Understanding the Structure of Hydrophobic Surfactants at the Air/Water Interface from Molecular Level

Zhang, Li; Liu, Zhi-Pei; Ren, Tao; Wu, Pan; Shen, Jia-Wei; Zhang, Wei; Wang, Xinping

doi:10.1021/la5030586

Cited by 26 publications

(11 citation statements)

References 32 publications

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“…Numerous MD simulation studies of lipids and surfactants at the air–water interface have been performed to investigate the monolayer properties and collapse mechanism. − However, simulations of monolayers at the liquid–liquid interface are rather limited. ,− Shi and Guo performed all-atom MD simulation of sodium dodecyl sulfate (SDS)-type surfactants at the water-trichoroethylene interface and observed the formation of a swollen micelle for the shorter chain SDS surfactant while the longer sodium tetracosyl sulfate (STS) formed an ordered condensed phase and did not undergo a collapse transition. Li et al used dissipative particle dynamics to investigate the interfacial properties of CTAB surfactants at the oil–water interface and found that the microstructures formed depend on the oil–water ratio.…”

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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“…As shown in Table 1 and Figure explanations for this phenomenon [32]. The isopropylidene group interrupts the crystalline structure of the surfactant, and thus surfactant IV-D does not align or pack well at the liquid-air interface.…”

Section: Insert Schemementioning

confidence: 95%

Fluorinated pyridinium and ammonium cationic surfactants

Yake

Corder

Moloy

et al. 2016

Journal of Fluorine Chemistry

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“…where V cal is the total physical volume of surfactant molecular fragments, 54,55 and V meas is the total volume occupied by a surfactant molecule at the water-CO 2 interface. In this work, F surf for the di-CF4 molecule was calculated to be 0.788 lower than the experimental value of 0.970.…”

Section: Surfactant Coveragementioning

confidence: 99%

Molecular dynamics study of di-CF4 based reverse micelles in supercritical CO₂

Liu

Tang

Fang

et al. 2016

Phys. Chem. Chem. Phys.

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Reverse micelles (RMs) in supercritical CO (scCO) are promising alternatives for organic solvents, especially when both polar and non-polar components are involved. Fluorinated surfactants, particularly double-chain fluorocarbon surfactants, are able to form well-structured RMs in scCO. The inherent self-assembly mechanisms of surfactants in scCO are still subject to discussion. In this study, molecular dynamics simulations are performed to investigate the self-aggregation behavior of di-CF4 based RMs in scCO, and stable and spherical RMs are formed. The dynamics process and the self-assembly structure in the RMs reveal a three-step mechanism to form the RMs, that is, small RMs, rod-like RMs and fusion of the rod-like RMs. Hydrogen-bonds between headgroups and water molecules, and salt bridges linking Na ions, headgroups and water molecules enhance the interfacial packing efficiency of the surfactant. The results show that di-CF4 molecules have a high surfactant coverage at the RM interface, implying a high CO-philicity. This mainly results from bending of the short chain (C-COO-CH-(CF2)-CF3) due to the flexible carboxyl group. The microscopic insight provided in this study is helpful in understanding surfactant self-assembly phenomena and designing new CO-philic surfactants.

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Understanding the Structure of Hydrophobic Surfactants at the Air/Water Interface from Molecular Level

Cited by 26 publications

References 32 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

Fluorinated pyridinium and ammonium cationic surfactants

Molecular dynamics study of di-CF4 based reverse micelles in supercritical CO₂

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Understanding the Structure of Hydrophobic Surfactants at the Air/Water Interface from Molecular Level

Cited by 26 publications

References 32 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

Fluorinated pyridinium and ammonium cationic surfactants

Molecular dynamics study of di-CF4 based reverse micelles in supercritical CO2

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Product

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Molecular dynamics study of di-CF4 based reverse micelles in supercritical CO₂