Deuteron spin relaxation and molecular dynamics of a nematic liquid crystal (5CB) in cylindrical microcavities

Spin–lattice and spin–spin relaxation times of deuterium nuclei have been measured for a nematic liquid crystal confined in cylindrical channels of diameter 0.2 μm. In the isotropic phase the relaxation in the MHz regime is not affected by the confinement. The possibility of rotating the cylinders with respect to the magnetic field enables the first direct measurements of the anisotropy of deuteron relaxation of a monomeric liquid crystal in the nematic phase. The observed temperature dependence of the spin–spin relaxation rate in the isotropic phase roughly obeys the (T−T*)−1 law and allows the determination of the average time the molecules reside at the wall, which is 5×10−5 s for 5CB at the lecithin coated surfaces. In the nematic phase the spin–spin relaxation rate is affected by order director fluctuations and rotation induced by translational diffusion at orientations with a nonhomogeneous director distribution with respect to the magnetic field.