The effect of molecular self-diffusion on NMR linewidth and relaxation in micellar lyotropic phases

Publisher Website
Google Scholar
Abstract
The effect of molecular translational diffusion on the NMR linewidth and relaxation in lyotropic systems with finite aggregates has been studied. Here the molecular rotation induced by the translational motion of the molecule along a curved surface strongly modulates the intramolecular dipolar coupling. The corresponding autocorrelation functions are evaluated for rigid spherical, cylindrical and discotic micelles. The dependence of the NMR linewidth and relaxation rates T-11 and T-1 1ρ on the micellar shape and in particular on its anisotropy (i.e. elongation of the cylinder and flatness of the disc) is calculated. The expressions for the frequency and angular dependence of both relaxation rates are derived. The effect of Brownian micellar rotation, which is in some cases an important competing slow relaxation mechanism, is estimated as well. The possible application of NMR for the determination of micellar shape, anisotropy and orientational order is discussed