Effect of molecular weight of polymeric solvent on ion conductive behavior in poly(propylene oxide) solution of liclo4

Abstract

Ion conductive behavior of LiClO4 in poly(propylene oxide) (PPO) was studied. PPO solutions of LiClO4 had ionic conductivity of 10−4—10−6 S cm−1 at [LiClO4]/[PO unit]=0.01—0.1. The concentration dependence of conductivity showed a maximum at [LiClO4]/[PO unit]=0.04. The increase in the molecular weight of PPO lowered the conductivity. The viscosity of the electrolyte solution increased enormously with an increase in [LiClO4]/[PO unit], and was higher for higher molecular weight of PPO. The increase in viscosity results from solvation of the polar and flexible PPO main chain to LiClO4, which acts as transient crosslinking points between PO units. The equivalent conductance was influenced not only by the viscosity but also by the molecular weight of PPO. At low viscosity (<104 cP), the equivalent conductance decreased with an increase in the molecular weight of PPO. With an increase in viscosity (>104 cP), the dependence of the equivalent conductance on the molecular weight of PPO diminished. © 1983 The Society of Polymer Science, Japan.