Dielectric study on the shear-induced structural changes in the nematic and the smectic-A phases of 4-n-octyl-4'-cyanobiphenyl (8CB).

Dielectric measurements under steady shear flow are made to clarify the shear induced structural changes in the nematic (N) and the smectic-A (SA) phases of 4-n-octyl-4'-cyanobiphenyl (8CB). In the N phase, the temperature dependence of the dielectric permittivity shows a characteristic behavior, which can be consistently interpreted based on the shear-induced structures suggested by x-ray scattering; flow alignment of the director and some dynamical structures characterized by different precessional motions of the director. For the shear-induced structural change in the SA phase, it is suggested that undulation instability would play an important role.