Conductive polymer composites have aroused wide interests from both academia and industry in the field of functional materials. Addition of diverse conducting fillers such as carbon black [1,2], graphite [3], and metal fiber or powder [4] into thermoplastic polymers through melt mixing is an effective approach to fabricate conductive composites. Because a great amount of the fillers, generally greater than 15 wt% [5], were required for the host polymer to become conductive, resulting in both poor processability and inferior mechanical properties, the practical applications of these conventional composites were largely restricted. On the other hand, commercial exploitation of isotactic polypropylene has been expanded rapidly due to its attractive characters of low cost, low weight, heat distortion above 100°C, and extraordinary versatility in terms of properties, applications and recycling. The introduction of nanoscopic fillers of high anisotropy enhances a wide range of performance of the polypropylene nanocomposites, such as mechanical, thermal and conductive properties, at a relatively small loading [6]. Graphite is a layered mineral composed of weakly bonded graphene sheets with a large aspect ratio. Abstract. Various surfactants of different molecular weights, including alkylamine, poly(oxypropylene) diamine (POP), and maleic anhydride grafted polypropylene (PPgMA) oligomers, were used for simultaneous funtionalization and reduction of graphite oxide (fGO). In this study, the effect of molecular weight and compatibility of the surfactants on the morphology and properties of the nanocomposites are reported. Wide-angle X-ray diffraction (WAXD) exhibited a definite interlayer thickness for GOA (alkylamine intercalated GO), however, the diffraction peaks were nearly suppressed for fGOs combining ODA with either POP (GOAP) or PPgMA (GOAE). The uniform dispersion of the fGO flakes in the polypropylene matrix resulted in the significant increase in both the degradation temperature and the crystallization temperature. A single characteristic melting peak of monoclinic (!) crystalline phase was observed from DSC traces, which was consistent with WAXD results. Dynamic mechanical analysis clearly indicated increase in both the storage modulus and the glass transition temperature of the nanocomposites due to the enhanced affinity between fGO and the polypropylene matrix. However, GOAP composite showed lower E" and T g than GOAE because POP is less compatible with the matrix than PPgMA oligomer. Dielectric analysis also showed significant increase in both dielectric permittivity and dielectric loss at low frequency regimes with GOAE showing maximum dielectric properties. The finely dispersed GOAE and its compatibility with polymer matrix manifested the interfacial polarization, which gave rise to much greater #" and #$ than other nanocomposites.
