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Polymorphism, Preferred Orientation and Morphology of Propylene-Based Random Copolymer Subjected to External Force Fields

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dc.contributor.advisor Benjami Hsiao. en_US
dc.contributor.author Mao, Yimin en_US
dc.contributor.other Department of Chemistry en_US
dc.date.accessioned 2012-05-17T12:21:40Z
dc.date.accessioned 2015-04-24T14:48:25Z
dc.date.available 2012-05-17T12:21:40Z
dc.date.available 2015-04-24T14:48:25Z
dc.date.issued 2011-08-01 en_US
dc.identifier Mao_grad.sunysb_0771E_10641.pdf en_US
dc.identifier.uri http://hdl.handle.net/1951/56070 en_US
dc.identifier.uri http://hdl.handle.net/11401/71655 en_US
dc.description.abstract Crystallization of propylene-based random copolymers was investigated by using time-resolved wide- and small-angle X-ray scattering (WAXS/SAXS) techniques. With low content of 1-butylene as comonomer, both gamma- and alpha-phase of polypropylene crystals co-existed in the system with the gamma-phase being the dominant modification. When a step shear was applied, the c-axis of the gamma-phase oriented horizontally, while that of the alpha-phase pointed to the vertical direction (i.e., the shear direction). Crystallization was greatly enhanced by the shear. Uniaxial stretching experiments were also performed on the same sample at different temperatures. At high temperature (373K), the gamma-phase adopted a distinctive tilted `cross-beta' configuration. During stretching, the gamma-phase was gradually transformed into the alpha-phase with parallel chain packing. Lamellar branching was also observed at this temperature, but was not observed at lower temperatures. The stress associated with the mid-temperature (333K) deformation was found to be much higher than those at other temperatures, where this observation could be explained by the fragmentation of lamellar crystals as evident from the profile analysis of the WAXS data. At low temperate (e.g. 298K), the WAXS pattern was featured with prominent equatorial diffuse scattering due to the mesomorphic phase. The nature of the mesomorphic phase could be modeled with tiny beta-phase crystals with about 50% oriented amorphous phase. The thermal stability and reversibility of the gamma-to-alpha phase transition were investigated by heating of the stretched sample to a temperature close to the nominal melting temperature and subsequent cooling to crystallization temperature of 373K, where the in-situ re-crystallization process was monitored. The heating process was found to remove residues of the gamma-phase with tilted `cross-beta' configuration, whereby the newly grown gamma-phase adopted a parallel orientation mode. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Chemistry -- Physical chemistry en_US
dc.subject.other morphology, orientation, polymorphism, polypropylene, random copolymer, X-ray scattering en_US
dc.title Polymorphism, Preferred Orientation and Morphology of Propylene-Based Random Copolymer Subjected to External Force Fields en_US
dc.type Dissertation en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember Stanislaus Wong en_US
dc.contributor.committeemember Joseph Lauher en_US
dc.contributor.committeemember Andy Tsou. en_US

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