Surface Adsorption and Micelle Formation of Dodecyltrimethylammonium Chloride and Dodecylammonium Chloride Mixture

Abstract The miscibility of dodecyltrimethylammonium chloride (DTAC) and dodecylammonium chloride (DAC) in the adsorbed film at water/air interface and in the micelle was investigated by measuring the surface tension of the aqueous solution of surfactant mixture as a function of the total molality and composition of surfactants. The compositions of surfactants in the adsorbed film and micelle were evaluated by use of the thermodynamic equations developed previously. The results indicated that DTAC and DAC molecules mix slightly nonideally in the adsorbed film and micelle. Furthermore, the composition of DAC in the micelle was found to be remarkably smaller than that in the adsorbed film at the critical micelle concentration. It was concluded that the bigger hydrophilic group of DTAC is geometrically favorable for the micelle formation.