Micromechanics of Surfactant Microstructures

Force balance and stability criteria have been used to distinguish among various shapes of surfactant aggregates. the model aggregate is assumed to be liquidlike in the interior with a bounding interfacial region. Inclusion of higher moments of surface excess stress leads to the conclusion that not all spheres are stable, that stable short cylinders of ∼3-3.5 length to diameter ratio can exist (cylindrical micelles) and even grow to infinite lengths (cylinders in hexagonal liquid crystals), and that there are regions where only lamellar structures are possible. a model relating surface packing to surface tension and the higher order effects shows that cylindrical structures can compete with spherical ones, except at high packing densities where only lamellar forms can exist and except when the interfacial energies are ultralow, the latter case being established separately. a model for the isotropic surfactant phase allows one to obtain a persistence length in terms of the surface properties. © 1987 American Chemical Society