VTF TO ARRHENIUS CROSSOVER IN TEMPERATURE-DEPENDENCE OF CONDUCTIVITY IN (PEG)(X)NH4CLO4 POLYMER ELECTROLYTE

We have studied the temperature variation of conductivity and H-1 NMR linewidth of (PEG)(x)NH4ClO4 (x = 20, 30, 46, 100, 200, & 1000) polyme r electrolyte systems. The temperature dependence of the conductivity shows two distinct behaviors, the low temperature VTF dependence cross ing over to Arrhenius dependence at higher temperatures. The departure from the VTF behavior is found to be composition dependent. NMR spect ra indicate the presence of large fractions of crystalline regions tha t start to melt around the crossover temperature. We understand the de viation from the VTF behavior as a consequence of this crystalline to elastomer transition. (C) 1998 John Wiley & Sons, Inc.