STRUCTURE OF THE POLY(ETHYLENE OXIDE) SODIUM-PERCHLORATE COMPLEX PEO3-NACLO4 FROM POWDER X-RAY-DIFFRACTION DATA

The crystal structure of the poly(ethylene oxide)-sodium perchlorate complex has been refined by the Rietweld method, using soft chemical constraints, from powder X-ray diffraction data. PEO3-NaClO4 crystallises in the monoclinic system, space group P2(1)/a, a = 18.319(1) angstrom, b = 8.3459(6) angstrom, c = 8.5784(7) angstrom, beta = 123.14(1)-degrees, Z = 4. The complex is isomorphous with the PEO3-Nal complex, and is composed of a helical polymer chain wrapped around the alkali-metal cation. Perchlorate ions associate with the Na+ ions in a zig-zag manner, resulting in five-fold co-ordination around the Na+, comprising three oxygens from the polymer chain and one each from the surrounding perchlorate ions. This is the first example of the full structural characterisation of a polymer electrolyte complex by powder diffraction methods, and demonstrates that this should become a powerful technique in the understanding of the structure-property relationships of these materials.