Unexpected Formation of Atactic Blocks in Propylene/1‐Pentene Copolymers from rac‐Me2Si(2‐MeBenz[e]Ind)2ZrCl2

Summary: Supplementary experimental findings are reported in addition to those presented in a previous paper dealing with the microstructure of propylene/1-pentene copolymers prepared with rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2. The fractionation results which demonstrate that the atactic part of the copolymer can not be separated from the isotactic one confute the hypothesis suggested by other authors according to which the catalyst used could contain a percent of impurities of the meso (aspecific) form. This evidence is in agreement with the observed narrow polydispersities and the almost random distribution of the comonomers (rP · rCm ≈ 1) which are typical of single site catalysts. 13C NMR methyl region of pentane-soluble (a) and pentane-insoluble (b) fractions of copolymer prepared with MBI.