Synthesis and Physicochemical Properties of Amino Acid Ionic Liquid 1-Butyl-3-methylimidazolium Aspartate and Binary Mixture with Methanol

An amino acid based ionic liquid [Bmim][Asp], 1-butyl-3-methylimidazolium aspartate, and a binary mixture system composed of [Bmim][Asp] and methanol were synthesized and prepared, respectively. The density, surface tension, and electrical conductivity of the pure IL and the binary system were measured or estimated by the extrapolation method at different temperatures. The physicochemical properties of the IL or the binary system like the molecular volume, standard molar entropy, lattice energy, parachor, speed of sound, molar enthalpy of vaporization, interstice volume, thermal expansion coefficient, excess volume, and so forth were estimated by empirical and semiempirical equations. The glass transition temperature was determined by the differential scanning calorimetry (DSC). The status of intermolecular interaction based on the excess volume change of the IL mixture was discussed at 298.15 K. By Vogel-Fulcher-Tamman (VFT) and Castell-Amis (CA) equations, the relationship between the electrical conductivity and temperature or concentration of the IL and binary system were described, respectively. The results indicate that the VFT and CA equations are fit for the IL and the mixture, respectively, and the change of methanol concentration can obviously influence the electrical conductivity of the binary IL mixture.