Copolymerization of ethylene with 1-hexene, 1-octene and 1-decene catalyzed by [1.8-C10H6(NR)(2)]TiCl2 [R = (SiBuMe2)-Bu-t (1)] and [ArN(CH2)(3)NAr]TiCl2 [Ar = 2,6-(Pr2C6H3)-Pr-i (2)] complexes-MMAO (MMAO = methyl isobutyl aluminoxane) catalyst systems have been explored. It was revealed that alpha-olefin contents in the resultant copolymer are highly dependent upon catalyst complex used. The resultant copolymer with 1 gave relatively broad molecular weight distributions, consisting of high and low molecular weight copolymers. On the other hand, it was difficult to prepare high molecular weight (M-w > 100, 000) copolymer with low alpha-olefin content if complex 2 was employed as the catalyst component. The resultant copolymers prepared by both 1 and 2 have been analyzed by DSC, C-13 NMR, and CFC (cross-fractionation chromatography). The design of catalyst structure as well as ligands is thus necessary to prepare the desired ethylene/alpha-olefin copolymers by non-metallocene type catalyst. (C) 2000 Elsevier Science Ltd. All rights reserved.