Micellization and Solvation Properties of Newly Synthesized Imidazolium- and Aminium-Based Surfactants

This work aimed to study the solvation properties of newly synthesized cationic surfactants: 1-hexyl-1-methyl-1H-imidazol-1-ium bromide (R₆Im), 1-dodecyl-1-methyl-1H-imidazol-1-ium bromide (R₁₂Im), N,N,N-tributylhexan-1-aminium bromide (R₆N₄), and N,N,N-tributyldodecan-1-aminium bromide (R₁₂N₄) in water and ethanol-water solvents with a 0.237 mole fraction of ethanol at 298.15 K using conductivity, refractive index, surface tension, and density measurements. Critical micelle concentration (CMC) for the synthesized surfactants was determined and discussed. Thermodynamic parameters including association constant, molal volume, and polarizability were calculated and discussed. Some surface properties of surfactants including excess surface concentration and minimum area per molecule were also calculated and discussed. A good agreement was found between the CMC values obtained from different techniques, such as conductivity, refractive index, and surface tension. Imidazolium surfactants had been proved to decrease the CMC and increase the association constant with the increase of ethanol mole fraction, while tributylamine had been proved to increase the CMC and decrease the association constant with the increase of ethanol mole fraction. Also, imidazolium surfactants had been proved to have higher CMC than tributylamine, which may be related to higher solvation of imidazolium surfactants than that of tributylamine. Both surfactants (R₁₂Im) and (R₁₂N₄) were proved to have lesser CMC.