Conformationally rigid and flexible surfactant binary (pseudoternary) mixed micelle with mutual synergistic interaction

Abstract

Molar excess Gibbs energy of a binary mixed micelle with a conformationally flexible and rigid surfactant can be represented by first-order Margules function. Excess entropy comes from the conformational entropy rather than the configurational entropy. Such a binary mixed micelle with the synergistic interactions between micellar building blocks can be considered a pseudoternary mixed micelle from the conformationally rigid surfactant, twisted (globular) conformation of the conformationally flexible surfactant, and elongated conformation of the same surfactant. Excess entropy of such mixed micelles can be approximated with a microcanonical ensemble of the conformationally flexible surfactants. Particles of these surfactants are distributed between the average lower energy (elongated conformation) and the average higher energy (twisted conformation). A new structural parameter of mixed micelles was introduced - the parameter of disorder, which represents the molar fraction of the conformation with an average higher energy (twisted conformation) of the conformationally flexible surfactant in the mixed micellar pseudophase. Influence of the new structural parameter on the conformational rigid surfactant's excess chemical potential is discussed.