Mixed Micellization of n-Alkyltrimethylammonium Bromides and Dodecyl Polyoxyethylene Ethers

Abstract

The surface activity and micellization of binary cationic–nonionic mixtures of surfactants viz alkyltrimethylammonium bromides (C₁₂TABr, C₁₄TABr, C₁₆TABr, C₁₈TABr) and dodecyl polyoxyethylene ethers (C₁₂E_5, C₁₂E₈, C₁₂E₁₀, C₁₂E_12, C₁₂E₁₅) in water at mole fractions (0–1) were examined by surface tension measurements. The composition of mixed micelles and the interaction parameter (β) were evaluated from the critical micelle concentrations (CMCs) of single and mixed systems using Rubingh's theory; the negative β values indicate an overall attractive interaction which is predominant for C₁₂TABr + C₁₂E₁₅ as compared other mixed systems. In all mixed systems examined, deviation from ideal behavior was seen. Activity coefficients (f ₁ and f ₂) of C_nTABr/C₁₂E_m (n = 12, 14, 16, 18 & m = 5, 8, 10, 12, 15) mixed systems show the extent of ideality of individual surfactant. The stability of the mixed micelles is discussed in the light of Maeda's treatment. Mixed micelles of C₁₆TABr with C₁₂E_m were also examined by viscosity and dynamic light scattering. Micellar growth was favored with increased hydrophobicity of either surfactant.

Keywords:

• Interaction parameter
• mixed micelles
• surfactants

This work was supported by CSIR Project No. 01(2068)/06/EMR-II, India.

Notes

Part of the special issue, Surface and Colloid Chemistry Without Borders: An International Festschrift for Professor Per Stenius on the Occasion of His 70th Birthday.