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The role of dormant sites in propene polymerization using methylalumoxane activated metallocene catalysts
Author(s) -
Jüngling Stephan,
Mülhaupt Rolf,
Stehling Udo,
Brintzinger HansHerbert,
Fischer David,
Langhauser Franz
Publication year - 1995
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19950970121
Subject(s) - propene , metallocene , polymerization , chemistry , catalysis , ligand (biochemistry) , polymer chemistry , medicinal chemistry , organic chemistry , polymer , biochemistry , receptor
Propene polymerization of methylalumoxane (MAO) activated rac ‐Me 2 Si(Benz[e]Indenyl) 2 ZrCl 2 ( BI ) and rac ‐Me 2 Si(2‐Me‐Benz[e]Indenyl) 2 ZrCl 2 ( MBI ) was studied to investigate the influence of the ligand substitution pattern and the role of dormant sites. Poly(propene) end group composition as well as regio‐ and stereoirregularities were examined by means of 1 H‐ and 13 C‐NMR spectroscopy. Dormant sites, resulting from 2, 1‐propene insertion, were reactivated either by β‐hydrogen transfer to propene, yielding 2‐butenyl end groups, or by 1, 2‐insertion of propene, yielding regioirregularities. Propene polymerization in the presence of hydrogen gave n‐butyl end groups and less regioirregularities as expected for hydrogenolysis of such dormant sites. Methyl substitution in 2‐position of the benz[e]indenyl ligand suppressed β‐hydrogen transfer to propene, and increased molecular weight with increasing propene concentration. Also, activation energy increased from 30 kJ/mol ( BI /MAO) to 59 kJ/mol ( MBI /MAO). For both catalysts activity depended on propene concentration. The order of reaction relative to propene was 1.7.