NMR and dielectric studies of nano-confined nematic liquid crystals

Orientational order and mobility of nematogens adsorbed in nanoporous glass are investigated by H-1 and C-13 NMR and broadband dielectric spectroscopy. For the mesogen 5CB, we detect local nematic order in cavities of 2.5, 5.0 and 7.5 nm diameter. Quantitative measurements of the order parameter are reported. The nematic-isotropic transition temperature is lowered by approximately 16K compared to the bulk phase. The N-I transition is smooth, of second or weakly first order. At low temperatures, order parameters of approximate to 0.7 are reached. Crystallisation (N-Cr) is suppressed considerably, at least to below 220K. A surface layer of mesogenic molecules at the pore walls with considerably retarded molecular dynamics is detected.