Preparation and ionic conductivity of composite polymer electrolytes based on hyperbranched star polymer

Abstract

Hyperbranched star polymer HBPS-(PPEGMA) x was synthesized by atom transfer radical polymerization (ATRP) using hyperbranched polystyrene (HBPS) as macroinitiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomer. The structure of the prepared hyperbranched star polymer was characterized by 1H NMR, ATR-FTIR, and GPC. Polymer electrolytes based on HBPS-(PPEGMA) x , lithium salt, and/or nano-TiO2 were prepared. The influences of lithium salt concentration and type, nano-TiO2 content, and size on ionic conductivity of the obtained polymer electrolytes were investigated. The results showed that the low crystallinity of the prepared polymer electrolyte was caused by the interaction between lithium salt and polymer. The addition of TiO2 into HBPS-(PPEGMA) x /LiTFSI improved the ionic conductivity at low temperature. The prepared composite polymer electrolyte showed the highest ionic conductivity of 9 × 10−5 S cm−1 at 30 °C when the content of TiO2 was 15 wt% and the size of TiO2 was 20 nm.