Higher alpha-olefin polymerizations catalyzed by rac-Me2Si(1-C5H2-2-CH3-4-Bu-t)(2)Zr(NMe2)(2)/Al(iBu)(3)/[Ph3C][B(C6F5)(4)]

Polymerizations of higher alpha-olefins, 1-pentene, 1-hexene, 1-octene, and 1-decene were carried out at 30 degrees C in toluene by using highly isosp ecific rac-Me2Si(1-C5H2-2-CH3-4-Bu-t)(2)Zr(NMe2)(2) (rac-1) compound in the presence of Al(iBu)(3)/[CPh3] [B(C6F5)(4)] as a cocatalyst formulation. Bo th the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the p i-ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly d ue to the steric hindrance. Highly isotactic poly(alpha-olefin)s of high mo lecular weight (MW) were produced. The MW decreased from polypropylene to p oly(1-hexene), and then increased from poly(1-hexene) to poly(1-decene). Th e isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1-pentene) > poly(1-hexene) > poly(1-octene ) > poly(1-decene). The similar dependence of the lateral size on the melti ng point of polymer was recorded by differential scanning calorimetry (DSC) . H-1 NMR analysis showed that vinylidene group resulting from beta-H elimi nation and saturated methyl groups resulting from chain transfer to cocatal yst are the main end groups of polymer chain. The vinylidene and internal d ouble bonds are also identified by Raman spectroscopy. (C) 2000 John Wiley & Sons, Inc.