Supported metallocene catalysis as an efficient tool for the preparation of polyethylene/carbon nanotubes nanocomposites : effect of the catalytic system on the coating morphology

Homogeneous or periodical surface coating of multiwalled carbon nanotubes (MWNTs) can be achieved by in situ polymerization of ethylene as catalyzed directly from the nanotube surface- treated by a highly active metallocene-based complex, e.g., Cp*2ZrCl2/methylaluminoxane. This polyethylene (PE) coating allows for the break-up of the native nanotube bundles. Immobilization of methylaluminoxane onto the surface of the carbon nanotubes was evidenced by scanning electron microscopy (SEM) and confirmed by X-ray photoelectron microscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The thermal behaviour and degradation were studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) was used to image polymer-coated MWNTs, showing either a relatively smooth or a textured polymer coating present on the surface of individual, debundled nanotubes, i.e., PE/MWNT nanohybrid sausage-like or shish-kebab-like structures, respectively. It was clearly demonstrated that by modifying the design of the catalytic complexes, it was possible to tune by a reproducible way the morphology of the PE coating around the MWNTs.