Bicontinous structures, surfactants

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. 

It appears that the role of increasing salinity is to change the mean curvature of the surfactant sheetlike structure from a value favoring closure on the oil-rich regions (swollen inverted micelles). In between, in bicontinous microemulsion having comparable amounts of oil and water, the preferred mean curvature must be near zero. 

Comparable to the binary systems (water-surfactant or oil-surfactant), self-assembled structures of different morphologies can be obtained ranging from (inverted) spherical and cylindrical micelles to lamellar phases and bicontin-uous structures. To map out these regions, a phase diagram is most useful. 

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