Lecithin microemulsion gels: an NMR study

Abstract

Lecithin gels in cyclohexane have been studied by NMR spectroscopy with a multinuclear approach.
\nA precise correlation exists between previously published1-4 shear viscosity, a macroscopic property, and
\nthe line width of the 31P NMR resonance. At constant waterllecithin ratio ( WO = 8) near the condition
\nof maximal shear viscosity, the 3lP spin-spin relaxation time as a function of lecithin concentration defines
\nthe range in which a gel-forming condition is present. Light scattering data i.e. hydrodynamic and gyration
\nradii6 at low lecithin concentration as a function of WO match extremely well the corresponding 3lP line
\nwidth curve. During the gel formation process water mobility increases and, contrary to the expectation
\nbased on the established model, no evidence of fatty chains entanglement is found. Instead a marked
\nstiffening of the trigliceride moiety and the phosphate is found, while the polar head and the fatty chains
\ndo not show loss in mobility.