A new immobilized catalytic system, cross-linked poly(acrylic acid) (PAA) resin immobilized cobalt(II)/copper(II) bimetallic catalyst, was successfully employed for atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). Well-defined poly(methyl methacrylate) (PMMA) with low polydispersity (PDI = 1.27) was synthesized using PAA/Co(II)/Cu(II) catalyst without any additional ligand or soluble deactivator. As the immobilized catalyst could be effectively separated from the polymer solution by simple centrifugation after polymerization, colorless PMMA (Co residue < 1 ppm, Cu residue similar to 4 ppm) was achieved. Both main catalytic activity and good controllability over polymerization were retained by the recycled catalyst after reused several times. The catalyst was characterized by SEM. EDX, TGA and ESR techniques. The polymerization reaction mechanism was presented. (c) 2007 Elsevier B.V. All rights reserved.