Synthesis of hybrid polymer/graphene materials using miniemulsion polymerization

Abstract

The goal of this research has been to exploit the amphiphilic properties of graphene oxide (GO) for the preparation of well-dispersed polymer-graphene nanocomposites. In order to achieve this aim, the synthesis of nano-dimensional GO was conducted according to a recent method for the preparation of small and uniform GO. The ability of GO to function as surfactant was demonstrated in miniemulsion polymerization of styrene and other vinyl monomers of different polarities, in the absence of conventional surfactant. Miniemulsion polymerization was chosen due to its unique characteristic which enables the initial entrapment of GO on the surface of monomer droplets. The formation of ‘armoured’ particles indicated the presence of GO at the surface of particles, consistent with its surface active properties. Polymer particles with diameters ranging from -500 nm to a few microns, with relatively broad particle size distributions were observed. The polarity of the monomers was found to strongly influence the emulsion stability; monomers with a relatively small polar component (based on Hansen solubility parameters) such as styrene, lauryl methacrylate and benzyl methacrylate, generate stable emulsions that can be effectively polymerized. The differences in pH of the emulsion investigated in this research exerted a relatively minor influence on the polymerization, whereas the ionic strength on the other hand had a more significant effect – the presence of a suitable concentration of NaCl resulted in increased colloidal stability and narrower particle size distribution. Poly(styrene-co-butyl acrylate)/GO film resulting from miniemulsion polymerization was visually homogeneous with evidence of preserved ‘armoured’ particles, hence presenting an efficient method for the preparation of polymer/graphene nanocomposites.