Interfacial and Micellar Properties of Binary Mixtures of Sodium Cholate and Sodium Deoxycholate with Cetyl Pyridinium Chloride

Interfacial and micellar properties of binary mixtures of Sodium Cholate (NaC) and Sodium Deoxycholate (NaDC) with Cetyl Pyridinium Chloride (CPC) have been investigated by surface tension and conductometric methods. The surface tension method has evidenced significantly low critical micelle concentration (CMC) whereas higher CMC values have been realised by the conductometric method. The results have been processed for estimating the maximum interfacial adsorption (Γ_max), minimum amphiphile area at the interface (A_min), free energy of adsorption (ΔG⁰_ad), free energy of micellization (ΔG⁰_m) and the fraction of counter-ion binding (p) as a function of mixture composition. Following regular solution theory of Rubingh, amphiphile composition, their interaction and activity coefficients in the mixed micelles have been estimated. Both synergism and antagonism have been observed. The amphiphile composition in the mixed micelle significantly differs from the stoichiometric composition.