Copolymerization of ethene with styrene using different methylalumoxane activated half-sandwich complexes

Ethene was copolymerized with styrene using five different methylalumoxane (MAO) activated half-sandwich complexes of the general formula Me₂Si(Cp)(N R)MCl₂, varying the substituents on the cyclopentadienyl ring and the substituent on the amide (Cp = tetramethylcyclopentadiene CBT , 1-indenyl IBT , 3-trimethylsilyl-1-indenyl SIBT , or fluorenyl FBZ , R = tert-butyl (complexes CBT, IBT, SIBT, FBZ ) or benzyl CAT ), as well as the metal center (M = Ti, except FBZ : M = Zr). Polymerization behavior was analyzed with respect to catalyst activity and polymerization kinetics, styrene incorporation, copolymer microstructure, and molecular weight. All complexes produced random poly(ethene-co-styrene) without any regioregular or stereoregular microstructure. Complex CBT showed the highest catalytic activity, the fluorenyl-substituted complex FBZ produced the highest molecular weight polymer, and complexes SIBT and CAT promoted high styrene incorporation. Cp-substitution pattern influenced deactivation of the catalytic system with bulky substituents of the Cp-ring slowing down deactivation at the expense of styrene incorporation. Moreover, deactivation was accelerated with increasing styrene concentration. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1571–1578, 1997