[31P] -Nuclear magnetic resonance (NMR) spin lattice relaxation times (T1) have been measured for lecithin-nonpolar solvent-water as a function of added water for three solvents, namely, benzene, carbon tetrachloride and cyclohexane. In benzene and carbon tetrachloride systems, where spherical reverse micelles are formed, [31P]-NMR T1, values increase linearly with added water. However, in cyclohexane, the trends in the [31P]-T1 values indicate very different micellisation processes. Even at the lowest concentration of added water, the [31P]-T1 values in this solvent are substantially larger than the corresponding values in benzene and carbon tetrachloride, which is attributed to the intramolecular chlorinephosphate interaction being the weakest in cyclohexane. At a higher water content of six mols of water per mol of lecithin in cyclohexane solvent, the [31P]-T1 values show a sharp decrease indicating a sudden change in the dynamics of the phosphate group, and this confirms the on set of ‘reverse micelle-to-liquid crystalline’ phase transition observed in this system by other spectroscopic and physical techniques.
Volume 45, 2020
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