Abstract
We describe here the implementation of methylene-bridged binuclear "constrained geometry catalyst" (μ-CH 2-3,3′) {(η 5-indenyl)[1-Me 2Si( tBuN)](ZrMe 2)} 2 (Cl-Zr 2) to produce high-M w branched polyethylene. In ethylene homopolymerization, ∼70x increases in molecular weight are achieved with (C1-Zr 2) vs (μ-CH 2CH 2-3,3′){(η 5-indenyl)[1-Me 2Si( tBuN)](ZrMe 2)} 2 (C2-Zr 2) under identical polymerization conditions using (Ph 3C +) 2[1,4-(C 6F 5) 3BC 6F 4B(C 6F 5) 3] 2- (B 2) as the cocatalyst for both. With MAO as the cocatalyst, ∼600x increases in polyethylene molecular weight are achieved with (μ-CH 2CH 2-3,3′){(η 5- indenyl)[1-Me 2Si( tBuN)](ZrCl 2)} 2 (C2-Zr 2Cl 4) and (μ-CH 2-3,3′) {(η 5-indenyl)[1-Me 2Si( tBuN)](ZrCl 2)} 2 (C1-Zr 2Cl 4) vs mononuclear [1-Me 2Si(3-ethylindenyl)( tBuN)]ZrCl 2 (Zr 1Cl 2). In the ethylene + 1-hexene copolymerization, C1-Zr 2 enchains 3x more 1-hexene than does C2-Zr 2 under identical polymerization conditions (B 2 as cocatalyst). With MAO as the cocatalyst, C2-Zr 2Cl 4 enchains 3.5x more, and C1-Zr 2Cl 4 4.2x more, 1-hexene than does Zr 1Cl 2. When the polar solvent C 6H 5Cl is used as the polymerization medium, dramatic compression in the dispersion of polymerization activities and molecular weights is found. Both homopolymerization and copolymerization results argue that achievable Zr-Zr spatial proximity significantly influences chain transfer rates and selectivity for comonomer enchainment and that such proximity effects are highly cocatalyst and solvent sensitive.
Original language | English |
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Pages (from-to) | 9015-9027 |
Number of pages | 13 |
Journal | Macromolecules |
Volume | 38 |
Issue number | 22 |
DOIs | |
Publication status | Published - Nov 1 2005 |
ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry