Effects of head group size on micellization of cetyltrialkylammonium bromide surfactants in water–ethylene glycol mixtures

Micellization of cetyltrialkylammonium bromide (alkyl = methyl, ethyl, propyl, and butyl) surfactants has been studied in various water–ethylene glycol, EG, mixtures. This study provided the opportunity of investigating how, for a given hydrophobic tail length, the head group size determines the effect of the addition of EG on the micellization process. Conductivity, surface tension, spectroscopic and steady-state fluorescence measurements were carried out. The influence of additional methylenes in the headgroups on the Gibbs energy of micellization, Δ G M ° , was found to derive from changes in the solvophobic Gibbs energy contribution and from variations in the electrostatic headgroups interaction contribution.