Densities, electrical conductances, and spectroscopic properties of glycyl dipeptide + ionic liquid ([C12mim]Br) + water mixtures at different temperatures

Densities, conductivity, fluorescence and UV–vis absorption spectroscopy of glycyl dipeptide + ionic liquid (1-dodecyl-3-methylimidazolium bromide ([C12mim]Br)) + water mixtures have been measured at different temperatures. From density data, the standard partial molar volume ( V 2 , ϕ 0 ) , standard partial molar volume of transfer for three glycyl dipeptides from water to aqueous [C12mim]Br solutions (ΔtVo), partial molar expansibility ( E ϕ ° ) and Heplerʹs constant have been calculated. Through the electrical conductivity measurements, the critical micellar concentration (ccmc) and a series of thermodynamic parameters of micellization of [C12mim]Br in aqueous glycyl dipeptide solutions are evaluated. Effects of temperature and hydrocarbon chain length of the glycyl dipeptides on the volumetric properties of dipeptides and critical micelle concentration (ccmc) of [C12mim]Br were examined. The pyrene fluorescence spectra were used to study the change of micropolarity produced by the interactions of [C12mim]Br with glycyl dipeptides, and the aggregation behavior of [C12mim]Br. From the results of UV–vis absorption spectra, the binding constant between dipeptide and [C12mim]Br above the ccmc was determined.