Solvation of ionic liquids based on N-methyl-N-alkyl morpholinium cations in dimethylsulfoxide - volumetric and compressibility studies

The density and sound velocity of the solutions of ionic liquids based on N-alkyl-N-methyl-morpholinium cations, N-ethyl-N-methylmorpholiniumbis(trifluoromethanesulfonyl) imide, N-butyl-N-methylmorpholinium bis(trifluoromethanesulfonyl) imide, N-methyl-N-octyl-morpholinium bis(trifluoromethanesulfonyl)imide and N-decyl-N-methylmorpholinium bis(trifluoromethanesulfonyl) imide in dimethylsulfoxide were measured at T = (298.15 to 318.15) K and at atmospheric pressure. The apparent molar volume and apparent molar compressibility values were evaluated from density and sound velocity values and fitted to the Masson equation from which the partial molar volume and partial molar isentropic compressibility of the ILs at infinite dilution were also calculated at working temperatures. By using the density values, the limiting apparent molar expansibilities were estimated. The effect of the alkyl chain length of the ILs and experimental temperature on these thermodynamic properties is discussed. In addition, molecular dynamics simulations were used to interpret the measured properties in terms of interactions of ILs with solvent molecules. Both, volumetric measurements results and molecular dynamics simulations for ionic liquids in dimethylsulfoxide were compared and discussed with results obtained for the same IL in acetonitrile. (C) 2015 Published by Elsevier Ltd.