Copolymerization of ethylene with 1-octene and 1-octadecene using constrained geometry catalysts 2(3,4-diphenylcyclopentadienyl)-4,6-di-tert-butylphenoxytita- nium dichloride (1), 2-(3,4-diphenylcyclopentadienyl)-6tert-butylphenoxytitanium dichloride (2), 2-(3,4-diphenylcyclopentadienyl)-6-methylphenoxytitanium dichloride (3), and 2-(3,4-diphenylcyclopentadienyl)-6-phenylphenoxytitanium dichloride (4) was studied in the presence of Al(Bu-i)(3) and [Ph3C][B(C6F5)(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 also examined. The 1/TIBA/B catalyst system exhibits high catalytic activity and produces high molecular weight copolymers. The melting temperature and the degree of crystallinity of the copolymers show a decrease with the increase in the comonomer incorporation. (c) 2008 Wiley Periodicals, Inc.