Cationic and anionic surfactants interaction in water and methanol water mixed solvent media

The micellar properties between dodecyltrimethylammonium bromide (DTAB) and sodium dodecylsulfate (SDS) in water and 0.10, 0.20, and 0.30 volume fractions of methanol in methanol -water mixed solvent media have been studied by conductivity and surface tension measurements at 293.15 K. The concentration of dodecyltrimethylammonium bromide varied from 0.0001 to 0.03 mol.L-1 in the presence of -0.01 mol.L-1 sodium dodecylsulfate and the concentration of sodium dodecylsulfate varied from 0.001 to 0.015 mol. L-1 in the presence of -0.005 mol.L-1 dodecyltrimethylammonium bromide. Hence, the concentrations of cationic rich (DTAB-SDS) and anionic rich (SDS-DTAB) solutions have been taken in the ratio of 3:1. The critical micelle concentrations (cmc) of DTAB-SDS and SDS-DTAB solutions have been determined by conductivity and surface tension measurements at 293.15 K. The physicochemical properties such as Gibb's free energy of micellization (Delta G degrees,), free energy of surfactant tail transfer (Delta G degrees(trans)), maximum surface excess concentration (T (max)), area occupied by surfactant molecule (Amin), surface pressure at the cmc (pi(cmc)), packing parameters (P) and standard free energy interfacial adsorption (Delta G degrees(ads)) are calculated in water, 0.10, 0.20 and 0.30 volume fractions of methanol -water at 293.15 K. Addition of methanol significantly affects the physicochemical properties between DTAB and SDS. With increasing concentration of methanol, the cohesive force and the dielectric constant decrease that affects the micellization and other physicochemical properties. The micellization between DTAB and SDS have been assessed in terms of different solvent parameters. The ratio of the solvent surface tension to the limiting surface tension at the cmc has been used as the solvophobic effect. (C)2016 Elsevier B.V. All rights reserved.