Polymer compatibility, phase separation and high ambient conductivity in low — dimensional polymer electrolyte blends with lithium salts

AC and DC conductivities of complexes of Li salts with the amphiphilic helical polyether poly2,5,8,11,14-pentaoxapentadecamethylene(5-hexadecyloxy-1,3-phenylene)] (I) (Type A complexes) and blends of I with copolymers of poly(tetramethylene oxide) oligomer coupled with either — (CH₂-)- (polymer IIC1) or — (CH₂)₁₂ — (IIC12) (Type C complexes) are reported. Whereas Type A complexes give reversible AC impedance plots log σ vs. 1/T plots which are ca. 10⁻⁷ S cm⁻¹ at ambient, the Type C blends rise to ca. 10⁻³ S cm⁻¹ at 100 °C and on cooling to ambient maintain this high level. In Type C systems with IIC12 this transformation is stable and permanent. Optical microscopy reveals phase separation of extensive well-organised lamellae of the Type A phase from the Type C blend following heating. Polymer II resides in thin layers in the interlamellar spaces serving to transfer ions between them. DC data at ambient temperatures for Li | I : II : Li salt | Li cells indicate conductivities 10⁻³ to 10⁻² S cm⁻¹ over extended periods (24 hours). Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.