Fabrication of Graphene–Polyimide Nanocomposites with Superior Electrical Conductivity

Abstract

We report on the fabrication of a novel class of lightweight materials, polyimide-graphene nanocomposites (0.01-5 vol %), with tunable electrical conductivity. The graphene-polyimide nanocomposites exhibit an ultra-low graphene percolation threshold of 0.03 vol % and maximum dc conductivity of 0.94 S/cm, which we attribute to excellent dispersion, extraordinary electron transport in the well-dispersed graphene, high number density of graphene nanosheets, and the π-π interactions between the aromatic moieties of the polyimide and the carbon rings in graphene. The dc conductivity data are shown to follow the power-law dependence on the graphene volume fraction near the percolation threshold. The ac conductivity of the nanocomposites is accurately represented by the extended pair-approximation model. The exponent s of the approximation is estimated to be 0.45-0.61, indicating anomalous diffusion of charge particles and a fractal structure for the conducting phase, lending support to the percolation model. Low-temperature dc conductivity of the nanocomposites is well-approximated by the thermal fluctuation-induced tunneling. Wide-angle X-ray scattering and transmission electron microscopy were utilized to correlate the morphology with the electrical conductivity. The lack of maxima in X-ray indicates the loss of structural registry and short-range ordering.

Advances in Polyimide‐Based Materials for Space Applications

“…Meng et al have shown the use of an interconnected PI‐supported 3D graphene structure as a basis for flexible electrodes for lithium‐ion batteries. Recently, Yoonessi et al produced a graphene–PI nanocomposite containing well‐dispersed graphene nanosheets. The maximum conductivity achieved was 0.96 S cm −1 at a filler content of 5 vol%.…”

“…Figure c shows a scanning tunneling microscopy (STM) image at atomic resolution of the 3D‐C with a hexagonal symmetry modulation of 0.246 nm periodicity . Figure d shows an SEM image depicting the interconnected macroporous structure of the 3D‐C/PI electrode produced by Meng et al Figure e shows a low‐magnification transmission electron microscope (TEM) image revealing the dispersion of the graphene layers and stacks in the nanocomposite produced by Yoonessi et al, with graphene concentration of 1.23 vol%. Both high particle number density of the graphene layers and stacks were evident.…”

“…e) TEM image of a graphene–PI nanocomposite, showing the local dispersion of the graphene nanosheets and expanded graphene clusters and fractal. Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…The inset shows fit of the data to the power law predicted by the percolation theory. Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…The conductivity of the graphene nanosheet–PI composite produced by Yoonessi et al is shown in Figure b as a function of the graphene volume fraction. The results indicate that the percolation transition to a conducting nanocomposite occurs at a graphene concentration of 0.03 vol%, and that the maximal conductivity (0.94 S cm −1 ) is attained at higher graphene concentration (5 vol%).…”