Fractionation and Crystallization of Isotactic Poly(propylenes) Prepared with a Heterogeneous Transition Metal Catalysts

Summary: A series of poly(propylenes) (PPs) were prepared by slurry polymerization using a MgCl₂-supported transition metal catalyst. Two different external donors (EDs) were used: diphenyl dimethoxysilane (DPDMS) and methylphenyl dimethoxysilane (MPDMS). The molecular weight (MW) of the PPs was controlled using molecular hydrogen that was used as a transfer agent. To obtain materials with differing molecular weight and similar tacticities, polymers were fractionated with prep-TREF. DSC analyses of blends of TREF fractions showed that the crystallization behaviour of the polymer blends are strongly affected by the configuration (tacticity) and MW of the PP.