The grafting of carboxyl-terminated liquid rubbers, specifically polybutadiene (BR-COOH) and nitrile rubber (NBR-COOH), was investigated in the presence of scandium trifluoromethanesulfonate (Sc(OTf)(3)) as a catalyst, on silica nanoparticles and on carbon black surfaces. In the absence of the catalyst, the grafting of the liquid rubbers onto silica nanoparticles and carbon black minimally proceeded. In contrast, terminal-carboxyl groups of the liquid rubbers readily reacted with amino groups on silica and phenolic hydroxyl groups on carbon black in the presence of Sc(OTf)(3) to give BR-grafted and NBR-grafted silica and carbon black. After the grafting reaction, Sc(OTf)(3) was easily recovered and the recovered Sc(OTf)(3) could be reused in the grafting of the liquid rubbers onto silica and carbon black. In addition, when an excess of silica nanoparticle and carbon black was reacted in the absence of solvent, the crosslinking reactions of the liquid rubbers by silica nanoparticles and carbon black proceeded in the presence of Sc(OTf)(3). (C) 2008 Elsevier Ltd. All rights reserved.