Tandem Action of Early−Late Transition Metal Catalysts for the Surface Coating of Multiwalled Carbon Nanotubes with Linear Low-Density Polyethylene

Abstract

The homogeneous surface coating of multiwalled carbon nanotubes with linear low-density polyethylenes, containing from 3 to 34 branches per 1000 carbon atoms, has been achieved for the first time by combining the polymerization-filling technique (PFT) with tandem copolymerization catalysis. This method, which takes advantage of the use of ethylene as single monomer feed, allows for the breakup of the native nanotube bundles and provides an effective way to control the branching in the PEs produced at the nanotube surface. TEM micrographs of the composite materials have shown an interesting dependence of the PE-coating morphology on the experimental parameters of the tandem system.

Easy one-pot method to control the morphology of polyethylene/carbon nanotube nanocomposites using metallocene catalysts

“…6b with CpZrCl 2 /MWCNT/MAO system. Such structure was recently reported for PE nanocomposites when modified MAO was used, employing a more tedious experimental procedure or different catalyst [10,30,36,37]. The morphology of this coating was dramatically influenced by the metal center.…”

“…The morphology of this coating was dramatically influenced by the metal center. When Zr catalysts are used, as discussed above the CNTs are in fact decorated with disc-shaped objects (arrows), corresponding to PE single crystal lamellae, resulting in a new nanohybrid morphology ("shishkebab"-like structures) [30,[36][37][38]. The central shish is the carbon nanotube while the kebabs are formed by PE chains as shown in Figs.…”

Olefin oligomerization, homopolymerization and copolymerization by late transition metals supported by (imino)pyridine ligands

“…TEM micrographs of the composite materials prepared by this technique show an interesting dependence of the PE-coating morphology on the experimental parameters of the tandem system [87].…”

“…Heterogeneous co-catalysts such as silica gel supported PHT (partially hydrolyzed trimethylaluminum) [19] or physicochemical supported methylalumoxanes [86,87] (s-MAO or s-MMAO; see also cfr 6.2) have been also proposed as activators for iminopyridyl dihalide complexes. However, MAO and MMAO remain the most active and used co-catalysts in ethylene polymerization/oligomerization.…”

“…Textured surface coating of multi-walled carbon nanotubes (MWCNTs) with LLDPEs has been successfully achieved by Giambastiani and co-workers combining the tandem copolymerization protocols with the polymerization filling technique (PFT) [86,87]. This method can be conveniently described as a fourstep process which involves (i) the physico-chemical anchoring of the co-catalyst, MMAO, onto the CNT surface, (ii) the addition of the oligomerization and copolymerization pre-catalysts and their subsequent activation at the surface of the nanofillers (Scheme 23, left), (iii) the surface-initiated tandem copolymerization of ethylene and ␣-olefins and, (iv) the growth and precipitation of LLDPE onto the CNTs leading to their coating (Scheme 23, right).…”