Estimation for size of reverse micelles formed by AOT and SDEHP based on viscosity measurement

The size of reverse micelles formed by Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) single and AOT-sodium di(2-ethylhexyl) phosphate (SDEHP) mixed surfactants useful in protein separation and enzyme reaction, was estimated from viscosity measurement of surfactant/isooctane solution. Reversed micellar solution was prepared by injection method. At molar ratio of water to surfactant, WO, lower than 2, no reverse micelles of AOT appeared to form in isooctane. AOT reverse micelle size as estimated in this study agrees with published results obtained by other techniques. AOT–SDEHP reverse micelle shape was noted to vary from sphere to ellipsoid and size to decrease with greater molar fraction of SDEHP.