Magnetic-Field-Induced Liquid Phase Transformation of an Ionic Liquid N,N,N-Trimethyl-N-propylammonium Bis(trifluoromethanesulfonyl)imide

An ionic liquid, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA TFSI), was transformed from a liquid phase to another fluidic phase by application of the threshold magnetic field at constant temperature (T). The magnetic-field-induced (MFI) phase transformation was detected by the electric potential generated between two Pt electrodes set to the bottom and upper parts in a TMPA TFSI liquid during sweep of the magnetic field (B). The magnetic susceptibility and Verdet constant of TMPA TFSI also were slightly changed over 3 T. The MFI phase formation was almost completed within 3 h after TMPA TFSI liquid was exposed to a 6 T magnetic field, as demonstrated by the melting behavior of TMPA TFSI solid frozen instantaneously under 6 T. Multivariate analysis of the Raman spectra suggested that the MFI transformation should be associated with the conformational change of the transoid-to-cisoidlike species of TFSI ions. A B-T phase diagram of TMPA TFSI is proposed.