Composite material with high dielectric constant and low dielectric loss obtained through grafting of cyano groups in imidazolium ionic liquids

A strong polar cyano group was introduced to increase the interfacial polarization between filler and matrix, thereby improving the dielectric properties of polymer composites. 3-Cyanomethyl-1-vinyl imidazolium bromide (CMVImBr) ionic liquid was first synthesized, copolymerized with divinylbenzene on the surface of carbon nanotubes (CNTs) to form a core–shell structured hybrid, and then compounded with epoxy to prepare a filler-well-dispersed composite with high dielectric constant . The dielectric constant of the composites reached 139 at 1 kHz when the filler content was 20%, and the dielectric loss was only 0.088. The cyano groups and ionic bonds from CMVImBr played a significant role in increasing the dielectric constant owing to interfacial polarization. Moreover, the crosslinked polymer shells decreased the dielectric loss and served as electrical barriers between CNTs , which are desirable properties for electronic devices.