CONDUCTIVITY AND VISCOSITY OF LIQUID POLYMER ELECTROLYTES PLASTICIZED BY PROPYLENE CARBONATE AND TETRAHYDROFURAN

Viscosity and conductivity measurements were carried out on polymer electrolytes based on LiClO4 and two liquid polyethers, viz. a poly(tetrahydrofuran) sample and a copolymer of ethylene oxide and propylene oxide (50/50 by weight), of molecular weights 2000 and 1700 respectively. Addition of 10% by weight of the plasticizers tetrahydrofuran (THF) and propylene carbonate (PC) produced a decrease in viscosity and an increase in conductivity in both types of polymer electrolyte. However, the increase in molal conductivity (Λ) was relatively modest on addition of THF but was abnormally large for PC, especially at low salt concentrations (c). Also, with PC as plasticizer the frequently-observed maximum in the plot of Λ vs c 1 2 was absent and ionic motion appeared to be "decoupled" from that of the polymeric solvent. The results are interpreted on the basis that both solvents plasticize the polymer but PC, being the solvent of higher permittivity, also interacts strongly with the salt and reduces ion-pairing. © 1990.