Ethylene homopolymerization and ethylene/alpha-olefin copolymerization were carried out using unbridged and 2-alkyl substituted bis(indenyl)zirconium dichloride complexes such as (2-MeInd)(2)ZrCl2 and (2-BzInd)(2)ZrCl2. Various concentrations of 1-hexene, 1-dodecene, and 1-octadecene were used in order to find the effect of chain length of alpha-olefins on the copolymerization behavior. In ethylene homopolymerization, catalytic activity increased at higher polymerization temperature, and (2-MeInd)(2)ZrCl2 showed higher activity than (2-BzInd)(2)ZrCl2. The increase of catalytic activity with addition of comonomer (the synergistic effect) was not observed except in the case of ethylene/1-hexene copolymerization at 40 degrees C. The monomer reactivity ratios of ethylene increased with the decrease of polymerization temperature, while those of cu-olefin showed the reverse trend. The two catalysts showed similar copolymerization reactivity ratios. (2-MeInd)(2)ZrCl2 produced the copolymer with higher M-w than (2-BzInd)(2)ZrCl2. The melting temperature and the crystallinity decreased drastically with the increase of the alpha-olefin content but T-m as a function of weight fraction of the alpha-olefins showed similar decreasing behavior. (C) 2000 John Wiley & Sons, Inc.