Structure of the poly(ethylene oxide)–sodium perchlorate complex PEO3–NaClO4 from powder X-ray diffraction data

Abstract

The crystal structure of the poly(ethylene oxide)–sodium perchlorate complex has been refined by the Rietveld method, using soft chemical constraints, from powder X-ray diffraction data. PEO₃–NaClO₄ crystallises in the monoclinic system, space group P2₁/a, a= 18.319(1)Å. b= 8.3459(6)Å, c= 8.5784(7)Å, β= 123.14(1)°, Z= 4. The complex is isomorphous with the PEO₃–NaI 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.