Promoting the electrical conductivity of polyimide/in-situ reduced graphene oxide nanocomposites by controlling sheet size

Polyimide (PI)-based nanocomposite films have found promising applications in electronics. However, despite their superior thermomechanical properties, PI/graphene oxide (GO) nanocomposites have a lower electrical conductivity compared to the case when pre-reduced graphene oxide (rGO) is used. To address this gap, we aimed to increase the electrical conductivity of PI/GO nanocomposite films without sacrificing other properties by forming in-situ reduced GO (irGO) particles and enhancing their aspect ratio. We produced GO nanosheets with various sizes via the modified Hummer method and used them to prepare PI/irGO nanocomposites via in-situ polymerization. The in-situ reduction of GO particles occurred along with the thermal imidization. Analysis of IR spectroscopy, XRD patterns, DMTA, and SEM images suggested the formation of chemical bonds between GO particles and PI matrix, which fortified the interface compared to PI/rGO nanocomposites. Thermal analyses revealed that enhancing the sheet size led to a decrease in the degradation rate below 200 °C and an increase in the ash residual. More importantly, the electrical resistance of PI/irGO was significantly decreased, even below that of the PI/rGO nanocomposite, by increasing the size of the nanosheets. These results are promising for the application of PI/irGO nanocomposites in electronics, and they may even replace PI/rGO nanocomposites when higher thermomechanical properties are desired.