Short chain-branched polyethylene produced by [(CH3)(2)C(eta-C5H4)(eta-C9H6)]ZrCl2 and [CH2(CH2)(4)C(eta- C5H4)(eta-C9H6)]ZrCl2 metallocene catalyst

[(CH3)(2)C(eta-C5H4)(eta-C9H6)]ZrCl2 and [CH2(CH2)(4)C(eta-C5H4)(eta-C9H6]Z rCl2 metallocene catalysts were prepared and employed in a study of ethylen e polymerization in the presence of cocatalyst methylaluminoxane. The resul tant polymers were characterized by C-13-NMR. The signals 11.1 and 26.6 ppm , arising from C-1 and C-2 respectively, were detected. This result reveale d that the resultant polymer is a short chain-branched polyethylene. A resu ltant polymer sample was fractionated with a preparative temperature rising elution fractionation (TREF) technique. The fractionation results indicate that it is possible that there is a complicated polymerization mechanism d uring the polymerization of ethylene. A possible mechanism of short chain b ranch formation in ethylene polymerization was suggested. (C) 2000 Elsevier Science Ltd. All rights reserved.