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 (V2,ϕ0), standard partial molar volume of transfer for three glycyl dipeptides from water to aqueous [C12mim]Br solutions (ΔtVo), partial molar expansibility (Eϕ°) and Hepler's 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.