Electro-responsive electrorheological effect and dielectric spectra analysis of topological self-crosslinked poly(ionic liquid)s

By changing the amount of vinylimidazole grafted on phenyl ring, we designed and prepared a series of topological self-crosslinked poly(ionic liquid)s (TS-PILs) with different number of spacer arms by free radical polymerization. The influences of the number of spacer arms on the electrorheological (ER) effect of TS-PILs in insulating carrier liquid were studied by rheological test under electric stimulus and the influence mechanism was analyzed by broadband dielectric spectroscopy. It was found that the ER effect of TS-PILs containing organic counterion bis(trifluoromethane sulfonylimide) (TFSI^-) increased with the increase of the number of spacer arms. Broadband dielectric spectra analysis showed that the increased ER effect with the number of spacer arms was attributed to the increase of interfacial polarization strength and the decrease of electrode polarization with the number of spacer arms. Activation energy analysis indicated that increasing the number of spacer arms could promote ion pair dissociation and ion number density but inhibit long-range movement of ions, which was responsible for the increase of interfacial polarization strength and the decrease of electrode polarization. The results provided a guidance insight for the design and preparation of high-performance crosslinked PIL-based ER materials.