Composites prepared by penetrating poly(ethylene oxide) chains into graphene interlayers

Abstract

Polymer electrolytes play important roles in the development of lithium polymer rechargeable batteries because they can lead to a flexible laminated structure with tailormade geometries. Polymer electrolytes are ionically-conducting polymers formed by dispersing a salt at the molecular level in a high molecular weight polymer, such as poly (ethylene oxide) (PEO). These materials have attracted strong interest for technological applications as solid electrolytes in electrochemical devices, such as batteries, display devices, and sensors. Although PEO-based polymer electrolytes exhibit fast ionic conduction in the molten state, the poor conductivity results from the retardation of ionic transport imposed by the highly crystalline phase at ambient temperature. By adding a liquid plasticizer or organic polar solvent into polymer electrolytes, the ionic conductivity can be improved by the enhanced segment motion and an amorphous phase. Graphene is a single layer of carbon atoms in a hexagonal lattice that has attracted because of its novel electronic and mechanical properties. These unique properties make it a choice as an inorganic filler to improve the electrical, thermal and mechanical properties of the composite materials. Graphene has potential for improving the electrical conductivity of polymers. In recent years, a range of processing routes has been reported for graphene-based composites. Among the other factors, the nature of the bonding interaction at the interface between the filler and matrix has significant implications for the final composite properties. In addition, most dispersion methods produce composites that are non-covalent assemblies, where the polymer matrix and filler interact through relatively weak dispersive forces. In melt mixing, a polymer melt and filler (in dried powder form) are mixed under high shear conditions. Similar to solution mixing, melt mixing is often considered to be more economical (because no solvent is used) and more compatible with many current industrial practices. Melt compounding using commercial resins and conventional compounding devices, such as extruder and mixer, is more attractive compared to in situ exfoliation and solution mixing because this approach provides manufacturers with many degrees of freedom with regard to the selection of polymer grades and graphene content. Most PEO-based composites are prepared by intercalation-exfoliation method with clays. In this study, various composites were prepared by the interpenetration of PEO chains into the interlayers of graphene by heating blends of the two components. The composites were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD).