTALLIZED FROM SOLUTION.
Item
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Title
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EPOXIDATION OF TRANS-1,4-POLYISOPRENE LAMELLAS CRYSTALLIZED FROM SOLUTION.
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Identifier
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AAI8801709
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identifier
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8801709
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Creator
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ELKAYAM, ABRAHAM.
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Contributor
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Arthur E. Woodward
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Date
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1987
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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, Physical
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Abstract
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Selective epoxidation of double bonds in combination with C-13 NMR spectroscopy has been employed to explore the morphology of trans-poly-1,4 isoprene (TPI) folded chain lamellas from a hexane solution. The folded chain lamellas were suspended in 2-ethoxy ethanol (cellosolve) and reacted with m-chloroperbenzoic acid (MCPBA), a mild, quantitative, but highly selective reagent at 0 C, until the rate of reaction diminished to zero and leveled off. The reacted crystals were dissolved in CDCl{dollar}\sb3{dollar} and the C-13 NMR spectra observed at 50.32 MHZ. It was expected that the surface folds would react completely and that the crystal stems would not react leading to a block structure. The fraction epoxidized, Fe, the average number of monomer units in the reacted blocks, {dollar}\langle{dollar}B{dollar}\rangle{dollar}, and the average number of monomer units in the unreacted blocks, {dollar}\langle{dollar}A{dollar}\rangle{dollar}, were obtained. The effect of molecular weight and crystallization temperature on the epoxidized fraction and the average block lengths for TPI lamellas was also studied. An increase in the averages of {dollar}\langle{dollar}B{dollar}\rangle{dollar} and Fe with decreasing molecular weight commences at an Mv value between 22,000 and 67,000 and is attributed to the importance of noncrystallizing chain ends at the lower molecular weights. The discrepancy between values of monomer units in the reacted blocks, {dollar}\langle{dollar}B{dollar}\rangle{dollar}, for the noncrystalline fraction from density measurements on dry samples and from chemical reactions on lamellas kept in suspension, is found to decrease at low molecular weights. The average number of monomer units per fold for lamellas from hexane, as obtained from {dollar}\langle{dollar}B{dollar}\rangle{dollar} at large molecular weights, is five, which is evidence for a predominance of adjacent reentry folding. From the molecular weight dependence of {dollar}\langle{dollar}B{dollar}\rangle{dollar} and Fe the number of monomer units in the two noncrystallizing chain ends was calculated.
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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.
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Program
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Chemistry
