Thermodynamic properties and intermolecular interactions of ionic liquids [DEME][BF4] or [DEME][TFSI] and their binary mixture systems with GBL

Two novel ionic-liquid-based binary mixture systems of N,N-diethyl-N-(2-methoxyethyl)- N -methylammonium tetrafluoroborate ([DEME][BF 4 ]), or N,N-diethyl- N -methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([DEME][TFSI]) + γ-butyrolactone (GBL) are prepared over the whole concentration range (mole fraction from 0–1). Some important thermodynamic properties and parameters of the pure ILs and two systems were measured and calculated. The temperature dependences of the transport properties (viscosity and conductivity) were described by the Vogel–Fulcher–Tamman (VFT) equation. The excess molar volumes ( V   E ) were obtained from the experimental densities and fitted to Redlich–Kister (R–K) polynomial equation. The DSC analysis, the shifts of the infrared (IR) spectrum, and COSMO–RS methodology based on DFT calculations were combined to explain the interaction information of GBL molecules and cations/anions of the selected systems. The stable optimized structures, interaction energies, and charge distributions were further obtained. Those maybe slight enlighten the application of similar mixture systems in future.