Electrorheological and dielectric characteristics of semiconductive polyaniline-silicone oil suspensions

We report experimental results of the electrorheological (ER) and dielectric characteristics of an ER fluid made of suspensions of semiconductive polymer (polyaniline) particles in silicone oil. We found that the shear stress of this ER fluid at different applied electric fields can be scaled into a universal curve by the dynamic yield stress which increases linearly with the square of the electric field strength. We also studied the effect of conductivity on the ER performance of these ER fluids. The results show that the ER performance can be improved by increasing the conductivity of the polyaniline particles. We also found that the difference in ER characteristics due to changing conductivity is consistent with the relaxation time obtained from the dielectric spectrum observed for these ER fluids.