Crystallization oftrans-1,4-polyisoprene and of epoxidized segmented block copolymer derivatives from solution.
Item
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Title
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Crystallization oftrans-1,4-polyisoprene and of epoxidized segmented block copolymer derivatives from solution.
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Identifier
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AAI9000076
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identifier
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9000076
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Creator
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Zemel, Irina S.
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Contributor
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Adviser: Arthur E. Woodward
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Date
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1989
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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
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Abstract
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Crystallization of trans -1,4- Polyisoprene (TPI) from the mixed solvent pair hexane/2-pentanone was carried out and the effect on the morphology of seeding and solvent composition studied. {dollar}\alpha{dollar} TPI lamellas obtained by crystallization from a single solvent, hexane, at 20{dollar}\sp\circ{dollar}C and by mixed solvent crystallization at 40{dollar}\sp\circ{dollar}C were characterized using DSC, FTIR and density measurements. TPI crystals were reacted in suspension using an excess of meta-chloroperbenzoic acid (MCPBA) at 0{dollar}\sp\circ{dollar}C. The resulting segmented block copolymers were quantitatively analyzed by 75.47 MHz C-13 NMR and the average number of monomer units in the reacted ({dollar}\langle{dollar}B{dollar}\rangle{dollar}) and unreacted ({dollar}\langle{dollar}A{dollar}\rangle{dollar}) blocks were thus obtained. The {dollar}\langle{dollar}A{dollar}\rangle{dollar} of 14.5 and 18 monomer units was found for block copolymers originated from 20 and 40{dollar}\sp\circ{dollar}C crystallized TPI respectively. A {dollar}\langle{dollar}B{dollar}\rangle{dollar} of 10 was found for both types of block copolymers. The block copolymers were dissolved and precipitated from various solvents at different temperatures depending on the solvent. Morphology of the resulting structures was studied by electron microscopy. All precipitated block copolymer samples exhibit sharp melting endotherms. The melting temperature and the endotherm shapes depend on the crystallization solvent and block copolymer type. Evidence for complete rejection of epoxidized blocks from the crystal core of block copolymers crystallized from solution is found: FTIR spectra of crystallized block copolymers were characteristic of either {dollar}\beta{dollar}, {dollar}\alpha{dollar}, or both {dollar}\alpha{dollar} and {dollar}\beta{dollar} crystalline forms of TPI depending on the sample, amorphous TPI and amorphous epoxidized TPI. No additional bands were detected in the FTIR spectra of the crystallized block copolymers. Crystallized block copolymers were subjected to a second epoxidation in suspension followed by C-13 NMR analysis. The results of the NMR analysis show that the crystalline stem length of the crystallized block copolymers depend only on the crystallization conditions, while the number of monomer units per amorphous fold depends on both the crystallization conditions and the length of the pure unepoxidized TPI blocks in the copolymer. Results of the NMR analysis are in agreement with the FTIR results.
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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.
