Electric field induced stress moduli of polythiophene/polyisoprene suspensions: Effects of particle conductivity and concentration

Electrorheological properties of polythiophene/polyisoprene suspensions were investigated in the oscillatory shear mode under electric field varying from 0 to 2 kV/mm. Poly(3‐thiophene acetic acid) particles were synthesized via an oxidative polymerization and doped with perchloric acid in order to vary electrical conductivity. ER responses can be enhanced with increasing electric field strength, particle electrical conductivity, and particle concentration. The storage modulus (G′) increases dramatically by 3 and 4 orders of magnitude, with the variations of particle conductivity and particle concentration as the electric field strength is increased from 0 to 2 kV/mm The results can be interpreted in terms of the difference in the polarizability between the particles and the matrix, and the particle agglomeration existing at high particle electrical conductivity and high particle concentration. The suspensions exhibit the transitions from the fluid‐like behavior to the solid‐like behavior at the critical electric field strengths. In particular, the sol‐to‐gel transitions occur at lower electrical field strengths with higher particle electrical conductivity and at higher particle concentration.