Structurally Related Scaling Behavior in Ionic Systems
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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We examine the density scaling properties of two ionic materials, a classic aprotic low molecular weight ionic liquid, 1-butyl-3-methylimidazolium bisperfluoroethylsulfonylimide BMImBETI, and a polymeric ionic liquid, poly3-methyl-1,2,3-triazolium bistrifluoromethylsulfonylimide TPIL. Density scaling is known to apply rigorously to simple liquids lacking specific intermolecular associations such as hydrogen bonds. Previous work has found that ionic liquids conform to density scaling over limited ranges of temperature and pressure. In this work, we find that the dc-conductivity of BMImBETI accurately scales for density changes of 17 however, there is a departure from scaling for TPIL for even more modest variations of temperature and pressure. The entropy of both ionic samples conforms to density scaling only if the scaling exponent is allowed to vary linearly with magnitude of the entropy.