Polymerization behavior of C 1-symmetric metallocenes (M = Zr, Hf): From ultrahigh molecular weight elastic polypropylene to useful macromonomers

Alexander Schöbel, Dominik Lanzinger, Bernhard Rieger

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The C1-symmetric metallocenes rac-[1-(9-η5- fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η5-indenyl)ethane] zirconium dichloride (1) and rac-[1-(9-η5-fluorenyl)-2-(5,6- cyclopenta-2-methyl-1-η5-indenyl)ethane]hafnium dichloride (2) are known to produce elastic polypropylene. They were investigated concerning their temperature stability during the polymerization of propene. After activation of these complexes with triisobutylaluminum (TIBA)/[CPh 3][B(C6F5)4], first polymerization experiments (80-100 C) afforded moderate to high activities. However, at these polymerization temperatures, the molecular weights of the produced polymers are significantly decreased, resulting in a waxy appearance and, therefore, a loss of the elastic behavior. The main reason for this behavior, especially for the more significant decrease of the molecular weight in the case of hafnocene 2 compared with zirconocene 1, was revealed to occur due to a fast β-methyl transfer reaction. Hence, hafnocene 2 can form polymer chains with a high selectivity toward allylic chain ends. These macromonomers can be used in the catalytic insertion polymerization for the formation of new grafted copolymers. Initial copolymerization experiments with ethene were conducted.

Original languageEnglish
Pages (from-to)427-437
Number of pages11
JournalOrganometallics
Volume32
Issue number2
DOIs
StatePublished - 28 Jan 2013

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