Polymerization of propylene with tetrabenzylzirconium

Tetrabenzylzirconium (ZrBz4) was synthesized and used as catalyst for the polymerization of propylene in toluene in the temperature range from 0°C to 65°C. The isotacticity of the produced polymer was analysed (by IR and NMR spectroscopy) as well as the molecular weight distribution (by gel permeation chromatography). No colloidal particles could be usually observed after the polymerization, but both the isotacticity and the Q value (Mw/Mn) calculated from the molecular weight distribution curve increased with increasing polymerization period. The Q value was estimated always far greater than 2, which would be obtained in the case of homogeneous polymerization. From these results, it was concluded that isotactic polymer derives from polymerization on small (invisible) colloidal particles formed by decomposition of ZrBz4 during the course of polymerization.