The effect of polyaniline layer deposited on silica particles on electrorheological and dielectric properties of their silicone–oil suspensions

Investigation of the electrorheological (ER) effect of silicone–oil suspensions of silica particles coated with polyaniline (PANI) base in a DC electric field revealed that breaking stress, as a criterion of the intensity of the ER phenomenon, steeply increased at first with coating thickness. At relatively low PANI content (weight fraction ≈0.05), it reached a value several times higher than that with suspension of uncoated silica. Then it became virtually constant or slightly increased. The frequency spectra of dielectric characteristics of these systems reflect high relaxation times. The results suggest that the interfacial polarization of particles is predominantly controlled by polarizability of their surface layer, and the influence of the layer thickness is of secondary importance.