Adsorption and Wetting Phenomena Associated with Graphon in Aqueous Surfactant Solutions

Greenwood, F. G.; Parfitt, G. D.; Picton, N. H.; Wharton, David

doi:10.1021/ba-1968-0079.ch011

Cited by 36 publications

(34 citation statements)

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“…Manne et al observed periodicities about twice the surfactant length. Therefore, the idea of an alternating head-to-tail packing in a monolayer of horizontally adsorbed surfactant molecules, as the reorientation model suggested, 32,33,45 is not supported by these observations. The plane of the carbon skeleton of alkyl derivatives can be oriented either perpendicular to or parallel with the substrate surface.…”

Section: Discussionmentioning

confidence: 84%

“…36 These results challenge current views on how ionic surfactant molecules assemble on hydrophobic substrates. Apart from some electrophoretic mobility measurements 40,[42][43][44] and contact angle measurements, 45 earlier studies of the adsorption of ionic surfactants on carbon-type surfaces were mainly restricted to the analysis of the adsorption isotherms [37][38][39][40][41][42][43][44][45] and the general conclusions, regarding the structure of the adsorption layer at surface saturation, supported the formation of a vertically adsorbed monolayer. The interpretation of the few calorimetric data available for relevant systems led to similar conclusions.…”

Section: Introductionmentioning

confidence: 99%

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Calorimetric Evidence of the Formation of Half-Cylindrical Aggregates of a Cationic Surfactant at the Graphite/Water Interface

1998

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The adsorption of a cationic surfactant, dodecyltrimethylammonium bromide (C 12 TAB), from aqueous solutions on graphitized carbon black has been investigated from 288.15 to 318.15 K using a versatile, automated measuring system, which has been designed for the simultaneous measurement of the adsorption isotherm and the calorimetric enthalpies of displacement at the solid/liquid interface. At low concentrations, the surfactant molecules form a flat monolayer on the graphite surface. The enthalpy of monolayer formation is apparently not (or only slightly) dependent on the temperature and is independent of the surface coverage (-61 kJ‚mol -1 ). The adsorption proceeds further as the concentration in the bulk solution is increased to the cmc. In this region, the enthalpy of displacement is again nearly independent of the surface coverage but depends strongly on the temperature: -10.7, -17.5, and -29 kJ‚mol -1 at 288.15, 298.15, and 318.15 K, respectively. The mechanism of the adsorption and the morphology of the high-density adsorbate structure have been analyzed in terms of the classical reorientation model (reorientation of the adsorbed surfactant molecules from a horizontal to a vertical orientation, accompanied by further adsorption from the bulk solution) and in terms of a recent concept of interfacial aggregation (formation of half-cylindrical surface micelles templated by an epitaxially bound surfactant monolayer). The results of the thermodynamic analysis strongly support the formation of C 12 TAB half-cylinders at the graphite/water interface.

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Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Calorimetric Evidence of the Formation of Half-Cylindrical Aggregates of a Cationic Surfactant at the Graphite/Water Interface

1998

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“…To determine the shape of the adsorbed structure, it is also useful to quantitatively compare the data presented here to the adsorption isotherm of SDS on graphon measured by Greenwood et al 5 To convert their values of area density to our periodicity requires an estimate of the width of a hydrocarbon chain. The minimum width is the van der Waals radius of a hydrocarbon chain, approximately 0.6 nm.…”

Section: Results and Analysismentioning

confidence: 99%

“…5,6 Greenwood et al 5 showed that adsorption was first measurable at about 1 mM SDS, reached a plateau at approximately half maximum density from about 2 to 4 mM, and then reached a maximum at about 7 mM SDS. Similar results were obtained by Zettlemoyer.…”

Section: Introductionmentioning

confidence: 99%

Organization of Sodium Dodecyl Sulfate at the Graphite−Solution Interface

1996

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The aggregated structure of sodium dodecyl sulfate (SDS) adsorbed to the graphite-solution interface has been determined. Atomic force microscopy reveals that SDS adsorbs in periodic structures when the solution concentration is in the range 2.8-81 mM. Using previously obtained adsorption isotherms, we deduce that these structures are hemicylindrical, but we are not able to determine their length. The long axes of the hemicylinders lie parallel in grains which typically extend over (500 nm) 2 to (1000 nm) 2 , but the grain size can be reduced by adsorption of other species from solution. Two basic types of grain boundaries have been identified: broad boundaries, where the periodicity of both grains continue into the boundary for several periods, and narrow boundaries, where one or both of the hemicylindrical arrays terminate within a short distance. The period within each grain decreases when the concentration of SDS or the concentration of added NaCl is increased and approaches the diameter of bulk micelles at high concentration. In NaCl solutions, the period is proportional to the solution Debye length. We propose that this is a result of a decrease in interaggregate spacing rather than a decrease in aggregate size. Using a simple geometric argument, we suggest that the curvature of surfactant aggregates on hydrophobic surfaces will usually be lower than that of aggregates in bulk solution with which they are in equilibrium.

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“…For a model hydrophobic surface, carbon black has been chosen [22,23], and Figure 5.5 shows the typical results for the adsorption of sodium dodecyl sulphate (SDS) onto two carbon black surfaces, namely Spheron 6 (untreated) and Graphon (graphitised), which also describes the effect of surface treatment. For a model hydrophobic surface, carbon black has been chosen [22,23], and Figure 5.5 shows the typical results for the adsorption of sodium dodecyl sulphate (SDS) onto two carbon black surfaces, namely Spheron 6 (untreated) and Graphon (graphitised), which also describes the effect of surface treatment.…”

Section: Adsorption Of Ionic Surfactants On Hydrophobic Surfacesmentioning

confidence: 99%

Adsorption of Surfactants at the Air/Liquid, Liquid/Liquid, and Solid/Liquid Interfaces

2014

Formulation of Disperse Systems

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Adsorption and Wetting Phenomena Associated with Graphon in Aqueous Surfactant Solutions

Cited by 36 publications

References 0 publications

Calorimetric Evidence of the Formation of Half-Cylindrical Aggregates of a Cationic Surfactant at the Graphite/Water Interface

Calorimetric Evidence of the Formation of Half-Cylindrical Aggregates of a Cationic Surfactant at the Graphite/Water Interface

Organization of Sodium Dodecyl Sulfate at the Graphite−Solution Interface

Adsorption of Surfactants at the Air/Liquid, Liquid/Liquid, and Solid/Liquid Interfaces

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