Polymer compatibility, phase separation and high ambient conductivity in low — dimensional polymer electrolyte blends with lithium salts
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AC and DC conductivities of complexes of Li salts with the amphiphilic helical polyether poly[2,5,8,11,14-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).
KeywordsPhase Separation Polymer Electrolyte Tetramethylene Lithium Salt Impedance Plot
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