Water content and related physical properties of aliphatic quaternary ammonium imide-type ionic liquid containing metal ions

Takuma Katase, Susumu Imashuku, Kuniaki Murase, Tetsuji Hirato, Yasuhiro Awakura

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

The ionic liquid, trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA-Tf2N), has a wide electrochemical window of more than 5 V and is considered to be hydrophobic because of two -CF3 groups in its Tf2N- anion. However, a small amount of water remains in the ionic liquid even after dehydration in vacuo, which causes some problems in metal electrodeposition when using the ionic liquid as a solvent. We measured the water content of the ionic liquids, TMHA-Tf2N containing M(Tf2N)n (M=H, Li, Mg, Ni, Cu, Zn, La, and Dy; n=1, 2, or 3), as well as their kinematic viscosity and electrical conductivity in the temperature range of 25-130 °C. Furthermore, differential scanning calorimetry was performed for these ionic liquids to find their glass transition temperature, crystallization temperature, and melting temperature. The water content of TMHA-Tf2N containing M(Tf2N)n salts decreased with an increase in temperature. At the same time, the kinematic viscosity decreased and the electrical conductivity increased. By measuring the optical absorption spectrum, it was found that the metal ions in TMHA-Tf2N were hydrated. The addition of M(Tf2N)n to TMHA-Tf2N, increased the water content at a constant temperature, which resulted in slight increases in the kinematic viscosity and decrease in the electrical conductivity. A Walden-like plot of the electrical conductivities against the kinematic viscosities, measured over various temperatures and water contents, gave a single straight line.

Original languageEnglish
Pages (from-to)502-510
Number of pages9
JournalScience and Technology of Advanced Materials
Volume7
Issue number6
DOIs
Publication statusPublished - 2006 Sep

Keywords

  • Conductivity
  • Residual water
  • Room temperature molten salt
  • Thermal property
  • Viscosity

ASJC Scopus subject areas

  • Materials Science(all)

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