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

Colorimetric determination of the free phospholipids present in concentrated fluorocarbon emulsions indicates that the amount of phospholipids adsorbed at the fluorocarbon/water interface increases when a mixed fluorinated/hydrogenated compound, C6F13C10H21, is added as a stabilizer. 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 angstrom2, indicating tighter molecular packing of the surfactant. This effect was not observed when C10F21Br was used as a stabilizer, implying that the fluorocarbon/hydrocarbon compound is located preferentially at the fluorocarbon/water interface rather than dispersed throughout the fluorocarbon phase. The interfacial film structuring effect of the mixed fluorocarbon/hydrocarbon ''dowel'' molecule is more effective when the dispersed fluorocarbon is linear rather than cyclic. (C) 1994 Academic Press, Inc.