Static H-2-H-2 Dipole Interactions in a Lyotropic Liquid-Crystal - A 2Dqe Study

Abstract

The 2H NMR two-dimensional quadrupolar-echo spectra of an α-deuterated surfactant in an aligned hexagonal lyotropic liquid crystal were recorded. Whereas only indications of 2H-1H and 2H-2H dipole splittings were observed in the F2 spectra, these residual interactions were displayed in the F1, spectra as an apparently Lorentzian peak. When gated 1H decoupling was used, the 2H-2H dipole splittings became visible in the F1 spectra as three (apparently Lorentzian) peaks. From a fit to the experimental lineshape the frequencies, relative amplitudes, line-widths, and phases of these peaks were determined. The ratio between the 2H-2H dipole and 2H quadrupole splittings was found to be |q| = 0.0041. Since q values of about −0.0040 have been obtained in lamellar phases, these results indicate that the α-methylene angular distribution function with respect to the local surface normal of the cylindrical aggregates may not deviate significantly from threefold symmetry.