Abstract
Polypropylene was synthesized using binary metallocene catalysts, rac-ethylenebis-(1-η5-indenyl)-zirconium dichloride (rac-Et(Ind)2ZrCl2: Cata A) and zirconocene dichloride (Cp2ZrCl2: Cata B), in the presence of ZnEt2. The results indicated that ZnEt2 was an effective agent in modulating isotactivity of polypropylene. Moreover, it was found that the [mmmm] pentad value of polypropylene prepared in the presence of diethyl zinc decreased to 84, and the new peaks of [rmmr] and [rmrr + mmrm] appeared, in contrast to the peaks from polyproplene obtained in the absence of diethyl zinc. Therefore, the possible reason was the occurrence of chain-shuttling polymerization in the CataA/CataB/ZnEt2 catalyst system.
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