Guest molecules in Triton X-100 microemulsion: studied by positron annihilation technique and absorption spectroscopy

Positron annihilation lifetime measurements have been performed in water in oil (w/o) microemulsion (ME) of Triton X-100/butanol, n-heptane system in the presence of additives, UO+22 and p-nitro phenol (PNP). The microenvironment of the guest molecules in the ME phase was studied by the positronium (Ps) reaction-rate constant. The Ps reaction rate constant values with UO+22 in ME changed gradually as a function of water content in ME phase where as a considerable enhancement of Ps reaction rate constants with PNP was observed in the same phase. Furthermore, the solubilization of the probe molecules in the different microphase of the ME system was investigated through the UV-VIS absorption spectra. The results show that UO+22 ions were preferentially occupied in the polar water pool of ME but PNP molecules were distributed in the interfacial region (intermediate polarity) of the ME phase.