A composite based on exfoliated graphite (EG) and polystyrene was prepared by a poIymerization-frlling technique. With augmentation of filled EG, the molecular weight of polystyrene in the resulting composite increased and the molecular weight distribution decreased. The glass transition temperature of the polystyrene was determined by dynamic mechanical analysis (DMA) and showed that it increases to 123.74 degreesC. The thermal degradation behavior of the composite was studied using thermogravimetry (TG) and showed a higher thermal stability than that of pure poIystyrene and polystyrene/EG composite prepared by melt-blending. The DC conductivity of the composites prepared by the polymerzation-filling technique and melt-blending, respectively, were measured. (C) 2001 Elsevier Science Ltd. All rights reserved.