Comparison of electrorheological properties of some polyaniline derivatives

In this study, electrorheological (ER) properties of various polyaniline derivatives, namely: poly(o-toluidine) (POT), poly(N-methyl aniline) (PNMAn), poly(N-ethyl aniline) (PNEAn), and poly(2-ethyl aniline) (P2EAn) were investigated. Effects of various parameters such as; particle size, particle conductivity, suspension's sedimentation stability, flow times, concentration, electric field strength, shear rate, frequency and temperature onto ER activity of these polyaniline derivatives/silicone oil (SO) suspensions were investigated. Average particle diameters (d50) of four samples were determined by dynamic light scattering as 8.51, 9.08, 11.22 and 13.46 μm for P2EAn, PNEAn, PNMAn and POT, respectively. It was found that POT has the highest conductivity with a value of 6.87 × 10−7 S m−1, and P2EAn has the lowest with 1.01 × 10−7 S m−1, among the polyaniline derivatives examined. Fifty four percent of sedimentation ratio was measured after 30 days for all the polyaniline derivatives/SO suspensions studied. The highest electric field viscosity was observed for POT/SO suspensions as η = 1.04 kPa s. The maximum excess shear stress was obtained for the POT suspensions (25 wt.%) as Δτ = 917 Pa at E = 2 kV/mm.