Swelling behavior and local topology of an [Formula Presented] (sponge) phase

The swelling behavior of an [Formula Presented] (sponge) surfactant phase was studied by the small angle x-ray scattering technique; we show that it is well described by the recently computed swelling law for minimal surfaces. In addition, the self-diffusion coefficient [Formula Presented] of several probes within the bilayers of the [Formula Presented] phase was measured by the fluorescent recovery after fringe pattern photobleaching technique. The variation of [Formula Presented] with the surfactant volume fraction provides a clue for the topology of the surface over which the midsurface of the bilayers is draped. This allows us to determine the location of the neutral surface near the polar-apolar interface of the bilayers.