LIQUID-GAS-LIKE TRANSITION IN MICROEMULSIONS INVESTIGATED BY THERMODYNAMICAL AND ELECTRICAL MEASUREMENTS

This is a first presentation of differential scanning microcalorimetric and (di-) electric measurements on phase separation of a single-phase three-component ionic microemulsion into two coexisting droplet phases. For certain compositions this transition resembles a liquid-gas phase transition close to its critical point. Contrary to what was expected, it is shown that the transition is accompanied by two peaks in the specific heat preceded by a narrow dip. The temperature of the dip coincides with a peak in the static dielectric constant and significant changes of the electrical conductivity. It is concluded that this structure is due to rearrangement of droplets. Internal degrees of freedom of the surfactant-coated water droplets are proposed to be responsible for these modifications of the thermodynamic properties with respect to usual liquid-gas transitions.