Composites, surface tension data

A simple attempt to estimate the composition in mixed micelles from surface tension data at the CMC was made by Funasaki and Hada using a mass balance condition [57]. Indeed the composition of micelles and the bulk solution containing two surfactants can be related to the surfaee tension values at the CMC. The material balance for this system takes the form... 

Motomura et al. proposed a method of evaluation of various thermodynamic properties of micellar solutions from the surface tension data in the framework of the pseudophase treatment of micellisation [50, 52-55]. According to these authors, the micellar composition at the CMC can be found from the functional dependence of the CMC on the overall surfactant mole fraction using an analogy to the method proposed by Nguyen et al. [49], The approach of Motomura et al. [50] gives also a possibility to determine the relation between the composition of the surface layer and the micelles. Application of the Gibbs-Duhem equation to the whole... 

T data are presented on the same energy scale as the surface tension data for a fully fluorinated, partially chain-branched oil of high viscosity at 25 and average composition good straight... 

The surface tensimi is also a linear function of the composition. However, due to the fact that clean surfaces are difficult to obtain, the deviations are rather large (Fig. 10). A thorough literature review on surface tension data of ionic liquids has... 

The synergism observed in solutions of mixed dissimilar surfactants is governed by monomer-micelle equilibria and the interaction in micelles. The concentration of surfactant monomers below the cmc is so dilute that interactions between surfactant monomers are insignificant. The composition of mixed micelles has been determined from surface tension data, electric conductivity, NMR, selfdiffusion measurements, fluorescence quenching, solubilization, ultrafiltration, and gel filtration. Complete nonmixing of a fluorinated surfactant and a hydrocarbon surfactant, partial mixing, and the existence of two types of mixed micelles or one mixed micelle has been reported. 

The composition of mixed micelles in solutions containing NF and sodium tridecyl sulfate (STrS) above cmc was determined from the surface tension data... 

In most systems the variation of the surface tension with composition is much lower. Data for some binary liquids are shown in Figure 6.23. A limited degree of segregation is expected in these systems. 

Pic. 17. Dependence of solvent properties pertinent to RPC on composition of water-acetonitrile mixtures at 2S C. Surface tension y data were obtained from Timmermans U34)i the viscosity and dielectric constant < data were taken from Timmermans (134) and Doubdret and Morenas (137), respectively. Reprinted from Horvdth and Melander (129), J. Chromatogr. Sci., with permisskw from Preston Publications.

The Gibbs adsorption theory (Birdi, 1989,1999, 2002, 2008 Defay et al., 1966 Chattoraj and Birdi, 1984) considers the surface of liquids to be monolayer. The surface tension of water decreases appreciably on the addition of very small quantities of soaps and detergents. The Gibbs adsorption theory relates the change in surface tension to the change in soap concentration. The experiments that analyze the spread monolayers are also based on one molecular layer. The latter data indeed conclusively verifies the Gibbs assumption (as described later). Detergents (soaps, etc.) and other similar kind of molecules are found to exhibit self-assembly characteristics. The subject related to self-assembly monolayer (SAM) structures will be treated extensively (Birdi, 1999). However, no procedure exists that can provide information by direct measurement. The composition of the surface of a solution with two components or more would require additional comments. 

The studies reported in the literature have suggested that the surface tension of Cu depends on its surrounding environment it is higher in vacuum and varies as vacuum > H2 > CO. Well-rounded particles are likely to form when the surface tension is low. In CO, the surface tension is lowered to the extent that the Cu prefers to spread out as sheets rather than as three-dimensional spherical particles. Experiments carried out on real (practical) powder catalysts are consistent with the data from the model systems. As in the model systems, sintering by Cu particles is dominant, the particles growing to several tens of nanometres. The type and extent of sintering depend on the exact composition of the bimetallic catalyst. For Cu > Ru, ETEM studies show the sintering of Cu to be primarily by particle coalescence. 

The surface tension was stated (Section 6.4.5), on general grounds, to be related to the surface excess of species in the interphase. The surface excess in turn represents in some way the structure of the interface. It follows therefore that electrocapillaiy curves must contain many interesting messages about the double layer at the electrode/ electrolyte interface. To understand such messages, one must learn to decode the electrocapillary data. It is necessary to derive quantitative relations among surface tension, excess charge on the metal, cell potential, surface excess, and solution composition. 

Size-resolved chemical information is much more difficult to obtain. The many applications of the differential mobility analyzer in measuring properties of size-classified particles are important tools for the characterization of aerosol systems, but the approaches demonstrated to date yield limited data. Vapor pressures, surface tension, and optical absorption have been measured on mobility-classified aerosols. Direct measurements of the distribution of chemical composition with particle size are needed. Elemental... 

P12.5 The following data taken from the Handbook of Chemistry and Physics demonstrate how the surface tension at 323.15 K of (methanol + water) and (ethanol + water) solutions changes with composition... 

C with two feed compositions are shown in Tables I and II. Surface tension has been measured as a function of time, and the viscosity of the solutions are shown along with surface tension. The data clearly show that as the viscosity increases with time, surface tension increases, and the higher the rate of increase of viscosity, the higher the rate of increase of surface tension. It has been shown for silicone polymers that as the viscosity increases from an increase in molecular weight, the surface tension increases (27). A step growth copolymerization mechanism, as mentioned earlier for the sulfur-DCP solutions, will have an increase of molecular weight with time, and the surface tension behavior appears to support this mechanism. 

Thirdly, it will be important to gain more direct information on the stability of outer-sphere precursor states, especially with regard to the limitations of simple electrostatic models (Sect. 4.2). One possible approach is to evaluate Kp for stable reactants by means of differential capacitance and/or surface tension measurements. Little double-layer compositional data have been obtained so far for species, such as multicharged transition-metal complexes, organometallics, and simple aromatic molecules that act as outer-sphere reactants. The development of theoretical double-layer models that account for solvation differences in the bulk and interfacial environments would also be of importance in this regard. 

The mutual solubility of ozone and oxygen at —183° and —195.5° C. has been determined by measuring the magnetic susceptibility and vapor pressure (4) of solutions, and a critical solution temperature of —180° C is indicated. The vapor pressure-composition data, combined with vapor pressure data for liquid ozone (1), were used to interpret the phase diagram of the system ( ). Measurements of the density and viscosity of solutions and the surface tension of liquid ozone are reported. 

Eutectic mixtures of quaternary ammonium salts with Lewis or Brpnsted acids were described as ILs [156], The conductivity, viscosity, density, and surface tension of a number of glycolic mixtures with choline chloride were measured over the mole fraction range 0-0.33. The data were fitted to hole theory. It was proposed that the composition at which the measured conductivity matched the theoretical value... 

Once a complete set of interfacial tension data have been assembled as a function of electrode potential and solution composition, they may be differentiated to obtain the relative surface excess. For example, if the solution contains a single electrolyte and the reference electrode is reversible to the anion in the... 

The LFHB model or the former LFAS (lattice fluid associated solution) modeP° can provide the needed equations for the chemical potential as a function of composition. The picture that emerges from application of the LFHB and LFAS models in this case is, essentially, identical. For the chemical potential. Equation 2.30 can be combined with Equation 2.A23 of Appendix 2.A to provide the required expression. On the other hand, the experimental data can be correlated to provide the appropriate expressions a(X2> for the surface tension. - ... 

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