Copolymerization of ethene with styrene using CGC catalysts: The effect of the cyclopentadienyl ligand substitution on the catalyst activity and copolymer structure
Abstract
The ethene-styrene copolymerization has been investigated using the dimethylsilylene-bridged (amidocyclopentadienyl)dichlorotitanium(IV) complexes [TiCl2 eta 5-1-(t-BuSiMe2N-κN)-2,3,4-Me3-5-R-C5] where R = Me (1), H (2), Bu (3), Ph (4), 4 fluorophenyl (5), and but-2-en-2-yl (6) in combination with methylalumoxane (MAO) as catalysts. The nature of the substituent R strongly influenced the catalyst activity and selectivity and the copolymer microstructure and molecular weight.
The catalysts derived from 1 3 were by about one order more active than those derived from 4 6. At the optimum Al/Ti molar ratio 900, the highly active catalysts produced a pseudo random copolymer (95-97 wt %) containing up to 47.8 mol % of incorporated styrene.
The low-active catalysts gave mixtures of a pseudo-random copolymer (76 - 85 wt %) with polyethene (10 wt %) and polystyrene sequences (3 - 7 wt %). The X-ray diffraction crystal structures of 2 and 4 were determined.