Composition of Stearic Acid Monolayers from Calcium-Containing Substrates

Bagg, J.; Abramson, Maxwell; Fichman, Martin.; Haber, Mary D; Gregor, Harry P.

doi:10.1021/ja01068a001

Cited by 74 publications

(15 citation statements)

References 2 publications

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“…This is dependent on the polarity and the surface charge density of the monolayer-water interface and other factors. Similar results were observed by other researchers [9,16,171. In their studies, electrolytes (metal ions, H+ or OH-ions) in the interfacial region have higher concentrations than in the bulk.…”

Section: Acid-base Equilibria Of Hhq At Air-water Interfacesupporting

confidence: 92%

Acid-base equilibria of air-water monolayers ofN-hexadecyl-8-hydroxy-2-quinolinecarboxamide

Ouyang

Tai

Tang

1996

Mol Eng

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The surface pressure-area (T-A) isotherms of N-hexadecyl-8-hydroxy-2-quinolinecarboxamide (HHQ) monolayers at an air-water interface on subphases with different pH values were investigated. The monolayer of HHQ was expanded and unstable on acidic subphases, while it was condensed and stable on basic subphases. The acid-base equilibrium of HHQ was investigated in an aqueous dioxane solution and at the air-water interface. The association-dissociation of HHQ with H+ ions in the interfacial region was very different from that in the aqueous dioxane solution. Some information regarding the packing density, phase transition and degree of ionization of the head group under different experimental conditions has been obtained.

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Section: Acid-base Equilibria Of Hhq At Air-water Interfacesupporting

confidence: 92%

Acid-base equilibria of air-water monolayers ofN-hexadecyl-8-hydroxy-2-quinolinecarboxamide

Ouyang

Tai

Tang

1996

Mol Eng

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“…In experiments where a monolayer source was used, the monolayers were deposited by the method of Langmuir-Blodgett described by Blodgett (1935). Half the surface (52 x 10 mm area) of the IRE was submerged in a Langmuir trough containing water with enough hydrochloric acid to reduce the pH to 4.0 as suggested by previous workers (Bagg et al, 1964). Stearic acid was spread on the water surface from a hexane solution, compressed with an oleic acid piston.…”

Section: Methodsmentioning

confidence: 99%

Surface diffusion of stearic acid on aluminum oxide

1974

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By means of infrared internal reflection spectroscopy we measured the time dependence of the surface concentration of stearic acid molecules over a well defined region of the surface. The molecules were diffusing into this region from a source comprising a compressed monolayer or bulk crystalline material outside the field of view. By these measurements in conjunction with solutions to the diffusion equations we determined the diffusion coefficient D, of stearic acid on the (0001) plane of a-alumina.We also determined the dependence of D, upon the amount of water CO-adsorbed on the surface. When the surface was free of reversibly adsorbed water, D, had a value of about 2 x 10-7 cm2/s. As the surface coverage of coadsorbed water increased to about a monolayer D, increased to a maximum value of about 4 x 10-5 cm2/s. With further additions of surface water D, then decreased and became less than 10-8 cm2/s at coverages slightly less than about two monolayers. In the region of its maximum value the temperature dependence of D, indicated SCOPEAn accurate experimental method is needed to measure surface diffusion rates on nonporous surfaces. Plane surfaces provide simple models for the study of the general phenomenon of surface flux which contributes to transport through catalyst pellets, adsorbent beds, and the diffusion barriers used in important separation processes. Most previous studies of surface diffusion have been based on a determination of total diffusive flow through porous materials. Gas chromatography, nuclear magnetic resonance, and neutron scattering spectroscopy have been employed for this purpose. The contribution due to Knudsen flow is then calculated and subtracted from the total. The difference is attributed to surface diffusion. Clearly, this approach is not applicable to nonvolatile species, but it is the least volatile component in any system which is most affected by surface diffusion.The direct measurements of surface diffusion on solids previously reported were by Beischer (1951) and Rideal and Tadayon (1954). They determined the diffusion coefficient of stearic acid on mica by means of radioactive tracer techniques. Our method is also based on a direct observation of transport in adsorbed layers on planar surfaces. It uses the somewhat simpler and more generally applicable technique of Internal Reflection Spectroscopy (IRS) to measure time dependent surface concentration. The results are combined with approximate solutions of the Fick diffusion equations under appropriate boundary conditions to give surface diffusion coefficients.Water adsorbed on a solid surface often has a dramatic effect upon the rates of interphase exchange or chemical reactions at that surface. In at least one case, where surface transport is the slow step, it has been shown that the marked effect of adsorbed water on the rate of reaction is due to its influence on the rate of diffusion (Levy and Boudart, 1974). In this paper we report the effect of coadsorbed water on the surface diffusion of stearic acid on aluminum ...

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“…On the other hand, the satisfactory linear dependence of the experimental results in the theoretical 0 a~+ vs. 0/ scale required by Equation (16) (Ig (1 -8) 2 aM2+ / established in References [4] and [6], is not substantiaUy sensible to the presence of the additional factor, because of the almost linear shape of the function Ig 2-8 vs. 8. This factor, however, alters the values of 4 (15) gex found in [4][5][6]16] as well as the slopes of the straight lines which give co and A1, 2 (see further).…”

Section: (2-o)4+mentioning

confidence: 98%

“…Moreover, often in studies employing the LangmuirBlodgett technique, the values of the surface pressure at which the transfer (or the interaction with the counterions) is carried out are not reported [13] or the transfer (reaction) does not take place at strictly maintained H .... t [15].…”

Section: (2-o)4+mentioning

confidence: 99%

Equilibrium constants of ion exchange reactions between fatty acid monolayers and dissolved counterions

Petrov

Platikanov

1987

Colloid & Polymer Sci

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Equations for equilibrium constants of ion exchange between fatty acid monolayers and subsolution counterions are derived. The approach of Matsubara et al. [4], where the monolayer is considered as a two-dimensional regular mixture is employed, but the different molar volumes of its components are taken into account. Using the equations obtained the Kex values are calculated on the basis of published data on the monolayer composition in the systems Cd2+/HArch, Ba2+/HArch, Ca2+/HSt, pb2+/ HSt and Cu 2 +/HSt. The stability constants of the corresponding soaps formed in the monolayer are also obtained.

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Composition of Stearic Acid Monolayers from Calcium-Containing Substrates

Cited by 74 publications

References 2 publications

Acid-base equilibria of air-water monolayers ofN-hexadecyl-8-hydroxy-2-quinolinecarboxamide

Acid-base equilibria of air-water monolayers ofN-hexadecyl-8-hydroxy-2-quinolinecarboxamide

Surface diffusion of stearic acid on aluminum oxide

Equilibrium constants of ion exchange reactions between fatty acid monolayers and dissolved counterions

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