Surface and Solution Properties of Alkanediyl-α,ω-bis(dimethylcetylammonium bromide) Gemini Surfactants in the Presence of Additives

Herein, we report the results of a study of surface and micellar properties of alkanediyl-alpha,omega-bis(dimethyl-cetylammonium bromide) gemini surfactants in pure aqueous solutions and also in the presence of alcohols (butanol, hexanol) and amines (butylamine, hexylamine). Parameters studied include cmc (critical micelle concentration), C-20 (concentration required to reduce the surface tension of the solvent by 20 mN center dot m(-1)), Gamma(max), (maximum surface excess concentration at the air/solution interface), and A(min) (minimum area per surfactant molecule). These parameters indicate mixed micellization between the surfactants and alcohols/amines; therefore, surfactant-additive interactions in mixed micelles and mixed monolayers, as well as activity coefficients, are also calculated. All the results show that high additive concentrations destabilize micelles: Delta G(ex), (excess free energy of micellization) becomes more negative at low additive concentrations (i.e., micelles stabilize) and less negative at high concentrations (i.e., micelles destabilize).