Biocompatible Lecithin Organogels: Structures and Phase Equilibria

ANGELICO R;CEGLIE A;COLAFEMMINA G;LOPEZ F;MURGIA, SERGIO;OLSSON U;PALAZZO G.

2005-01-01

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Abstract

The microstructure of organogels formed upon the addition of tiny amounts of water to a solution of lecithin in fatty acid esters (viz. isopropylpalmitate and ethyloleate) was investigated by means of molecular self-diffusion measurements. In both systems lecithin and water form disconnected cylindrical reverse micelles. The ternary phase map for the lecithin/water/isopropylpalmitate has been investigated in detail. The organogel exists in a narrow region close to the lecithin-oil binary axis; for higher water content equilibrium between lamellae and reverse micelles is found. Lamellar phase occupies the lecithin-rich region, close to the lecithin corner (with the exception of a small island of hexagonal phase) and coexists with neat water close to the water-lecithin axis. The remaining part of the phase map shows the threephase coexistence of water, oil, and lamellar phase.