Electrorheological properties of perchloric acid-doped polythiophene suspensions

Poly(3-thiopheneacetic acid), PTAA, was synthesized via an oxidative polymerization and doped with perchloric acid to control its conductivity. The rheological properties of the HClO4-doped PTAA\silicone oil suspensions were measured in oscillatory shear to investigate the effects of electric field strength, particle concentration, and particle conductivity on electrorheological (ER) characteristics. The PTA -based ER fluids exhibit Aviscoelastic behavior under an applied electric field and the ER response is amplified with increase of electric field strength. The dynamic moduli, G and G, increase dramatically by ten orders of magnitude when the field strength is increased to 2 kV\mm. The suspensions exhibit a transition from fluid-like to solid-like behavior as the field strength increases, and reach a saturated ER response at a field strength of 1 kV\mm. Increase of particle concentration and particle conductivity result in a lower transition field strength. Scaling arguments are presented which successfully superpose the scaled moduli at various electric field strengths onto a single master function of the dimensionless frequency.