Rheology of the Sponge Phase of the SDS–Hexanol–Brine System

We have studied the rheological properties of the sponge phases (or L₃) of the sodium dodecyl sulfate (SDS)–hexanol–brine (NaCl 20 g/l) system at different bilayer volume fractions. The most concentrated samples display a Newtonian behavior even at high shear rates, while the more diluted ones depart from it, probably due to a transition from the sponge to a lamellar structure. Two linear variation zones were observed when the viscosity was measured as a function of bilayer volume fraction. The effect of temperature on the rheology of a sample with bilayer volume fraction of 0.024 is discussed, and also how the addition to the system of polyethylene glycol, a water-soluble polymer, affects this transition.