Counterion specificity as the determinant of surfactant aggregation

Brady, James E.; Evans, D. F.; Warr, Gregory G.; Grieser, Franz; Ninham, Barry W.

doi:10.1021/j100400a024

Cited by 148 publications

(159 citation statements)

References 2 publications

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“…The k value increases rapidly with increasing C s , and breaks at about 1 mmolkg -1 , and then increases gradually above the concentration. This is the same behavior observed in common surfactant solutions 20) . In order to make clearer the concentration dependence of k, we applied a differential conductivity method.…”

Section: Resultssupporting

confidence: 86%

Partition Coefficients of 1-Alkanols between Water and DDAB Vesicle Membrane Determined by Differential Conductivity Method

et al. 2009

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The partition coefficients of 1-alkanols between water and didodecyldimethylammonium bromide (DDAB) vesicle membrane, and the change of the degree of counter-ion dissociation on DDAB vesicle caused by the solubilization of 1-alkanols were determined from electric conductivity measurements. A good linear relationship was obtained between logarithmic value of the partition coefficient and carbon number of alkyl chain in 1-alkanols. The standard transfer free energy change per methylene group was evaluated from the slope of this straight line. On the other hand, the effect of 1-alkanols on the degree of counter-ion dissociation was independent of carbon number of 1-alkanols. Comparing the results of the present system with those of sodium dodecylsulfate (SDS) micelle/1-alkanol system, it was found that the interior of DDAB vesicle membrane is more hydrophobic than that of SDS micelles. Furthermore, the increase in counter-ion dissociation caused by solubilized 1-alkanols was much lesser for DDAB vesicles than SDS micelles.

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Section: Resultssupporting

confidence: 86%

Partition Coefficients of 1-Alkanols between Water and DDAB Vesicle Membrane Determined by Differential Conductivity Method

et al. 2009

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“…Loosely speaking, the ion binding model holds for cosmotropic ions only (according to the classical Hofmeister terminology) [3]. Similar conclusions are derived when the counterion of cationic surfactants is replaced, as in the case of micelles and vesicles [35,36].…”

Section: Specific Ion Effects and Head Group Hydration Vs Hydrocarbomentioning

confidence: 56%

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Ninham

Larsson

Nostro

2017

Colloids and Surfaces B: Biointerfaces

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a b s t r a c tHofmeister, specific ion effects, hydration and van der Waals forces at and between interfaces are factors that determine curvature and microstructure in self assembled aggregates of surfactants and lipids; and in microemulsions. Lipid and surfactant head group interactions and between aggregates vary enormously and are highly specific. They act on the hydrophilic side of a bilayer, micelle or other self assembled aggregate. It is only over the last three decades that the origin of Hofmeister effects has become generally understood. Knowledge of their systematics now provides much flexibility in designing nanostructured fluids.The other side of the coin involves equally specific forces. These (opposing) forces work on the hydrophobic side of amphiphilic interfaces. They are due to the interaction of hydrocarbons and other "oils" with hydrophobic tails of surfactants and lipids. The specificity of oleophilic solutes in microemulsions and lipid membranes provides a counterpoint to Hofmeister effects and hydration. Together with global packing constraints these effects determine microstructure.Another factor that has hardly been recognised is the role of dissolved gas. This introduces further, qualitative changes in forces that prescribe microstructure.The systematics of these effects and their interplay are elucidated. Awareness of these competing factors facilitates formulation of self assembled nanostructured fluids. New and predictable geometries that emerge naturally provide insights into a variety of biological phenomena like anaesthetic and pheromone action and transmission of the nervous impulse (see Part 2).

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“…A similar effect has been observed for strongly hydrated ions as hydroxide and acetate, inducing enhanced bilayer curvature of (positively charged) didodecyldimethylammonium bromide (DDAB) lamellae. 3, 48 Nonetheless, along with the increasing LiCl concentration also the electrical double layer repulsion will disappear and at 1.1 m, the van der Waals attractions between micelles will triumph over repulsions, and the micelles will phase separate from solution before packing in a lamellar array has been completed. Further addition of LiCl leads to further dehydration of the headgroups and all other ions.…”

Section: Discussionmentioning

confidence: 99%

Micelle to Lamellar Aggregate Transition of an Anionic Surfactant in Dilute Aqueous Solution Induced by Alkali Metal Chloride and Tetraalkylammonium Chloride Salts

Sein¹,

Engberts²

1995

Langmuir

116

101

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Micelles of the anionic surfactant sodium dodecylbenzenesulfonate (NaDoBS) in dilute aqueous solution can be transformed into lamellar aggregates by the addition of alkali metal chloride (LiCl to CsCl) and tetraalkylammonium chloride (alkyl is methyl or n-butyl) salts. Depending on the type of cation, concentration of salt, and isomeric purity of the alkyl chain of the surfactant, different types of phases are observed: large unilamellar vesicles, multivesicular vesicles, and flocculated multilamellar vesicles (lamellar droplets). Over limited concentration ranges, some salts induce phase separation in a surfactant-rich and a surfactant-lean phase. The formation of the different phases was monitored by turbidity and fluorescence depolarization measurements, whereas the phases were characterized by light microscopy, freeze-fracture electron microscopy, and confocal scanning laser microscopy. Thermodynamic aspects of aggregation, in particular the counterion binding characteristics, were studied by microcalorimetry and conductivity. On a molecular level, the packing in a lamellar array can be explained largely in terms of a change in counterion binding and, to a lesser extent, by a decrease of the hydration of the headgroup and the counterion. A better counterion binding is facilitated by a less hydrated cation or by an increase of the electrolyte concentration. The formation of different types of lamellar aggregates is due to different types of interactions between lamellar layers or between aggregates: largely repulsive for stable dispersions of unilamellar vesicles to attractive down to short distances for the flocculated lamellar droplets.

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Counterion specificity as the determinant of surfactant aggregation

Cited by 148 publications

References 2 publications

Partition Coefficients of 1-Alkanols between Water and DDAB Vesicle Membrane Determined by Differential Conductivity Method

Partition Coefficients of 1-Alkanols between Water and DDAB Vesicle Membrane Determined by Differential Conductivity Method

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Micelle to Lamellar Aggregate Transition of an Anionic Surfactant in Dilute Aqueous Solution Induced by Alkali Metal Chloride and Tetraalkylammonium Chloride Salts

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