ABSTRACT

The liquid blend type ER materials are composed of two (or more) immiscible liquids. Inoue et al.8) and Tajiri et al.9) reported that a liquid crystalhne polymer (LCP)/dimethylsiloxane (DMS) blend shows an ER effect. In this blend, DMS forms a continuous phase and LCP forms droplets, and LCP droplets elongate in the field direction under the electric field. Kimura et al.10) reported that UPPG/DMS blends show the stress increase or decrease depending on the viscosity ratio of the components. In the UPPG/DMS blends, the ER effect occurs only if UPPG forms droplets under no field. If the UPPG content is low (UPPG fraction from between 17 to 66 vol %), the UPPG droplets elongate and bridge the electrodes by applying the electric field (see Fig.4). When UPPG fraction is somewhat larger (75 vol%), the application of the field irreversibly changes the UPPG phase into the matrix and the DMS phase into droplets (electrically induced phase inversion). The flow curve of these materials is qualitatively similar to that of the homogeneous type ER materials (see Fig.5). In the liquid blend type ER materials, the ER effect is caused by the change of domain structure by the electric field. However, the behavior of the domains is rather complicated and many problems still remain to be solved.