Stereoblock polypropene from the Ziegler‐Natta catalyst system TiCl₄/octylsodium

Propene polymerization in the presence of the heterogeneous catalyst system TiCl 4 /Na‐octyl yielded polymers with unusually high molecular weights and relatively high amounts of prevailingly syndiotactic stereosequences. The characterization of such polymers proved that a fraction of the active species were able to invert their stereocontrol — from isospecific to prevailingly syndiospecific — during the growth of individual macromolecules. This suggests that, in principle, at least in conditions of limited occurrence of chain transfer reactions, the stereo‐chemical environment of the catalytically active metal in a heterogeneous Ziegler‐Natta system may not be invariant during the process of chain growth, even for the most stereospecific active species.