Ionically conductive thin polymer films prepared by plasma polymerization; Preparation and characterization of ultrathin films having fixed sulfonic acid groups with only one mobile species

Ultrathin solid polymer electrolyte membranes containing sulfonic ester groups were prepared by polymerization of methyl benzenesulfonate and octamethylcyclotetrasiloxane in a glow discharge plasma. The sulfonic ester groups of the plasma polymer were transformed to lithium sulfonate groups by treatment with lithium iodide. Hybridization of this plasma polymer containing the lithium sulfonate groups with poly(ethylene oxide) (average Mw 300) resulted in the formation of a single lithium ion conductive film. The hybrid polymer electrolyte films were about 1 {mu}m thick, pinhole-free, adherent to various substrates, and showed ionic conductivities at 60{degrees}C of the order of 10{sup {minus} 6} S cm{sup {minus} 1} (10{sup 2} {Omega} cm{sup 2} resistance per unit area of as-prepared solid polymer electrolyte). This material shows promise for electrochemical applications such as all solid-state lithium batteries, sensors, and electrochemical display devices.