Grafting of polystyrene on nitrogen-doped multi-walled carbon nanotubes

Polymer grafting of polystyrene (PS) on nitrogen-doped multiwall carbon nanotubes (CN _x) was successfully obtained by a "grafting from" technique. The production method involves the immobilization of initiators, using wet chemistry, onto the nanotube surface, followed by an in situ surface-initiated polymerization. The polymer-grafting carbon nanotubes synthesis includes the free radical functionalization of CN _x and the "controlled/living" Nitroxide Mediated Radical Polymerization (NMRP). The obtained products were studied using several microscopic techniques as scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS). The characterization also includes thermogravimetric analysis (TGA), Raman spectroscopy, infrared spectroscopy, and electron spin resonance (ESR), among others. The analyzed samples were also compared with solutions fabricated by physical blending of the polymer and CN _x nanotubes. These results indicate that the nanotube radical functionalization, the chemical grafting, and the polymerization reaction were obtained over CN _x when NMRP method was successfully used, giving rise to a uniform PS layer of several nanometers grafted on the outer surface of the CN _x nanotubes. Several properties of the PS-grafted CN _x nanotubes were also studied. It is shown that the production method leads to a narrower distribution of the external diameters. Moreover, their solubilization in organic solvents is greatly improved. Finally, the dispersion of PS-grafted CN _x into a PS matrix is studied to determine the differences in filler dispersion and interfacial adhesion strength, in comparison with nanocomposites elaborated with as-produced CN _x.