Polymer-Stabilized Graphene Dispersions At High Concentrations In Organic Solvents for Nanocomposite Production

Liquid phase exfoliation and dispersion of graphene, i.e. single layer graphite, is a critical challenge for bulk processing of graphene for use in advanced materials and devices.  We demonstrate a simple and effective dispersion of pristine (unfunctionalized) graphene at high concentrations in a wide range of organic solvents by use of a stabilizing polymer (polyvinylpyrrolidone, PVP). These polymer-stabilized graphene dispersions are shown to be aggregation-resistant and readily redispersible even after freeze-drying. These dispersions are then used as a strong and conductive nano-filler for polymer nanocomposites. In particular, PVP/graphene nanocomposites may be produced via in situ polymerization of vinyl pyrrolidone loaded with dispersed graphene, resulting in excellent load transfer and improved mechanical properties. Also, graphene-based epoxy nanocomposites with enhanced mechanical and electrical properties at a very low loading have also been achieved.  The electrical conductivity increases by 7 orders of magnitude and the tensile strength increases by 25 % in a 0.3 wt% graphene based epoxy nanocomposite compared to the baseline epoxy. Compared with the prior literature, we achieve higher concentrations and lower percolation threshold for our pristine graphene dispersions and composites, respectively.