Aggregation of diester-bonded cationic gemini surfactants in the presence of ethylene glycol: An electrical conductivity study

Aggregation behavior and thermodynamics of micellization of diester-bonded cationic gemini surfactants (12-Z1-12, 14--Z1-14, 12-Z2-12, 14-Z2-14) have been studied in ethylene glycol-water (EG-water) binary mixtures by conductometric method in the temperatures ranging from 298.15 to 313.15 K. With increasing length of hydrophobic chain and spacer, the values of critical micelle concentration (CMC) decrease, and degree of counterion association (beta) increases. While with increasing temperature and concentration of ethylene glycol, the values of CMC increase, and beta decrease. The thermodynamic parameters of micellization were determined from the temperature dependence of CMC values. The Gibbs energy values were found to be negative, and the negative values increased with the increase in the length of hydrophobic chain and spacer of surfactant, and with the decrease in temperature and volume fraction of ethylene glycol. (C) 2016 Elsevier B.V. All rights reserved.