Abstract
The concentration at which a surfactant forms a micelle called the critical micelle concentration CMC. Therefore, micellar aggregates formation causes significant changes on surfactant physical properties, such as conductivity and surface tension. Here, the self association and CMC of the anionic surfactant, sodium dodecyl sulfate (SDS), and the cationic surfactant, cetylpyridinum bromide (CPB) have been investigated. Electric conductivity and surface tension techniques have been employed to reveal the surfactant CMC in aqueous solutions. The measurements have been accomplished on a range of concentrations at different temperatures. Obtained data were used to evaluate several parameters, including maximum surface excess concentration (Γmax), minimum area per molecule (Amin), surface pressure at CMC (�"#" ) and critical packing parameter (CPP). As the temperature increases the onset micellization tends to take place at higher concentrations due to dehydration of surfactant hydrophilic head groups. Thus, the CMC for each surfactant increases with increasing the system temperature. Surface parameters Γmax and Amin elucidate comparatively less availability of SDS molecules at the air-water interface, and CPB is more surface active than that of SDS.