The Oxidative Polymerization Of 2,6-dimethylphenol In Water With Cu(Ⅱ)-PVI Complex Catalysts

Poly(2,6-dimethyl-1.4-phenylene) (PPO) as an engineering plastic with perfect properties has been widely used in various areas, such as automotive industries, electrical and business equipments. In industry, the oxidative polymerization of 2,6-dimethylphenol (DMP) to form PPO was carried out in organic solutions, therefore, both a solvent recovery process and an antiexplosive reactor are required. From the view of green chemistry, the use of water as reaction medium can make the process environmentally benign, which is important in theory and practice.Poly(N-vinylimidazole) (PⅥ) ligands with different molecular weights were synthesized and coordinated with Cu(II) to form Cu(Ⅱ)-PⅥcomplexes. Compared with conventional Cu(Ⅱ)-low molecular weight ligand complexes, high catalytic efficiency was observed in the polymerization of DMP in water catalyzed by Cu(Ⅱ)-PVI complexes. The stoichiometric ratio between imidazole groups in PVI and copper ions was found to be 4 by applying continuous variation analysis. The influence of the Cu(Ⅱ)-PVI complex concentration and imidazole/Cu(Ⅱ) molar ratio on the oxidative polymerization of DMP were studied. It was found that both the yield and molecular weight of PPO increased significantly with the catalyst concentration, but decreased with imidazole/Cu(Ⅱ) molar ratio. The molecular weight of PVI also played an important role in the improvement of catalytic efficiency. The high catalytic efficiency of Cu(Ⅱ)-PVI complex may be ascribed to the concentration effect of the catalyst and substrate.Cu(Ⅱ)-PVI complex catalyst immobilized on magnetic nanoparticles of has been prepared.1H-NMR, BET, TEM, FTIR, EA and TGA have been used to analyze the morphology and structure of the grafted PVI chain on the surface of Fe3O4 The stoichiometric ratio between imidazole groups in grafted-PVI and copper ions and the complex formation constant were obtained by AAS analysis. The immobilized Cu(Ⅱ)-PVI complex catalyst was used to catalyze the oxidative polymerization of DMP in water and showed excellent C-O/C-C selectivity to form PPO. After polymerization, the immobilized Cu(Ⅱ)-PVI complex catalyst was collected by an external magnetic field and used in the next run with an additional grafted-PVI and copper ions. In the three rounds of oxidative polymerization of DMP. the recovery of magnetic nanoparticles immobilized Cu(Ⅱ)-PVI catalyst was above 95% with a small decrease in the yield of PPO. These results demonstrated that the recycle and reuse of the catalyst in the oxidative polymerization of DMP in aqueous medium have been realized.