Electrorheology of polyindole

Polyindole particles were prepared by the oxidative polymerization, where ammonium peroxydisulfate was used as an oxidant at several mole ratios to indole. Prepared spherical micrometre-sized polyindole particles were further used as a dispersed phase in silicone-oil electrorheological (ER) fluids and their rheological behaviour was investigated in the presence and in the absence of an electric field. While different oxidant-to-indole mole ratios did not affect the size and morphology of the particles, their electric and dielectric properties were significantly changed. The highest ER effect was observed for the ER fluid based on the particles with low oxidant-to-indole mole ratio (1:1). Such system exhibited yield stress around 100 Pa at 10 wt% concentration of solid phase. Chain-like structures created upon an application of an electric field were further investigated using an optical microscopy, where significant disparities were found according to electric and dielectric properties of the particles. These findings clearly show that varying mole ratio between the indole and oxidant provides systems with tuneable ER effect.