Dielectric relaxation of nematic liquid crystal confined in porous matrices

Using dielectric spectroscopy in the frequency range 0.1 Hz-1.5 GHz, we investigated the dynamic properties of pentylcianobiphenyl (5CB) confined in porous matrices with randomly oriented, interconnected pores as well as in parallel cylindrical pores with different pores sizes. The confinement has a strong influence on the dielectric properties of LC which resulted in the appearance of a low frequency relaxational process (f less than or equal to 10 KHz) absent in bulk and a strong modification of modes due to the molecular rotation around short axis and librational motion. From qualitative point of view the dielectric behavior of LC in random and cylindrical pores is similar. So we conclude that the finite size effect due to the confinement and existence of LC-pore wall interface have more influence on the properties of LC than the influence due to different porous structure.