Miniemulsion polymerization using graphene oxide as surfactant: In situ grafting of polymers

The occurrence of covalent grafting of polymer chains onto graphene oxide (GO) sheets during aqueous miniemulsion radical polymerizations of common vinyl monomers has been investigated. Styrene, benzyl methacrylate and t-butyl methacrylate were polymerized via miniemulsion polymerization using GO as sole surfactant, and the characterization of GO isolated post-polymerization was investigated by a range of experimental techniques (Fourier-Transform Near Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Photoelectron spectroscopy (XPS), Raman spectroscopy and X-Ray Diffraction (XRD)). All experimental techniques show consistently that significant grafting occurs for all three monomers under these conditions. Furthermore, Raman spectroscopy indicated that the mechanism of grafting involves the sp² carbons present in the GO structure, and not the oxygen-containing functional groups (e.g. epoxy, hydroxyl and carboxyl). The extent of grafting was quantified by XPS, revealing that polymer grafting occurred at levels in the approximate range of 20-60 wt% (grafted polymer relative to total mass of GO and grafted polymer). Miniemulsion polymerization using GO as surfactant is an attractive approach for synthesis of polymer/GO nanocomposites, and the present results are important in regards to the specific structures and performances of such materials.