Fluorene end-labeled polystyrene was prepared by atom transfer radical polymerization with 9-bromofluorene as the initiator. Reactions were carried out in bulk or tetrahydrofuran solutions at temperatures of 80 degrees C or above. Analysis by gel permeation chromatography indicated that the polymers formed had low polydispersities with molecular weights consistently 2-5 times higher than calculated based on monomer-to-initiator ratios. Coupling of two fluorenyl radicals, formed by activation of the 9-bromofluorene, was found to compete with initiation, leading to the higher-than-expected molecular weight values while giving rise to a fluorene dimer. UV-vis spectrometry indicated near-quantitative fluorene labeling of the polystyrene. (c) 2005 Wiley Periodicals, Inc.