In this work, ethylene-1-hexene copolymers were synthesized with a tandem catalysis system that consisted of a new trimerization catalyst bis(2-dodecylsulfanyl-ethyl) amine-CrCl3/MAO (1/MAO) and copolymerization catalyst Et(Ind)(2)ZrCl2/ MAO (2/MAO) at atmosphere pressure. Catalyst 1 trimerized ethylene with high activity and excellent selectivity in the presence of a relatively low amount of MAO. Catalyst 2 incorporated the 1-hexene content and produced ethylene-1-hexene copolymer from an ethylene-only stock in the same reactor. Adjusting the Cr/Zr ratio and reaction temperature yielded various branching densities and thus melting temperatures. However, broad DSC curves were observed when low temperatures and/or high Cr/Zr ratios were employed due to an accumulation of 1-hexene component and composition drifting during the copolymerization. It was found that a short pretrimerization period resulted in more homogeneous materials that gave unimodal DSC curves. (C) 2007 Wiley Periodicals, Inc.