Effect of organic counterions and positional isomerism on the micellization of sodium dioctyl sulfosuccinate
N. Sultana and K. Ismail
Department of Chemistry, North-Eastern Hill University, Shillong - 793022
Critical micelle concentration (cmc) values of sodium dioctyl sulfosuccinate (AOT) in aqueous medium in the presence of anilinium hydrochloride (AHC), o-toluidine hydrochloride (OTHC) and p-toluidine hydrochloride (PTHC) were determined at 25°C from the surface tension and fluorescence methods, whereas the micellar size was estimated from the dynamic light scattering method. Organic counterion and presence of positional isomerism in it influence the cmc of AOT very significantly. For e.g., addition of 1 mmol kg-1 AHC, OTHC and PTHC decreases the cmc of AOT by nearly 32, 48 and 72 %, respectively. These organic counterions induce special counterion binding behavior of AOT as in the case of inorganic counterions. To estimate the counterion binding constant, the modified Corrin – Harkins (CH) equation is applicable instead of the CH equation.
Keywords: AOT, Critical micelle concentration, counterion binding constant, modified CH equation, hydrodynamic radius.