The functionalization of carbon black surface with atom transfer radical polymerization (ATRP) initiating sites and subsequent ATRP of n-butyl acrylate (n-BA) and t-butyl acrylate (t-BA) from the surface of carbon black is reported. The polymerizations were carried out using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine as the primary catalytic system in anisole at 70 degrees C. The initiator density on carbon black surface was tuned and the effect of initiator density on the polymers grafted on the surface was illustrated. Polymerizations were also performed in the presence of a sacrificial initiator to indirectly monitor the molecular weight evolution of polymers formed in the system. Block copolymerization of t-BA initiated from poly(n-BA) grafted carbon black was conducted to achieve water-dispersible carbon black composites after cleavage of the t-butyl groups. (c) 2005 Wiley Periodicals, Inc.