CONDUCTIVITY AND DIELECTRIC-CONSTANT OF PPO AND PPO-BASED SOLID ELECTROLYTES FROM DC TO 6 GHZ

The conductivity and dielectric response of poly(propylene oxide) (PPO) and the polymeric solid electrolytes (PPO)(8)NH4CF3SO3, (PPO)(16)NaI, (PPO)(10)NaI, and (PPO)(8)NaI were studied in the frequency range from dc to 6 GHz and the temperature range from 173 to 323 K with the objective of elucidating the dynamic factors that affect ion transport in polyether electrolytes. The temperature dependencies of the primary alpha-relaxation of PPO and the dc electrical conductivity of the salt complexes are consistent with this relaxation playing a key role in ionic conduction in polymer electrolytes. For the salt complexes, the alpha-relaxation appears to be shifted to lower frequencies relative to pure PPO, and this is attributed to virtual cross-linking. High-frequency room temperature measurements permit for direct comparison of the dielectric properties of (PPO)(8)NH4CF3SO3 with a supercooled amorphous (PEO)(8)NH4CF3SO3 complex. A dissimilarity between optical dielectric constants and those measured at approximately 3 GHz for the salt complexes suggests the presence of a high-frequency ionic relaxation as predicted by the dynamic bond percolation model. The relative influence of segmental mobility and ion-ion interactions on the dc conductivity of polymer salt complexes is discussed.