Conductive Nanocomposites Reinforced with Exfoliated Graphite Nanoplatelets (GNPs)

Abstract

Graphite nanoplatelet (GNP)/polystyrene (PS) nanocomposites were prepared by in situ exfoliating polymerization. Potassium (K) was intercalated into GNPs at an elevated temperature in vacuum to form Kgraphite intercalation compounds (K-GIC) with different stages. The stage of K-GIC was manipulated by changing the mole ratio of K to graphite during intercalation process. K-GICs were then exfoliated at room temperature in vacuum by polymerization of styrene vapor in the intercalated galleries. Electrical conductivities of GNP/PS nanocomposites thus obtained were found to depend on the intercalation stage. The stage-I GNP/PS nanocomposite showed a conductivity lower than 10 S/cm at 10 wt% of GNP, and stage IV and higher were required to get conductivity higher than 10 S/cm. Thermal stability was investigated with DSC (differential scanning calorimetry) and TGA (thermogravimetric analysis). In addition, the microand nano-structures of exfoliated GNPs in nanocomposites were investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The stage-I GNP/PS nanocomposite showed little graphite crystalline peak in X-ray diffraction (XRD), an indication that most of the graphene layers were separated from one another because of in situ exfoliation during polymerization. The graphite crystalline peak increased with increasing stage index. The first stage GNP/PS nanocomposite showed their thickness to be as small as 2 nm after melting.