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.

Dually crosslinked graphene oxide reinforced alginate/polyvinyl alcohol (PVA) double network (DN) hydrogels were prepared via a facile freeze/thaw method followed by soaking in a Ca²⁺ solution. The morphology and structure of the hydrogels were systematically examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The effects of pH, dosage of hydrogel, adsorption time, and temperature on the adsorptive property of DN hydrogels towards methylene blue (MB) were also studied. Results indicated that the hydrogels exhibited typical 3D porous structures and had an efficient adsorption effect towards MB due to strong interactions between DN hydrogels and MB molecules. The adsorption isotherm was found to coincide with the Langmuir model with a monolayer adsorption. The highest adsorption capacity of DN hydrogels for MB was examined as 480.76 mg·g⁻¹.