Surface properties of cationic-nonionic mixed surfactant systems

Surface properties of the binary cationic-nonionic mixed systems (dodecyltrimethylammonium bromide + n-dodecyl-beta-D-maltoside and dodecyltrimethylammonium bromide + n-dodecyl-beta-D-glucoside) have been investigated by measuring the surface tension of aqueous solutions as a function of the total concentration and mole fraction of surfactants. The experimental results were analysed thermodynamically applying the Motamura theory, which allows for calculation of the composition of mixed monolayers and micelles as well as the excess free energy of adsorption and micelle formation, corresponding to mutual interactions between surfactants in mixed adsorbed film and micelle. Phase diagrams of adsorption and micelle formation and values of the excess Gibbs energy for both of the investigated systems were compared. The obtained results indicate that dodecyltrimethylammonium bromide mixes nonidealy with each of the investigated surfactants in both adsorbed film and micelle and proved that the size of hydrophilic group influences on the interactions between components in formed aggregates. (C) 2004 Elsevier B.V. All rights reserved.