Dielectric measurements under steady shear flow are made to clarify the shear induced structural changes in the nematic $\left(N\right)$ and the smectic-$A$ $\left(S_A\right)$ phases of 4-n-octyl-$4^{\prime }$-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 $S_A$ phase, it is suggested that undulation instability would play an important role.

• Received 17 May 2006

DOI:https://doi.org/10.1103/PhysRevE.74.051708