MORPHOLOGICAL STUDY OF TRANS 1,4-POLYBUTADIENE CRYSTALS GROWN FROM SOLUTION.
Item
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Title
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MORPHOLOGICAL STUDY OF TRANS 1,4-POLYBUTADIENE CRYSTALS GROWN FROM SOLUTION.
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Identifier
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AAI8312382
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identifier
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8312382
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Creator
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TSENG, SUSAN YU.
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Contributor
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Dr. A. E. Woodward
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Date
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1983
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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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Molecular weight fractions of trans 1,4-polybutadiene, prepared.;by fractional crystallization, were characterized by gel permeation.;chromatography and were found to have M(,n)'s(' )of 4.7 x 10('3) to 1.2 x 10('5) and M(,w)/M(,n)(' )of 1.3 to 2.7. The morphologies of self-seeded solution crystallized samples prepared from these fractions were studied by photomicroscopy and electron microscopy. The physical properties were studied using small angle X-ray scattering, density measurement, differential scanning calorimetry and chemical reaction at the crystal surface with m-chloroperbenzoic acid in toluene solution. These properties are related to the % crystallinity, the distribution of the disordered fraction and the type of chain folding in the TPBD crystals.;Single lamellas with few screw dislocations were found for crystals grown from dilute solutions (0.01% to 0.02%). A more complicated multilamella supermolecular structure was found for concentrated solution (1% to 10%) grown crystals. (An increase in lamellar thickness, L, vs. crystallization temperature were discovered in this research.) For dilute solution grown crystals the heat of transition from DSC was found to be proportional to the specific volume. For crystals prepared from one fraction (M(,n)(' )=(' )2.8 x 10('4)) secondary endotherms in the crystal-crystal transition region were observed. These secondary endotherms are attributed to nonisothermal crystallization and crystallization of an adsorbed polymer layer. Other types of crystal defect/disordered fraction and their relationship to the amorphous density are discussed.;The number of monomer units per chain fold, U, and the number of monomer units per chain end, c/2, were obtained from an equation that relates these two parameters to the crystal thickness, L(,c), the fraction of double bonds at the crystal surfaces, F(,s), the crystal repeat distance along the polymer chain, R, and(' )M(,n). It is concluded that the length of chain ends in each molecule is proportional to the lamellar thickness, 0.79 L/R, and the number of monomer units per chain fold, U, decreases with decreasing crystallization temperature and molecular weight.;A method of using ('13)C nmr spectrum to study chain folding is discussed. Satisfactory agreement of U values from F(,s) with those from direct measurement was found.
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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
