Experimental Surface Tension Data Research Articles

Physical and Transport Properties of Bis(trifluoromethylsulfonyl)imide-Based Room-Temperature Ionic Liquids: Application to the Diffusion of Tris(2, 2 ′ -bipyridyl)ruthenium(II)

The densities, viscosities, molar conductivities, and surface tensions of room temperature ionic liquids based on the bis(trifluoromethylsulfonyl)imide anion and the 1-(1-butyl)-3-methylimidazolium, 1-butyltrimethylammonium, 1-(1-butyl)-1-methyl- pyrrolidinium, 1-(1-butyl) pyridinium, and 1-ethyl-3-methylimidazolium cations were measured as a function of temperature over the range from . The surface tension of tri-(1-butyl)methylammonium bis(trifluoromethylsulfonyl)imide is also reported. Linear equations were fitted to the experimental density and surface tension data, and the Vogel–Tammann–Fulcher equation for glass-forming liquids was fitted to the experimental viscosity and conductivity data. The surface energies, surface entropies, and critical temperatures were estimated from the temperature dependence of the surface tension data. All of the liquids studied obey the fractional Walden rule and fall only slightly below the ideal line, indicating that they possess high ionicity. In each case, the viscosity shows only modest decoupling from the conductivity as the temperature is increased. Diffusion coefficients for the oxidation of tris(2,-bipyridyl)ruthenium(II) were measured in the six ionic liquids as a function of temperature. The hydrodynamic radius of tris(2,-bipyridyl)ruthenium(II) was estimated from the Stokes–Einstein equation and was found to be remarkably close to the crystallographic radius of this species.

Bulk and surface properties of liquid Sb–Sn alloys

The mixing behaviour of liquid Sb–Sn alloys has been described in terms of energetics and structure through the study of their thermodynamic, surface, transport and structural properties by using the Complex Formation Model (CFM) in the weak interaction approximation and by postulating SbSn chemical complexes as energetically favoured. The new Sb–Sn surface tension experimental data, obtained by the pinned drop method at temperatures ranging from 513 to 1023 K , have been analysed in the framework of the CFM and compared with the calculated values as well as with the corresponding literature data. The structural characteristics of Sb–Sn melts are described by the two microscopic functions, i.e. the concentration fluctuations in the long-wavelength limit and the Warren–Cowley short-range order parameter.

Classic Force Field for Predicting Surface Tension and Interfacial Properties of Sodium Dodecyl Sulfate

A classical force field capable for accurately predicting surface tensions, surface concentration, and other interfacial properties is reported for sodium dodecyl sulfate (SDS). This force field is proposed by combining parameters from well established force fields for components of the air/SDS/water interface and optimized by adjusting the van der Waals diameter of sulfate oxygen to fit experimental data of surface tension. The force field parameters are transferable; as good agreement with experimental data is achieved from independent calculations on activity derivatives of aqueous solution of sodium methyl sulfate using the Kirkwood-Buff theory. The adjusted parameter effectively modulates the electrostatic interactions of solvated ions in solutions. This modification has a strong impact to surface tension and location and mobility of sodium cations but minimal impact to properties such as density profiles of bulk phase and conformations and orientations of surfactant chain, for which consistent results compared with previous studies are obtained.

Coarse-Grained Potential Models for Phenyl-Based Molecules: I. Parametrization Using Experimental Data

A coarse-grained intermolecular potential has been parametrized for phenyl-based molecules. The parametrization was accomplished by fitting to experimental thermodynamic data. Specifically, the intermolecular potentials, which were based on Lennard-Jones functional forms, were parametrized and validated using experimental surface tension, density, and partitioning data. This approach has been used herein to develop parameters for coarse-grained interaction sites that are applicable to a variety of phenyl-based molecules, including analogues of the amino acid side chains of phenylalanine and tyrosine. Comparison of the resulting coarse-grain model to atomistic simulations shows a high level of structural and thermodynamic agreement between the two models, despite the fact that no atomistic simulation data was used in the parametrization of the coarse-grain intermolecular potentials.

Extended scaled particle theory for surface tension prediction of liquid mixtures

By extending the scaled particle theory (SPT) with six conditions adapted to Carnahan–Starling equation of state, SPT6-CS, (D.W. Siderius, D.S. Corti. J. Chem. Phys. 127, 144502 (2007)) a new expression for surface tension prediction of binary mixtures was obtained. The results of calculations are compared with those obtained from the SPT with three conditions, SPT3 (J.L. Lebowitz, E. Helfland, E. Praestgaard. J. Chem. Phys., 43, 774 (1965)). The results revealed that in spite of their simplicity, the studied models are in fairly good agreement with the experimental data. In addition, the results show that the obtained expression fitted very well with surface tension experimental data of binary alkane mixtures at different temperatures.

Surface tension and density measurement of liquid Si–Cu binary alloys

Surface segregation is very important for understanding the surface tension of binary systems. In case of a regular solution, the surface segregation is calculated using the Butler model. However, in the case of a complex system, like those forming intermetallic compounds, it is difficult to express the surface segregation. In order to discuss surface segregation in systems forming intermetallic compounds, we measured the density and surface tension of a Si–Cu binary system. We found the effect of clusters in both density and surface tension experimental data. The composition dependence of surface tension was expressed by a modified ideal solution model.

Estimation and Prediction of the Physicochemical Properties of Imidazolium-Based Ionic Liquids

The physicochemical properties of ionic liquids (ILs) at 298.15 K could be estimated and predicted in terms of empirical and semi-empirical equations as well as by interstice model theory. In this paper, the molecular volume, density, standard molar entropy, lattice energy, surface tension, parachor, molar enthalpy of vaporization, interstice volume, interstice fraction, and thermal expansion coefficient are discussed. These properties were first estimated by experimentally determining the density and surface tension for 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim][EtSO4]), 1-butyl-3-methylimidazolium octylsulfate ([C4mim][OcSO4]), and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([C2mim][NTf2]). The molecular volume and parachor of the three homologues of the imidazolium-based ILs [C(subscript n)mim][EtSO4], [C(subscript n)mim][OcSO4], and [C(subscript n)mim][NTf2] (n=1-6) were predicted and their densities and surface tensions were obtained. Other properties were also calculated using the obtained density and surface tension values. The predicted density was compared to the experimental values for [C4mim] [NTf2] and [C2mim] [OcSO4], which shows that the deviation between experimental and predicted data are within experimental error. Finally, we compared the values for the molar enthalpy of vaporization estimated by Kabo's empirical equation with those predicted by Verevkin's simple rule for [C2mim] [EtSO4], [C4mim][OcSO4], [C2mim] [NTf2], [C4mim][NTf2], N-butyltrimethylammonium bis (trifluoromethylsulfonyl)imide [N4111][NTf2], N-methyltrioctylammonium bis (trifluoromethylsulfonyl)imide ([N8881][NTf2]), and N-octyl-3-methylpyridinium tetrafluoroborate ([m3opy][BF4]) and found that the values obtained by these two equations were in good agreement with each other. Therefore, we suggest that the molar enthalpy of vaporization of ILs can be predicted by Verevkin's simple rule when experimental data for density and surface tension are not available.

Adsorption layer characteristics of multi-component surfactants solutions

An approximate model is derived for calculating the surface pressure, adsorption and rheological characteristics of multi-component surfactant mixtures from the adsorption parameters of the individual compounds. The proposed theory is validated with exact theoretical values and experimental data of equilibrium surface tensions and dilation rheology of binary mixtures of reorientable surfactants. It was shown that the given approximation for two, three and more components provides good agreement with the exact model for binary mixtures. The bubble profile analysis tensiometry is applied for studying the equilibrium surface tension and the rheological behaviour of mixed ternary C14EO8, C12EO5 and C10EO5 solutions in a wide range of total concentrations and surface oscillation frequencies. By comparison of experimental data with the calculated results it is possible to show that the proposed theoretical approach allows an accurate description of the adsorption and dilational rheological behaviour of the studied ternary surfactant mixtures.

Thermodynamics and surface properties of liquid Cu–B alloys

The study of the thermodynamic and the surface properties of liquid Cu–B alloys can help better understanding of a complex interfacial chemistry related to liquid Cu–brazes in contact with boride substrates. Despite a simplicity of the Cu–B phase diagram, only a few thermodynamic data are available in the literature, while in the case of the surface properties a complete lack of data is evident. The quasi-chemical approximation (QCA) for the regular solution has been applied to describe the mixing behaviour of liquid Cu–B alloys in terms of their thermodynamic and surface properties as well as the microscopic functions. In view of joining processes related to liquid Cu–brazes/solid boride systems a particular attention is paid to the surface properties of the Cu-rich part of the system and the calculated values are substantiated by the new surface tension experimental data of liquid Cu and Cu–10 at.% B alloy. The tests have been performed by the sessile-drop method under the same experimental conditions. Considering the experimental uncertainties, the effect of oxygen on the surface tension of liquid Cu and Cu–10 at.% B alloy has been analysed by simple model that combines the physical property data included in Butler’s equation with the oxygen solubility data and it gives the same results as Belton’s adsorption equation.

Application of the MSA-based models in correlating the surface tension for single and mixed electrolyte solutions

Experimental values for surface tension of single and mixed electrolyte solutions were correlated using the models based on the perturbation theory. The Mean Spherical Approximation (MSA) model, coupled with the Ghotbi–Vera (GV) and the Mansoori et al. (BMCSL) equations of state, were used to correlate the experimental values of the surface tension. The results showed that the models can favourably correlate the experimental values for single electrolyte solutions. However, it was observed that the GV–MSA model can more accurately predict the surface tension for single electrolytes, especially at higher concentrations. Two different expressions for concentration dependency of cation hydrated diameters were used. Therefore, in terms of such dependency different forms of the models, i.e., GV–MSA1, GV–MSA2, BMCSL–MSA1 and BMCSL–MSA2 were introduced. It should be stated that the prediction of the surface tension for the mixed electrolyte solutions were made without introducing any new adjustable parameters. The results showed that GV–MSA2 model can predict more accurately the surface tension of electrolyte mixtures particularly at higher concentrations. Finally, the GV–MSA model was directly used to correlate the experimental results for the surface tension for both single and mixed electrolyte solutions with 2 and 4 adjustable parameters. The results showed that both of the models can accurately predict the experimental data of surface tension. These models can favourably fit and also, predict the surface tension of single electrolyte solutions with less than 1% average absolute relative deviation (AARD). The prediction capability of the proposed models is also acceptable for mixtures of electrolytes.

Development of a QSPR correlation for the parachor of 1,3-dialkyl imidazolium based ionic liquids

Ionic liquids have received significant interest from both academia and industry for a wide range of applications which often requires knowledge of their thermophysical properties. Quantitative structure–property relationship correlations and group contribution methods for thermophysical properties of ionic liquids are a basic necessity for the development of computer aided molecular design approaches for these liquids and subsequently offer the potential for designing an ionic liquid having a desirable set of thermophysical properties. However, the limited availability of experimental thermophysical data and their quality have prevented the development of such tools. Based on previously reported experimental surface tension data, a correlation of the parachors with the molar volume of the ionic liquids has been developed. The predicted parachor values have been shown to be in good agreement with the experimental data. A maximum deviation of <5% was observed in the predicted parachor when using 561 data points based on 41 1,3-dialkyl imidazolium based ionic liquids. The correlations developed, herein, can be used to evaluate the parachor and hence either density or surface tension of ionic liquids for use in computer aided molecular design of potential ionic liquids.

New Methodology to Determine Equilibrium Surfactant Adsorption Properties from Experimental Dynamic Surface Tension Data

In this paper, we explore a novel approach to predict equilibrium adsorption properties from experimental dynamic surface tension (DST) data and the known rate-limiting adsorption kinetics mechanism, an approach that has never been pursued in the DST literature. Specifically, we develop a new methodology to predict the equilibrium surface tension versus surfactant bulk solution concentration (ESTC) behavior of nonionic surfactants from experimental DST data when the adsorption kinetics rate-limiting mechanism is diffusion controlled. The new methodology requires the following three inputs: (1) experimental DST data measured at a single surfactant bulk solution concentration, Cb, (2) the diffusion coefficient of the surfactant molecule, D, and (3) a single equilibrium surface tension data point, to predict the entire ESTC curve applicable over a wide range of surfactant bulk solution concentrations which are less than, or equal to, Cb. We demonstrate the applicability of the new methodology by predicting the ESTC curves of the two alkyl poly (ethylene oxide) nonionic surfactants C12E4 and C12E6, and validate the results by comparing the predictions with (a) equilibrium surface tension measurements, (b) surface-expansion measurements, and (c) pendant-bubble dynamic surface tension measurements for t<approximately 100-200 s (when the assumption of diffusive transport of surfactant molecules in the bulk solution is valid). Very good agreement is obtained between the predictions and the measurements in (a), (b), and (c) for both C12E4 and C12E6. On the basis of these results, we conclude that the new methodology presented here represents an efficient method to predict reliable ESTC curves for nonionic surfactants.

On the Calculation of Liquid–Vapor Interfacial Thickness Using Experimental Surface Tension Data

In this paper we investigate the vapor–liquid interfacial thickness of several pure fluids using a new method. In this method, the surface thickness is obtained using experimental surface tension data, and its dependence on the temperature is evaluated. The interfacial width is found to increase with increasing temperature and goes to infinity when the temperature approaches its critical value. Also, we find that a plot of ln δ versus ln {(1−Tr)−1} is linear, in which δ and Tr are the interfacial thickness and reduced temperature, respectively. In this method, the equation of state obtained from the Statistical Associating Fluid Theory (SAFT EOS), which is molecular based, is accepted.

Prediction of the surface tension of binary systems based on the partial least squares method

To predict the surface tension of binary liquid systems, an empirical model is proposed using the partial least squares (PLS) based on the multivariate statistical analysis method. Required parameters for the PLS method to predict the surface tension of binary systems are composed of the thermophysical properties of only pure substances such as critical temperature, critical pressure, critical volume, molar volume, viscosity and vapor pressure for input data block (X) and the reported experimental surface tension data for output data block (Y). The data set for the experimental surface tension of binary liquid systems is divided into the training set for regression and the test set for predicting. An average relative error (%) results of regression and prediction indicate that the PLS method can be a useful tool for predicting the surface tension of liquid binary systems.

New Model for the Correlation of the Surface Tension Based on Friction Theory

A new correlation method for the surface tension of fluids is proposed, which is based on friction theory applied to the interface of a two-phase system. The substance properties enter the model by a regular equation of state. Here we derive the method and test it with the Lennard-Jones 12-6 fluid as the reference system using molecular dynamics simulations of the vapor-liquid interface in combination with a new Lennard-Jones 12-6 equation of state. Further correlations of experimental surface tension data based on the Peng-Robinson and the PC-SAFT equations of state are presented. As a result, we find that the method allows an accurate correlation of the surface tension of pure fluids.

Automated foam index test: Quantifying air entraining agent addition and interactions with fly ash–cement admixtures

The use of a new automated foam index test (AFIT) instrument is discussed as a quantitative approach to observe air entraining agent (AEA) interactions with and to measure proper AEA dosage into cement–fly ash mixtures. Based on measuring acoustic emission from bubbles bursting on top of and in water–cement–ash mixtures after AEA addition, AFIT uses computer control to automate steps taken and quantities used during foam index testing, including: water addition; AEA titration; admixture agitation; and acoustic emission data acquisition. Variation of these steps is investigated relative to determining the dynamics of AEA adsorption onto the solid surfaces within water–cement–ash mixtures. Working within time durations needed for AEA equilibration, different water dilution and titration levels of AEA helped elucidate influences of equilibration on the AFIT-determined foam index values. A mathematical discussion about AFIT foam index curves is offered that relates changes in foam stability to surface tension and interactions with free calcia as AEA's are titrated into ash and cement–ash mixtures. Correlations between experimental surface tension data and the foam index curves are also presented. The potential of applying the AFIT to control air content in concrete with and without fly ash is also examined relative to using the C231 ASTM testing procedure on concrete mixes.

Surface and bulk properties of square-well fluid with variable range

Some of the thermodynamic properties, including bulk andsurface properties, of square-well fluids with ranges of interaction1.1≤λ≤3 have been investigated. Properties of vapor–liquid interfaces are obtained using densityfunctional theory, in which the Helmholtz free energy functional of the surface region isbased on hard sphere repulsive interactions between molecules under the local densityapproximation, and the attractive interactions between molecules are represented by asquare-well potential at the mean field level of approximation. Moreover, the vapor–liquidphase equilibrium, thermodynamic regularities and critical behavior of square-well fluidsare studied and a new regularity in the behavior of the reduced bulk modulus versusthe attractive range parameter is reported. We have also optimized square-wellpotential parameters using the surface tension experimental data for several purefluids.

Surface tension of liquid binary alloys – theory versus experiment

Abstract In the present study, we compare available experimental surface tension data with two theoretical concepts: the Butler equation and a multilayer model in which the surface is described as a stacking of atomic layers. The experimental data were measured systematically over a wide temperature and concentration range using electromagnetic levitation and the oscillating drop technique. Three classes of alloys are studied: alloys with rather weak or no segregation, alloys with strong segregation, and associate forming alloys.

Thermodynamics and surface properties of liquid Bi–In alloys

The mixing behaviour of liquid Bi–In alloys has been described in terms of energetics and structure through the study of their thermodynamic, surface and structural properties by using the Complex Formation Model (CFM) in the weak interaction approximation and by postulating BiIn-chemical complexes as energetically favoured. The new Bi, In and Bi–In surface tension experimental data set, obtained by the large drop method in the temperature range 553–873 K, has been analysed in the framework of the CFM and compared with the calculated values as well as with corresponding literature data. The structural characteristics of Bi–In melts are described by the two microscopic functions, i.e. the concentration fluctuations in the long-wavelength limit and the Warren–Cowley short-range order parameter.

Interfacial properties of semifluorinated alkane diblock copolymers

The liquid-vapor interfacial properties of semifluorinated linear alkane diblock copolymers of the form F(3)C(CF(2))(n-1)(CH(2))(m-1)CH(3) are studied by fully atomistic molecular dynamics simulations. The chemical composition and the conformation of the molecules at the interface are identified and correlated with the interfacial energies. A modified form of the Optimized Parameter for Liquid Simulation All-Atom (OPLS-AA) force field of Jorgensen and co-workers [J. Am. Chem. Soc. 106, 6638 (1984); 118, 11225 (1996); J. Phys. Chem. A 105, 4118 (2001)], which includes specific dihedral terms for H-F blocks-and corrections to the H-F nonbonded interaction, is used together with a new version of the exp-6 force field developed in this work. Both force fields yield good agreement with the available experimental liquid density and surface tension data as well as each other over significant temperature ranges and for a variety of chain lengths and compositions. The interfacial regions of semifluorinated alkanes are found to be rich in fluorinated groups compared to hydrogenated groups, an effect that decreases with increasing temperature but is independent of the fractional length of the fluorinated segments. The proliferation of fluorine at the surface substantially lowers the surface tension of the diblock copolymers, yielding values near those of perfluorinated alkanes and distinct from those of protonated alkanes of the same chain length. With decreasing temperatures within the liquid state, chains are found to preferentially align perpendicular to the interface, as previously seen.