Hw. Long et al., XENON NMR-STUDY OF A NEMATIC LIQUID-CRYSTAL CONFINED TO CYLINDRICAL SUBMICRON CAVITIES, Journal of physical chemistry, 99(31), 1995, pp. 11989-11993
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.