Decanol system

Finally in this section, Swager [200] reported amphiphilic complexes of oxova-nadium(IV) (Figure 108) which he studied in both binary (surfectant plus water) and ternary (surfactant plus water plus decanol) systems, finding both lamellar (L ) and hexagonal (Hi) phases. 

The nonaqueous systems also form liquid crystals analogous to aqueous systems in ternary systems with an added weakly hydrophilic component. SDS has been extensively employed in studies of ternary and quaternary systems with glycerol or formamide, a long-chain alcohol, and, sometimes, hydrocarbon [97-101], In the SDS-glycerol-decanol system the lamellar phase swells extensively, even more so than in water [97], While no liquid crystals form at room temperature in the binary systems, a D-phase occurs when decanol is added. 

O. Decanol-free mesophase +. Mesophase containing decanol System NaCy-decanol-H20... 

All three additives have roughly the same alkyl chain length and volume as sodium octanoate (decanol is just a bit bigger). The phase behavior of octanol/sodium octa-noate/water is available but the decanol system has received the most attention by far. We see that decanol mixes in the system to form a large lamellar region, and even an inverse hexagonal phase. This is because the alcohol group always resides at the water/... 

Kunieda, H., and Miyajima, A. (1989) Anomalous three-phase behavior in a water/ octaethyleneglycol dodecyl ether/ decanol system. J. Colloid Interface Sci., 129, 554-560. 

Acharya, D., Lopez-Quitela, M.A., Kunieda, H., Oshimura, E., and Sakamoto, K. (2003) Phase behavior and effect of enantiomerism on potassium N-dodecanoyl alaninate/water/decanol systems./. Oleo Sci., 52, 407-420. 

Alekseeva, M.V., and Moiseenko, M.F. (1982) Experimental study and calculation of liquid-vapor equilibria in the n-propaiu>l/hexane/n-decanol system, Khim. ThermodinJiastorov 5, 179-195. 

Amaral L, Helene MM (1988) Nematic domain in the sodium lauryl sulfate/water/decanol system. J Phys Chem 92 6094-6098... 

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... 

A final example of the simulation of a complex system is a series of MD simulations of bilayer membranes. Membranes are crucial constituents of living organisms they are the scene for many important biological processes. Experimental data are known for model systems for example for the system sodium decanoate, decanol and water that forms smectic liquid crystalline structures at room temperature, with the lipids organized in bilayers. 

Figure 3- Snapshot from an equilibrated simulation of a smectic bilayer system sodium ions (A), decanoate ions (chain with forked end) and decanol molecules (linear chain). The projection of all atoms is given.

On the other hand, with microemulsions based on an anionic surfactant and a long chain alcohol, was fairly low for certain concentrations, indicating that distinct water droplets in a hydrophobic medium may form. The system investigated by Lindman et al (29-34) was based on octanoic acid - decanol -octane-water. This means that the anionic "surfactant" used contains only seven carbon atoms in the alkyl chain which is fairly short. With longer chain surfactants, one would expect well defined "water cores" provided the alcohol is also long-chain. Such well defined "water cores" have also been confirmed by Lindman et a (34) for the Aerosol OT - hydrocarbon system. 

Silica Gels. The acid-catalyzed alkoxide sol-gel process produces gels (17). Frib-erg and coworkers (40-50) pioneered the extension of this process to silica synthesis in microemulsions both aqueous and nonaqueous microemulsions were used. For aqueous microemulsions, experiments were conducted mostly with the SDS/ pentanol/water/acid system. A representative flow diagram is shown in Figure 2.2.9. The nonaqueous microemulsion systems utilized included CTAB/decanol/ decane/formamide and AOT/decane/glycerol (44-46,49,50). The experimental approach followed the sequence nonaqueous microemulsion preparation, water addition, and then TEOS addition. 

Figure 8. Schematic of mesomorphous structures in phase E, D, and F in the three-component system sodium octanoate-decanol-water (1)...

Figure 9. Phase diagram for the three-component system sodium octanoate-n-decanol-water at 20°C (1). Concentrations expressed as weight percent.

To characterize the mesophases thermodynamically, it is desirable to have detailed knowledge of the regions in which phases B and C exist in the model system sodium octanoate-decanol-water. The heats at which the mesophases are formed are somewhat easier to obtain than the chemical potentials. Table I gives some examples of the few calorimetric values available (14, 15). 

So far it has not been possible to measure the chemical potentials of the components in the mesophases. This measurement is possible, however, in solutions which are in equilibrium with the mesophases. If pure water is taken as the standard state, the activity of water in equilibrium with the D and E phases in the system NaC8-decanol-water is more than 0.8 (4). From these activities in micellar solutions, the activity of the fatty acid salt has sometimes been calculated. The salt is incorrectly treated as a completely dissociated electrolyte. The activity of the fatty acid in solutions of short chain carboxylates has also been determined by gas chromatography from these determinations the carboxylate anion activity can be determined (18). Low CMC values for the carboxylate are obtained (15). The same method has shown that the activity of solubilized pentanol in octanoate solutions is still very low when the solution is in equilibrium with phase D (Figure 10) (15). 

In the ternary system NaCg-decanol-water the influence of the polar/apolar solubilizate on the formation of micelles and mesoaggregates can be seen clearly (Figure 9). Quite often the following rules of thumb for the influence of the solubilizate can be used ... 

Laser-Raman spectroscopy is a new method with considerable potential for providing an explanation of how the surroundings inside the aggregates influence the crystalline state of the hydrocarbon chains and other groups (25, 26). It seems probable, however, that an important area of research on the phase equilibria proper would concentrate on attempts to throw light on the exact thremodynamic criteria for the association processes. Ekwalls studies of the water activities of mesophases in the system water-decanol-sodium caprylate are an example of such research (4). However, thermodynamic treatment of the association processes presupposes measurements of the activities of several... 

Solyom and Ekwall (20) have studied rheology of the various pure liquid crystalline phases in the sodium caprylate-decanol-water system at 20 °C, for which a detailed phase diagram is available. Their experiments using a cone-and-plate viscometer show that, in general, apparent viscosity decreases with increasing shear rate (pseudo-plastic behavior). Values of apparent viscosity were a few poise for the lamellar phase (platelike micelles alternating with thin water layers), 10-20 poise for the reverse hexagonal phase (parallel cylindrical micelles with polar... 

Figure 5. 23Na NMR spectra of a lamellar mesophase sample of the system sodium octanoate-decanol-water. The rf field amplitude was increased in the order a,b,c,dt Peaks arising from double quantum transitions are clearly shown (cf. Figure 1).

Kedari et al. (101) studied the influence of adding a modifier on a solvent extraction with an Ir(IV)-Cyanex 923 system. Cyanex 923 is a commercial neutral organo-phosphorus extractant widely used for extraction of metal ions or inorganic acids. They observed that decanol is not efficient as a modifier probably because of an interaction with Cyanex 923. TBP can only be used at 4 M HC1 otherwise the efficiency is poor. This highlights the fact that the interaction of the modifier with the extractant can modify the efficiency of the extraction. 

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