Thermophysical Properties of Binary Amide Anion-Based Ionic Liquids; TMPAFSA<i>_x</i>TFSA₁₋<i>_x</i>

Abstract

An ionic liquid system based on two amide anions; bis(fluorosulfonyl)amide anion (FSA − ) and bis(trifluoromethanesulfonyl)amide anion (TFSA − ), with a quaternary ammonium cation; N,N,N-trimethyl-N-propylammonium cation (TMPA + ), was investigated over entire composition range. The system showed the binary phase diagram and the eutectic point was 5.5°C around the anion ratio of 1:2 (FSA − : TFSA − ). Polymorphic behavior of solidified ionic liquid was observed by X-ray diffraction (XRD) and discussed comparing with ionic liquids composed of other anion; (fluorosulfonyl) (trifluoromethylslufonyl)amide anion (FTA − ) or tetrafluoroborate anion (BF 4 − ). In addition, the phase diagram of the ionic liquid system containing lithium cation with binary anion was confirmed. Raman spectroscopy suggested that lithium cation interacts more preferentially with TFSA − than FSA − .