Metallocene systems in propylene polymerization: Effect of triisobutylaluminum and lewis bases on the behavior of catalysts and properties of polymers

For two stereospecific metallocene catalysts, namely, syndiospecific Ph₂CCpFluHfMe₂ and isospecific rac-Me₂SiInd₂ZrMe₂, the introduction of Lewis bases into a reaction medium was shown to promote a marked rise in the efficiency of catalytic systems. In the case of the syndiospecific metallocene, the maximum effect of the base (a 10-fold increase in activity) was achieved using the (Ph₂CCpFluHfMe₂ + Ph₃N)/CPh₃B(C₆F₅)₄ catalytic system in the presence of Al-i-Bu₃ at a molar ratio of Al: Hf: B: N = 15: 1: 1: 1. When the polymerization of propylene was carried out in the presence of Al-i-Bu₃ and Ph₃N, an elastomeric stereoblock syndio/atactic polypropylene was produced. For the (rac-Me₂SiInd₂ZrMe₂ + amine)/CPh₃B(C₆F₅)₄ catalytic system, a 15-to 30-fold increase in activity was observed upon introduction of amines of the aniline type: Me₂NPh, Me-n-BuNPh, and NPh₃.