Dimethyl siloxane bisphenol-A polycarbonate block polymer was evaluated for its ability to dissociate lithium salts within a single-phase polymer matrix so as to invoke lithium ion conductivity. This strategy exploits the idea that carbonate oxygen, within a single-phase carbonate-siloxane polymer matrix, will facilitate extensive ionic dissociation of introduced lithium salts, and that furthermore elastomeric behavior of the matrix under ambient temperature conditions will lead to enhanced mobility of lithium ions. Since solvating capacity of the polymer matrix is dependent upon the presence of oxygen in a flexible molecular group dimethyl siloxane bisphenol-A polycarbonate was chosen because it contains a carbonate oxygen within the polymer matrix and is a flexible polymer when cured. Ionic conductivities similar to those reported for polyethylene oxide were observed due to the inclusion of a plasticizer solvent and lithium salt into the dimethyl siloxane bisphenol-A polycarbonate matrix. (C) 2000 Elsevier Science Ltd. All rights reserved.