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Effect of Titanium on Fluxional Behavior of Unbridged Metallocene Catalysts
Author(s) -
Polo Eleonora,
Losio Simona,
Zecchi Gaetano,
Bertini Fabio,
Sacchi Maria Carmela
Publication year - 2004
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.200400350
Subject(s) - titanium , zirconium , cyclopentadienyl complex , tacticity , differential scanning calorimetry , catalysis , materials science , microstructure , metallocene , moiety , polymer chemistry , polymerization , ligand (biochemistry) , chemical engineering , chemistry , composite material , organic chemistry , polymer , metallurgy , thermodynamics , biochemistry , physics , receptor , engineering
Summary: Thanks to the use of a ligand consisting of a saturated ring fused to the cyclopentadienyl moiety, which sensibly increases the stability of titanocenes, it was possible to investigate the oscillating behavior of titanium catalysts in propylene polymerization for the first time. The titanium‐based catalysts yield poly(propylene)s with new and interesting microstructures. Indeed, in spite of the significantly lower isotactic pentad content [ mmmm ], the average lengths of the isotactic blocks ( N iso ) are similar or even higher than that obtained with the zirconium‐based homologues. Accordingly, differential scanning calorimetry (DSC) analysis shows melting peaks which are more evident than those obtained with the zirconium homologues. The study of the microstructure of the poly(propylene)s obtained with these catalysts allowed us to participate in the still open discussion on the oscillating mechanism of unbridged metallocenes.The titanium‐based catalysts employed in this study.