• Polymer(Korea)
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• v.35 no.6
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• pp.505-512
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• 2011

Effects of structural features of 4 dinuclear constrained geometry catalysts having paraxylene derivative bridge (DCGC) on copolymerization of ethylene and 1-hexene were investigated. The bridges of three catalysts have para-xylene backbone with a different substituent at benzene ring. The substituents were hydrogen (Catalyst 1), isopropyl (Catalyst 2), n-hexyl (Catalyst 3) and 1-octyl (Catalyst 4). It was found that Catalyst 1 having hydrogen as a substituent exhibited the greatest activity among the four dinuclear CGCs. On the other hand, Catalyst 2 containing isopropyl as a substituent showed the smallest activity. Very interestingly, Catalyst 2 was able to produce about 6 times higher molecular weight polymer than Catalyst 3 and 4. Catalyst 3 and 4 having a long alkyl chain substituent revealed the biggest comonomer response to generate polyethylene copolymer containing more than 40% 1-hexene contents. These results suggest that the control of the substituent of para-xylene bridge of dinuclear CGC can provide a proper method to adjust the microstructure of polyethylene copolymers.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.516-521
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• 2007

The copolymerization characteristics of a newly-synthesized catalyst, $rac-Me_2Si(2-p-tolylindenyl)_2ZrCl_2$, and its analogue, $rac-Me_2Si(Ind)_2ZrCl_2$, were examined in the ethylene/1-octene copolymerization while varying the concentration of 1-octene in the reaction mixture. The activity of $rac-Me_2Si(2-p-tolylindenyl)_2ZrCl_2$ catalyst was decreased with increase of comonomer concentration, which is different from the usual comonomer effect of the metallocene catalysts with a bridge structure. The contents of 1-octene in the copolymer from the catalyst with 2-p-tolyl substituent were higher than those from the catalyst without that substituent. The melting point, crystallinity, and molecular weight decreased with comonomer content which was more apparent for $rac-Me_2Si(2-p-tolylindenyl)_2ZrCl_2$ catalyst.

• Polymer(Korea)
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• v.35 no.1
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• pp.77-86
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• 2011

Polymerization properties of six dinuclear constrained geometry catalysts (DCGC) were investigated. The different length bridges of three catalysts were para-phenyl (Catalyst 1), para-xylyl (Catalyst 2), and para-diethylene phenyl (Catalyst 6). The other three DCGC have the same para-xylyl bridge with the different substituents at the phenyl ring of the bridge. The selected substituents were isopropyl (Catalyst 3), n-hexyl (Cataylst 4), and n-octyl (Catalyst 5), It was found that the longer catalyst not only exhibited a greater activity but also prepared a higher molecular weight copolymer. The catalyst 3 having a bulky isopropyl substituent revealed the lower activity but formed the highest molecular weight polymer comparing with the other alkyl substituted DCGCs. These results were able to be understood on the basis of the electronic and steric characteristics of the bridge. This study confirms that the control of the bridge structure of DCGC may contribute to control the microstructure of polymers.