NEMATIC ORDERING IN POROUS GLASSES - A DEUTERIUM NMR-STUDY

A deuterium NMR study of the pentylcyanobiphenyl liquid crystal confin ed to a controlled pore glass matrix with pore radii of 12, 150, and 2 00 nm was performed. In the 12-nm sample the nematic to isotropic tran sition is gradual. In the nematic phase the absorption spectrum is sub stantially narrowed due to translational diffusion of nematic molecule s, which is effective because of the inhomogeneous nematic ordering. T he external magnetic field influence is negligible. The onset of nemat ic ordering is bulklike in the 150- and 200-nm samples. There, the abs orption spectrum is strongly affected by the external magnetic field. The 150-nm sample exhibits memory effects depending on history of temp erature and external field changes.