Effect of 1-alkanols/salt on the cationic surfactant micellar aqueous solutions—A dynamic light scattering study

The effect of 1-alkanols viz., ethanol, 1-butanol and 1-hexanol on five quaternary salts based cationic surfactants in water and in presence of 0.1 M salts has been systematically investigated by viscosity and dynamic light scattering (DLS) technique. The concentration for surfactant varying in non-polar tail, polar head and counterion was kept constant (∼50 mM) throughout. The viscosity data are less detailed, but confirm the general trend of micellar growth and transitions. Influence of 1-butanol on critical micelle concentration (CMC) and degree of counterion dissociation (() was also investigated conductometrically. These measurements were done to supplement the role of counterions in exploring the binding phenomenon due to the effect of salt and alcohol during micellization. The effect of 1-alkanols upon the viscosity and micelle hydrodynamic diameter (Dh) of micelles in the presence of salt at varying concentration and temperature was also examined in detail to explain the hydrophobic interactions and electrostatic effects.

Combined effect of NaBr concentrations (□) 0.1 M (●) 0.2 M and (▵) 0.5 M with varying concentration of 1-butanol (%w/v) for 50 mM CTAB at 30 °C.Figure optionsDownload as PowerPoint slideHighlights
► To examine extensively the solubilization behavior of n-alkanols/salt in cationic surfactant micelles by dynamic light scattering technique.
► Effect of hydrophobicity, concentration, temperature and role of counterions on the hydrodynamic micellar size and viscosity.
► Micellar transformation from spherical to ellipsoidal micelles and further to large rod-likes is also observed.