In situ synthesis of the reduced graphene oxide-polyethyleneimine composite and its gas barrier properties

The ternary roles of polyethyleneimine (PEI) as a reducing agent, a surface modifier and a polymer host have been presented to fabricate reduced graphene oxide (RGO) based composite films with improved gas barrier property. The PEI functionalized RGO dispersion is prepared and filtered to fabricate thin films with a brick and mortar structure. The simultaneous reduction and functionalization of graphene oxide (GO) by PEI are confirmed by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy analysis. The good dispersion of graphene sheets in the PEI matrix and the layered structure is confirmed by X-ray diffraction and field emission scanning electron microscopy analyses. Thermogravimetric analysis also confirms the removal of oxygen functionalities from GO and the attachment of PEI chains to the RGO sheets. The electrical conductivity of the RGO film is found to be 492 S m^-1 at low content of PEI (PEI:GO = 0.02:1), and increasing the PEI content leads to a decrease in the electrical conductivity of the films. In contrast, the water dispersibility and gas barrier properties increase with increasing PEI content in the composite film.