Apparent molar volume, conductivity, and fluorescence studies of ternary systems of dipeptides + ionic liquids ([Cnmim]Br, n = 10, 14) + water at different temperatures

Abstract

Densities, conductivities, and fluorescence spectra of two imidazolium ionic liquids ([Cnmim]Br, n = 10, 14)-glycyl dipeptide-water mixtures were measured as a function of temperature. The density data have been utilized to calculate the apparent molar volumes, standard partial molar volumes (V 2,φ 0 ), standard partial molar volumes of transfer from water to aqueous ionic liquids solutions (Δt V°), the hydration number (N H), partial molar expansibility (E φ 0 ), and Hepler’s constant of glycyl dipeptides. Through the electrical conductivity measurements, the c cmc values at different temperatures and a series of thermodynamic parameters (ΔG , ΔH , and ΔS ) of micellization of [Cnmim]Br (n = 10, 14) in aqueous glycyl dipeptides solutions are evaluated. The pyrene fluorescence spectra were used to study the change of micropolarity produced by the interaction of [Cnmim]Br with glycyl dipeptide, and the aggregation behavior of [Cnmim]Br (n = 10, 14). The results shown above have been explained in terms of solute–solvent interactions and structural changes in the mixed solutions. The interaction between [Cnmim]Br (n = 10, 14) and glycyl dipeptide is affected by temperature and hydrocarbon chain length of the dipeptides.