The copper (I)-catalyzed azide-alkyne cycloaddition click reaction was successfully applied to prepare well-defined 3, 6, and 12-arms polystyrene and polyethylene glycol stars. This study focused particularly on making perfect star polymers with an exact number of arms, as well as developing techniques for their purification. Various methods of characterization confirmed the star polymers high purity, and the structural uniformity of the generated star polymers. In particular, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry revealed the quantitative transformation of the end groups on the linear polymer precursors and confirmed their quantitative coupling to the dendritic cores to yield star polymers with an exact number of arms. In addition to preparing well-defined polystyrene and poly(ethylene glycol)homopolymer stars, this technique was also successfully applied to amphiphilic, PCL-b-PEG star polymers. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012