Lamellar versus isotropic structures in dilute phases of fluid membranes

The sponge phase of a mixed surfactant system

“…We have extended a previous study of Hoffmann et al [7] and showed that these phases can be stable in concentrated systems and at all proportions of ionic and non-ionic surfactants.…”

“…Its structure is similar to that of a bicontinuous phase. It can be pictured as a melted cubic phase, where the passages divide space in two independent regions [7]. Macroscopically, it presents some interesting properties such as a very low viscosity and flow birefringence.…”

Fluctuating Euler characteristics, topological disorder line, and passages in the lamellar phase

“…This transition must be accompanied by topological fluctuations, since microemulsion is a bicontinuous structure characterized by large and negative Euler characteristics, whereas the ideally ordered lamellar phase has zero Euler characteristics ͑in the system with periodic boundary conditions͒. Porte et al 7 suggested that the topological fluctuations associated with this transition are wormhole passages which form spontaneously joining the layers in the lamellar phase. Each passage changes the Euler characteristics by Ϫ2 and therefore a lamellar phase with many passages has large and negative Euler characteristics.…”

Shear banding in a lyotropic lamellar phase. I. Time-averaged velocity profiles

“…Depending on the range of concentrations, one can observe different structures: for instance, long cylinders of some microns long (wormlike micelles) or infinite surfactant bilayers (membranes). In the latter case, because of the interactions, the membranes can form periodic stacks, referred to as lamellar phases and noted L α , or randomly connected continuous structures, called sponge phases and noted L 3 [30,31]. In a lamellar phase, the smectic period d, i.e.…”