WATER SOLUBILIZATION INVESTIGATIONS OF PHOSPHATIDYLCHOLINE REVERSE MICELLES

Egg lecithin reverse micelles formed in non-polar solvents were studied by water-solubilization investigations and temperature-dependent C-H stretching Raman spectra. It was noted that lecithin reverse micelles in selected organic solvents undergo a phase transition from liquid crystal to gel via the formation of a viscous phase on adding increasing amounts of water. The gels thus obtained are thermoreversible, i.e. by heating and cooling one can induce transition from gel to non-viscous phase and vice versa, via the formation of the viscous phase. The fact that the C-H stretching vibrations of acyl chains in the Raman spectra are sensitive to phase changes in the lecithin reverse-micellar system was exploited in the present work. It was proposed that the acyl chain randomness increases in the series gels, viscous phase and nonviscous phase. In gels, a population of disordered acyl chain conformation is still found, perhaps due to the packing requirements which are essential for gel formation.