Propylene Polymerization with Sterically Hindered Unbridged 2-Arylindene Metallocenes
| Autor: | Robert M. Waymouth, Gregg M. Wilmes, Shirley Lin |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
chemistry.chemical_classification
Zirconium Polymers and Plastics Chemistry Organic Chemistry chemistry.chemical_element Polymer Post-metallocene catalyst Inorganic Chemistry chemistry.chemical_compound Monomer Polymerization Tacticity Polymer chemistry Materials Chemistry Thermoplastic elastomer Metallocene |
| Zdroj: | Macromolecules. 35:5382-5387 |
| ISSN: | 1520-5835 0024-9297 |
| DOI: | 10.1021/ma012241c |
| Popis: | Metallocene catalyst systems derived from bis(2-phenylindenyl)zirconium dichloride (1) yield elastomeric polypropylenes of low to intermediate tacticity. The sterically hindered metallocene bis(2-(3,5-di-tert-butylphenyl)indenyl)zirconium dichloride (2) produces polypropylenes of much higher isotacticity than 1 ([mmmm] = 78% vs 44% in liquid propylene). Kinetic profiles of polymerizations conducted with 1/MMAO and 2/MMAO reveal that the initial rates of polymerization increase with increasing temperature; the activity of both catalysts decreases with time, but the decrease is less pronounced for 2/MMAO than for 1/MMAO. The polymer microstructure is highly dependent upon polymerization conditions: isotacticity decreases with increasing temperature and decreasing monomer concentration. Lower tacticity polypropylenes ([mmmm] = 40%) generated with 2/MMAO at low monomer concentrations contain a high percentage of [mmrm] stereoerrors, which is indicative of a stereoblock microstructure comprised of isotactic s... |
| Databáze: | OpenAIRE |
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