A series of four arm stars with copolymer arms composed of poly(tert-butyl-glycidylether)-b-Polyglycidol were prepared using a multi-step process based on anionic ring-opening polymerization. Control of the length of the arms and the number of functional (hydroxyl) reactive groups was achieved by anionic polymerization. Stars with molar masses up to 12200 g/mol were prepared. The amphiphilic character of the star structure was varied using different polyglycidol block lengths. The star structure and molar mass of the obtained stars were characterized by SEC MALLS and NMR spectroscopy. The temperature behavior of an aqueous solution of the obtained polymers was also investigated. The phase transition temperature was strongly dependent on the hydrophilic hydrophobic balance of the star structure and varied in the range of 25-59 degrees C. As shown by DLS and SEM, the stars formed temperature-sensitive spherical aggregates in aqueous solution. The aggregates may be used for controlled transport and release of active compounds. (C) 2010 Elsevier Ltd. All rights reserved.