AMMONIUM BIS(ETHYLHEXYL) PHOSPHATE - A NEW SURFACTANT FOR MICROEMULSIONS

The ammonium salt of the metal ion extractant bis(ethylhexyl) hydrogen phosphate (HDEHP) has been found to stabilize water-in-oil (w/o) micr oemulsions over a wide range of omega (=[H2O]/[NH(4)DEHP]) and tempera ture. Such extensive solubilization has not been observed for Gp I, II , or III metal salts of HDEHP. In the absence of added water, SANS mea surements show the formation of rod-shaped reversed micelles which pro gressively decrease in length as waters added in the range omega < 5. At constant omega the rod length increases with surfactant concentrati on. For omega > 5 spherical droplet w/o microemulsions are formed with the droplet size increasing in proportion to omega. Analysis of SANS data gives the head group area of NH4-DEHP in the surfactant layer of larger spherical microemulsion droplets as 63 +/- 3 A(2).