Paving the way to solubility through volatility: Thermodynamics of imidazolium-based ionic liquids of the type [CnC1Im][I

Abstract

Ionic liquids are effectively used for manufacturing of nanoparticles for thermoelectric generators and in the field of hydrogen storage. Development and optimization of these processes require knowledge of the thermodynamic properties of ionic liquids. Thermochemical study of the series of 1-alkyl-3-methylimidazolium iodides is presented in this work. Vapor pressures and vaporization enthalpies have been measured by using quartz-crystal microbalance. Solution enthalpies were measured by using solution calorimetry. Thermodynamics of aqueous solutions, solubility parameters and miscibility of ILs in eleven organic solvents were derived and discussed. The absence of thermal decomposition of [C4C1Im][I] under vaporization conditions has been demonstrated experimentally and theoretically. It has been shown that vaporization enthalpies are linearly dependent on the chain length of the alkyl substituent and linearly dependent on the surface tension. Aqueous-phase enthalpies of formation of alkyl imidazolium cations have been derived with help of solution calorimetry.