Microstructure of polypropene samples produced with different homogeneous bridged indenyl zirconium catalysts. Clues on the structure and reactivity relation
✍ Scribed by Georg Schupfner; Walter Kaminsky
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 542 KB
- Volume
- 102
- Category
- Article
- ISSN
- 1381-1169
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✦ Synopsis
Propene bulk polymerization
with rat-ethylenebis( 1-indenyl) zirconium dichloride, ethylenebis(4,5,6,7-tetrahydro-lindenyl)zirconium dichloride, dimethylsilylbis( I-indenyl)zirconium dichloride, dimethylsilylbis (4,5,6,7-tetrahydro-lindenyl)zirconium dichloride/methylaluminoxane (MAO) were carried out at polymerization temperatures from 0 to 60°C. The regio-irregularities, racemic placements and their succession, which are known to cause depression of the melting point of isotactic polypropene produced with homogeneous catalysts, were studied and compared. Only stereospecific 2,1 -insertions were detectable and found to increase with temperature. 1,3-insertion shows up only for catalyst with tetrahydroindenyl ligands and replaces the 2, l-insertions at elevated polymerization temperatures. A racemic propene placement occurring after a 2,1 -insertion sequence is found to a minor extent compared to regular meso enchainment.