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

Densities, conductivities, and fluorescence spectra of two imidazolium ionic liquids ([C_nmim]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 (Δ_t 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 _m ^o , ΔH _m ^o , and ΔS _m ^o ) of micellization of [C_nmim]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 [C_nmim]Br with glycyl dipeptide, and the aggregation behavior of [C_nmim]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 [C_nmim]Br (n = 10, 14) and glycyl dipeptide is affected by temperature and hydrocarbon chain length of the dipeptides.