Nematic ordering in porous glasses: A deuterium NMR study

A deuterium NMR study of the pentylcyanobiphenyl liquid crystal confined to a controlled pore glass matrix with pore radii of 12, 150, and 200 nm was performed. In the 12-nm sample the nematic to isotropic transition is gradual. In the nematic phase the absorption spectrum is substantially narrowed due to translational diffusion of nematic molecules, which is effective because of the inhomogeneous nematic ordering. The external magnetic field influence is negligible. The onset of nematic ordering is bulklike in the 150- and 200-nm samples. There, the absorption spectrum is strongly affected by the external magnetic field. The 150-nm sample exhibits memory effects depending on history of temperature and external field changes.