DSC SPECTRA AS THERMAL FINGERPRINTS OF PERCOLATIVE MICROEMULSIONS

Three component percolative W/O microemulsions were studied by differe ntial scanning calorimetry. Water-AOT-Decane, D2O-AOT-Decane, Water-AO T-Isooctane and Water-Ca(AOT)(2)-Decane systems were analyzed. Thus by changing, in the order, the dispersed phase, the dispersing medium, a nd by modifying the interphase region. The thermal history of the samp les was monitored by a suitable thermal program. Following the latter, first order phase transitions associated with the freezing and/or mel ting of the two massive phases were obtained, as well as the higher or der phase transition associated with the percolation process. From the melting spectra an estimate of the amount of water bound to the hydro philic groups of the AOT as well as of that of oil bound to the hydrop hobic surfactant tails was obtained. The latter result shows a differe nce in the behaviour of the continuous oily phase at the O/W interphas e. From the freezing spectra, the percolative character of the microem ulsion was evidenced by the exotherms associated with the freezing of the water phase.