Design of highly ion conductive polyether/salt hybrids

Abstract

Several kinds of charged groups, carboxylate, sulfonate, benzenesulfonate, sulfonamide, pyridinium, or triethylammonium groups were introduced to the terminal of poly(ethylene oxide) (PEO) oligomers to analyze the effect of the terminal charged structure on the bulk ionic conductivity. For cation conductors, the ionic conductivity increased with increasing the dissociation constant of the terminal group due to the increase in the number of carrier ions for the same MW of the PEO part. The glass transition temperature ( T g) of the matrices increased with decreasing the MW of the PEO part from 2000 to 200. Since the segmental motion of the matrix considerably affects the mobility of carrier ions, the ionic conductivity is a maximum when the T g of matrix is a minimum. The PEO/salt hybrids with larger cations showed higher ionic conductivity because of the decrease of surface charge density. PEO oligomers having pyridinium or triethylammonium group were prepared with various anions. In these anion conductors, the ionic conductivity showed less dependence on the MW of the PEO part than for cation conductors. Furthermore, the smaller anions showed higher ionic conductivity in contrast to the cation conductor. The interaction of the anions with the ether oxygen should be much weaker than that for the cations, and the phase condition of these PEO/salt hybrids is scarcely affected.