Molecular dynamics study of the water/n-alkane interface

Xiao, Hongling; Zhen, Zhen; Sun, Huai; Cao, Xun; Li, Zhenquan; Song, Xinwang; Cui, Xiaohong; Liu, Xinhou

doi:10.1007/s11426-010-0118-8

Cited by 26 publications

(22 citation statements)

References 28 publications

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“…In the absence of SDS, the orientation of DMSO is determined by the orientation distribution of water or hexane in the vicinity of interface, depending on which side the DMSO molecule is located. As reported by Xiao et al (2010), in a water/n-alkane interface system, the water molecules (more specifically, the dipole axis of water) presented a slight orientation preference of cos θ ¼0.03 at the interfacial center (z ¼ 0), which was gradually reduced to a minimum value of cos θ ¼ À0:03 at z ¼ À0:3 nm (i.e., a position within the interfacial region while close to water-rich phase) and thereafter increased and became zero when z o À 1:0 nm (i.e., in Fig. 5.…”

Section: Dynamic Properties Of the Transport Processsupporting

confidence: 60%

Effect of surfactant SDS on DMSO transport across water/hexane interface by molecular dynamics simulation

Hu¹,

Lv²,

Zhao³

et al. 2015

Chemical Engineering Science

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Section: Dynamic Properties Of the Transport Processsupporting

confidence: 60%

Effect of surfactant SDS on DMSO transport across water/hexane interface by molecular dynamics simulation

Hu¹,

Lv²,

Zhao³

et al. 2015

Chemical Engineering Science

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“…The graph suggests that the water dipole moment orients near the interface. The orientational persistence length of water near a hydrophobic interface is 0.440 nm and is in good agreement with previous studies [45,46]. As is suggested by van Buuren et al [46], at the interface the number of neighboring water molecules available for hydrogen bonding is smaller, and the water molecules orient themselves to create more possibilities for hydrogen bonding.…”

Section: Characterization Of the Interface: Orientation Of Water Molesupporting

confidence: 91%

Molecular dynamics study of rhodamine 6G diffusion atn-decane–water interfaces

2015

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Two-dimensional diffusion of a rhodamine 6G fluorescent tracer molecule at the n-decane/water interface was studied with all-atom molecular dynamics (MD) simulations. In agreement with experimental data, we find increased mobility of the tracer at the n-decane/water interfaces in comparison to its mobility in bulk water.Orientational ordering of water and n-decane molecules near the interface is observed, and may change the interfacial viscosity as suggested to explain the experimental data.However, the restricted rotational motion of the rhodamine molecule at the interface suggests that Saffman-Delbrück model may be a more appropriate approximation of rhodamine diffusion at n-decane/water interfaces, and, without any decrease in interfacial viscosity, suggests faster diffusion consistent with both experimental and simulation values.

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“…That result is consistent with previous molecular simulations of alkane-water slabs that found the alkane to be more parallel at the interface than in the bulk of the liquid [10,11]. The first goal of this study is to identify which property controls the interfacial ordering of alkanes.…”

Section: Introductionsupporting

confidence: 89%

Strength of Alkane–Fluid Attraction Determines the Interfacial Orientation of Liquid Alkanes and Their Crystallization through Heterogeneous or Homogeneous Mechanisms

Qiu

Molinero

2017

Crystals

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Abstract:Alkanes are important building blocks of organics, polymers and biomolecules. The conditions that lead to ordering of alkanes at interfaces, and whether interfacial ordering of the molecules leads to heterogeneous crystal nucleation of alkanes or surface freezing, have not yet been elucidated. Here we use molecular simulations with the united-atom OPLS and PYS alkane models and the mW water model to determine what properties of the surface control the interfacial orientation of alkane molecules, and under which conditions interfacial ordering results in homogeneous or heterogeneous nucleation of alkane crystals, or surface freezing above the melting point. We find that liquid alkanes present a preference towards being perpendicular to the alkane-vapor interface and more parallel to the alkane-water interface. The orientational order in the liquid is short-ranged, decaying over~1 nm of the surface, and can be reversed by tuning the strength of the attractions between alkane and the molecules in the other fluid. We show that the strength of the alkane-fluid interaction also controls the mechanism of crystallization and the face of the alkane crystal exposed to the fluid: fluids that interact weakly with alkanes promote heterogeneous crystallization and result in crystals in which the alkane molecules orient perpendicular to the interface, while crystallization of alkanes in the presence of fluids, such as water, that interact more strongly with alkanes is homogeneous and results in crystals with the molecules oriented parallel to the interface. We conclude that the orientation of the alkanes at the crystal interfaces mirrors that in the liquid, albeit more pronounced and long-ranged. We show that the sign of the binding free energy of the alkane crystal to the surface, ∆G bind , determines whether the crystal nucleation is homogeneous (∆G bind ≥ 0) or heterogeneous (∆G bind < 0). Our analysis indicates that water does not promote heterogeneous crystallization of the alkanes because water stabilizes more the liquid than the crystal phase of the alkane, resulting in ∆G bind > 0. While ∆G bind < 0 suffices to produce heterogeneous nucleation, the condition for surface freezing is more stringent, ∆G bind < −2 γ xl , where γ xl is the surface tension of the liquid-crystal interface of alkanes. Surface freezing of alkanes is favored by their small value of γ xl . Our findings are of relevance to understanding surface freezing in alkanes and to develop strategies for controlling the assembly of chain-like molecules at fluid interfaces.

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Molecular dynamics study of the water/n-alkane interface

Cited by 26 publications

References 28 publications

Effect of surfactant SDS on DMSO transport across water/hexane interface by molecular dynamics simulation

Effect of surfactant SDS on DMSO transport across water/hexane interface by molecular dynamics simulation

Molecular dynamics study of rhodamine 6G diffusion atn-decane–water interfaces

Strength of Alkane–Fluid Attraction Determines the Interfacial Orientation of Liquid Alkanes and Their Crystallization through Heterogeneous or Homogeneous Mechanisms

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