Enhancing the dielectric properties of polymethyl methacrylate by using low loading graphene encapsulated styrene-butyl acrylate copolymer microspheres

Abstract

With the rapid development of the electronics industry and electronic products, polymer nanocomposites with high dielectric constant and low dielectric loss will have great potential in various applications. In this work, a novel structure was obtained by absorbing reduced graphene oxide on the surfaces of styrene butyl-acrylate copolymer (rGO@SBA) microsphres through soap-free emulsion polymerization technique. Fourier-transform infrared spectrum characterization revealed the successful fabrication of rGO@SBA microspheres. SEM and TEM results indicated that rGO nanosheets were successfully loaded on the surface of SBA microspheres and the average diameter of rGO@SBA was increased to 650 nm. High dielectric permittivity rGO@SBA composites were obtained when the rGO loading was approximated to 2 wt%. The dielectric permittivity of rGO@SBA composites with 2 wt% rGO was 339 times higher than that of neat SBA. Furthermore, the electrical conductivity was also obviously enhanced. However, the dielectric loss of rGO@SBA composites was also inevitably increased. The rGO@SBA microspheres were further melt blended with polymethyl methacrylate (PMMA) matrix to obtain rGO@SBA/PMMA composites. The glass transition temperature of PMMA was increased with the content of rGO. The dielectric permittivity of rGO@SBA/PMMA composite with only 0.14 wt% rGO was increased to 15.5 at 1 kHz. On the other hand, the dielectric loss was controlled in a low level. SEM observation implied a segregated dispersion of rGO@SBA was realized in PMMA matrix. Our strategy provides a facile method to prepare high dielectric constant and low dielectric loss of rGO filled polymer composites through the fabrication of rGO encapsulated polymer microspheres.