Effect of Substituent on Titanocene/MMAO Catalyst for Ethylene/1-Hexene Copolymerization
Copolymerization of ethylene with 1-hexene was carried out using two ansa-fluorenyl titanium derivative complexes. The substituent effect on the catalytic activity, monomer reactivity ratio and polymer property was investigated. It was found that the presence of t-Bu groups on fluorenyl ring exhibited remarkable catalytic activity and produced polymer with high molecular weight. However, these catalysts produce polymer with narrow molecular weight distribution, indicating the characteristic of single-site metallocene catalyst. Based on C NMR, we can observe that monomer reactivity ratio was affected by catalyst structure. The rH values of complex 2 were lower than that of complex 1 which might be result from the higher steric hindrance leading to a reduction of 1hexene insertion step. Keywords—Constrained geometry catalyst, linear low density polyethylene, copolymerization, reactivity ratio
Copolymerization of olefins with Kaminsky‐Sinn‐type catalysts
Copolymerizations of ethylene with propene, ethylene with 1-hexene and propene with 1-hexene were performed at 40°C under atmospheric using three kinds of Kaminsky-Sinn-type catalysts which differ in stereospecificity: Cp2ZrCl2-methylaluminoxane (MAO) (aspecific); Et[IndH4]2 ZrCl2-MAO (isopecific); i-Pr(Cp)(Flu)ZrCl2-MAO (syndiospecific). 
 
The 13C NMR analysis of copolymers showed that the incorporation of higher olefins decreases in the following order: i -Pr(Cp)(Flu)ZrCl2-MAO > Et[IndH4]2ZrCl2-MAO > Cp2ZrCl2-MAO, and that stereospecificity is retained even in the copolymerization. 
 
The product of monomer reactivity ratios (r1 · r2) indicates that poly(propene-co-1-hexene) is a statistically random copolymer whereas both poly(ethylene-co-propene) and poly(ethylene-co-1-hexene) have somewhat alternating character regardless of catalyst stereospecificity.
Copolymerization of ethylene and 1-hexene with Et(Ind)2ZrCl2 in hexane
Abstract Copolymerizations of ethylene and 1-hexene were carried out in hexane at 60°C by using ethylenebis(indenyl)zirconium dichloride as catalyst and methylaluminoxane (MAO) as cocatalyst in presence of triisobutylaluminum (TIBA). The influence of the alkylaluminum concentration and AlTOTAL/Zr molar ratio on the catalyst activity and comonomer incorporation are evaluated. Increasing the TIBA concentration, the MAO solubility augments in the polymerization milieu, as well as the catalyst activity and the comonomer incorporation. Increasing the AlTOTAL/Zr molar ratio, catalyst activity becomes higher, while comonomer incorporation remained constant at around 8 wt% for molar ratios between 0 and 5000. For AlTOTAL/Zr molar ratios higher than 5,000 comonomer incorporation increased gradually. Under the same experimental conditions dimethylsilylbis(indenyl)zirconium dichloride showed higher thermal stability and led to higher comonomer incorporation.