Star polystyrene-b-hyperbranched polyglycidol: Synthesis and ionic conductivity

Abstract

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· OEt2 as the catalyst. The chemical structures of these block copolymers were characterized by using 1H and 13C 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 Tg of HPG segments at low concentrations, however, decreased the Tg at high concentrations. The Tg 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. © 2008 Wiley Periodicals, Inc.