In this work, novel star-hyperbranched block copolymers containing four polystyrene arms and hyperbranched polyglycidol at the end of each arm (SPS-b-HPG) have been synthesized. The polystyrene arms were prepared through atom transfer radical polymerization of styrene starting from a four-arm initiator. The hydroxyl-terminated PS star polymers served as precursors for the cationic ring-opening polymerization of glycidol using BF3 center dot OEt2 as the catalyst. The chemical structures of these block copolymers were characterized by using H-1 and C-13 NMR. DSC analysis indicated that the star-hyperbranched block copolymers exhibited two distinct glass transition temperatures corresponding to the linear PS and the HPG segments, respectively. The addition of LiClO4 increased the T-g of HPG segments at low concentrations, however, decreased the T-g at high concentrations. The T-g of PS segments was not affected by the addition of salts at all. Furthermore, the interaction of sPS-b-HPG with LiBr was studied by using viscosity analysis based on the Jones-Dole equation. The star-like PS core strengthened the interaction of sPS-b-HPG with Li ions that could facile the inhomogeneous distribution of Li cations and anions in different phases, which is important in polymeric electrolytes for lithium chemical power sources. The ionic conductivity of one sPS-b-HPG/LiClO4 electrolyte was measured to be higher than that of HPG/LiClO4 electrolyte. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 949-958, 2009