Enhancing Electroresponsive Electrorheological Effect and Temperature Dependence of Poly(ionic liquid) Particles by Hard Core Confinement

Monodisperse core-shell-structured SiO ₂ @poly(ionic liquid) (SiO ₂ @PIL) particles are prepared by the polymerization of ionic liquid monomer on the surface of methacryloxypropyltrimethoxysilane-modified SiO ₂ particles. The electroresponsive electrorheological (ER) effect of SiO ₂ @PIL particles when dispersed in insulating carrier liquid is investigated and compared with that of pure poly(ionic liquid) (PIL) particles based on temperature-modulated rheology under electric fields. It is demonstrated that hard SiO ₂ core not only enhances the ER effect of PIL particles but also improves the temperature dependence of ER effect. By dielectric spectroscopy analysis, the mechanism behind the property enhancement was discussed. It indicates that the hard SiO ₂ core can not only increase the interfacial polarization strength of SiO ₂ @PIL particles by core-shell architecture but also restrain the segment relaxation or softening of the PIL shell and influence the ion dynamics above the calorimetric glass transition of PILs by the so called "substrate confinement effect", and this should be responsible for the enhanced electroresponsive ER effect and temperature stability of the SiO ₂ @PIL particles.