A Pressure-Induced Phase Transition in a Ternary Microemulsion with an Assembly of a New High-Pressure Cell and Small-Angle X-Ray Scattering Apparatus

A small-angle X-ray scattering (SAXS) apparatus for use at high pressure was developed in order to investigate pressure-induced phase transition in a ternary microemulsion consisting of dioctyl sulfosuccinate sodium salt (AOT), water and n-decane. A high-pressure cell was designed to study structural phase transitions in complex fluids, and a SAXS software was developed to measure dynamical structural change of the sub-second order or a successive structural change with temperature variation. The observed SAXS profiles were explained by combining two models for small-angle neutron scattering (SANS), and the results obtained from SANS were reproduced. A pressure jump experiment from the high-pressure lamellar phase to the low-pressure phase was also carried out.