Application of Prigogine-Flory-Patterson theory to excess molar volume of mixtures of 1-butyl-3-methylimidazolium ionic liquids with N-methyl-2-pyrrolidinone

The densities of two binary mixtures formed by 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] and 1-butyl-3-methylimidazolium hexafluoro phosphate [bmim][PF6] with compound N-methyl-2-pyrrolidinone have been determined over the full range of composition and range of temperature from (298.15 to 313.15)K and at atmospheric pressure using a vibrating-tube densimeter (DMA4500). Excess molar volumes, V-m(E), have been obtained from these experimental results, and been fitted by the fourth-order Redlich-Kister equation. From the experimental results, partial molar volumes, apparent molar volume and partial molar volumes at infinite dilution were calculated over the whole composition range. Our results show that V-m(E) decreases slightly when temperature increases in the systems studied. The experimental results have been used to test the applicability of the Prigogine-Flory-Patterson (PFP) theory. The results have been interpreted in terms of ion-dipole interactions and structural factors of the ionic liquid and these organic molecular liquids. (C) 2008 Elsevier Ltd. All rights reserved.