Poly(methyl methacrylate)-b-polystyrene (PMMA-b-PS) containing a benzo-15-crown-5 unit at the junction point was prepared by combining atom transfer radical polymerization and nitroxide-mediated radical polymerization. For this purpose, 6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxa-benzocyclopentadece ne-2-carboxylic acid 3-(2-bromo-2-methyl-propionyloxy)-2-methyl-2-[2-phenyl-2-(2,2,6,6-tetram ethylpiperidin-1-yloxy)-ethoxycarbonyll-propyl ester (3) was synthesized and used as an initiator in atom transfer radical polymerization of methyl methacrylate in the presence of CuCl and pentamethyldiethylenetriamine at 60 degrees C. A linear behavior was observed in both plots of ln([M](0)/[MI]) versus time and M-N,M-GPC versus conversion indicating that the polymerization proceeded in a controlled/living manner. Thus obtained PMMA precursor was used as a macroinitiator in nitroxide-mediated radical polymerization of styrene (St) at 125 degrees C to give well-defined PMMA-b-PS with crown ether per chain. Kinetic data were also obtained for copolymerization. Moreover, potassium picrate (K+ picrate) complexation of 3 and PMMA-b-PS copolymer was studied.