STATISTICAL-MECHANICS OF RANDOM BICONTINUOUS PHASES

We consider a random wave description of bicontinuous microemulsions, where the structure is specified by a correlation length xi and a preferred wave vector k0. The entropy of the system is calculated as the information content of a random field with an experimentally determined spectral distribution. Together with the elastic energy which has been previously derived by Teubner, we can minimise the free energy of the system and thus estimate the value of the elastic modulus keppa of the film. For example, in water - toluene - SDS/butanol microemulsions the parameters xi and k0 obtained from fits to the neutron scattering data lead to values for kappa of about two units of kT.