Star polymers composed of a hyperbranched poly(arylene oxindole) (PArOx) core and arms of different length formed by poly[di(ethylene glycol) methyl ether methacrylate] (PDEGMA) or copolymer poly [di(ethylene glycol) methyl ether methacrylate-ran-oligo(ethylene glycol) methyl ether methacrylate] P(DEGMA-ran-OEGMA) were obtained via atom transfer radical polymerization. The stars obtained were thermoresponsive. The cloud point temperatures (T-cp) depended upon the composition of the arms and the concentration of stars in solution. Comparison of the sizes determined using light scattering techniques in acetone and water below T-cp confirmed that the stars existed in water as isolated macromolecules. The unimolecular structure of the stars below T-cp was proved by AFM and cryo-TEM. Above T-cp, a significant increase in particle size with the concentration was observed. Encapsulation of a hydrophobic dye in stars was studied by UV-VIS and fluorescence spectroscopy. The results indicate that stars obtained are prospective carriers for biomolecules. (C) 2012 Elsevier Ltd. All rights reserved.