Electrorheological behaviour of suspensions of doped polyaniline nanofibers containing carbon nanoparticles dispersed in silicone oil

Abstract

Electrorheological (ER) fluids has been paying a lot of attention due to their potential use in active control of various devices in mechanics, biomedicine or robotics. ER fluid consisting of polarizable particles dispersed in a non-conducting liquid is considered to be one of the most interesting and important smart fluids. This work presents the effect of the dopant, camphorsulfonic acid (CSA) or citric acid (CA), on the eletrorheological behaviour of suspensions of doped PANI nanostructures dispersed in silicone oil, revealing its key role. The influence of carbon nanoparticles concentration has also been studied for these dispersions. All the samples showed an ER effect, which increased with electric field and nanostructures concentration and decreased with silicone oil viscosity. However, the magnitude of this effect was strongly influenced not only by carbon nanoparticles concentration but also by the dopant material. The ER effect was much lower with a higher carbon nanoparticles concentration and doped with citric acid. The latter is probably due to the different acidities of the dopants that leads to a different conductivity of PANI nanostructures. Furthermore, the effect of the carbon nanoparticles could be related to its charge trapping mechanism while the charge transfer through the polymeric backbone occurs by hopping. PANI/CSA composite nanostructures dispersed in silicone oil exhibited the highest ER activity, higher than 3 decades increase in apparent viscosity for low shear rates and high electric fields, showing their potential application as ER smart materials.