Conductometric Studies on Micellization of Cationic Surfactants in the Presence of Glycine

Values of the critical micelle concentration (cmc) and degree of counterion dissociation (alpha) of four cationic surfactants: cetyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC) and benzyldimethylhexadecylammonium chloride (BDHAC) in aqueous-glycine medium (concentration of glycine (Gly) varied from 0 to 0.20 mol center dot dm(-3)) were determined through conductometric measurements at 303 K. The effect of temperature on the micellization in the presence of 0.10 mol center dot dm(-3) Gly were studied for the surfactants CTAB, CPC and BDHAC. With respect to the concentration of Gly, a decrease in the cmc was observed for CTAB, CPC and CPB whereas an increase was observed for BDHAC. A regular increase in alpha was obtained for CPB, CPC and BDHAC with respect to the concentration of Gly whereas values were roughly constant in the case of CTAB. Thermodynamic parameters were computed from the temperature dependence of the cmc values and it was found that the micellization process is exothermic. Compensation of enthalpy and entropy was observed for the micellization of CTAB, CPC and BDHAC in the presence of 0.10 mol center dot dm(-3) Gly.