IONIC-CONDUCTION OF LITHIUM AND MAGNESIUM SALTS WITHIN LAMINAR ARRAYSIN A SMECTIC LIQUID-CRYSTAL POLYMER ELECTROLYTE

Three polymers having the structure shown below where R = -C16H33 or - C12H25 and n = 5 or 6 (coded C16O5, C16O6 and C12O6), have been synthe sised and their complexes with LiClO4, LiBF4, LiCF3SO3 LiBr and Mg(ClO 4)(2) have been prepared. [GRAPHICS] Using thermal analysis, polarised light microscopy, small-angle (SAXS) and wide-angle X-ray scattering techniques (WAXS) techniques and energy-minimised modelling it is show n that the complexes having greater than or equal to 0.5 mol salt per polymer repeating unit form smectic liquid-crystal structures above th e side-chain melting temperatures [e.g. 43.5 degrees C for C16O5-LiClO 4 (1:1)]. The salt is complexed to the two-dimensional helical polyeth er backbone layers which are separated by hydrocarbon layers. In contr ast to expectation from conventional polymer electrolyte behaviour, th e ionic conductivities of the lithium salt complexes in the liquid-cry stal phases are greatest for systems having the most extensive two-dim ensional organisation and follow the sequence C16O5 > C16O6 > C12O6. M g(ClO4)(2) complexes with C16O5 and C16O6 are similarly organised in t wo dimensions. The results suggests that ionic mobility is most extens ive within the plane of the polyether layers and there is no evidence for 'tunnelling' through the hydrocarbon material.