Studies on aggregation and counterion binding nature of didodecyldimethylammonium bromide in presence of added salts

Abstract

The critical micelle concentration of double chained cationic surfactant didodecyldimethylammonium bromide (DDAB) are determined in the presence of added counterions, viz., bromide, chloride and, benzoate, using surface tension, conductance and fluorescence methods. The main highlight of the article is the existence of two break-points in the surface tension isotherms of DDAB, depending on the type and amount of added counterion. At some concentrations of added counterions, normal surface tension behavior is also observed with only one break-point in the surface tension isotherm. The variation in the cmc value of DDAB with counterion concentration is studied using well-known Corrin-Harkins and modified Corrin-Harkins equations. The information gathered about the aggregation behavior of DDAB in the presence of added counterions is expected to be useful in view of DDAB’s wide utility in commercial, chemical and pharmaceutical field.