From monolayers to bilayers: Effective rigidity and compressibility in asymmetric ternary amphiphilic systems.

Abstract

Fluctuation effects in lamellar phases of ternary asymmetric amphiphilic systems are considered. These systems are characterized by two length scales corresponding to the thickness of the oil and water layers. For large separations between the amphiphilic layers, the dominant contribution to the free energy can be written in the Helfrich form if an effective bending rigidity is introduced that is allowed to depend on the water and oil layer thicknesses. The scaling form of this effective rigidity is determined from Monte Carlo simulations of an asymmetric three-layer system. An expression for the effective layer compressibility is derived, which can be expressed in terms of the effective bending rigidity. These effects lead to pronounced corrections of the scattering exponents ${\mathrm{\ensuremath{\eta}}}_{\mathit{m}}$, which can be measured in scattering experiments.