Reverse micelles packing parameter

Figure 9.2 Calculation of the surface packing parameter. Via x I, which determines to some extent the form of the aggregate. For V/(a x 1) c. 1, bilayers are preferentially formed when this ratio is less or more than one, spherical aqueous and reverse micelles are formed, respectively. Self-assembly may be described in terms of the curvature that exists at the hydrocarbon-water interface.

The formation of crystalline arrays of spheres and cylinders is also favoured in reversed micelles to achieve nearly uniform molecular dimensions. Although the curvatures of these surfaces are constant, it is not possible to pack the volumes between the spheres or cylinders with units of equal surfactant parameter. This inhomogeneity is due to variations in the spacing... 

Fig. 3. Packing Parameter (P=v/aolc). (a) Spherical Micelle (P3).

The method of deducing solute location from the scattering peak shift in the case of spherical reversed-micelles can be generalized to the case of connected structures (56). For instance, consider the model case of a bicontinous structure, close to the electrical antipercolation threshold. Take the polar volume fraction to be in the range 0.3 to 0.4 and the specific area to be E = 0.02 A /A, which corresponds to a 0.5 M solution of a classical surfactant. In addition, consider a chain length of 15 A and an initial surfactant packing parameter of Po = 1.25. 

The difference in order parameters at the water droplet film in gel emulsions and the inside of the reverse micelles in the single isotropic phase indicated that the surfactant molecules at the water droplet film are more tightly packed compared to those in reverse micelles. The observed difference in the apparent order parameter between the ordinary emulsions and the gel emulsions suggested that, when the fraction of water in the system is around 0.99, most of the surfactant molecules are adsorbed at the oil-water interface and no reverse micelles are present in the continuous oil phase. ... 

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