Supporting effect of methylaluminoxane on propene polymerization with monocyclopentadienylalkyltitanium derivatives Original Research Article

Propene polymerization was carried out by Cp∗Ti(CH2Ph)3, [t-BuNSiMe2(C5Me4)]TiMe2 and [t-BuNSiMe2Flu]TiMe2 combined with dried or SiO2-supported methylaluminoxane (MAO). The dried MAO system generally showed higher activity and gave higher molecular weight polypropenes than the SiO2-supported MAO system. The decrease in the activity by changing the cocatalyst from dried MAO to SiO2-supported MAO was, however, more significant in the cases of [t-BuNSiMe2(C5Me4)]TiMe2 and [t-BuNSiMe2Flu]TiMe2. The molecular weight distribution of the produced polymers indicated that uniform active species were formed from Cp∗Ti(CH2Ph)3 regardless of the cocatalyst employed while the active species derived from [t-BuNSiMe2(C5Me4)]TiMe2 and [t-BuNSiMe2Flu]TiMe2 combined with SiO2-supported MAO were inhomogeneous. The microstructure of the produced polymers were independent of the cocatalyst used, and [t-BuNSiMe2Flu]TiMe2 catalysts produced syndiotactic polypropenes with less regioirregular structure. The Cp∗Ti(CH2Ph)3/SiO2-supported MAO system showed a steady polymerization rate with frequent chain transfer at 0 °C while the [t-BuNSiMe2(C5Me4)]TiMe2/SiO2-supported MAO system produced the polypropenes with long chain lifetime accompanied by slow deactivation at 0 °C.