CURVATURE ELASTICITY MODELS OF MICROEMULSIONS

We review the theory of curvature elasticity of thin, fluid films star ting with a phenomenological formalism motivated by microscopic, physi cal examples. The effects of finite compressibility of the layer, exch ange of molecules between the film and the solution, and the intrinsic bending stiffness of the film are taken into account; these degrees o f freedom account for all the important molecular modes of the system. The effects of fluctuations of the number of molecules in the film (w hich is in equilibrium with surfactant molecules or micelles in soluti on) and in the area per molecule about its equilibrium value is shown to soften the curvature elastic moduli. The relationship of the bendin g moduli to the pressure distribution in the film is discussed and it is demonstrated that isotropic liquid films have no bending modulus, i n the continuum limit. The bending moduli for charged membranes and fo r block copolymers are estimated. Finally, some recent experimental me asure of curvature elasticity are discussed and compared with the theo ry.