Soap micelles

Emulsion Polymerization. Emulsion polymerization takes place in a soap micelle where a small amount of monomer dissolves in the micelle. The initiator is water-soluble. Polymerization takes place when the radical enters the monomer-swollen micelle (91,92). Additional monomer is supphed by diffusion through the water phase. Termination takes place in the growing micelle by the usual radical-radical interactions. A theory for tme emulsion polymerization postulates that the rate is proportional to the number of particles [N. N depends on the 0.6 power of the soap concentration [S] and the 0.4 power of initiator concentration [i] the average number of radicals per particle is 0.5 (93). 

Monomer molecules, which have a low but finite solubility in water, diffuse through the water and drift into the soap micelles and swell them. The initiator decomposes into free radicals which also find their way into the micelles and activate polymerisation of a chain within the micelle. Chain growth proceeds until a second radical enters the micelle and starts the growth of a second chain. From kinetic considerations it can be shown that two growing radicals can survive in the same micelle for a few thousandths of a second only before mutual termination occurs. The micelles then remain inactive until a third radical enters the micelle, initiating growth of another chain which continues until a fourth radical comes into the micelle. It is thus seen that statistically the micelle is active for half the time, and as a corollary, at any one time half the micelles contain growing chains. 

Figure 27.1 A soap micelle solubilizing a grease particle in water. An electrostatic potential map of a fatty acid carboxylate shows how the negative charge is located in the head group.

When the CMC determination is made by surface tension measurements, the resulting curve appears without minimum as a single surfactant. It is probable that an inversion takes place through the adsorption of the LSDA onto the surface of the Ca soap micelle, so that complete precipitation does not occur [23]. Zhang and Xiao [32] are of the opinion that the dispersion comes from the union of LSDA with the free ionic soap molecules. The particles from the soap-LSDA mixture are far larger than the corresponding soap molecules in soft water and therefore result in turbidity in hard water. 

Kurzendorfer [23] is of the opinion that in lime soap dispersions inversion does occur but that due to adsorption of LSDA on the surface of the lime soap micelle agglomeration is delayed, so that complete precipitation does not occur. 

Soap making, 22 723 as industry, 22 723, 724 raw materials in, 22 732-736 ternary soap-water systems and, 22 727 Soap micelles... 

Monomers may be polymerized using a water-soluble initiator while dispersed, by agitation, in a concentrated soap solution. In this emulsion system initiation occurs in the aqueous phase and propagation occurs in the soap micelles. Since the growing macroradicals are not terminated until a new free radical enters the micelle, high molecular weight products are rapidly obtained. The rate of polymerization and DP is proportional to the number of activated micelles. 

The experimental verification of Gibbs theorem. Since the osmotic pressure of a solution is generally difficult to measure, it is simplest to choose a case such that Raoult s law holds good and the concentration of the solution may be used in place of osmotic pressure. The solution should therefore be dilute and should be a true solution the solute, that is, must be dispersed as simple molecules and not as molecular aggregates like soap micelles. These conditions were obtained by Donnan and Barker Proc. 

Corrin, M. L Klevens, H. B and Harkins, D. (1946). The determination of critical concentrations for the formation of soap micelles by the spectral behavior of pinacyanol chloride. J. Chem. Phys., 14,480-6. 

The kinetic studies indicated that the rate of equilibrium between large monoolein-bile salt aggregates and small monolein-bile salt aggregates was very fast. Information is needed on the rate of exchange of polar lipids between micelles since these aggregates have different structures than soap micelles, where the exchange rates are believed to be rapid (15, 21). 

Long-chain fatty acids are insoluble in water, and their titration curves are concentration-dependent because of the formation of organized aggregates (acid soaps, soap micelles, fatty acid precipitates) which concentrate protons at the surface. At concentrations above the critical micellar concentration, solutions of long-chain fatty acid soaps manifest a diprotic curve when they are titrated from pH 10 to 4 (23). The first... 

An interesting class of polyeleclrolytes, denoted by polysoaps, is obtained by attaching soap-like molecules to the polymer chain. Such a polysoap is for instance produced by the quaternization of polyvinyl-pyridine with /r-dodecyl bromide. The polysoap molecules differ from ordinary poly electrolytes in that they may reach protein-like compactness in solution. They behave like prefabricated soap micelles and solubilize hydrocarbons and other compounds insoluble in water,... 

F Salts of Carboxylic Acids as Soaps. Micelle Formation... 

Figure 18-4 Schematic diagram of a soap micelle in water solution...

In liquid crystals or LC-glasses one looks for orientational order and an absence of three-dimensional, long-range, positional order. In liquid crystals, large scale molecular motion is possible. In LC-glasses the molecules are fixed in position. The orientational order can be molecular or supermolecular. If the order rests with a supermolecular structure, as in soap micelles and certain microphase separated block copolymers, the molecular motion and geometry have only an indirect influence on the overall structure of the material. 

Mesophases of supermolecular structure do not need a rigid mesogen in the constituent molecules. For many of these materials the cause of the liquid crystalline structure is an amphiphilic structure of the molecules. Different parts of the molecules are incompatible relative to each other and are kept in proximity only because of being linked by covalent chemical bonds. Some typical examples are certain block copolymers50 , soap micelles 51 and lipids52. The overall morphology of these substances is distinctly that of a mesophase, the constituent molecules may have, however, only little or no orientational order. The mesophase order is that of a molecular superstructure. 

The mechanism of emulsion polymerisation is complex. The basic theory is that originally proposed by Harkins21. Monomer is distributed throughout the emulsion system (a) as stabilised emulsion droplets, (b) dissolved to a small extent in the aqueous phase and (c) solubilised in soap micelles (see page 89). The micellar environment appears to be the most favourable for the initiation of polymerisation. The emulsion droplets of monomer appear to act mainly as reservoirs to supply material to the polymerisation sites by diffusion through the aqueous phase. As the micelles grow, they adsorb free emulsifier from solution, and eventually from the surface of the emulsion droplets. The emulsifier thus serves to stabilise the polymer particles. This theory accounts for the observation that the rate of polymerisation and the number of polymer particles finally produced depend largely on the emulsifier concentration, and that the number of polymer particles may far exceed the number of monomer droplets initially present. 

If one provides the system with preformed nuclei, for example in the form of "seed" latex particles, monomer droplets (in sufficient number), dust, or monomer-swollen soap micelles, the AG will have been provided and the system progresses on a downward slope (dashed curve in Figure 1) from the beginning. This constitutes heterogeneous nucleation. Since it is energetically favored, it will tend to occur whenever such conditions obtain. 

A mesomorphic (liquid-crystal) phase of soap micelles, oriented in a hexagonal array of cylinders. Middle soap contains a similar or lower proportion of soap (e.g., 50%) as opposed to water. Middle soap is in contrast to neat soap, which contains more soap than water and is also a mesomorphic phase, but has a lamellar structure rather than a hexagonal array of cylinders. Also termed clotted soap . See Neat Soap. 

Hobbs, M.E. (1951) The effect of salts on the critical concentration, size, and stability of soap micelles. /. Phys. Colloid Chem., 55(5), 675-83. 

The applications of colloid solutions are not restricted to paints and clay. They are also to be found in inks, mineral suspensions, pulp and paper making, pharmaceuticals, cosmetic preparations, photographic films, foams, soaps, micelles, polymer solutions and in many biological systems, for example within the cell. Many food products can be considered colloidal systems. For example, milk is an interesting mixture containing over 100 proteins, mainly large casein and whey proteins [6,7]. 

In this paper, a means is demonstrated for experimentally determining the percent of monomer conversion at which soap micelles disappear from the system during emulsion polymerization. By applying the mathematics and latex particle surface area which a soap molecule will occupy, developed for the soap titration particle size measurement procedure, the average particle size of the finished latex can be calculated. In fact, under some circumstances It might even be feasible to adjust monomer content. 

Cross-section of a soap micelle with a grease particle dissolved in the interior... 

Solubilization has been used for many years in the formulation of phenolic antiseptic and disinfectant solutions. In the case of Cresol and Soap Solution (Lysol) and Chloroxylenol Solution B.P., soap micelles are used to solubilize the phenolic substances. The soap (anionic surfactant) is formed by reaction of potassium hydroxide with a suitable oil such as linseed oil (in Cresol and Soap Solution) or castor oil (in Chloroxylenol Solution). The solubilizing potential of surfactant solutions for hydrophobic species has also been exploited in the design of cholelitholytic solvents for gallstone dissolution with some limited success. 

Two theories were held before the intensive research (56,57) in America during the recent war firmly established the idea that the initial reaction occurred within the soap micelles. 

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