Homopolymerization of ethylene and copolymerization of ethylene and 1-hexene with bridged metallocene/methylaluminoxane catalysts: the influence of the bridging moiety

Ethylene and 1-hexene have been copolymerized with the catalyst system 9-fl uorenylidene-1-cyclopentadienylidene-2-hex-5-enylidene zirconium dichloride /PHT (PHT = partially hydrolyzed trimethylaluminum). The resultant polymer has been characterized. The product of the copolymerization parameters r(1) . r(2) indicates a statistical distribution of the monomers in the produce d poly(ethylene-co-1-hexene). Various ansa-bis(fluorenylidene) and ansa-flu orenylidene cyclopentadienylidene zirconium dichloride complexes have also been used as catalyst precursors to homopolymerize ethylene and copolymeriz e ethylene and l-hexene heterogeneously. For these reactions, the relations hips between "bite-angle", polymerization activity, and comonomer incorpora tion have been investigated using PHT/silica gel and MAO/silica gel as alum inoxane type cocatalysts. The effect of comonomer on the catalytic activity is generally positive for MAO/silica gel catalysts and negative for PHT/si lica gel catalysts. (C) 2000 Elsevier Science B.V. All rights reserved.