Ionic conductivity structure property relationship in gel electrolytes on the basis of oligo(ethyleneglycol)23 dimethacrylate plasticized with oligo(ethyleneglycol)11 dimethyl ether

This paper reports dielectric spectroscopic studies completed by electrochemical measurements in combination with DSC and PFG-NMR investigations to study the charge carrier transport in gel electrolytes, which were prepared by photoinitiated polymerization of oligo(ethylene glycol)(23) dimethacrylate [(EG)(23)DMA] in the presence of oligo(ethylene glycol)(11)dimethyl ether [(EG)(11)DME] as plasticizer and LiCF3SO3. The resulting films show a glass transition at about -60 degrees C and the melting of the plasticizer around -12 degrees C. Below the glass transition two relaxation processes were observed by dielectric spectroscopy, which most likely are to be related to the gamma relaxation of the EG groups and the beta relaxation of the methacrylate groups. The high-temperature behavior of the dielectric response is dominated by the conductivity, which is weakly dependent on the frequency in this temperature range. The permittivity goes through a maximum at room temperature and decreases with further enhancement of the temperature in connection with an increase in ionic aggregation indicated by growing deviations from the Nernst-Einstein relationship. These deviations expressed as a Haven ratio are discussed as the contribution of bounded species that do not take part in the conductivity to the overall diffusivity, either by an enlarged content of these species, C-b, Or by an enhancement of their self-diffusivity, D-b.