Theory of Shape Transitions in Microemulsions
We construct the mean-field phase diagram for microemulsion shapes in the dilute globule limit. The phenomenological bending energy of a globule is motivated by a microscopic model of the elasticity of the surfactant layer. We find spherical, lamellar and cylindrical phases to be stable. In the novel cylindrical phase, the cylinders are rigid for lengths smaller than a persistence length ξc; for lengths larger than ξc‚ the cylinders can behave like polymers in solution. As the persistence length and the degree of polymerization depend on the concentration of dispersed phase, these cylindrical microemulsions should exhibit interesting concentration dependence for the radius of gyration and viscosity.
KeywordsFree Energy Disperse Phase Surfactant Molecule Persistence Length Cylinder Radius
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