Investigation of electrokinetic and electrorheological properties of polyindole prepared in the presence of a surfactant

In this study, synthesis of polyindole (PIN) was carried out without and with the presence of a sodium dodecyl sulfate (SDS) surfactant (SPIN), using FeCl3 as an oxidizing agent. The synthesized materials were subjected to various characterizations techniques namely: particle size, magnetic susceptibility, elemental analysis, density, conductivity, dielectric constant, FTIR, 1H NMR, TGA, XRD, and SEM. Characterization results revealed the successful preparation of the homopolymers of PIN and SPIN. Zeta (ζ)-potentials of the samples were measured in aqueous and non-aqueous (silicone oil, SO) media. Electrokinetic properties of PIN and SPIN in aqueous media were determined by ζ-potential measurements in the presence of various electrolytes (NaCl, BaCl2, AlCl3, Na2SO4) and surfactants (cetyltrimethyl ammonium bromide, SDS, and Triton X-100). Besides, the effect of pH onto ζ-potentials of the materials was also examined. The suspensions prepared in SO were subjected to external electric field strength and their electrorheological (ER) properties were investigated. Then the effects of shear rate, frequency, and temperature onto ER activities of the suspensions were examined. Further, creep and creep–recovery tests were applied to the PIN/SO and SPIN/SO suspension systems and reversible non-linear viscoelastic deformations observed under applied electric field.

► Aggregated morphology was determined for PIN, spherical and porous hollows and everniae form morphologies were recorded for SPIN.
► The PIN/SO and SPIN/SO systems showed almost similar electrokinetic attitudes and a typical shear thinning non-Newtonian viscoelastic behavior, vibration damping capability at elevated frequencies, and enhanced storage moduli with increasing temperature.
► Non-linear recoverable viscoelastic manner was revealed from the creep–recovery experiments under external electric field.