The association of some novel cationic surfactants in benzene

Abstract

The mean aggregation number, 〈 n〉, of di-(ethyl,2-ethylhexanoate) ammonium salts, methyl, dimethyl di-(2-ethylhexylpropionate) ammonium salts and dielectric increment, Δϵ, and dipole moment, μ, of dimethyl di-(2-ethylhexylpropionate) ammonium nitrate and perchlorate progressively increased with increasing surfactant concentration in benzene, while μ/〈 n〉 (μ = dipole moment of an aggregate) for latter surfactants decreased as 〈 n〉 increased, indicating nonmicellar association patterns. The substituents constituting the polar head and counterions affected the association. The increase in 〈 n〉 with different counterions was in the order HSO 4 − > NO 3 − > ClO 4 − > CI −. The application of pseudo-phase model to the experimental data failed to detect micellar association and the critical micelle concentration for the cationic surfactants and no agreement was observed between multiple-equilibrium model and real systems. The experimental results were correlated with those of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in benzene. The other factors affecting the aggregation process were discussed in terms of the solute-solute and solute-solvent interactions.