The role of functional groups on graphene oxide in epoxy nanocomposites

The role of functional groups on the surface of graphene oxide (GO) upon its ability to reinforce an epoxy resin has been investigated. It is known that a base-washing process removes oxidative debris from as-prepared GO and reduces the number of functional groups in the material. Both as-prepared (aGO) and base-washed graphene oxide (bwGO) fillers were incorporated into an epoxy resin matrix and the mechanical properties of the different nanocomposites were investigated. The best levels of reinforcement were found with the addition of low loadings of aGO while the bwGO gave inferior levels of reinforcement at the same loading level. Raman spectroscopy was used to both assess the dispersion of the fillers and efficiency of stress transfer to the GO in the nanocomposites during deformation. It was found that for a given filler loading the aGO materials had the most uniform dispersion of filler and the largest Raman band shifts per unit strain, indicating the importance of the presence of functional groups in both dispersing the GO and giving good interfacial stress transfer in the nanocomposites.