ABOUT THE MECHANISM OF STABILIZATION OF FLUOROCARBON EMULSIONS BY MIXED FLUOROCARBON HYDROCARBON ADDITIVES

Colorimetric determination of the free phospholipids present in concen trated fluorocarbon emulsions indicates that the amount of phospholipi ds adsorbed at the fluorocarbon/water interface increases when a mixed fluorinated/hydrogenated compound, C6F13C10H21, is added as a stabili zer. The polar head surface area of the phospholipids in emulsions of C8F17Br was reduced from ca. 85.8 +/- 1.3 angstrom2 to 74.1 +/- 1.1 an gstrom2, indicating tighter molecular packing of the surfactant. This effect was not observed when C10F21Br was used as a stabilizer, implyi ng that the fluorocarbon/hydrocarbon compound is located preferentiall y at the fluorocarbon/water interface rather than dispersed throughout the fluorocarbon phase. The interfacial film structuring effect of th e mixed fluorocarbon/hydrocarbon ''dowel'' molecule is more effective when the dispersed fluorocarbon is linear rather than cyclic. (C) 1994 Academic Press, Inc.