Microstructures of poly(1-butene) and poly(ethylene-co-1-butene) produced by zirconocene/methylaluminoxane catalysis.
Item
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Title
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Microstructures of poly(1-butene) and poly(ethylene-co-1-butene) produced by zirconocene/methylaluminoxane catalysis.
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Identifier
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AAI9630530
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identifier
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9630530
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Creator
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Zhang, Jianbin.
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Contributor
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Adviser: George Odian
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Date
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1996
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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 | Chemistry, Physical
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Abstract
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Low molecular weight (ca 2000) poly(1-butene) and poly(ethylene-co-1-butene) were synthesized at 100{dollar}\sp\circ{dollar}C and 90{dollar}\sp\circ{dollar}C respectively using rac-(dimethylsilyl)bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride(I) and methylaluminoxane (MAO) as cocatalyst. The products were characterized by NMR ({dollar}\sp1{dollar}H and {dollar}\sp{13}{dollar}C), size exclusion chromatography (SEC) and vapor pressure osmometry (VPO).;The number-average molecular weight of poly(1-butene) was determined as 1910, 2025 and 2055 by SEC, VPO and NMR, respectively. The poly(1-butene) is 84% isotactic and has high regioselectivity (ca. 95% 1,2-addition). Both saturated and unsaturated end groups were characterized by NMR. Vinylidene and trisubstituted double bonds comprise approximately 67% and 29%, respectively, of the unsaturated end groups with the remainder consisting of vinylene and vinyl double bonds. n-Butyl and sec-butyl groups constitute the saturated end groups in the approximate ratio 10:1. There is a slight excess of saturated end groups relative to unsaturated end groups. These results are discussed in terms of a reaction mechanism of initiation and propagation with various chain-transfer reactions ({dollar}\beta{dollar}-hydride transfer with and without rearrangement, transfer to aluminum, transfer to vinylidene end groups, and {dollar}\beta{dollar}-alkyl transfer).;For poly(ethylene-co-1-butene) samples, comonomer composition, triad sequence distribution, and end groups were analyzed by {dollar}\sp1{dollar}H and {dollar}\sp{13}{dollar}C NMR. The average polymer molecule contains about one double bond and one saturated end group. The unsaturated end groups were formed almost exclusively by transfer from propagating chains containing 1-butene as the terminal unit. At least 98% of the unsaturated end groups are vinylidene and trisubstituted double bonds, which are present in the approximate ratio 3:1. Saturated end groups result from the initiation process and chain transfer to aluminum. Both ethylene and 1-butene are involved in initiation but ethylene more than 1-butene. The product is a random copolymer with very short blocks (no longer than 2-3 monomer units) of both ethylene and 1-butene. The comonomer sequence distributions determined by {dollar}\sp{13}{dollar}C NMR were fitted to first-order Markovian statistics, which allowed calculation of the monomer reactivity ratios. The results are discussed in terms of a reaction mechanism consisting of initiation, propagation and chain transfer reactions.;Different poly(1-butene) samples were synthesized using rac-(dimethylsilyl)bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride(I)/MAO at different temperatures for different polymerization times and catalyst concentrations. 1-Butene was also polymerized by using meso-(dimethylsilyl)bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride(I)/MAO, and cationic zirconocene catalyst system (also called non-coordination anion system) rac-(dimethylsilyl)-bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dimethyl/{dollar}\phi{dollar}NHMe{dollar}\sb2{dollar}B({dollar}\rm C\sb6F\sb5)\sb4.{dollar} The resulting polymers were analyzed by NMR ({dollar}\sp1{dollar}H and {dollar}\sp{13}{dollar}C), SEC and IR.
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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.
