Materials with high anhydrous proton conduction at intermediate temperatures (100-200 1C) have attracted remarkable interest for applications in a polymer electrolyte membrane fuel cell (PEMFC). Especially, for the development of PEMFC technology, an anhydrous proton-conductive material, which is low cost and benign for the environment, has been desired. In this study, an anhydrous proton conductor was prepared by mixing double-stranded DNA (dsDNA), the most important genetic material of living organisms, and the imidazole (Im) molecule, a heterocyclic molecule. This DNA-Im composite material showed a thermal stability owing to electrostatic interaction between the phosphate group of DNA and ÀN¼ group of the Im molecule. In addition, DNA-Im showed an anhydrous proton conduction of 5.2Â10 À3 S cm À1 at intermediate temperature. On the other hand, the single-stranded DNA-Im composite material did not show high anhydrous proton conduction. Therefore, the high anhydrous proton conduction in dsDNA-Im composite material was due to the arrangement of phosphate groups along the one-dimensional molecular chain. These results suggested that the DNA-Im composite material possesses two proton-conducting pathways in the composite material.

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