Ionic Conductivity and Dielectric Properties of Poly(ethylene oxide) Graft Copolymers End-capped with Sulfonic Acid

Both anions and cations are mobile and carry the electrical charge in most polymer electrolytes. A single ion conductor with purely cationic conduction can be realized by incorporation of the anion into the polymer chain. In order to obtain pure lithium ion conductors we prepared two types of graft copolymers, namely poly(amide 12-graft-ethylene oxide) and poly(ethylene-co-vinyl alcohol-gr aft-ethylene oxide), respectively, and end-capped the poly(ethylene oxide) grafts with sulfonic acid groups. Lithium salts of the graft copolymers were made by neutralizing the sulfonic acid groups with lithium hydroxide. Films of the neutralized polymers were prepared by solution casting. The thermal properties of the films were evaluated from DSC measurements. Complex impedance spectroscopy gave information on the ionic conductivity and dielectric relaxations. The highest conductivity, at 80 degrees C, 2*10(-5) S/cm was obtained for poly(amide 12-graft-ethylene oxide)