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Copolymerization of Ethylene with 1‐Hexene Using Sterically Hindered Tris(pyrazolyl)borate Titanium (IV) Compounds
Author(s) -
Gil Marcelo P.,
dos Santos João H. Z.,
Casagrande Jr. Osvaldo L.
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20010101)202:2<319::aid-macp319>3.0.co;2-9
Subject(s) - 1 hexene , comonomer , ethylene , copolymer , methylaluminoxane , catalysis , polymer chemistry , chemistry , cationic polymerization , steric effects , hexene , boron , organic chemistry , metallocene , polymerization , polymer
The copolymerization of ethylene/1‐hexene was studied using {Tp Ms }TiCl 3 ( 1 ) (Tp Ms = hydridotris(3‐mesitylpyrazol‐1‐yl) and {Tp Ms* }TiCl 3 ( 2 ) (Tp Ms* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)) com‐ pounds in the presence of methylaluminoxane at 65°C. For both catalysts it was observed that the productivities decreased with increasing the 1‐hexene concentration in the milieu exhibiting a negative comonomer effect . The highest productivities and 1‐hexene incorporations were achieved in the case of {Tp Ms* }TiCl 3 catalyst system. The resulting copolymers were not soluble in TCB even at 165°C. 1‐hexene incorporations were very low: ca. 1.2 and 3.3 mol‐%, respectively for ( 1 ) and ( 2 ). The r 1 and r 2 parameters for both ( 1 ) and ( 2 )/MAO catalyst systems clearly indicated a strong tendency of these catalytic precursors to preferentially promote ethylene homopolymerization. According to X‐ray photoelectron spectroscopy, from the analysis of the Ti 2p 3/2 peak, Tp Ms* catalyst seems to present a stronger cationic character after MAO treatment, which can explain in part its higher catalyst activity.