The highly efficient Cu(Ⅰ)-aromatic amine complex catalysts for the synthesis of poly (2,6-dimethyl-1,4-phenylene oxide) with controllable molecular weight

Although copper-aliphatic amines have been extensively used as catalysts for the polymerization of 2,6-dimethylphenol (DMP) to poly (2,6-dimethyl-1,4-phenylene oxide) (PPO), the high polydispersity index (PDI) of PPO and high content of 3,3′,5,5′-tetramethyl-4,4'diphenoquinone (DPQ) in PPO significantly affect the physical properties of PPO. In this study, different CuBr-aromatic amines have been used as catalysts for synthesizing PPO. CuBr–N-methylbenzylamine shows a high yield of PPO (94.4 %) with the low DPQ yield (0.46 %) and PDI (1.33) in the presence of 0.1 % H2O, which facilitates the formation of dinuclear Cu(Ⅱ) species. In addition, the low dielectric constants (2.43 and 2.25) and low dielectric loss factors (1.07 × 10−3 and 1.29 × 10−3) of the PPO synthesized by CuBr–N-methylbenzylamine and CuBr-4-aminopyridine again indicate that aromatic amines are more appropriate for the synthesis of PPO with superior dielectric properties. Meanwhile, the high-molecular-weight PPO can be successfully redistributed to low-molecular-weight PPO by adding DMP in the presence of CuBr–N-methylbenzylamine, and the decreased Tg values from 212.5 to 187.8 °C with decreasing Mn values from 2.7 × 104 to 5.5 × 103 indicate the improved processability of the low-molecular-weight PPO. This study provides new insights on important roles of aromatic amines in the synthesis of PPO.