Polypyrrole metacomposites with different carbon nanostructures

Polypyrrole (PPy) nanocomposites incorporating different carbon nanostructures (CNS), including graphenes of different sizes, carbon nanofibers (CNFs) and carbon nanotubes (CNTs), have been successfully synthesized using a surface initiated polymerization (SIP) method. The effects of graphene size, loading level and surface functionality on the electrical conductivity and dielectric permittivity of their corresponding nanocomposites have been systematically studied. The electron transportation mechanism has been investigated, which follows a quasi 3-d variable range hopping (VRH) behavior in the nanocomposites. Meanwhile, CNFs and CNTs with the same loading as graphene are also comparatively studied. Scanning electron microscopy and transmission electron microscopy results indicate that the PPy coating on one-dimensional carbon nanostructures, such as CNFs and CNTs, is more smooth and uniform than that on the two-dimensional graphenes. PPy/CNTs nanocomposites exhibit the lowest resistivity, followed by the composites incorporating the smaller sized graphene without surfactant. More interestingly, a negative permittivity is found in each composite system, which can be easily controlled by adjusting the nanofiller loading, morphology and surface functionality. TGA results indicate that the thermal stability of the polymer nanocomposites (PNCs) is affected by the graphene loading rather than the different nanostructures.