Synthesis and properties of heptadecane-functionalized poly(propylene oxide) based single-ion polymer electrolytes

Lithium methacrylate and heptadecane-functionalized poly(propylene oxide) (PPO) methacrylate based single-ion polymer electrolytes have been synthesized by radical copolymerization and neutralization. The thermal and electrical properties of the polymer electrolyte have been characterized by differential scanning calorimetry (DSC) and AC impedance spectroscopy, respectively. The results showed that the crystalline melting behavior of PPO segment was changed significantly by the presence of lithium ion due to the coordinative interaction and enhanced crystallinity. The ionic conductivity was 1.8 × 10−7 S cm−1 at 25 °C in the case of the lithium ion concentration of [PO]:[Li] = 30:1 due to the single-ion nature but its transference number reached roughly 1, indicating no migration of counter anions. Inspection with control sample suggested that the polymer electrolyte with ion conduction channel formed by a self-assembly is favored to realize relatively high ionic conductivity and decoupled lithium ion motion. The contact angle measurement onto the polymer electrolyte surface showed a strong hydrophobic wetting behavior due to the integrated hydrophobic nature of PPO and heptadecane alkyl chains.