Interfacial and micellization properties of pure surfactants with similar hydrocarbon chain length (C16H33) and different polar head in aqueous medium

The study of surfactant properties are significant for the production of pharmaceutical and anti-corrosion products, detergents and enhanced oil recovery. In the present work, the formation of micelles in different types of surfactants, i) cationic (cetyl pyridinium chloride, CPC, and cetyl trimethylammonium bromide, CTAB) and ii) non-ionic (Brij-C2, Brij-C12, Brij-C15 and Brij-C20) has been investigated in aqueous medium by tensiometric technique at 298.15 K. These surfactants (CPC, CTAB, Brij-C2, Brij-C12, Brij-C15 and Brij-C20) have the same hydrophobic chain length (C16H33) and different polar head groups. The major focus in this research is on the effect of polar head groups on critical micelle concentration (CMC), the standard free energy of micellization ( ), Gibbs adsorption energy ( ) and some interfacial parameters, for example, surface excess concentration (max), minimum surface area per surfactant molecule (Amin), surface pressure at CMC (CMC) and pC20(= −log(C20). The results obtained show that the micellization properties of surfactants has more spontaneous and favorable conditions in nonionic structures. In Brij family surfactants, values of and πcmc at CMC point decreased with increasing the number of oxyethylene groups (or hydrophilic section) from Brij-C2 to Brij- C20. Also, increase in hydrophilicity of head groups of Brij series surfactants by more incorporation of oxyethylene groups enhanced their solubilization capacity in bulk solution.