Effect of electric field on the rheology of ferroelectric liquid crystal MORA-8

Effects of electric field on the theology, electrorheological effects, are investigated on ferroelectric smectic C* phase of 4-(6-methyl)octyl-resorcy lidene-4'-octylaniline (MORA-8). When an electric field is applied in smect ic C* phase, an increase of the shear stress is observed with its behavior depending on the shear rates; at higher shear rates the shear stress increa ses monotonously with the electric field strength, but at lower shear rates the shear stress increases monotonously until about 2 kV mm(-1), but above this field it discontinuously decreases to lower values, which is followed by an increase at higher electric fields. In close vicinity of the smectic C* to isotropic phase transition point, a field induced decrease of the sh ear stress is observed. These ER behaviors are discussed on the basis of th e field induced orientational changes of the smectic layer and the director and a possible field induced structural change. (C) 2001 Elsevier Science B.V. All rights reserved.