Synthesis, polymerization and cation conductive properties of (ω‐carboxy)‐oligo(oxyethylene) methacrylate

Alkali‐metal salts of (ω‐carboxy)oligo(oxyethylene) methacrylate (CME₁₂M, M = Li or Cs) have been synthesized and polymerized to prepare solid polymer electrolytes. These types of solid polymer electgrolytes provide a homogeneous phase, since these polymers have a flexible main chain, an oligo(oxyethylene) side chain for ion conduction, and a carrier ion source in one repeating unit. The AC conductivity of P(CME₁₂Li) homopolymer is 8.9 × 10⁻⁹ S cm⁻¹ at 30°C, while that of P(CME₁₂Cs) is 3.3 × 10⁻⁶ S cm⁻¹ at 30°C, which is the highest value among single ion conductors, have been reported as polyelectrolyte “homopolymer” without any additives. High ionic conduction of P(CME₁₂Cs) is due to low glass transition temperature (T_g = −54°C) and weaker ion–ion and ion–dipole interaction of Cs⁺ than that of Li⁺.