Abstract
Our molecular design of the polymer solid electrolyte based on rubbery state of polymer is presented. Biocompatible segmented polyurethane elastomers with poly (oxyethylene)-poly(oxytetramethylene)-poly(oxyethylene) segments were used at first for the matrix of solid electrolyte. Next, oligomeric poly(oxyethylene) (PEO) chains were grafted to polysiloxane main chain to afford rubbery matrix for ion conduction when doped with lithium perchlorate. The latter showed higher conductivities than the former. However, the mechanical properties of the latter were poor, and its crosslinking resulted in the lower conductivity. Copolymer polymerized from ethylene oxide and epichlorohydrin was evaluated as a solid electrolyte. The epichlorohydrin units did not contribute to the ion conduction resulting in relatively low conductivities, though it was good in term of mechanical properties. Our final molecular design of the ion conductive matrix was the high molecular weight comb-shaped PEO with oxyethylene segments as side chains. Both main and side chains are oxyethylene units and the molecular weight was in the order of 106. The side oxyethylene units discouraged crystallization of PEO. Excellent conductivities were observed on doping with lithium salts.
