Dielectric relaxation in bulk and cylindrically confined octylcyanobiphenyl (8CB)

The dielectric relaxation spectrum over the frequency range 10² to 1.8×10⁹ Hz of 4-octyl-4'-cyanobiphenyl, 8CB, in bulk and confined to 200 nm diameter cylindrical pores is reported. We used matrices with parallel cylindrical pores, obtaining different alignments of the molecular director depending on the treatment. Results show that there are two relaxations in the isotropic phase and in the mesophases for parallel alignment and three for perpendicular alignment. The molecular origin of theses modes and the effect of the confinement on their dynamics are discussed. To compare properly the results for bulk and confined 8CB, a re-scaling of the experimental data is proposed.