Dynamic Soap Micelles

As amphiphilic organic molecules, soap molecules, resulting from the reaction between organic acids and mineral bases (metal hydroxide, metal carbonate, etc), aggregate into reverse micelles when they are introduced into nonpolar media such as mineral oils or nonpolar solvents. The hydrophdic (mineral) part wUl agglomerate in the core of the micelles and the nonpolar queues will constitute the surrounding shell. Such assemblies are in dynamic equilibrium with single molecules dispersed at the CMC in the solvent. 

Depending on the metal atom valence and on the synthesis process, various types of soap molecules can be obtained. In the case of stoichiometric additives, also called neutral soap, soap molecules syntheses will correspond to the following reactions [17, 18]  

Monovalent ions RCOOH - - MeOH RCOOMe -I- H2O Divalent ions 2 RCOOH -I- Me(OH)2 (RCOO)2 Me -I- 2H2O 

In the case of lead soaps, for x = 1 mass spectroscopy studies allows the following molecular formula to be determined [21]  

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Micelle formation is briefly discussed in Section 2.2.5, item 4 see especially Figure 2.8. Soap micelles typically contain 50 to 100 molecules, and the radius is roughly 2nm (about the length of a surfactant molecule). The core of a micelle contains a little water, at most one molecule per surfactant molecule. The size and shape of the micelles closely depend on the molecular configuration of the surfactant. Micelles are dynamic structures. They are not precisely spherical, and surfactant molecules move in and out. Characteristic times for these processes are a matter of debate, but they seem to be of the order of 10 ps. Presumably, a micelle can disappear in 10-100 ms upon dilution. 

By covalent linkage of different types of molecules it is possible to obtain materials with novel properties that are different from those of the parent compounds. Examples of such materials are block-copolymers, soaps, or lipids which can self-assemble into periodic geometries with long-range order. Due to their amphiphilic character, these molecules tend to micellize and to phase-separate on the nanometer scale. By this self-assembly process the fabrication of new na-noscopic devices is possible, such as the micellization of diblock-co-polymers for the organization of nanometer-sized particles of metals or semiconductors [72 - 74]. The micelle formation is a dynamic process, which depends on a number of factors like solvent, temperature, and concentration. Synthesis of micelles which are independent of all of these factors via appropriately functionalized dendrimers which form unimolecular micelles is a straightforward strategy. In... 

When an emulsifier or soap is dissolved in water, the solute molecules associate to form small clusters called micelles. The hydrocarbon parts of the emulsifier molecules constitute the interior of the micelles, the surface of which is formed by the ionic groups of the emulsifier. A small fraction of the soap is molecularly dissolved in the water and there is a dynamic equilibrium between the micelles and these single molecules in the aqueous phase. Micelles are of colloidal size, consisting of a relatively small number of soap molecules of the order of 100 molecules. This corresponds to a diameter of about 50 A., if one assumes the cluster to be spherical. At the concentrations usually employed in emulsion polymerization, there are some 10 micelles per milliliter of water. 

Naturally the micelles formed will not be as flat as shown schematically in Fig. 39c. In spots with a large dissociation the surface will De curved (see Fig. 36 large force A). The undissociated spots form the places where the micelles can be attached to each other. As a result a sort of network is formed and the solution acquires its elastic and strongly viscous properties. It cannot be too strongly emphasriied that we are dealing here with a dynamic system. The smallest air bubble rises slowly but surely upwards in such a soap gel. This means that the mutual attachment of the micelles is of relatively short duration. 

The Introductory lecture was given by Professor H. Freundlich, now of University College, London. Micelles composed of amphiphilic molecules form a bewildering array of structures as a function of soap concentration, pH and salt concentration. The highly dynamic nature of micelles was stressed. 

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