Polyethylene (PE), alkoxyamine- and thiol-terminated PEs (PE-TEMPO and PE-SH, respectively) can be converted to macroradicals using a peroxide, a thermal cleavage of the alkoxyamine and a hydrogen transfer reaction of the thiol, respectively. The addition of these macroradicals to multiwalled carbon nanotubes (MWCNTs) were compared by performing grafting reactions at 160 degrees C in 1,3-dichlorobenzene as solvent. Raman spectroscopy was utilized to follow the introduction of PE on the MWCNTs' surface while thermogravimetric and elemental analysis indicated the extent of this grafting. The grafting ratio was found to be in the range of 19-36 wt %. PE-functionalized MWCNTs were imaged by transmission elec-tronic microscopy showing a PE layer with various thicknesses covering the surface of nanotubes. It was found that higher levels of grafting were obtained using PE-2,2,6,6-tetramethyl-piperidinyl-1-oxy and PE-SH rather than a radical grafting reaction in which dicumyl peroxide, PE, and MWCNTs were reacted. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 957-965, 2011