Interfacial tensions and viscosities in multiphase systems by surface light scattering (SLS)

Koller, Thomas M.; Prucker, Tobias; Cui, Junwei; Klein, Tobias; Fröba, Andreas P.

doi:10.1016/j.jcis.2018.11.095

Cited by 20 publications

(8 citation statements)

References 71 publications

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“…For fluids with relatively small viscosities and/or large surface or interfacial tensions, an oscillatory behavior of surface fluctuations is found by examining typically investigated wavelengths of fluctuations below about 10 µm [48][49][50]. This enables a simultaneous determination of viscosity and surface tension by SLS [48,[50][51][52][53][54]. Fluids with relatively large viscosities and/or small surface or interfacial tensions show an overdamped behavior of surface fluctuations (ω q = 0) [48,49], which holds also for all present measurements.…”

Section: Surface Light Scatteringmentioning

confidence: 99%

Surface Tension and Viscosity of Binary Mixtures of the Fluorinated and Non-fluorinated Ionic Liquids [PFBMIm][PF6] and [C4C1Im][PF6] by the Pendant Drop Method and Surface Light Scattering

et al. 2020

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Mixtures of fluorinated and non-fluorinated ionic liquids (ILs) show a distinct structural organization in the bulk and at the surface. To understand how such microscopic effects influence the macroscopic bulk and surface properties of IL mixtures, knowledge of corresponding thermophysical properties including viscosity and surface tension is required yet lacking. With the intention of investigating surface enrichment effects of the fluorinated IL [PFBMIm][PF 6 ] (3-methyl-1-(3,3,4,4,4pentafluorobutyl)imidazolium hexafluorophosphate) in mixtures with the structurally similar, non-fluorinated IL [C 4 C 1 Im][PF 6 ] (1-butyl-3-methylimidazolium hexafluorophosphate) observed with angle-resolved X-ray photoelectron spectroscopy (ARXPS), the pendant drop method and surface light scattering (SLS) were applied in the present study to determine surface tension and dynamic viscosity between (293 and 368) K. By adding small amounts of [PFBMIm][PF 6 ] up to 9 mol %, a distinct increase in the viscosity and decrease in the surface tension of the mixtures relative to the properties of pure [C 4 C 1 Im][PF 6 ] was found. This behavior reflects the nanosegregated structure in the bulk and at the surface of the binary IL mixtures. Using the results about the pronounced surface enrichment of the fluorinated chain of [PFBMIm][PF 6 ] quantified by ARXPS, a linear mixing rule for the surface tension of the IL mixtures based on the surface tensions of the pure ILs and the surface concentration of their most surface-active groups is suggested.

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Section: Surface Light Scatteringmentioning

confidence: 99%

Surface Tension and Viscosity of Binary Mixtures of the Fluorinated and Non-fluorinated Ionic Liquids [PFBMIm][PF6] and [C4C1Im][PF6] by the Pendant Drop Method and Surface Light Scattering

et al. 2020

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“…This technique probes the dynamics of thermal surface fluctuations at phase boundaries in a contactless way in macroscopic thermodynamic equilibrium and enables the absolute determination of viscosity and/or surface tension [20,21]. Besides its use within thermophysical property research [21], SLS has been applied to characterize interfaces of complex fluids including IL-cosolvent mixtures [22], surfaces covered by adsorbed layers [20], and multiphase systems [23]. From the study of the dynamics of the surface fluctuations with a defined wave vector that is reflected by the temporal behavior of the scattered light intensity, viscosity or surface tension and -for ILs with relatively low-viscosity -both properties are accessible with typical uncertainties (k = 2) of 3 % and below; see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

Combined Surface Light Scattering and Pendant-Drop Experiments for the Determination of Viscosity and Surface Tension of High-Viscosity Fluids Demonstrated for Ionic Liquids

et al. 2022

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The present study provides a strategy for the determination of the viscosity and surface tension of high-viscosity fluids in the form of ionic liquids (ILs) at equilibrium conditions by combining surface light scattering (SLS) and the pendant-drop (PD) method within one experimental setup. Through the study of the same sample under identical conditions by both methods inside a closed system, the surface tension determined via the PD method can be directly used to evaluate the dynamics of surface fluctuations of ILs with an overdamped behavior probed by SLS for accessing their viscosity. In connection with the SLS experiments, variations in the applied detection geometries in reflection and transmission direction and in the probed wave vectors down to relatively small values were also addressed. The reliability and self-consistency of SLS and the PD method applied within the same sample cell has been proven by investigating the reference fluids tris(2-ethylhexyl) trimellitate (TOTM) and n-dodecane featuring relatively high and low viscosities. For the two studied model ILs of opaque to non-transparent color, i.e., the hydrophobic 1-methyl-3-octylimidazolium hexafluorophosphate ([OMIM][PF6]) and the hydrophilic 1,3-bis(2-(2-methoxyethoxy)ethyl)imidazolium iodide ([(mPEG2)2Im]I), the combination of PD measurements and SLS experiments in reflection direction performed at ambient pressure between (303 and 373) K allowed access to the viscosity and surface tension with typical relative expanded uncertainties of (4 and 2) %. These results agree well with own viscosity data from capillary viscometry and experimental data in the literature, demonstrating the performance of the novel approach for the contactless in-situ measurement of viscosity and surface tension of fluids with relatively high-viscosity such as ILs.

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“…For the absolute determination of the liquid viscosity and the interfacial tension in macroscopic thermodynamic equilibrium, the contactless, optical technique surface light scattering (SLS) is used in this work as well as previous publications. − Using this method, the temporal behavior of light scattered from microscopic surface fluctuations at a phase boundary is analyzed and related to the fluid properties according to the complete theoretical description of the dynamics of surface waves. , This SLS technique has been successfully applied to a variety of reference fluids and multiphase systems ,− with typical expanded uncertainties ( k = 2) of both properties of 2%.…”

Section: Introductionmentioning

confidence: 99%

Viscosity, Interfacial Tension, and Density of Binary-Liquid Mixtures of n-Hexadecane with n-Octacosane, 2,2,4,4,6,8,8-Heptamethylnonane, or 1-Hexadecanol at Temperatures between 298.15 and 573.15 K by Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

et al. 2021

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This work contributes to the characterization of three binary liquid hydrocarbon-based mixtures via the determination of density, viscosity, and interfacial tension over the entire concentration range up to temperatures of 573.15 K. The oscillating-tube method, surface light scattering (SLS), and equilibrium molecular dynamics (EMD) simulations are applied to analyze the influences of chain length, branching, and hydroxylation on the aforementioned thermophysical properties. For probing these effects, the three binary systems of n-hexadecane (1) with n-octacosane (2), 1-hexadecanol (2), or 2,2,4,4,6,8,8-heptamethylnonane (2), each with mole fraction of x 1 = 0.25, 0.5, or 0.75, are investigated in macroscopic thermodynamic equilibrium at or close to saturation conditions at temperatures between 298.15 and 573.15 K. Based on the experimental results for the liquid densities, liquid viscosities, and interfacial tensions with average expanded uncertainties (k = 2) of 0.10, 2.0, and 1.8%, respectively, our previously published modification to the optimized potentials for the liquid simulations (OPLS) force field for long hydrocarbons (L-OPLS) is evaluated for its transferability to liquid mixtures in EMD simulations. Considering all simulation results, the average absolute relative deviations for the density, viscosity, and interfacial tension are 0.74, 27, and 14%, respectively. Experimental results are also applied for the evaluation of simple prediction models based on pure-component properties. Especially at high temperatures, such simple mixing rules perform well. At lower temperatures, however, nonidealities like surface enrichment or the formation of molecule clusters in the mixture are more likely to dominate fluid behavior, leading to a failure of the simple mixing rules. To explain this observation, partial-density profiles and radial distribution functions from simulations, giving access to the fluid structure on a microscopic level, are evaluated.

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Interfacial tensions and viscosities in multiphase systems by surface light scattering (SLS)

Cited by 20 publications

References 71 publications

Surface Tension and Viscosity of Binary Mixtures of the Fluorinated and Non-fluorinated Ionic Liquids [PFBMIm][PF6] and [C4C1Im][PF6] by the Pendant Drop Method and Surface Light Scattering

Surface Tension and Viscosity of Binary Mixtures of the Fluorinated and Non-fluorinated Ionic Liquids [PFBMIm][PF6] and [C4C1Im][PF6] by the Pendant Drop Method and Surface Light Scattering

Combined Surface Light Scattering and Pendant-Drop Experiments for the Determination of Viscosity and Surface Tension of High-Viscosity Fluids Demonstrated for Ionic Liquids

Viscosity, Interfacial Tension, and Density of Binary-Liquid Mixtures of n-Hexadecane with n-Octacosane, 2,2,4,4,6,8,8-Heptamethylnonane, or 1-Hexadecanol at Temperatures between 298.15 and 573.15 K by Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

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