The grafting of polystyrene with controlled molecular weight and narrow molecular weight distribution onto the carbon black surface through the trapping of polymer radicals formed by the thermal dissociation of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-terminated polystyrene (PSt-TEMPO) by the carbon black surface was investigated. PSt-TEMPO was prepared by living radical polymerization of St with the benzoyl peroxide/TEMPO system. When PSt having no terminal TEMPO moiety was heated with carbon black, no grafting of PSt onto the surface was observed. On the contrary, by the heating of PSt-TEMPO with carbon black in m-xylene at 125 degrees C, PSt with controlled molecular weight and narrow molecular weight distribution was grafted onto the surface : the percentage grafting of PSt(M-n = 3.2 x 10(3); M-w/M-n = 1.07) onto furnace black was determined to be 16.0%. On the basis of the above results, it is concluded that PSt radicals formed by the thermal dissociation of the C-ON bond between PSt and TEMPO are trapped by polycondensed aromatic rings of carbon black. The mole number of grafted PSt chains on the carbon black surface decreased with increasing molecular weight of PSt-TEMPO. PSt-grafted carbon black gave a stable colloidal dispersion in THF.