Phase diagram, surfactant-water

Recently, new ordered mesoporous silicas have also been synthesized by using self-organization of amphiphilic molecules, surfactants and polymers either in acidic or basic condition. A schematic phase diagram of water-surfactant is shown in the figure. 

Figure 8.7 shows the ternary phase diagram for water, hexanoic acid, and sodium dodecyl sulfate at 25 °C. Seven different areas are shown in the figure, which has been used to describe the solubilization of polar dirt by surfactant solutions in detergency applications. The following comments refer to these seven different regions and explain the labeling used in Figure 8.7 ...

FIG. 8.12 Rectangular figure shows the phase diagram for water-cyclohexane (at 5% surfactant) versus temperature. Superimposed ternary phase diagrams offer an interpretation of the phases present. (Redrawn, with permission, from M. L. Robbins, In Solution Chemistry of Surfactants, Vols. 1 and 2 (K. L. Mittal, Ed.), Plenum, New York, 1979.)... 

Phase diagrams of water, hydrocarbon, and nonionic surfactants (polyoxyethylene alkyl ethers) are presented, and their general features are related to the PIT value or HLB temperature. The pronounced solubilization changes in the isotropic liquid phases which have been observed in the HLB temperature range were limited to the association of the surfactant into micelles. The solubility of water in a liquid surfactant and the regions of liquid crystals obtained from water-surfactant interaction varied only slightly in the HLB temperature range. 

FIGURE 11.6 Example phase diagram oil-water-surfactant system. (Adapted from C12E10-water-oleic acid diagram van Os et al., 1993.)... 

The ideas underlying elemental structures models are to establish microstructures experimentally, to compute free energies and chemical potentials from models based on these structures, and to use the chemical potentials to construct phase diagrams. Jonsson and Wennerstrom have used this approach to predict the phase diagrams of water, hydrocarbon, and ionic surfactant mixtures [18]. In their model, they assume the surfactant resides in sheetlike structures with heads on one side and tails on the other side of the sheet. They consider five structures spheres, inverted (reversed) spheres, cylinders, inverted cylinders, and layers (lamellar). These structures are indicated in Fig. 12. Nonpolar regions (tails and oil) are cross-hatched. For these elemental structures, Jonsson and Wennerstrom include in the free energy contributions from the electrical double layer on the water... 

Fig. VI-18. Phase diagrams of water - hydrocarbon (oil) - nonionic surfactant system at three different temperatures. Winsor equilibria.

Figure 6 The principal phase diagram of water, hydrocarbon, and the nonionic surfactant polyethyleneglycol alkyl ether. W = water O = hydrocarbon O/W =oiI-in-water microemulsion W/0 = water-in-oil microemulsion 3P = three-phase region T = temperature. (After Shinoda [18-24].)...

Figure 10 Phase diagram of water/poly(oxyethylene) oleyl ether(POIE) system as a function of the volume fraction of EO chain in the surfactant molecule and weight fraction of POIE at 25°C (from Ref [77], with permission).

Fig. 1. Water content versus temperature phase diagram of water-undecane systems with 12% (w/w) non-ionic surfactant added to the hydrocarbon phase, realm of...

FIGURE 10.8 Ternary phase diagram of water (aqueous phase), PEG-35 castor oil (Cremophor EL, surfactant phase), and mixtnre of glycerol monocaprylocaprate and caprylic/capric triglycerides (1 3) (oil phase) at 37°C. (Adapted from Prajapati, H.N. et al., Pharm. Res., 29(1), 285, 2012.)... 

Figure 11.3 Fish-shaped phase diagram (surfactant weight fraction, y, and temperature, T, plane) of the ternary water-[bmim][PFJ-TX-100 at equal volumes of water and [bmim][PFJ. 1,2,2, and 3 correspond to one-phase, two-phase (water-in-IL droplet), two-phase (Il in-water droplet), and three-phase regions, respectively. From Anjum et al. [44].

Fig. 15.5. Ternary phase diagram of water, an anionic surfactant and iong-chain aicohoi (co-surfactant).

Figure 4.2. Schematic phase diagrams of water, oil and amphiphile (surfactant) mixtures, showing regions of the 1, 2 and 3 phases. The tie-lines within the 2 phase regions connect the compositions of the two phases in equilibrium. Reproduced by permission of the American Chemical Society (redrawn from Schwuger et al. (81))...

Figure 4.8. Tetrahedral representation of the phase diagram of water, oil, surfactant and cosurfactant. The slice taken at equal masses of oil and water (a = 0.5 shaded region) schematically shows the fish phase diagram. Reproduced by permission of the American Chemical Society (redrawn from Strey and Jonstromer (106))...

Figure 2.15 Phase diagrams of water (W)-Shellflex-131(H)-surfactant (S) systems at 25° C for non-ionic polyoxyethylene derivatives with average formula CioE4- (a) monodisperse (S-30), (b) broad monomodal (S-75), (c) bimodal (S-68) distributions of ethylene oxide chain length. The regions are numbered according to type (1) clear, isotropic, oil-rich (2) two-phase (3) clear or hazy, anisotropic, water-rich (4) solid phase (5) clear water-rich phase. From Bradley and Lissant [33] with permission.

Water-in-oil (W/0) microemulsions at low water content and oil-in-water (0/W) microemulsions at low oil content contain droplets of water in an oil continuum or droplets of oil in a water continuum that have been visualized (see Figure 1.7 top). The droplets are coated by a mixed film of surfactant + cosurfactant as represented in Figure 1.2. Such systems are referred to as Winsor IV systems. As the water or oil content is increased, the solubility limit of the water or oil is reached and the system becomes biphasic. It is then made up of a microemulsion phase and, as a second phase, the excess water or oil containing very small amounts of the other components of the system. The phase diagrams of water/surfactant/cosur-factant/oil systems have been much investigated.The biphasic systems with an 0/W microemulsion in equilibrium with excess oil are the so-called Winsor I systems, whereas Winsor II systems are made up of a W/0 microemulsion phase in equilibrium with excess water. In both Winsor I and Winsor II systems, the microemulsion phase has a droplet structure, as in Winsor IV systems. Winsor I and II systems can be... 

In particular, this parameterization approach has shortcomings in reproducing correctly the phase diagram of water, including, for example, water/vapor interfacial tension, and, as a consequence, it has flaws for what pertains the investigation of surfactant properties of lipid monolayer at the airAvater interface.Improvements of the MARTINI water model have been proposed via the use of a polarizable force field, but polarizable CG force fields remain poorly investigated so far in the field of CG simulations. 

Usually ion hydration is taken into account with different ion sizes. But such a simplified correction via decorated ions is by no means sufficient to explain drastic differences in colloidal systems, when for example hydroxide ions are replaced by bromide ions. > Ternary phase diagrams of water, ionic surfactants and oil can be completely different, depending on the type of the counterion that is used with the surfactant. Further, vesicular structures composed of surfactants may considerably swell or shrink, when counterions are exchanged, even if the charge of the ions is always the same. ... 

Figure C2.3.10. Ternary phase diagram of surfactant, oil and water illustrating tire (regular) and (reverse) L2 microemulsion domains.

Of all the characteristic points in the phase diagram, the composition of the middle phase is most sensitive to temperature. Point M moves in an arc between the composition of the bottom phase (point B) at and the composition of the top phase (point T) at reaching its maximum surfactant concentration near T = - -T )/2. (Points B and Tmove by much smaller amounts, also.) The complete nonionic-amphiphile—oh—water—temperature... 

FIG. 13 Phase diagram of a vector lattice model for a balanced ternary amphiphilic system in the temperature vs surfactant concentration plane. W -I- O denotes a region of coexistence between oil- and water-rich phases, D a disordered phase, Lj an ordered phase which consists of alternating oil, amphiphile, water, and again amphi-phile sheets, and L/r an incommensurate lamellar phase (not present in mean field calculations). The data points are based on simulations at various system sizes on an fee lattice. (From Matsen and Sullivan [182]. Copyright 1994 APS.)... 

A. Ciach, J. S. Hoye, G. Stell. Microscopic model for microemulsion. II. Behavior at low temperatures and critical point. J Chem Phys 90 1222-1228, 1989. A. Ciach. Phase diagram and structure of the bicontinuous phase in a three dimensional lattice model for oil-water-surfactant mixtures. J Chem Phys 95 1399-1408, 1992. 

With increasing water content the reversed micelles change via swollen micelles 62) into a lamellar crystalline phase, because only a limited number of water molecules may be entrapped in a reversed micelle at a distinct surfactant concentration. Tama-mushi and Watanabe 62) have studied the formation of reversed micelles and the transition into liquid crystalline structures under thermodynamic and kinetic aspects for AOT/isooctane/water at 25 °C. According to the phase-diagram, liquid crystalline phases occur above 50—60% H20. The temperature dependence of these phase transitions have been studied by Kunieda and Shinoda 63). 

An example for a partially known ternary phase diagram is the sodium octane 1 -sulfonate/ 1-decanol/water system [61]. Figure 34 shows the isotropic areas L, and L2 for the water-rich surfactant phase with solubilized alcohol and for the solvent-rich surfactant phase with solubilized water, respectively. Furthermore, the lamellar neat phase D and the anisotropic hexagonal middle phase E are indicated (for systematics, cf. Ref. 62). For the quaternary sodium octane 1-sulfonate (A)/l-butanol (B)/n-tetradecane (0)/water (W) system, the tricritical point which characterizes the transition of three coexisting phases into one liquid phase is at 40.1°C A, 0.042 (mass parts) B, 0.958 (A + B = 56 wt %) O, 0.54 W, 0.46 [63]. For both the binary phase equilibrium dodecane... 

FIG. 2 Example media (a) Surfactant-water phase diagram. (Reprinted from Ref. 206, Copyright 1991, with permission from Elsevier Science.) (b) Ordered periodic and bicontinuous structures. (Reprinted from Ref. 178 with permission from Academic Press, Ltd.) (c) Nonordered membrane structures from ternary microemulsions. (Reprinted with permission from Ref. 177, Copyright 1989, American Chemical Society.)... 

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