Synergistic effects in micellization and surface tension reduction in nonionic gemini S-10 and cationic RTAB surfactants mixtures

• We examined mixtures of nonionic gemini and classical cationic surfactants.
• Strong synergy in mixed micellization was stated in S-10 + RTAB surfactants mixtures.
• Synergy in surface tension reduction efficiency is weaker than in cmc reduction.
• The alkyl chain length affect the composition of mixed film and mixed micelle.
• S-10 incorporate into mixed film preferably than into mixed micelle.

Mixtures of nonionic gemini surfactant S-10 (α,α′-[2,4,7,9-tetrametyl-5-decyne-4,7-diyl]bis[ω-hydroxy -polioxyetylene] with cationic alkyltrimethylammonium bromides of different alkyl chain length (RTAB) were investigated. Basing on surface tension measurements the cmc values and other adsorption parameters were found. The Clint, Rubing’s and Rosen theories were applied for evaluation of the synergistic effects in mixed films and mixed micelles formation. The molecular interaction parameters have negative values in all investigated mixtures, which confirm attractive forces between components. The magnitude of this forces depends on mixtures composition and in mixed micelles was higher than that in mixed films. It has been documented that in the process of micellization strong synergy exists, while in mixed film formation it is not so evident and was stated only in surface tension reduction efficiency. The composition of mixed films is different than the composition of mixed micelles, because a molar fraction of S-10 in monolayers is much higher than its contribution in mixed micelles at the same bulk composition.

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