Fabrication of imidazolium-based poly(ionic liquid) microspheres and their electrorheological responses

Imidazolium-based poly(ionic liquid) (PIL) microspheres of poly(1-butyl-3-vinylimidazolium tetrafluoroborate) (P[C(4)VIm][BF4]) were synthesized through a dispersion polymerization process, which was confirmed by H-1 NMR, FT-IR and SEM. Rheological measurement at different electric field strengths indicated that the P[C(4)VIm][BF4] microspheres in dimethyl silicone oil (15 wt%) showed typical electrorheological (ER) performances including steady flow curves over the entire shear rate range. The ER fluid performed like a Newtonian fluid with very low shear viscosity at zero electric field, which implied the good affinity of the PIL particles with silicone oil. From the ER result, it is worth remarking that the good ER activity of the P[C(4)VIm][BF4]-based ER fluid is due to the high-density ion parts which can induce strong interfacial polarization.