Polypropylene fractions produced by binary metallocene catalysts

Because of the great economic interest in propylene-based polymers and the possibility of designing materials with desired properties with metallocene catalyst mixtures, we investigated the characteristics ofpolypropylenes produced by mixtures of SiMe 2 Ind 2 ZrCl 2 : dimethylsilane-bis(indenyl) zirconocene (1) and Et(Flu)(Cp)ZrCl 2 : ethylidene (fluorenyl cyclopentadienyl) zirconocene (2) in different proportions. The polymers were fractionated with solvents, and the fractions were characterized. We observed that the polymers produced by the different mixed systems showed lower weight-average molecular weights and only slightly broader molecular weight distributions than polypropylenes synthesized by the individual catalysts. We concluded that catalyst 1 acted independently of catalyst 2, producing polymers with the same isotacticity.