The effect of addition of polyethylene oxide (PEO) on the phase behavior of the TX-114/n-octane-n-butanol/water system is reported. It has been found that the addition of PEO results in a decrease in the amount of solubilized water in W/O microemulsion region, and an increase in the amount of solubilized water in lamellar liquid crystalling phase. The W/O microemulsion has been studied by using methylene blue as an absorption probe and 5-doxyl stearic acid (5-DNS) as a spinning probe. The result clearly indicates that there are three types of water present in the polar core: bound water, which interacts directly with ethylene oxide chains of the surfactant; trapped water, which is located between the ethylene oxide groups, with high mobility; bulk-like water, which forms at high water contents. In the presence of PEO, the polymer molecules can replace some bound water or trapped water molecules, which leads to a looser arrangement of ethylene oxide groups of the surfactants at the interface. This structure may induce the formation of higher aggregates.

Key words: POLYGLYCOL, NORMAL OCTANE, N-BUTANOL, WATER, MICROEMUSION, DISSOLVING