A multinuclear NMR approach to the study of the lyotropic system CTAB-D2O

CTAB-D2O liquid crystalline phase (CTAB = cetyltrimethylammonium bromide), type I according to magnetic anisotropy, has been investigated by means of H-2, N-14 and O-17 NMR at variable temperature. The residual quadrupolar sp littings of all these nuclei evidenced the alignment of the phase in the ma gnetic field. The interpretation of the data of D2O quadrupolar nuclei, com monly used in the study of lyotropic liquid crystalline phases, is complica ted because of water reorientation, exchange processes and variations of th e hydration degree. The N-14d quadrupolar splittings are much more reliable indicators of the orientation of surfactant aggregates since their interpr etation in terms of the order parameter is straightforward in this case bec ause the nitrogen nucleus is subject to an electric field gradient of axial symmetry and resides just in the head of the amphiphile.