DESIGN OF ALKALINE METAL-ION CONDUCTING POLYMER ELECTROLYTES

Polysiloxanes with covalently attached oligo ethylene oxide and di-t-b utylphenol (1), naphthol (II), and hexafluoropropanol (III) were synth esized. The crosslinked polymers with a hexamethylene spacer were also prepared. The ion conductivities of the Li, Na, and K salts were meas ured as a function of temperature. The highest conductivities for K an d Na of I at 30-degrees-C were 5.5 X 10(-5) and 5.0 X 10(-5) S/cm, res pectively, when the ratio of the ion to ethylene oxide unit was 0.014. On the other hand, Li conductivity was 8.0 x 10(-6) S/cm when the rat io between Li and ethylene oxide unit was 0.019. The maximum conductiv ities of Li ions of II and III were in the order of 10(-6) and 10(-7) S/cm at 30-degrees-C, respectively. When the polymers were crosslinked by a hexamethylene residue, the ion conductivities decreased while th e degree of crosslinking increased. The temperature dependence of the cation conductivities of these systems could be described by the Willi ams-Landel-Ferry (WLF) and the Vogel-Tammann-Fulcher (VTF) equation. T he results demonstrate that ion movement in these polymers is correlat ed with the polymer segmental motion. The order of ionic conductivity was K+ > Na+ much greater than Li+. This suggests that steric hindranc e and pi-electron delocalization of the anions attached to polymer bac kbone have a large effect on ion-pair separation and their ionic condu ctivities. Thermogravimetric analysis of the polymers indicated that t he degradation temperature for I and II were about 100-degrees-C highe r than for poly(siloxane-g-ethylene oxide). This is due to the antioxi dant properties of sterically hindered phenols and naphthols. (C) 1993 John Wiley & Sons, Inc.