Gel electrolyte films were prepared by a redox initiated copolymerization of oligo(ethylene glycol)(23) dimethacrylate and acrylonitrile in the presence of oligo(ethylene glycol)(11) dimethyl ether as a plasticizer and LiCF3SO3. The influence of the polar comonomer acrylonitrile on the conductivity and the cationic transference number was investigated. The materials show conductivities between 10(-4) and 10(-5) S cm and transference numbers in the range of 0.5 at room temperature. Pulsed field gradient-NMR (PFG-NMR) measurements were carried out to determine the diffusion coefficients of the plasticizer by(1)H-NMR and of LiCF3SO3 by F-19-NMR.