Graphene oxides (GO) were exfoliated in N,N-dimethylformamide by simple sonication treatment of the as-prepared high quality graphite oxides. By high-speed mixing of the pristine poly(amic acid) (PAA) solution with graphene oxide suspension, PAA solutions containing uniformly dispersed GO can be obtained. Polyimide (PI) nanocomposite films with different loadings of functionalized graphene sheets (FGS) can be prepared by in situ partial reduction and imidization of the as-prepared GO/PAA composites. Transmission electron microscopy observations showed that the FGS were well exfoliated and uniformly dispersed in the PI matrix. It is interesting to find that the FGS were highly aligned along the surface direction for the nanocomposite film with 2 wt % FGS. Tensile tests indicated that the mechanical properties of polyimide were significantly enhanced by the incorporation of FGS, due to the fine dispersion of high specific surface area of functionalized graphene nanosheets and the good adhesion and interlocking between the FGS and the matrix.

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In this paper, Co-Al layered double hydroxide (LDH) and carbon nanotubes (CNT) have been assembled to form exfoliated LDH nanosheet/carbon nanotube hybrids via electrostatic force. The assembling process and nanostructures of exfoliated LDH/CNT hybrids were investigated by zeta potential, Raman spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The assembly mechanism of LDH with CNT was also discussed. Furthermore, the unique three-dimensional (3D) hybrids thus prepared were used as reinforcing nanofillers to enhance the performance of polyamide 6 (PA6). It was found that the synergic effect of the CNT and LDH nanoplatelets resulted in homogeneous dispersion of the hybrid nanofillers throughout the PA6 matrix and strong combination with the matrix, thus providing an efficient mechanical improvement for the PA6 nanocomposites.

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