Sodium palmitate-water system, phase

Figure 21.38. Phase diagram of the sodium palmitate (NaP)/sodium chloride/water system at 90°C (reproduced from ref. (195) with permission of Academic Press)...

Multicomponent Systems. There are many mesomorphic systems in which at least two components are present. The most common variety is called a lyotropic mesophase it consists of a molecule with a hydrophilic and a hydrophobic portion dissolved in water. Since at least two components are present, there can be a coexistence of more than one phase. The classical method of investigating such systems consisted of mixing the two components together, centrifuging until the two phases were separate, and analyzing each phase. By NMR it is possible to make a qualitative analysis of each phase without separation in many cases. The sodium palmitate (NaP)-deuterium oxide (D20) system shows the sort of information which can come from such an analysis. The NaP-D20 system exists in several different mesomorphic phases in addition to the isotropic liquid and crystalline phases (6, 23, 36, 37). The mesophases are mainly of the smectic type although the lyotropic mesophase normally called middle does not have all the characteristics of a true smectic phase. 

Emulsion polymerization is similar to suspension polymerization in the sense that the reaction also takes place in the presence of a water phase and the applied monomer forms a second liquid phase. However, in this case the added radical initiator is not soluble in the monomer droplets but in the water phase. To allow the monomer to come into contact with the initiator an emulsifier is added to the reaction mixture that creates micelles in the systems. By diffusion processes both monomer molecules and initiator molecules reach the micelle. Polymerization takes places and a polymer particle suspended in the water phase forms that is much smaller than the original monomer droplet (see Figure 5.3.12 for a graphical illustration of these steps). At the end of the overall emulsion polymerization process, all monomer droplets have been consumed by the polymerization reaction in the micelles. Typical emulsifiers for emulsion polymerization are natural or synthetic detergents, such as, for example, sodium palmitate or sodium alkyl sulfonates. Emulsion polymerization is very versatile and is applied for many polymers [e.g., PVC, styrene copolymers, poly(methacryl esters)] in batch, semi-continuous, and continuous processes. In some cases, the obtained polymer particles in water are directly applied as technical products for coatings, lacquer applications, or as adhesives. In other cases the formed product is further treated to obtain the dry polymer. Note that the aqueous phase in emulsion polymerization always contains some isolated emulsifier and also some monomer. Moreover, the formed polymer contains the emulsifier as impurity. 

Fujiwara et al. studied the phase diagram of the a-sulfonated palmitic acid methyl ester sodium salt (SFMe)-water system by measuring the phase transition temperatures (T ) and the X-ray diffraction patterns for each solid phase of the ester sulfonate at various water contents [66]. The following phases could be recognized in the developed phase diagram ... 

Binary Soap-Water System Mixtures of soap in water exhibit a rich variety of phase structures (4, 5). Phase diagrams chart the phase structures, or simply phases, as a function of temperature (on the y-axis) and concentration (on the x-axis). Figure 2.1 shows a typical soap-water binary phase diagram, in this case for sodium pahnitate-water. Sodium palmitate is a fully saturated, 16-carbon chain-length soap. At lower temperatures, soap crystals coexist with a dilute isotropic soap solution. Upon heating, the solubility of soap increases in water. As the temperature is increased the soap becomes soluble enough to form micelles this point is named the Krafft point. The temperature boundary at different soap concentrations above which micelles or hquid crystalline phases form is named the Krafft boundary (5). 

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