New group 4 metallocenes as catalysts for polyolefin and nanocomposite = 폴리올레핀 및 나노복합체용 촉매로서의 새로운 4족 메탈로센

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A series of ortho or meta Lewis base functionalized unbridged zirconocenes, $[{1-(E_n-Ph)-3,4- Me_2C_5H_2}_2ZrCl_2]$ ($E=NMe_2$, OMe; n=1, 2), and a half-functionalized zirconocene, $[{1-(p-Me_2NC_6H_4)-3,4- Me_2C_5H_2 }{1-(p-tolyl)-3,4- Me_2C_5H_2}ZrCl_2]$, were prepared. The crystal structures of these compounds determined by X-ray diffraction revealed the presence of only $C_2$ -symmetric rac-like isomers in the asymmetric units. In combination with methylaluminoxane (MAO) cocatalyst, the meta-functionalized complexes afforded mixtures of polymers that exhibit multimelting transition temperatures and broad molecularweight distributions (MWDs) in propylene polymerization at atmospheric monomer pressure, whereas the ortho functionalized complexes did not give rise to polymerization. Stepwise solvent extraction of the polymer mixtures showed that the polymers consist of amorphous, moderately isotactic, and highly isotactic portions, the weight ratio of which is dependent on the reaction temperature. $^{13}C$ NMR spectral analysis indicated that the [mmmm] methyl pentad value of the isotactic portion reached around 90%. Among the meta-functionalized zirconocenes, the di-OMe-substituted one afforded the largest amount of the isotactic portion at all temperatures, and the portion comprised 82 wt% of the crude polymer obtained at 25 ℃. In contrast, propylene polymerization with the half-functionalized unbridged zirconocene resulted in the formation of nearly atactic polypropylene with a narrow MWD of around 2. These results corroborate the proposition that the rigid rac-like cation-anion ion pair of type $[rac- L_2 ZrP][Me-MAO]^-$ generated in situ, through Lewis acid-base interactions between the functional groups and $[Me-MAO]^-$, is responsible for the isospecific propylene polymerization with the given class of functionalized unbridged zirconocenes and further indicate that the formation of such ion pairs can be favored by difunctionalization at the meta positi...
Advisors
Do, Young-Kyuresearcher도영규researcher
Description
한국과학기술원 : 화학과,
Publisher
한국과학기술원
Issue Date
2009
Identifier
309374/325007  / 020055049
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학과, 2009.2, [ xiii, 199 p. ]

Keywords

polyolefin; isotactic polypropylene; Lewis bases; metallocenes; catalyst; 폴리올레핀; 이소택틱 폴리프로필렌; 루이스 베이스; 메탈로센; 촉매; polyolefin; isotactic polypropylene; Lewis bases; metallocenes; catalyst; 폴리올레핀; 이소택틱 폴리프로필렌; 루이스 베이스; 메탈로센; 촉매

URI
http://hdl.handle.net/10203/31723
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=309374&flag=dissertation
Appears in Collection
CH-Theses_Ph.D.(박사논문)
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