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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 1
BKCSDE 35(1)
January 20, 2014 

Isospecific Propylene Polymerization Behavior of Lewis Base Functionalized Unbridged Zirconocences under Bulk Conditions
Seung Woong Yoon, Hwa Kyu Kim, Seong Kyun Kim, Taewon Kim, Min Hyung Lee*, Youngkyu Do*
Metallocenes, Isotactic polypropylene, Lewis base, Bulk polymerization
Isospecific propylene polymerization behavior of meta- and para-Lewis base (E) functionalized unbridged zirconocenes ([1-(En-Ph)-3,4-Me2C5H2]2ZrCl2, E = NMe2, OMe; n = 1 or 2) was investigated under bulk conditions. Catalytic activity of the zirconocenes, and molecular weight and isotacticity of polypropylenes are found to be dependent on the position and number of the Lewis base functional groups in the zirconocenes. All the crude polypropylenes possess a broad molecular weight distribution and multi-melting transitions, indicating an involvement of multi-catalytic active species in the polymerization. The highest [mmmm] value of an isotactic portion of the polypropylenes reached 89%, which is higher than that (85%) from the wellknown C2-symmetric EBIZr (rac-Et(Ind)2ZrCl2) catalyst. These results support that the in situ generated, rigid rac-like cation-anion pair through the Lewis acid-base interactions between the functional groups of zirconocenes and methylaluminoxane anion is effective in the formation of isotactic polypropylene under bulk propylene polymerization conditions.
236 - 242
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