The interaction of electrolytes with non-ionic surfactant micelles

The effect of NaCl and HCl on two non-ionic surfactant micelles was studied using several techniques, including conductivity and ion-selective electrodes. Both surfactants exhibit opposite behaviour. When Tween 20 is titrated with HCl the conductivity notably increases in comparison with water, whereas that of Triton X-100 solutions do not change with respect to water until a certain HCl concentration is reached, when it increases. The hydrogen ion activity is lower in Triton X-100 solutions and higher in Tween 20 solutions than in pure water. Chloride ion activity is higher in Tween 20 solutions than in water, whereas in Triton X-100 the activity does not significantly differ from that in water. The activity of sodium ion is lower in Tween 20 solutions than in water, whereas that in Triton X-100 solutions does not differ from the titration of water. These phenomena are explained by the changes in conformation of the non-ionic headgroups, which capture water, and in some cases ions, modifying the activity of ions in the intermicellar solution.Fil: Morini, Marcela Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Messina, Paula Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Schulz, Pablo Carlos. Universidad Nacional del Sur. Departamento de Química; Argentin