Counter ion condensation on mixed cationic/nonionic micellar systems: Bjerrum's electrostatic condition

Abstract

Abstract:The association of counter-ions with mixedionic/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.

A systematic study of equilibrium structure, thermodynamics, and rheology of aqueous CTAB/NaNO3 wormlike micelles

“…where x CMC is the value of the CMC expressed in mole fraction units, and a is the degree of counter-ion dissociation, which for CTAB in water has been measured to be 0.18 [25]. Thus, DG mic ðT; PÞ ¼ DH mic ðT; PÞ À TDS mic ðT; PÞ ð 6Þ…”

Mixed Micellization of Dimeric (Gemini) Surfactants and Conventional Surfactants

“…At low X D the added cationic surfactants are probably entirely or nearly entirely dissociated, i.e., no counterions are bound by the micelles. Counterion binding by the mixed micelles starts only when X D reaches a certain value (52)(53)(54).…”

Interaction of Mixed Surfactants with Bacterial Lipopolysaccharide

“…Strong aggregation of surfactant at this composition dance with the size and structure of the surfactants. In the might have resulted in stacking of some negatively charged case of mixed surfactants addition of nonionic surfactant to counter ions of surfactant molecules (24). the cationic surfactant, further decrease in [h] was observed.…”