Tuning the Network Structure of Graphene/Epoxy Nanocomposites by Controlling Edge/Basal Localization of Functional Groups

Successful formation of a three-dimensional (3D) network of incorporated conductive fillers in a polymer matrix leads to achieve an electrically conductive nanocomposite at low filler loading levels. In this work, one- to three-layer edge and basal-functionalized graphene oxide (GO) nanosheets were synthesized via a novel method. Raman spectroscopy was employed to investigate the localization of oxygen-containing groups through the GO nanosheets. Afterward, the synthesized GO nanosheets were dispersed in an aqueous epoxy suspension to produce electrically conductive polymer nanocomposites. The formation of the interconnected 3D network structure of GO nanosheets through the epoxy matrix was studied by employing rheological approaches and imaging techniques. We postulated that oxygen-containing groups’ localization can effectively impact the polymer–GO nanosheet interactions, which, in turn, affect the 3D network formation of the nanosheets through the polymeric medium. After in situ thermal reduction of polymer nanocomposites at 225 °C, electrical conductivity measurements revealed that nanocomposites containing basal-functionalized graphene nanosheets featured higher electrical conductivity values compared to those for samples containing edge-functionalized graphene nanosheets. Hence, these results shed light on the importance of functional groups localization that can dictate the final properties.