Reverse micelle formation using a sodium di(n-octyl) phosphinate surfactant

Sodium di(n-octyl) phosphinate was synthesized, purified, and used as a sur factant to form reverse micelles in isooctane at (22 +/- 1)degrees C by the contact method, which yields a Winsor II system. Two cosurfactants were in vestigated: decanol and di(n-octyl) phosphinic acid, and the ionic strength of the aqueous phase was adjusted with sodium chloride. For both cosurfact ants, a minimum mole ratio of cosurfactant to surfactant was required to fo rm reverse micelles and solubilize an appreciable amount of water in the or ganic phase. The maximum water uptake was obtained at this minimum mole rat io. No water uptake was obtained above a maximum value of the mole ratio of cosurfactant to surfactant, The maximum mole ratio was about 1 for di(n-oc tyl) phosphinic acid independent of acid concentration. For n-decanol, the maximum mole ratio decreased from about 3 to about 1 as the alcohol concent ration increased from 0.15 to 0.30 m. The maximum water uptake increased wi th increasing cosurfactant concentration. (C) 1999 Academic Press.