Neutron and X-Ray Reflectivity Studies of the Adsorption of Aerosol-OT at the Air–Water Interface: The Structure of the Calcium Salt

Li, Z.X.; Lee, E.M.; Thomas, Robert K.; Penfold, J.

doi:10.1006/jcis.1996.4713

Cited by 20 publications

(15 citation statements)

References 13 publications

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“…Understanding the effect of surfactant structure on their ability to modify interfacial properties and form stable emulsions and microemulsions is a problem of great industrial and scientific importance. Since surfactants preferentially adsorb at an interface to form a monolayer, there have been extensive experimental − and theoretical − studies investigating the properties and behavior of surfactant monolayers at interfaces. The stability of surfactant monolayers adsorbed at an air–water interface as they undergo a reduction in the area per molecule via a lateral compression has also been well-studied. − Upon compression, the monolayers can undergo a 2D phase transition, as well as a collapse transition into various 3D structures. − At high surface coverage, the interfacial tension is very low or even negative, and the interface becomes unstable and can undergo mechanical buckling to increase the interfacial area.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Properties and Monolayer Collapse of Alkyl Benzenesulfonate Surfactant Monolayers at the Decane–Water Interface from Molecular Dynamics Simulations

et al. 2017

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The molecular structure of a surfactant molecule is known to have a great effect on the interfacial properties and the type of nanostructures formed. In this work, we have performed molecular dynamics simulations on six isomers of an alkyl benzenesulfonate surfactant to investigate the effect of the degree and position of aromatic substitution on the interfacial properties and on the collapse of the surfactant monolayer at a decane-water interface. The surface pressure of the monolayers was shown to increase with increasing surface coverage, until some of the monolayers become mechanically unstable and form large undulations. Shifting the primary alkyl chain of the surfactant from the para to the meta position was found to significantly affect the orientation of the surfactant head groups, while the attachment position of the benzene ring along the primary alkyl chain plays a greater role in the orientation of the surfactant tails. In general, to the extent considered in this work, our results suggest that additional alkyl substitution and meta substitution of the primary alkyl chains increase both the effectiveness and efficiency of the surfactants, and accelerate the onset of monolayer collapse. The interface was found to consist of an inner Helmholtz layer of partially dehydrated counterions in contact with the surfactant head groups, an outer Helmholtz layer of hydrated counterions, and a diffuse layer. The di- and trisubstituted surfactants formed nearly spherical swollen micelles encapsulating pure decane, which effectively solubilizes decane in water as a microemulsion. The monosubstituted surfactants formed elongated buds that protrude from the interface, but did not detach from the monolayer. To our knowledge, the role of aromatic substitution on interfacial properties has not been investigated by molecular simulations previously. The results from this work could provide insights to design improved surfactants by exploiting aromatic substitution to encapsulate material for drug delivery and other applications.

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Section: Introductionmentioning

confidence: 99%

Interfacial Properties and Monolayer Collapse of Alkyl Benzenesulfonate Surfactant Monolayers at the Decane–Water Interface from Molecular Dynamics Simulations

et al. 2017

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“…With the developments in technology, more and more spectroscopic tools have been applied in this field. X‐ray reflection1 and neutron reflection2–5 have been used to analyze the surface structure of liquids. The nonlinear optical methods are mainly used to determine the orientation of molecules on the surface 6, 7.…”

Section: Introductionmentioning

confidence: 99%

Surface structure of cationic surfactant solutions investigated by angular resolved X‐ray photoelectron spectroscopy with calibrated transmission function

Wang

Morgner

2011

Surface & Interface Analysis

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The main goal of the present work is to investigate the surface structure of cationic surfactant solutions by angular resolved X-ray photoelectron spectroscopy (ARXPS) after calibrating transmission function of the spectrometer. We have estimated the transmission function of the ARXPS spectrometer, and with it, we investigated solution of tetrabutylammonium iodide in a nonaqueous polar solvent. By genetic algorithm, the fractional concentration-depth profiles of constituents were reconstructed. These depth profiles evidence the enrichment of surfactant and the depletion of solvent in the surface regime and verify the separate distributions of oppositely charged surfactant ions. From those profiles we draw a conclusion that there is a preferred orientation for cation present at the surface, and the possibility for cation to take this orientation is related to its surface amount.

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“…There is now a large literature on the application of specular neutron reflection to hydrocarbon surfactants adsorbed at the air/water interface. − However, there is less work concerning its application to fluorinated surfactants, which is surprising considering their significant technological and industrial applications . An et al .…”

Section: Introductionmentioning

confidence: 99%

“…There is now a large literature on the application of specular neutron reflection to hydrocarbon surfactants adsorbed at the air/water interface. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] However, there is less work concerning its application to fluorinated surfactants, which is surprising considering their significant technological and industrial applications. 30 An et al 31 have studied the adsorption of several monovalent perfluorocarboxylates at the air/water interface, and Downes et al 32 have examined the adsorption of ammonium perfluorooctanoate (APFO) at the surface of its aqueous solution.…”

Section: Introductionmentioning

confidence: 99%

Effects of Hydrophobic Chain Structure on Adsorption of Fluorocarbon Surfactants with either CF₃− or H−CF₂− Terminal Groups

Downer¹,

Eastoe²,

Pitt³

et al. 1999

Langmuir

133

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Tensiometry and neutron reflection (NR) have been used to investigate the adsorption at the air/water interface of four fluorinated surfactants. These compounds were two single-chain carboxylatessodium perfluorononanoate (NaPFN) and sodium 9H-perfluorononanoate (HNaPFN)and two double-chain sulfosuccinatessodium bis(1H,1H-perfluoropentyl)-2-sulfosuccinate (DCF4) and sodium bis(1H,1H,5H-octafluoropentyl)-2-sulfosuccinate (DHCF4). The replacement of a terminal fluorine for hydrogen creates a permanent dipole in the hydrophobic chain tip which significantly affects the surfactant behavior. This change in structure leads to an increase in the critical micelle concentration (cmc) which was 10.0, 40.0, 1.6, and 16.0 mmol dm-3, respectively. At their cmc's the interfacial area per molecule was 41 and 44 Å2 for NaPFN and HNaPFN and 63 and 66 Å2 for DCF4 and DHCF4 as determined from NR. From tensiometry the values obtained were 43, 51, 56, and 65 Å2, respectively. For all four compounds the surface excess measured by tensiometry, using a prefactor of 2 in the Gibbs equation, was in reasonable agreement with that obtained from NR. Partial structure factors of the adsorbed layers were determined for all four surfactants. The widths of the surfactant distributions were found to be significantly broadened by roughness at the interface. The widths of the solvent distribution were about 5 Å for the carboxylates and essentially 6 Å for the sulfosuccinates. In all cases the measured separations of the water and surfactant distributions were 5 Å, indicating a greater penetration of water into the sulfosuccinate layers. The contribution of capillary waves to the surface roughness was examined in order to assess the static disorder of molecules in the adsorption layer. The presence of the chain dipole does not appear to cause any significant structural differences normal to the interface.

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Neutron and X-Ray Reflectivity Studies of the Adsorption of Aerosol-OT at the Air–Water Interface: The Structure of the Calcium Salt

Cited by 20 publications

References 13 publications

Interfacial Properties and Monolayer Collapse of Alkyl Benzenesulfonate Surfactant Monolayers at the Decane–Water Interface from Molecular Dynamics Simulations

Interfacial Properties and Monolayer Collapse of Alkyl Benzenesulfonate Surfactant Monolayers at the Decane–Water Interface from Molecular Dynamics Simulations

Surface structure of cationic surfactant solutions investigated by angular resolved X‐ray photoelectron spectroscopy with calibrated transmission function

Effects of Hydrophobic Chain Structure on Adsorption of Fluorocarbon Surfactants with either CF₃− or H−CF₂− Terminal Groups

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Neutron and X-Ray Reflectivity Studies of the Adsorption of Aerosol-OT at the Air–Water Interface: The Structure of the Calcium Salt

Cited by 20 publications

References 13 publications

Interfacial Properties and Monolayer Collapse of Alkyl Benzenesulfonate Surfactant Monolayers at the Decane–Water Interface from Molecular Dynamics Simulations

Interfacial Properties and Monolayer Collapse of Alkyl Benzenesulfonate Surfactant Monolayers at the Decane–Water Interface from Molecular Dynamics Simulations

Surface structure of cationic surfactant solutions investigated by angular resolved X‐ray photoelectron spectroscopy with calibrated transmission function

Effects of Hydrophobic Chain Structure on Adsorption of Fluorocarbon Surfactants with either CF3− or H−CF2− Terminal Groups

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Effects of Hydrophobic Chain Structure on Adsorption of Fluorocarbon Surfactants with either CF₃− or H−CF₂− Terminal Groups