Synthesis of polypyrrole-polycaprolactone composites by emulsion polymerization and the electrorheological behavior of their suspensions

Polypyrrole-polycaprolactone (PPy-PCL) composites were synthesized by emulsion polymerization to improve their mechanical and electrical properties by forming conducting polymer composites and hence enhance the electrorheological (ER) response. Various PPy-PCL composite particles were synthesized by controlling the amount of PCL. The ER response increased with increasing electric field strength and particle volume fraction. A power-law dependence, tau=K phi(m) E-n, showed a good fit to the yield stresses when m=2 and n=1.5. The dependence of E-1.5 is consistent with the conduction model and the dependence of phi(2) appears to be related to structural changes with the electric field, which leads to many-body interactions between the particles. The ER response also increased with increasing amount of PCL, but the dielectric properties and dc conductivities of the PPy-PCL composite particles and the dielectric properties of the PPy-PCL composite suspensions were not consistent with the ER behavior. However, the particle diameter increased with the increasing amount of PCL, which is consistent with the ER behavior. The ER behavior of various amounts of PCL fits tau=85.12d(4) E-3/2 quite well. The proportionality of d(4) appears to be due to the many-body interactions between the particles.