Dielectric study of the dilute part of a SDS/brine/alcohol system: A new sequence of phases?

We discuss in this letter the dilute part of the phase diagram of the pseudo-ternary system (brine + glycerol), SDS, hexanol through Freeze Fracture Electron Microscopy (FFEM) and dielectric measurements. The main conclusion is the observation of a large one-phase domain L* instead of an L4 phase as usually found in similar systems. This L* domain is connected to the sponge domain, through paths surrounding the lamellar phase. We show by FFEM that samples in the L* domain are mostly composed of vesicles. However, they present a dielectric behavior different from a vesicle phase. We conclude that L* is not a vesicle phase but is a sponge phase whose topology is different from the one found in the concentrated part of the L3 phase (see GAZEAU D., BELLOCQ A. M., Roux D. and ZEMB T., Europhys. Lett., 9 (1989) 447 and FORTE G., MARIGNAN J., BASSEREAU P. and MAY R. J. Phys. (Paris), 49 (1988) 511). These results bring new light on the sponge stability.