Ternary system, interfacial tension

Lattice models for bulk mixtures have mostly been designed to describe features which are characteristic of systems with low amphiphile content. In particular, models for ternary oil/water/amphiphile systems are challenged to reproduce the reduction of the interfacial tension between water and oil in the presence of amphiphiles, and the existence of a structured disordered phase (a microemulsion) which coexists with an oil-rich and a water-rich phase. We recall that a structured phase is one in which correlation functions show oscillating behavior. Ordered lamellar phases have also been studied, but they are much more influenced by lattice artefacts here than in the case of the chain models. 

Addition of poly(styrene-block-butadiene) block copolymer to the polystyrene-polybutadiene-styrene ternary system first showed a characteristic decrease in interfacial tension followed by a leveling off. The leveling off is indicative of saturation of the interface by the solubilizing agent. 

The low interfacial tensions between two liquids have been measured for different systems by using the pendant drop method. In the case of the quaternary system Ci2ll25S 3 tNa+H20+n-Butanol+Toluene, the interfacial data as measured by pendant drop method are compared with reported literature data, using other methods (with varying NaCl concentration). In order to understand the role of co-surfactant, ternary systems were also investigated. The pendant drop method was also used for measuring the interfacial tension between surfactant-H20/n-alcohol (with number of carbon atoms in alcohol varying from 4-10). The interfacial tension variation was dependent on both the surfactant and alcohol. 

These studies, carried out by measuring interfacial tensions, Yq , between aqueous and oil phases, by using the pendant drop method, show that this method is very useful for ternary and quaternary systems. In one system (A), NaDDS + H2O + n-butanol + Toluene... 

T. Sottmann and R. Strey Shape Similarities of Ultra-Low Interfacial Tension Curves in Ternary Microemulsion Systems of the Water-AUcane-CiEj Type. Ber. Bunsenges Phys. Chem. 100, 237 (1996). 

Movements in the plane of the interface result from local variations of interfacial tension during the course of mass transfer. These variations may be produced by local variations of any quantity which affects the interfacial tension. Interfaeial motions have been ascribed to variations in interfacial concentration (H6, P6, S33), temperature (A9, P6), and electrical properties (AlO, B19). In ternary systems, variations in concentration are the major factor causing interfacial motion in partially miscible binary systems, interfacial temperature variations due to heat of solution effects are usually the cause. 

In a blend of immiscible homopolymers, macrophase separation is favoured on decreasing the temperature in a blend with an upper critical solution temperature (UCST) or on increasing the temperature in a blend with a lower critical solution temperature (LCST). Addition of a block copolymer leads to competition between this macrophase separation and microphase separation of the copolymer. From a practical viewpoint, addition of a block copolymer can be used to suppress phase separation or to compatibilize the homopolymers. Indeed, this is one of the main applications of block copolymers. The compatibilization results from the reduction of interfacial tension that accompanies the segregation of block copolymers to the interface. From a more fundamental viewpoint, the competing effects of macrophase and microphase separation lead to a rich critical phenomenology. In addition to the ordinary critical points of macrophase separation, tricritical points exist where critical lines for the ternary system meet. A Lifshitz point is defined along the line of critical transitions, at the crossover between regimes of macrophase separation and microphase separation. This critical behaviour is discussed in more depth in Chapter 6. 

Figure 3.22 (right) represents the three-phase temperature intervals for Q2E4 and Q2E5 vs the number n of carbon atoms of n-alkanes (for the phase behaviour of ternary systems see Section 3.4.2, Figure 3.26). The left part of Figure 3.22 shows the detergency of these surfactants for hexadecane. Both parts of Figure 3.22 indicate that the maximum oil removal is in the three-phase interval of the oil used (n-hexadecane) [22]. This means that not only the solubilisation capacity of the concentrated surfactant phase, but probably also the minimum interfacial tension existing in the range of the three-phase body is responsible for the maximum oil removal. Further details about the influence of the polarity of the oil, the type of surfactant and the addition of salt are summarised in the review of Miller and Raney [23].

This behaviour has a particular importance for the soil removal process in detergency. During the oil removal from stained fabrics or hard surfaces, ternary systems occur where three phases coexist in equilibrium. As already pointed out above, in this region the interfacial tension is particularly low. Because the interfacial tension is generally the restraining force,... 

For A/B/C-h-D ternary blends, it is generally found that the block copolymer can significantly suppress the growth rate of phase-separated structure, due to the reduction of interfacial tension. In particular, even a repulsive block copolymer can considerably retard the phase separation process if the interaction energies in the system satisfy a proper condition. However, such a retardation effect by a block copolymer is highly dependent on the molecular structure of... 

Fig. 23. Ternary blend containing two homopolymers A and B and a symmetric AB diblock copolymer within the bond fluctuation model. All chains have identical length, N = 32. (a) Probability distribution at e = 0.054 and system size 48 x 48 x 96 in units of the lattice spacing (i e = 17). Upon increasing the chemical potential S/j of the copolymers the valley becomes shallower, indicating that the copolymers decrease the interfacial tension. One clearly observes a plateau around (f> = 1/2. This assures, that our system size is large enough to neglect interfacial interactions in the measurement of the interfacial tension, (b) Average number of copolymers as a function of the composition. The copolymer number is enhanced in the configuration containing two interfaces. From Muller and Schick [105]...

Figure 1.17 shows the scaling of interfacial tension curves for four ternary water-n-octane-QEj systems (see Fig. 1.16) and the quaternary system water-n-octane-(3-C8Gi-C Eo (see Fig. 1.15). As canbe seen, the scaled

The chemical reaction at the interface during processing influences the morphology and thus the material properties. During the reaction, block or graft copolymers are formed. These copolymers are expected to reduce the interfacial tension coefficient, and to prevent coalescence of the dispersed particles. Furthermore, the chemical reaction influences the interfacial thickness. It was shown by ellipsometry that as a result of the reactive compatibilization, the interfacial thickness in the ternary system, PA/SMA/ SAN, increased up to Al = 50 nm [Yukioka and Inoue, 1994]. 

Solubilization, Microemulsions and Emulsions. - Micellar solutions with both normal (Li) and reverse (L2) curvature, e.g. o/w and w/o type systems, can be swollen by oil and water to obtain water/oil/amphiphile ternary or pseudoternary systems. These systems have been widely used as solubilizing media for structural investigations of the immobilized solubilizate (a protein for instance), for drug delivery systems, and also for reaction media, (micellar catalysis). Ternary systems based on water, oil, and amphiphile mixtures can form a variety of Li and L2 monophasic regions. When these systems form isotropic solutions spontaneously, they are termed microemulsions. The formation of a microemulsion is related mainly to a substantial decrease of the interfacial tension (Yo/w) at the oil-water interface, due to the amphiphilic molecules located at the polar-apolar interface. This occurs in agreement with the typical equation ... 

Lewis Pratt, in 1953, were the first to report that the observed Marangoni convection in their experimental ternary systems was beneficial to hquid-hquid extraction processes because it increased mass transfer rates. The effect of density gradients on interfacial convection was studied by several researchers including Berg Morig (1969), who investigated the interaction between buoyancy and interfacial tension driven effects in ternary systems. The combined interfacial convection was also seen to be beneficial to mass transfer processes. 

Therefore the addition of a surfactant to a liquid-liquid system may either promote Marangoni convection or dampen interfacial motions, depending on the type of liquid-liquid system and surfactant. Stability criteria have been established for many years for ternary and binary systems and when the solute has surface-active properties, but they are still a long way from being able to predict the interfacial behaviour accurately. Plots of the variation of equilibrium interfacial tension with surfactant concentration may be used to give a good indication of the interfacial behaviour during mass transfer. 

The problem of solvent selection is relatively complex and a thorough treatment requires considerable information. In addition to basic liquid-liquid equilibrium data, knowledge of the phase densities, viscosities, and the liquid-liquid interfacial tension is also important. Moreover, the economics of IXE systems are often dominated by the solvent regeneration costs. If, for example, solvent regeneration b to be accomplished by extractive or azeotropic distillation, then vapor-liquM equilibrinm data for the ternary system must also be available. Insofar as the most interesting LLE systems ate often ffiose whidi are least ideal, the generation of a physical property data base to complete cost analysis is usually a sigruficant problem. 

The in situ-formed copolymer reduces the interfacial tension. In ternary systems of a major component (3) and two minor components (1 and 2), as schematically shown in Fig. 8.36, component 2 spreads over the component 1 particles when the spreading coefficient S, determined by a balance between the interfacial tensions r,/y, is positive. The 5 in a ternary system of EPR (ethylene-propylene rubber) (1)/PA(2)/PPS (poly(phenylene sulfide)) (3) defined by... 

Inteifacial Tension. The interfacial tension between immiscible phases which must be settled or disengaged should preferably be high for rapid action. Too high an interfacial tension on the other hand may lead to difficulties in the adequate dispersion of one liquid in the other7 while too low a value may lead to the formation of stable emulsions. Unfortunately, relatively few liquid interfacial-tension measurements for complete ternary systems have been made. As an extremely rough guide, the differences in the surface tensions with air of the contacted liquids may be used to estimate the order of magnitude of interfacial tension, but this will be at... 

The most spectacular effect is that of zero interfacial tension. Such an effect would lead, in the case of a two-component system and in the absence of other constraints, to a total molecular dispersion of the two constituents. For a pseudo-ternary system, e.g., water/oil plus some surfactant system located on the interface, this effect may produce an unusual dispersion state in which droplet dimensions are of the order of 100 A. Such transparent and fluid systems are known as microemulsions. Over the past few years, these systems... 

Methods. Interfacial tension was measured by the sessile bubble method. Density difference between demixed phases was measured by float method and differential re-fractometory. Details of the experimental methods have been described elsewhere. The volume ratio of separated phases was also measured to obtain the coexistence curve. The critical point was determined on the coexistence curve as a point at which the volume ratio was unity. The detailed method for ternary systems will be described elsewhere. 

Sottmann, T. and Strey, R., Shape similarities of ultra-low interfacial tension curves in ternary microemulsion systems of the water-alkane-C/Ey type, Ber. Bunsenges. Phys. Chem., 100, 237 (1996). 

Amphiphiles, the representatives of which are soap, surfactant and lipid, have a hydrophilic polar head and lipophilic nonpolar tails. They always remain on the interface between water and oil and form monolayers of surfactants in a water/oil/amphiphile ternary system. This monolayers or interfacial film reduce the surface tension between water and oil domains. In a three-component system the surfactant film exists in various topologically different structures such as micelles, vesicles, bicontinuous microemulsions, hexagonal arrays of cylinders or lamellar structures depending upon the pressure, temperature and the concentration of the components [1,2]. Microemulsions are thermodynamically stable, isotropic and transparent mixtures of ternary amphiphilic systems. When almost equal volume fractions of water and oil are mixed with a dilute concentration of surfactants, they take... 

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