Strong effect of NaBr on self-assembly of quaternary ammonium gemini surfactants at air/water interface and in aqueous solution studied by surface tension and fluorescence techniques |
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Authors: | Yi You Jianxi Zhao Rong Jiang Jingjing Cao |
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Institution: | (1) Department of Applied Chemistry, College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou, 350002, People’s Republic of China |
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Abstract: | The effects of NaBr on the adsorption of alkanediyl-bis-(dimethyl dodecyl- ammonium bromide) (referred to as C12-s-C12 2Br) at the air/water interface and on the micellization in the solution have been investigated by surface tension and fluorescence
techniques. The results showed that the addition of NaBr greatly enhances their efficiency and effectiveness in surface tension
reduction as well as the ability of micellization, even induces strong premicellar aggregation before the cmc. These were attributed to the unique molecular structure of gemini surfactant, where the flexible polymethylene chain was
the spacer linking the two quaternary ammonium heads. By a short spacer, the charges of the two quaternary ammonium head groups
are concentrated. Even for a long spacer (s = 12), since it is bent toward the alkyl tails, the similar effect is also produced. This results in the high sensitivity
of their ionic head groups to salt. Besides, the addition of salt also effectively promotes the hydrophobic interaction between
the alkyl tails of gemini surfactants.
The addition of NaBr strongly promotes the adsorption of quaternary ammonium gemini surfactants C12-s-C12 2Br at the air/water interface and the micellization in the solution. |
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Keywords: | Gemini surfactant Self-assembly Salt effect |
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