Oleic Acid Monolayers on Concentrated Salt Solutions

Gilby, A.R.; Heymann, E.

doi:10.1071/ch9520160

Cited by 5 publications

(23 citation statements)

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“…Surprisingly, the dependence of Γ el,s on C m is nonmonotonic for NaBr. This is not what could be expected from the previous studies, ,, which report approximately linear σ s ( C m ). The minimum of σ s means that, at low concentration, NaBr adsorbs at crystal’s spread monolayer, while at high C m it desorbs.…”

Section: Resultscontrasting

confidence: 99%

“…It is seen there that σ 0 – σ versus Γ –1 curves stand higher at increased concentration, and they follow the direct Hofmeister series: (σ 0 – σ) NaBr > (σ 0 – σ) NaCl . Both findings agree with the literature data. ,, …”

Section: Resultssupporting

confidence: 93%

“…Both findings agree with the literature data. 22,25,58 The effect of the salt on the phase transition is interesting, in light of the previous reports for significant effect of the electrolyte on the conditions of the phase transition in monolayers 31−33 and bilayers. 38 When the concentration of NaCl or NaF increases, the LE-LC phase transition occurs at higher surface tension σ t and at higher areas per molecule (Figure 5).…”

Section: ■ Resultsmentioning

confidence: 93%

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Adsorption of Ions at Uncharged Insoluble Monolayers

et al. 2016

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A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3-30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na(+) is specifically adsorbed, while Cl(-) remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na(+) seems to be the interaction of the ion with the dipole moment of the monolayer.

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Section: Resultscontrasting

confidence: 99%

Section: Resultssupporting

confidence: 93%

Section: ■ Resultsmentioning

confidence: 93%

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Adsorption of Ions at Uncharged Insoluble Monolayers

et al. 2016

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“…The latter could be extracted from the surface pressure versus area isotherms. The collapse area of OA is 27.6 Å 2 , approximately independent of the electrolyte . The partial molar volume V s of the surfactant headgroup is more difficult to determine.…”

Section: Resultsmentioning

confidence: 99%

Interactions between Small Inorganic Ions and Uncharged Monolayers on the Water/Air Interface

Peychev

Slavchov

2023

J. Phys. Chem. B

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The interaction of several simple electrolytes with uncharged insoluble monolayers is studied on the basis of tensiometric and potentiometric data for the surface electrolyte solution|air. The induced adsorption of electrolyte on the monolayer is determined via a combination of data for equilibrium spreading pressure and surface pressure versus area isotherms. We show that the monolayer-induced adsorption of electrolyte is not only strongly ionspecific but also surfactant-specific. The comparison between the ionspecific effects on a carboxylic acid monolayer at low pH and an ester monolayer shows that the anion series follows the same order while the cation series reverses. The effect of the electrolyte on the chemical potential of the monolayer shows attraction between the surfactant and the ions at low monolayer densities, but at high surface densities, repulsion seems to come into play. In nearly all investigated cases, a maximum of monolayer-induced electrolyte adsorption is observed at intermediate monolayer densities. This suggests specific interactions between the surfactant headgroup and the ions. The Volta potential data for the monolayers are analyzed on the basis of the equations of quadrupolar electrostatics. The analysis suggests that the ion-specific effect on the Volta potential is due to the ion-specific decrement of the bulk dielectric constant of the electrolyte solution. Moreover, we present evidence that in most cases the effect of the electrolyte on the orientation of the adsorbed dipoles cannot be neglected. Instead, the change in the ion distribution in the electric double layer seems to have a small effect on the Volta potential.

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“…There were only trace amounts of fatty acids with chain length greater than n = 18. For these short‐chain and unsaturated fatty acids we expect their collapse surface pressures to be in the range of 30–40 mN/m (minimum surface tension 32–42 mN/m) even in the salt environment of ocean water [ Gilby and Heymann , 1951; Persson et al , 2003], and we expect that these components are unable to form a rigid condensed monolayer that would collapse by attached folds or vesicles. Whereas it is known that for long‐chain saturated fatty acids and charged lipids, the collapse surface pressure of the condensed phase is typically higher than 30–40 mN/m, and it can be significantly raised in a salt environment [ Gopal and Lee , 2006; Grigoriev et al , 1999; Longo et al , 1993].…”

Section: Discussionmentioning

confidence: 99%

Dissolution of microbubbles generated in seawater obtained offshore: Behavior and surface tension measurements

2007

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[1] Ocean water samples were collected from Saint Andrew Bay and the Gulf of Mexico near Panama City, Florida, on board the R/V Athena. Optical microscopy observations of the dissolution of microbubbles generated in these water samples showed that the microbubbles remained spherical and their surfaces remained smooth during dissolution. Comparatively, these bubbles behaved like bubbles coated with expanded phase surfactants, as we show by directly observing the dissolution of sodium dodecyl sulfate (SDS) bubbles and citing our previous work involving dissolution of short-chain lipidcoated microbubbles. We apply Epstein and Plesset's model for the dissolution of a 15 to 25 mm radius microbubble to determine surface tension, appropriate for a dissolving bubble coated with expanded phase surfactant. Average surface tensions of dissolving bubbles obtained in multiple locations and from two depths (from the sea-air surface and 10 feet (1 foot = 0.3048 m) below the sea-air surface) range between 21 and 37 dyn/cm with a resulting dissolution time of at least 2 times that of a clean microbubble at an initial radius of 15 mm. We never observed a remnant particle upon completion of dissolution, consistent with the observed smooth dissolution. These visual observations are in contrast to several studies involving visual observations of dissolution of seawater microbubbles. Reasons for these differences are postulated. Generally, our results are consistent with microbubbles coated primarily with short-chain and unsaturated fatty acids or lipids, but with a minority fraction of a long-chain component, all remaining in an expanded phase. Similarities in occasional dimpled morphology and surface tension with SDS/1,2-dipalmitoyl-sn-glycero-3-phosphocholine -coated bubbles are used to come to this conclusion.Citation: Lozano, M. M., E. Talu, and M. L. Longo (2007), Dissolution of microbubbles generated in seawater obtained offshore: Behavior and surface tension measurements,

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Oleic Acid Monolayers on Concentrated Salt Solutions

Cited by 5 publications

References 0 publications

Adsorption of Ions at Uncharged Insoluble Monolayers

Adsorption of Ions at Uncharged Insoluble Monolayers

Interactions between Small Inorganic Ions and Uncharged Monolayers on the Water/Air Interface

Dissolution of microbubbles generated in seawater obtained offshore: Behavior and surface tension measurements

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