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

This is a first presentation of differential scanning microcalorimetri c and (di-) electric measurements on phase separation of a single-phas e three-component ionic microemulsion into two coexisting droplet phas es. For certain compositions this transition resembles a liquid-gas ph ase transition close to its critical point. Contrary to what was expec ted, it is shown that the transition is accompanied by two peaks in th e specific heat preceded by a narrow dip. The temperature of the dip c oincides with a peak in the static dielectric constant and significant changes of the electrical conductivity. It is concluded that this str ucture is due to rearrangement of droplets. Internal degrees of freedo m of the surfactant-coated water droplets are proposed to be responsib le for these modifications of the thermodynamic properties with respec t to usual liquid-gas transitions.