Conductometric and fluorescence probe analysis on molecular interactions between cationic surfactants in aqueous medium of glycyl dipeptide: Concentration and temperature effect

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on interactions of glycyl dipeptide in aqueous medium have been studied in varying concentrations (0.001, 0.005 and 0.010 mol.kg(-1)) at different temperatures (293.15 K to 293.15 K). The conductivity method has been employed to determine critical micelle concentration, CMC i.e. point of aggregation and the results have been discussed in terms of glycylglycine-CTAB/DTAB hydrophobic and electrostatic interactions in aqueous medium. The obtained CMC values reveal the fact that the micellization tendency of the surfactant increases in the presence of glycyl dipeptide. The CMC's of CTAB and DTAB have been found to decrease from 0.87 to 0.66 mmol.kg(-1) and 14.2-13.7 mmol.kg(-1) respectively as the [Glycyl dipeptide] increased from 0.001 to 0.010 mol.kg(-1). The temperature dependence of the CMC values has been established in terms of ion-ion, ion-polar and hydrophobic-hydrophobic group interactions around the hydrophobic part of surfactants. Furthermore, the standard thermodynamic parameters of micellization have been evaluated and interpreted which enable to grasp fully the ion-ion/ion-hydro philic interactions existing in the present ternary (surfactant-dipeptide-water) system. In addition, the pyrene fluorescence technique has been used to study the change of micropolarity produced by the interactions of surfactants with glycyl dipeptide and the aggregation behaviour (CMC determination) of surfactants. (C) 2016 Elsevier Ltd.