Interfacial Tension of the Water/<i>n</i>-Alkane Interface

Goebel, Anna; Lunkenheimer, Klaus

doi:10.1021/la960800g

Cited by 379 publications

(359 citation statements)

References 29 publications

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“…2 shows the normalized interfacial tension g 0 ¼ g/g 0 as a function of time for two iron oxide core sizes and three PEG molecular weights, where g 0 ¼ 53.2 mN m À1 is the interfacial tension of the pure water/n-decane interface. 51 Analogously to what was reported in preliminary studies, 40,52 we observe that the bulk concentration c and the PEG molecular weight have a strong influence on the adsorption kinetics. As the concentration of the NP suspension increases we observe that the initial value of g 0 decreases; this is due to the fact that as the droplet is formed, a given number of particles (increasing with concentration) is already adsorbed at the interface leading to a value of g < g 0 above a size-dependent bulk concentration.…”

Section: Interfacial Tension Measurementssupporting

confidence: 84%

Adsorption of core-shell nanoparticles at liquid–liquid interfaces

et al. 2011

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The use of nanoparticles as building blocks for the self-assembly of functional materials has been rapidly increasing in recent years. In particular, two-dimensional materials can be effectively selfassembled at liquid interfaces thanks to particle localization and mobility at the interface in combination with tailoring of specific interactions. Many recent advances have been made in the understanding of the adsorption and assembly at liquid interfaces of small hydrophobic nanoparticles stabilized by short-chain rigid dispersants but the corresponding studies on core-shell nanoparticles sterically stabilized by extended hydrophilic polymer brushes are presently missing. Such particles offer significant advantages in terms of fabrication of functional, responsive and bio-compatible materials. We present here a combination of experimental and numerical data together with an intuitive and simple model aimed at elucidating the mechanisms governing the adsorption of iron oxide nanparticles (5-10 nm) stabilized by low molecular weight poly(ethylene glycol) (1.5-10 kDa). We show that the adsorption dynamics and the structure of the final assembly depend on the free energy of the particles at the interface and discuss the thermodynamics of the adsorption in terms of the polymer solubility in each phase.

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Section: Interfacial Tension Measurementssupporting

confidence: 84%

Adsorption of core-shell nanoparticles at liquid–liquid interfaces

et al. 2011

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“…The size of water-carbon interaction was taken as the average of SPC/E water-water distance [86] and OPLS methylene-methylene distance [18], σ wc = 0.35 nm, and the strength of the water-carbon interaction, ε wc = 0.17 kcal·mol −1 , was parameterized to reproduce the experimental liquid water-liquid nonane surface tension γ lw [37]. Here we follow the same procedure to parameterize ε wc for mW water and PYS alkanes by matching the liquid-liquid surface tension γ lw of nonane-water, hexadecane-water and eicosane-water to their experimental counterparts [87,88], assuming that σ wc = 0.35 nm. The optimized strength of interactions between mW water and PYS alkanes ε wc are 0.22, 0.20, 0.19 kcal·mol −1 for nonane (C9), hexadecane (C16) and eicosane (C20), respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Larger simulation cells would be required for an accurate determination of the melting temperatures of alkanes models. a T m determined with (100) interface; b ref [96]; c at T = 295 K; d at T = 295 K from ref [87]; e T = 298 K; f at T = 299 K from ref [98]; g T = 307 K; h T = 219 K; i at T = 219.5 K from ref [99].…”

Section: Thermodynamics Of Pure Alkanesmentioning

confidence: 99%

“…Green, red, blue curves correspond to surface tensions of OPLS nonane (C9), PYS nonane (C9) and PYS hexadecane (C16), respectively. The surface tensions are computed at the same temperatures as in the experimental references: 295 K for nonane [87] and 313.15 K for hexadecane 97 . Solid squares represent the εwc at which experimental surface tension are reproduced.…”

Section: Strength Of the Alkane-solvent Attraction Determines Whethermentioning

confidence: 99%

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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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“…10 times) according the suggestions from Gaonkar and Newman 23 and Goebel and Lunkenheimer. 24 The initial purity of this compound was 97.75 wt %, and after purification, it was 99.88 wt %, as determined by gas chromatography (GC).…”

Section: Methodsmentioning

confidence: 99%

Viscosities of Liquid Fluorocompounds

et al. 2008

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In spite of their interest, viscosities of fluorocarbon compounds are scarce, and the available data are unreliable and of poor accuracy. In this work, viscosity measurements of linear, cyclic, aromatic, and R-substituted perfluorocarbons were carried out in the temperature range between (298.15 and 318.15) K using an Ubbelohde viscometer. The experimental results show that fluorinated compounds present viscosities considerably higher than their hydrocarbon homologues as expected. The viscosities increase from linear to aromatic to cyclic perfluorocarbons and within each family with the molecule size. The R-fluorine substitution by bromine increases the fluorocarbon viscosity due to the molecular weight increase. The Sastri-Rao method, a group contribution method for the liquid viscosity prediction, was applied for all the fluorocarbons where the viscosity was experimentally measured in this work. Using the new experimental data from this work, new group contribution values are proposed for fluorocarbon compounds allowing for a reduction of the average relative deviation from 12.0 % to 1.3 %.

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Interfacial Tension of the Water/n-Alkane Interface

Cited by 379 publications

References 29 publications

Adsorption of core-shell nanoparticles at liquid–liquid interfaces

Adsorption of core-shell nanoparticles at liquid–liquid interfaces

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

Viscosities of Liquid Fluorocompounds

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