Reversed micellar solution-to-bicontinuous microemulsion transition in sodium bis(2-ethylhexyl) phosphate/n-heptane/water system
- Auburn Univ., AL (United States)
The solution structures in the three-component system sodium bis(2-ethylhexyl) phosphate (NaDEHP)/n-heptane/water have been investigated by dynamic and static light-scattering, electrical conductivity, and {sup 31}P-NMR spectroscopic and viscometric measurements. A transition in the physicochemical properties was observed over a rather narrow range of W{sub o} (molar ratio of water to NaDEHP) values. Rodlike reversed micelles and swollen rodlike reversed micelles form when W{sub o}< 4. Beyond this W{sub o} range, phase separation occurs at low NaDEHP concentrations, and homogeneous one-phase microemulsions form at high NaDEHP concentrations. It is suggested that the n-heptane-continuous solution of water-swollen reversed micelles transforms to a bicontinuous microemulsion when W{sub o} increases beyond W{sub o} {approx} 4. The bicontinuous microemulsion region ranges between two local viscosity maxima at W{sub o}{approx} 4 and W{sub o}{approx} 100, and an oil-in-water (O/W) microemulsion exists when W{sub o}> 100. Local dynamic domain structures consistent with the bicontinuous microemulsion behaviors are proposed and discussed. 29 refs., 7 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG05-85ER13357
- OSTI ID:
- 45010
- Journal Information:
- Langmuir, Vol. 11, Issue 4; Other Information: PBD: Apr 1995
- Country of Publication:
- United States
- Language:
- English
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