Counter ion condensation on mixed cationic/nonionic micellar systems: Bjerrum's electrostatic condition |
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Authors: | C. Treiner M. H. Mannebach |
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Affiliation: | (1) Present address: Laboratoire d'Electrochimie, Université Pierre et Marie Curie, Paris, France |
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Abstract: | The association of counter-ions with mixed ionic/nonionic micelles has been investigated in the case of dodecyl/tetradecyl/ and hexadecyl-trimethylammonium bromide with two nonionic surfactants: dodecylpolyoxyethylene 23 and Triton X-100. The degree of association has been measured by potentiometry using a Bromide ion-selective electrode. Previous results with sodium and copper dodecylsulfate suggesting that in the nonionic-rich composition domain, bare mixed micelles are formed without associated counter-ions have been confirmed. These results are in agreement with the prediction of Bjerrum's condition for ion association. The effect of copper dodecylsulfate on the cloud point of Triton X-100 has also been determined as a means of investigating mixed micelles with multivalent counter-ions. The dramatic cloud point increase observed, even larger than with sodium dodecylsulfate, has been discussed as evidence of the solvation of divalent ions by ether groups, a factor which complicates the analysis of multivalent counterion condensation on mixed micelles. |
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Keywords: | Mixedmicelles counter-ioncondensation ionselectiveelectrodes cloudpoint alkyltrimethylammoniumbromides Triton X-100 |
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