Effect of electrolytes on non-ionic surfactant micelles

MORINI, M.A.; MESSINA, P.V.; SCHULZ, P.C.

Fortaleza

Simposio; 15th SIS Surfactant in Solution Symposium; 2004

Universidade Estadual Paulista

The effect of NaCl and HCl on two non-ionic surfactant micelles were studied by several techuiques, includilig conductivity and ion-selective electrodes. Both surfactants exhibit. opposite behaviour. The conductivity when Tween 20 is titrated with HCl notably increases in comparison with water, whereas Triton X-lOO do not change with respect to water until a certain HCl Concentration is reached, and then increases. The hydrogen ion actívity is lower in Triton X-lOO 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-l00 the activity do 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-lOO do not differ from the titration of water. These phenomena is explained by the changes in conformation of the nonionic headgroups, which captures water, and in some cases ions, modifying the activity of ions in the intermicellar solution.