Electrorheological properties of perchloric acid doped polythiophene suspensions

Poly(3-thiophene acetic acid), PTAA, was synthesized via an oxidative polymerization and doped with perchloric acid to control its conductivity. Rheological properties of the HClO4 doped PTAA/silicone oil suspensions were measured in the oscillatory shear mode to investigate the effects of electric field strength, particle concentration, and particle conductivity on ER characteristics. The PTAA based ER fluids exhibited a viscoelastic behavior under an applied electric field and the ER response enhanced with increasing electric field strength. The dynamic moduli, G' and G", dramatically increased by 10 orders of magnitude when the electric field strength was increased to 2 kV/mm. Effect of particle concentration and particle conductivity were apparent at moderate electric field strengths and the suspensions show saturated ER properties at electric field strength of 1 kV/mm. Moreover, the suspensions exhibited transition from fluid-like to solid-like behavior as electric field strength increased. Higher particle concentration and higher particle conductivity induced a lower transition electric field.