Electrorheological and dielectric analysis of self-crosslinked poly(ionic liquid)s with different flexible chain spacer

Three kinds of self-crosslinked poly(ionic liquid)s (S-PILs) with different flexible chain spacers, namely P[B2V][TFSI], P[C8DVIM][TFSI] and P[TEGDVIM][TFSI], were prepared. The influence of flexible chain spacer on electrorheological (ER) effect of S-PIL suspension in silicone oil under electric fields was studied by rheological method and dielectric spectroscopy. It is found that as the flexibility of chain spacer increases, the ER effect increases. However, the dielectric spectrum shows that the variation of ER effect is not completely consistent with that of interfacial polarization but is related to the competition between interfacial polarization induced by ion motion and electrode polarization formed by ion leakage. By combining wide-angle X-ray scattering spectra and ion activation energy analysis, we further clarify that the reason for the inconsistence of dielectric property and ER effect is not only related to the flexibility of chain spacer but also related to the interaction between oxygen on chain spacer and counter-anions in the S-PILs. The result provides an insight for the molecular design of S-PIL ER materials.