“Unusual Volumetric and Hydration Behavior of the catanionic System Sodium Undecenoate - Dodecyltrimethylammonium Bromide”.

MARÍA BELÉN SIERRA, MARCELA A. MORINI, PABLO C. SCHULZ, MARÍA LUJÁN FERREIRA

COLLOID AND POLYMER SCIENCE

Springer Berlin / Heidelberg

Año: 2005 vol. 283 p. 1016 - 1024

0303-402X

Following the studies on the effect of double bonds in the hydrophobic tail on the formation of catanionic aggregates, we studied the viscosity and density of the system Sodium Undecenoate (SUD) – Decyltrimethylammonium Bromide (DTAB) – water. We found that the partial molar volume and intrinsic viscosity of both, micellised and unmicellised mixtures, are non-ideal, dependent on the mixture composition and related to structural changes in micelles. These phenomena are caused by the presence of the double bond at the distal extreme of the SUD molecule, which has some affinity with water by formation of hydrogen bonds. In particular, as far as we know, this is the first report on non-ideal behavior of the partial molar volume in mixed micelles.   KEYWORDS: mixed micelles – partial molar volume - micelle hydration – sodium undecenoate – catanionic surfactant – dodecyltrimethyammonium bormide.