• Macromolecular Research
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• 제12권1호
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• pp.100-106
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• 2004

We have prepared the polymethylene-bridged, dinuciear, half-sandwich constrained geometry catalysts (CGC)［Zr(η$\^$5/:η$^1$-C$\_$9/H$\_$5/SiMe$_2$NCMe$_3$)］$_2$［(CH$_2$)$\_$n/］［n=6(9), n=12(10)］by treating 2 equivalents of ZrCl$_4$with the corresponding tetralithium salts of the ligands in toluene. $^1$H and $\^$13/C NMR spectra of the synthesized complexes provide firm evidence for the anticipated dinuciear structure. In $^1$H NMR spectra, two singlets representing the methyl group protons bonded at the Si atom of the CGC are present at 0.88 and 0.64 ppm, which are considerably downfield positions relative to the shifts of 0.02 and 0.05 ppm of the corresponding ligands. To investigate the catalytic behavior of the prepared dinuciear catalysts, we conducted copolymerizations of ethylene and styrene in the presence of MMAO. The prime observation is that the two dinuclear CGCs 9 and 10 are not efficient for copo-lymerization, which definitely distinguishes them from the corresponding titanium-based dinuclear CGC. These species are active catalysts, however, for ethylene homopolymerization; the activity of catalyst 10, which contains a 12-methylene bridge, is larger than that of 9 (6-methylene bridge), which indicates that the presence of the longer bridge between the two active sites contributes more effectively to facilitate the polymerization activity of the dinuciear CGC. The activities increase as the polymerization temperature increases from 40 to 70$^{\circ}C$. On the other hand, the molecular weights of the polyethylenes are reduced when the polymerization temperature is increased. We observe that dinuciear metallocenes having different-length bridges give different polymerization results, which reconfirms the significant role that the nature of the bridging ligand has in controlling the polymerization properties of dinuclear catalysts.

• Macromolecular Research
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• 제9권2호
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• pp.71-83
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• 2001

The metallocene compounds had been applied to the polymerizations of olefins and vinyl monomers with methylaluminoxane (MAO) cocatalyst, and they have usually one transition metal atom per molecule, i.e., mononuclear metallocene. Recently it has been found that the dinuclear metallocene compounds containing two transition metal atoms exhibit the peculiar polymerization behaviors for olefins and vinyl monomers. In this article, the dinuclear metallocenes are classified into four groups of dinuclear bent-metallocene, dinuclear ansa-metallocene, dinuclear constrained geometry catalyst and dinuclear half-metallocene, and then the synthesis of dinuclear metallocene of each group as well as the polymerization behaviors for ethylene, propylene, and styrene are described.

• 폴리머
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• 제35권1호
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• pp.77-86
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• 2011

굳은 특성을 가진 다리로 연결된 이핵 CGC 6개의 공중합특성을 조사하였다. 6개의 화합물 중에서 3개는 길이가 다른 para-phenyl (Catalyst 1), para-xylyl (Cata1yst 2), para-diethylene phenyl (Catalyst 6) 다리를 가진 화합물이며, 나머지 3개는 다리리간드는 para-xylyl 다리 기본구조를 가졌으나 치환체가 isopropyl (Catalyst 3), n-hexyl (Cataylst 4), n-octyl (Catalyst 5)인 화합물이었다. 이핵메탈로센 6가지와 Dow 촉매를 사용하여 에틸렌과 스티렌을 공중합시켜 다리리간드의 특성변화가 촉매의 중합특성과 이로부터 생성되는 공중합체의 특성에 미치는 영향을 조사하였다. 실험 결과 다리리간드의 길이가 증가함에 따라 촉매의 중합활성이 4배까지 향상되었으며 이로부터 생성되는 공중합체의 분자량도 증가하였다. 또한 para-xylyl 리간드의 치환체가 isopropyl에서 n-hexyl 및 n-octyl로 변함에 따라 중합활성은 증가하였으나 이로부터 생성되는 분자량은 감소하였다. 본 연구 결과는 촉매구조 변화에 의한 고분자 미세구조 조절이라는 고분자 합성의 가장 어려운 부분이 이핵메탈로센을 활용하여 어느 정도 현실화될 수 있음을 보여주는 결과이다.