Polymerizations of propene, 1-butene and 1-hexene were conducted with a mixture of rac- and meso-[dimethylsilylenebis(2-methylindenyl)]zirconium dichloride (1) combined with methylaluminoxane (MAO), triethylaluminium (AlEt3)/triphenylcarbenium tetrakis(pentafluorophenyl)borate (2) or triisobutylaluminium (AliBu3)/2 as a cocatalyst. The polymerization profiles of propene with rac-1 and meso-1 were determined from the rate of overall propene consumption and the fractions of isotactic and atactic polymers which were sampled during polymerization. An induction time to reach the maximum Rp (rate of polymerization) followed by gradual decay was observed in the case of using the systems rac-, meso-1-MAO and rac-1-AliBu3/2. Besides, a rapid drop of Rp from the initial value was found when using AlEt3/2. Molecular weights of the isotactic and atactic polymers sampled do not change during polymerization, and it is suggested that the change of [C*] (number of active centers) is reflected in the profiles of Rp. The rate ratio of rac-1 to meso-1 (Rp(rac)/Rp(meso)) in propene and 1-butene polymerizations decreases in the following order: AlEt3/2 > AIiBu3/2 > MAO. In the case of 1-hexene polymerization, the highest Rp(rac)/Rp(meso) value was obtained. This result indicates that the coordination of 1-hexene to the sterically hindered site of meso-1 is difficult compared with propene and 1-butene.
|ジャーナル||Macromolecular Chemistry and Physics|
|出版ステータス||Published - 1999 12 1|
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