A Cu(II)-poly(N-vinylimidazole) (PVI) complex was prepared and used to catalyze the oxidative polymerization of 2,6-dimethylphenol (DMP) to form poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) in water. The stoichiometric ratio between imidazole groups in PVI and copper ions was found to be 4 when continuous variation analysis was applied. Compared with a conventional Cu(II)-low-molecular-weight ligand complex, a high catalytic efficiency was observed in the polymerization of DMP catalyzed by the Cu(II)-PVI complex. The influence of the Cu(II)-PVI complex concentration and imidazole/Cu(II) molar ratio on the oxidative polymerization of DMP was studied. Both the yield and molecular weight of PPO increased significantly with the catalyst concentration and decreased with the imidazole/Cu(II) molar ratio. The molecular weight of PVI also played an important role in the improvement of the catalytic efficiency. The high catalytic efficiency of the Cu(II)-PVI complex may have been due to the concentration effect of the catalyst and substrate. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 109-115, 2011