Ethylene/α-olefin copolymerization by nonbridged (cyclopentadienyl) (aryloxy)titanium(IV) dichloride/AliBu_3/Ph _3CB(C_6F_5)_4 catalyst systems

摘要

A series of nonbridged (cyclopentadienyl) (aryloxy)titanium(IV) complexes of the type, (η~5-Cp′)(OAr)TiCl_2 [OAr = O-2,4,6-tBu_3C_6H_2 and Cp′ = Me_5C_5 (1), Me_4PhC_5 (2), and 1,2-Ph2-4-MeC_5H_2 (3)], were prepared and used for the copolymerization of ethylene with α-olefins (e.g., 1-hexene, 1-octene, and 1-octadecene) in presence of AliBu_3 and Ph_3CB(C_6F_5)_4 (TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was examined. The substituents on the cyclopentadienyl group of the ligand in 1-3 play an important role in the catalytic activity and comonomer incorporation. The 1/TIBA/B catalyst system exhibits the highest catalytic activity, while the 3/TIBA/B catalyst system yields copolymers with the highest comonomer incorporation under the same conditions. The reactivity ratio product values are smaller than those by ordinary metallocene type, which indicates that the copolymerization of ethylene with 1-hexene, 1-octene, and 1-octadecene by the 1-3/TIBA/B catalyst systems does not proceed in a random manner.