Volumetric, ultrasonic and spectroscopic (FT-IR) studies for the binary mixtures of imidazolium based ILs with 1,2-propanediol

• Macroscopic and molecular level interactions of imidazolium ionic liquids in alkoxyalkanols have been determined.
• VmE is positive over the whole composition range for all the investigated mixtures.
• ΔκSΔκS is positive at higher and negative at lower concentration of ionic liquid.
• Hydroxyl group interactions are prevailing between unlike components in mixtures of varying strengths.
• Microscopic level interactions are not reflected in the mixing macroscopic behavior.

Volumetric and ultrasonic properties of ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C4mim][NTf2] and 1-butyl-3-methylimidazolium methylsulfate [C4mim][C1OSO3] with 1,2-propanediol (1,2-PD) have been investigated using density, ρρ speed of sound, uu measurements over the entire composition range at T = (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K. The density values were used to calculate excess molar volume, VmE whereas speed of sound results have been used to calculate deviation in isentropic compressibility, ΔκSΔκS. Excess properties have been fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard deviations. Spectroscopic technique like Fourier transform infrared (FT-IR) has been utilized for analyzing molecular level interaction prevailing between the binary mixtures. FT-IR technique has been used to scrutinize the –OH interactions between the binary mixtures and the influence on the structural variations in the ionic liquid. The excess properties and spectroscopic data have been analyzed in terms of the effect of temperature and the change of the anion of ionic liquid.

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