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Transition Metal Complexes as Catalysts for the Homo‐ and Copolymerisation of Olefins and Non‐Conjugated Dienes
Author(s) -
Moniz Santos Jorge,
Ribeiro Maria Rosário,
Portela Manuel Farinha,
Cramail Henri,
Deffieux Alain
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(20011001)202:15<3043::aid-macp3043>3.0.co;2-v
Subject(s) - methylaluminoxane , catalysis , chemistry , metallocene , ethylene , polymer chemistry , diene , transition metal , polymerization , post metallocene catalyst , norbornene , polyethylene , organic chemistry , polymer , natural rubber
The copolymerisation of ethylene with 5,7‐dimethylocta‐1,6‐diene (5,7‐DMO) was conducted in the presence of a series of catalytic systems, based on different transition metal derivatives associated with methylaluminoxane (MAO): a metallocene‐based catalyst, Cp 2 ZrCl 2 (1) ; a constrained geometry catalyst (Me 4 Cp)SiMe 2 ( N‐tert ‐Bu)TiCl 2 (2) ; an iron‐based catalyst, [(ArN=C(Me)) 2 C 5 H 3 N]FeCl 2 (3) ; and a Brookhart‐type catalyst [Ar—N=C(An)C(An)=N—Ar]NiBr 2 (Ar = 2‐C 6 H 4 ( t ‐Bu)) ( 4 ). The metallocene catalyst (1) and the constrained geometry catalyst (2) are able to incorporate 5,7‐dimethylocta‐1,6‐diene (5,7‐DMO) into polyethylene chains. Although (2) shows lower overall activities than Cp 2 ZrCl 2 , similar 5,7‐DMO incorporation levels are obtained for much lower diene concentrations in the feed. The characteristics of the copolymers obtained with the two catalysts are compared. The iron catalyst (3) can only homopolymerise ethylene. However, the presence of 5,7‐DMO in the feed does not significantly affect the polymerisation activity. On the contrary, with the Brookhart system (4) , the presence of 5,7‐DMO as well as any of the tested dienes (5‐ethylidene‐2‐norbornene, 7‐methyl‐1,6‐octadiene and 1,5‐hexadiene) completely inhibits the polymerisation of olefins. A tentative mechanism, based on the chain migration mechanism proposed by Brookhart is suggested for the deactivation of the Ni catalyst.