Structure and dynamic properties of a polymer-induced sponge phase

The effect of polyethyleneglycol (PEG) on the phase behaviour of oil-rich s odium dodecyl sulphate, hexanol, water and dodecane mixtures has been inves tigated. PEG causes the disappearance of the 'sponge' phase and induces the formation of a new isotropic phase, labelled L-5. located between the micr oemulsion, L-2, and the lamellar, L-alpha, phases. Small angle neutron scat tering and electrical conductivity results show that at local scales the L- 5 phase consists of inverted bilayers, connected at larger scales. These fe atures suggest a sponge-like structure for the L-5 phase, a hypothesis whic h is further supported by a static and dynamic light scattering study.