Computational Study of the Structure and Behavior of Aqueous Mixed System Sodium Unsaturated Carboxylate-dodecyltrimethylammonium Bromide

Explanation of experimental results of mixed micelles of homologous surfactants through a MM2 bidimensional modeling

A computational modeling (in gas phase) to study the disposition of the homologous surfactants in a bidimensional simple model of mixed and homogeneous micelles was performed for the case of R-trimethylammonium bromide surfactants with different linear R lengths from R = C(5) to C(17). First, the bidimensional homogeneous (one component) micelle was modeled, and as a second step, heterogeneous (two components) bidimensional micelles were modeled. The difference in the number of carbon atoms between hydrocarbon chains of the surfactants in the heterogeneous micelles, Δn(C), ranged from 2 to 8. Results were contrasted with experimental data obtained at our own laboratory. The exothermic values of the steric energy changes showed strong attraction between components of homologous surfactants mixture, especially when one of the surfactants has a long chain. It may be argued that the inclusion of a shorter surfactant in the mixture and the twisting of the longer surfactant makes the bidimensional arrangement formation more exothermic. All predictions were in agreement with previous experimental results.

Effect of Double Bonds in the Formation of Sodium Dodecanoate and Sodium 10-Undecenoate Mixed Micelles in Water

The micellization of an aqueous mixture of sodium dodecanoate (SDD) and sodium 10-undecenoate (SUD) was studied with the theory of mixed micellization. A strong nonideality was found, with a preferential composition of mixed micelles. This phenomenon was interpreted on the basis of the interaction between the vinyl group and water by hydrogen bonding. The importance of the aliphatic pi electrons and water was stated.