Electrorheology and dielectric polarization of backbone, pendant and cross-linked poly(ionic liquid)s

Backbone, pendant and cross-linked poly(ionic liquid) (PIL) particles with the same ion pair and similar ion number density have been prepared and the electro-responsive electrorheological (ER) effect of their suspensions in insulating carrier liquid has been comparably studied by rheology and dielectric spectroscopy. It has found that the ER effect of cross-linked PILs is strongest and that of backbone PILs is weakest. Dielectric spectrum analysis has showed that the difference of ER effect is mainly due to the difference in the ion leakage and effective interfacial polarization of PIL particles under electric fields. Although the backbone PILs have the largest interfacial polarization strength, its ion leakage conductance is also largest and this results in its weakest ER effect. The cross-linked PILs well restrains the ion leakage conductance and the ER effect is largely enhanced. The difference in ion leakage conductance and ER effect is further related to the difference of PIL matrix structure according to X-ray diffraction characterization. This study clarified the influence of matrix structure on ER effect and dielectric polarization of PILs and provided a guidance for the design of PIL ER materials.