Aggregation Behavior and Micellar Properties of Sodium Salts of Naphthenic Acid Mixtures

The aim of this study was to investigate micellar and self-assembly properties of four sodium salts of naphthenic acid mixtures by determination and comparative analysis of their critical micelle concentration values at seven different temperatures ranging from 10 to 40 °C using spectrofluorophotometric measurements. It was concluded that fractions having the lowest percentage of aliphatic structures give the least flexible micelles due to sterically rigid structure of cyclic side chains, what makes them difficult to pack in the micellar core. Additionally, surface properties of aqueous solutions of investigated mixtures were studied by the determination of the maximum surface excess, Γ max and the minimum area per surfactant molecule (A min) values.