FROM MONOLAYERS TO BILAYERS - EFFECTIVE RIGIDITY AND COMPRESSIBILITY IN ASYMMETRIC TERNARY AMPHIPHILIC SYSTEMS

Fluctuation effects in lamellar phases of ternary asymmetric amphiphil ic systems are considered. These systems are characterized by two leng th scales corresponding to the thickness of the oil and water layers. For large separations between the amphiphilic layers, the dominant con tribution 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 effecti ve rigidity is determined from Monte Carlo simulations of an asymmetri c three-layer system. An expression for the effective layer compressib ility is derived, which can be expressed in terms of the effective ben ding rigidity. These effects lead to pronounced corrections of the sca ttering exponents eta m, which can be measured in scattering experimen ts.