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

Enhanced dielectric properties of polystyrene by using graphene incorporated styrene-butyl acrylate microspheres

In view of the current trend of capacitor materials, the development of capacitors with high dielectric permittivity and low dielectric loss is of great interest. In this work, the dielectric permittivity of reduced graphene oxide-incorporated styrene-butyl acrylate (rGO@SBA) composite microspheres synthesized by mini-emulsion polymerization was significantly improved. rGO with 2 wt% content gave a dielectric permittivity of 11 356 (at 1 KHz), which was 1925 times higher than that of pure SBA (5.9). SEM and TEM were conducted to observe the morphology and structure of the composite microspheres. After filling into polystyrene (PS), a segregated structure of (rGO@SBA) that enables a concentrated aggregation of rGO in SBA was fabricated. The dielectric permittivity of PS could reach 10.91 (at 1 KHz) by incorporating only 0.39 wt% rGO by using this segregated structure of (rGO@SBA). PS simply mixed with SBA microspheres and graphite (PS/rGO-SBA) was also fabricated as a comparison group to verify the effect of this segregated structure on the dielectric properties of the composites. After comparing the dielectric properties of PS composites with different structures, the enhancement in dielectric permittivity of the composites can be demonstrated.

The dielectric properties of rGO@SBA composite microspheres with core–shell structure and the effects of different preparation methods on the dielectric properties of PS were investigated.

Improvement of the electromechanical properties of thermoplastic polyurethane composite by ionic liquid modified multiwall carbon nanotubes

Carbon nanotubes (CNTs) were non-covalently modified by two categories of ionic liquids (ILs), including 1-vinyl-3-ethylimidazole bromide (VEIMBr) and 1-vinyl-3-hexylimidazole bromide (VHIMBr) in the ratio of 1:1 and 1:4, respectively. The surface interaction between CNTs and ILs was well-characterized by FTIR, Raman spectra, XPS, etc. Thermoplastic polyurethane (TPU) containing different amounts of CNTs/ILs was fabricated by melting blending method. TPU-CNTs/ILs composites exhibited simultaneously enhanced electromechanical properties with improved dielectric constant and lowered elastic modulus. The electromechanical sensitivity of sample TPU-3CNT/12VHIMBr increased by approximately 45 times in comparison with that of pure TPU at 200 Hz. Besides, improved dispersion of CNTs/ILs in the TPU matrix was also exhibited.