XENON NMR-STUDY OF A NEMATIC LIQUID-CRYSTAL CONFINED TO CYLINDRICAL SUBMICRON CAVITIES

NMR studies of xenon gas dissolved in the liquid crystal ZLI 1132 conf ined to submicron cylindrical cavities are reported. Spectra taken as a function of temperature yield a clear indication of the nematic to i sotropic phase transition of the confined liquid crystals. In the nema tic phase at 21 degrees C, the resonance line of dissolved Xe-129 exhi bits a chemical shift anisotropy of 15 ppm due to a random distributio n of director axes in the plane perpendicular to the long axis of the cylinder. The anisotropy and temperature dependence of the confined sy stem are compared to control experiments that use the bulk liquid crys tal. The quadrupolar splitting observed in the Xe-131 NMR spectrum of the confined liquid crystalline solution of xenon gas is slightly grea ter than that found in the bulk. Two-dimensional exchange NMR demonstr ates that the xenon atoms probe different average liquid crystal direc tors within a single cavity on a 20 ms time scale and that interpore e xchange occurs on a time scale of 400 ms. The exchange data indicate t hat changes in the orientation of the director within individual cavit ies occur on a length scale of about 2 mu m.