Densities, electrical conductances, and spectroscopic properties of glycyl dipeptide plus 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 ([C(12)mim]Br)) + water mixtures have been measured at different temperatures. From density data, the standard partial molar volume (V-2,phi(0)), standard partial molar volume of transfer for three glycyl dipeptides from water to aqueous [C(12)mim]Br solutions (Delta V-t(o)), partial molar expansibility (E-phi) and Hepler's constant have been calculated. Through the electrical conductivity measurements, the critical micellar concentration (c(cmc)) and a series of thermodynamic parameters of micellization of [C(12)mim]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 (c(cmc)) of [C(12)mim]Br were examined. The pyrene fluorescence spectra were used to study the change of micropolarity produced by the interactions of [C(12)mim]Br with glycyl dipeptides, and the aggregation behavior of [C(12)mim]Br. From the results of UV-vis absorption spectra, the binding constant between dipeptide and [C(12)mim]Br above the c(cmc) was determined. (C) 2014 Elsevier B.V. All rights reserved.