ER Effect on the Normal Stress and Induced Network Structure of Liquid Crystal Polymer

Abstract

There have been many reports on electrorheological (ER)1–4 suspensions because of their remarkable ER effect. Besides these two-phase systems, some one-phase system or homogeneous ER fluids5–14, such as polymeric liquids, have been developed. The homogeneous ER fluids are free from the problems seen in suspensions due to dispersed particles, e.g., sedimentation, aggregation, friction, which reduce the ER effect. We have been studying ER effects in polymeric liquids to establish a model for understanding the mechanism of the ER effects in such homogeneous systems6,12–14. Among the homogeneous ER fluids, polymers with flexible side chain connected with polar mesogenic group have a large ER effect8, 9. At present, the mechanism of the ER effect in these liquid crystal polymers (LCP) has been interpreted as the inhibition of the slipping between mesogenic domains by the flexible chains connecting them under an electric field. Detailed rheological examinations are necessary for further understanding of the mechanism.