Micellization and aggregation behavior of a series of cationic gemini surfactants (m-s-m type) on their interaction with a biodegradable sugar-based surfactant (octyl-β-D-glucopyranoside)

In this work, the interaction of a series of cationic gemini surfactants; m = 10,12 (s = 2); 14 (s =  2,4,5,6); 16 (s = 4,5,6) with a sugar-based surfactant; octyl-β-D-glucopyranoside (β-C8G) in presence of 5 mmol dm−3 NaBr at 30 °C has been investigated by tensiometry and viscometry. The critical micelle concentrations of pure surfactants as well as mixed systems were determined. The experimental results were interpreted using theoretical models of Rubingh and Rosen. These analyses allowed us to determine the interaction parameters, minimum surface area per molecule, surface excess, mixed micelle composition, free energies of micellization and adsorption, and activity coefficients through the whole concentration range. The results illustrate the effects of steric and electrical factors on mixed monolayer and mixed micelle formation and of surfactant–surfactant interactions therein. The cationic gemini surfactants and their mixtures with β-C8G show strong interactions at the air/water interface and a greater preference for adsorbing at the air/water interface relative to mixed micelle formation in the solution phase. Viscometric studies showed that the morphological behavior of the mixed micelles was dictated by the length of the spacer and alkyl chain of the gemini surfactants. Short spacers and long alkyl chain geminis have been found to have stronger ability to form larger assemblies.

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► Interaction of cationic conventional/gemini surfactants with β-C8G is studied.
► CMC decreases with increasing mole fraction of cationic surfactants.
► Synergistic interactions were found in the mixed micelles in all the combinations.
► Gemini surfactants are found to be more efficient in mixed micelle formation.