Syndiospecific Active Centers in a Model Catalyst System Ti(Oi-C3H7)4–Al(C2H5)2Cl/Mg(C4H9)2 Modified with 2,6-Dimethyl Pyridine

The article describes a modifying effect of 2,6-dimethyl pyridine (lutidine) in propylene polymerization reactions with a pseudo-homogeneous catalyst system Ti(Oi-C3H7)4–Al(C2H5)2Cl/Mg(C4H9)2. This catalyst system is a convenient model for the analysis of modifier effects (effects of “external donors”) in supported Ziegler–Natta polymerization catalysts. A combination of IR, 13C NMR and GPC data for polypropylene prepared with this catalyst in the presence of 2,6-dimethyl pyridine shows that the modifier converts a part of stereo-aspecific active centers (the centers producing atactic polypropylene), into syndiospecific centers.