Enhancing interfacial polarization and electrorheological effect of crosslinked poly(ionic liquid)s by doping aniline oligomer

Poly(ionic liquid)s (PILs) are providing potential platforms to develop next generation water-free polyelectrolyte-based electrorheological (ER) fluids because they well overcome water sensitivity problem of classic polyelectrolyte-based ER fluids by incorporating with large size fluoric counterions. Especially, crosslinked PILs (CPILs) can further broaden the working temperature range of ER effect compared to linear PILs. However, the crosslinking network easily restricts the ion dissociation due to decreased dielectric constant and thus weakens ion movement-induced interfacial polarization and ER effect. In this paper, we propose a way to improve ion dissociation and ion movement-induced interfacial polarization of CPILs by doping polar aniline oligomer to improve the dielectric constant of CPILs. Several kinds of CPILs are synthesized and then aniline oligomer is doped into CPILs by swelling method. The structure of doped CPILs is characterized by different techniques, the dielectric property of ER fluids of doped CPIL particles in silicone oil is analyzed by dielectric spectroscopy, and the ER effect of ER fluids of doped CPIL particles is measured by rheometer under electric fields. It shows that doping aniline oligomer can increase the dielectric intensity and decrease the relaxation time and corresponding activation energy of interfacial polarization and improve the ER effect of CPILs with a relatively loose crosslinking network, while doping aniline oligomer has no contribution to the interfacial polarization and ER effect of CPILs with a relatively tight crosslinking network.