Starlike polystyrenes composed of a microgel core and arms terminated with benzophenone groups were used as organic supports for a tridentate bis(imino)-pyridinyliron catalyst for ethylene polymerization in the presence of trimethylaluminum as a cocatalyst. The microgels were synthesized by the atom transfer radical polymerization of styrene initiated by 4-(1-bromoethyl)-benzophenone, with divinyl-benzene as the crosslinker. The bromine polystyrene chain ends prevented the ethylene polymerization reaction and bad to be removed. This was readily achieved with Cu-0 together with dodecanethiol as a transfer agent. When used as supports in the presence of trimethylaluminum and 2,6-bis[1-2,6(diisopropylphenyl)imino]ethylpyridynyl iron, these bromine-free, functionalized. polystyrene stars enabled the production of polyethylene beads of a spherical morphology and high bulk density with a catalytic activity similar to that under homogeneous reaction conditions. Moreover, the molar mass distribution of the polyethylene was narrow, suggesting limited transfer to trimethylaluminum. (c) 2006 Wiley Periodicals, Inc.