Improved dielectric properties for chemically functionalized exfoliated graphite nanoplates/syndiotactic polystyrene composites prepared by a solution-blending method

Exfoliated graphite nanoplates (xGNPs) were chemically functionalized by the 1,3 dipolar cycloaddition reaction of azomethine ylides. The introduction of organic groups on the external graphitic layers of xGNPs was confirmed by Fourier-transform infrared spectroscope, scanning electron microscope, transmission electron microscope, and thermal gravimetric analyzer. The resultant functionalized xGNPs (f-xGNPs) could be suspended in N-methyl-2-pyrrolidinone after ultrasonic treatment, which facilitated their homogeneous dispersion in syndiotactic polystyrene (sPS) matrix to form f-xGNPs/sPS composites by a solution-blending method. It was found that the existence of f-xGNPs increased the crystallization temperature but reduced the crystallization degree of sPS due to their strong interfacial interaction with sPS matrix. The dependences of electrical and dielectric properties of f-xGNPs/sPS composites on concentration of f-xGNPs and frequency were investigated. When the concentration of f-xGNPs is 10 wt.%, the electrical conductivity and the dielectric constant of f-xGNPs/sPS composites were 1.5 × 10−7 S/m and 36.4 at 1000 Hz, respectively, while the corresponding values of sPS were 3.8 × 10−10 S/m and 2.83, respectively. The enhanced and stable dielectric constant of f-xGNPs/sPS composites could be ascribed to the well dispersion of f-xGNPs in sPS matrix, resulting in the formation of a large number of microcapacitors.