Influence of alcohols on the critical micelle concentration of non-aqueous micellar solutions

Electrical conductivity and surface tension measurements of various surfactants, such as sodium caprylate, sodium laurate, sodium palmitate and sodium stearate micellar solution, containing methanol, ethanol, n-propanol, n-butanol and n-pentanol in N,N-dimethyl acetamide has been determined at various temperatures. Both methods show that micelles are formed in N,N-dimethyl acetamide solution in presence of n-alkanols. Critical micelle concentration (c.m.c) has been determined for each of the surfactants. Critical micelle concentrations have also been measured as a function of the concentration of alcohol added. It is suggested that alcohol addition leads to an increase in N,N-dimethyl acetamide penetration into the micellar interface that depends on the alcohol chain length. Thermodynamic parameters were evaluated for micellar systems in presence of n-alkanols to further explain the results. (C) 2000 Elsevier Science B.V. All rights reserved.