Mixed micelles of n-alkyltrimethylammonium bromides: influence of alkyl chain length

Abstract

The influence of chain length on the composition of micelles in a binary mixture of n-hexyltrimethylammonium bromide and n-octyl-, n-decyl-, n-dodecyl-, n-tetradecyl- and n-hexadecyltrimethylammonium bromides has been determined from an analysis of the variation of the critical micelle concentration (determined by conductivity techniques) as a function of solution composition. Using the theoretical treatment of Motomura, the composition of each compound in mixed micelles was evaluated. The nonideality of mixing was expressed in terms of the molecular interaction parameter β, obtained with the Holland and Rubingh theory. The molecular thermodynamic model of Puvvada and Blanckschtein was used to study the nonideal behaviour of the mixtures.