Homo- and copolymerization of ethylene and α-olefins over 1- and 2-siloxy-substituted ethylenebis(indenyl)zirconium and ethylenebis(tetrahydroindenyl)zirconium dichlorides

Petri Lehmus, Esa Kokko, Outi Härkki, Reko Leino, Hendrik J. G. Luttikhedde, Jan H. Näsman, Jukka V. Seppälä

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    62 Citations (Scopus)

    Abstract

    The influence of siloxy substitution of ethylene-bridged bis(indenyl)- and bis(tetrahydroindenyl)zirconium dichlorides on ethylene/α-olefin copolymerization and ethylene homopolymerization performance was investigated. Ethylene was copolymerized with 1-hexene and 1-hexadecene over rac-[ethylenebis(1-(tert-butyldimethylsiloxy)- 3-indenyl)]zirconium dichloride (1), rac-[ethylenebis(1-(tert-butyldimethylsiloxy)-4,5,6, 7-tetrahydro-3-indenyl)]zirconium dichloride (H1), rac-[ethylenebis(2-(tert-butyldimethylsiloxy)- 1-indenyl)]zirconium dichloride (2), and rac-ethylenebis(1-indenyl)zirconium dichloride (EBI) using methylaluminoxane (MAO) as cocatalyst. 1-Siloxy substitution was found to remarkably improve the copolymerization ability and 2-siloxy substitution to enhance the polymerization activity of ethylenebis(indenyl)zirconium dichlorides. Optimum homo- and copolymerization performance was observed at a very low Al(MAO) concentration, which for 2 could be reduced to a level of 0.2 mmol/dm3 by using a small amount of triisobutylaluminum. The 1-siloxy-substituted metallocene catalysts 1 and H1 (hydrogenerated 1) revealed decreasing comonomer incorporation and increasing induction times with increasing Al(MAO) concentration, which indicates the presence of unfavorable interactions between these metallocenes and MAO. Chain termination occurred mainly by chain transfer to the monomer and β-hydrogen transfer to the metal for catalysts with indenyl and tetrahydroindenyl ligands, respectively.

    Original languageEnglish
    Pages (from-to)3547-3552
    Number of pages6
    JournalMacromolecules
    Volume32
    Issue number11
    DOIs
    Publication statusPublished - 1999
    MoE publication typeA1 Journal article-refereed

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