Effects of Ligand and Cosolvent on Oxidative Coupling Polymerization of 2,6-Dimethylphenol Catalyzed by Chelating Amine-Copper(II) Complexes

摘要

The influence of chelating amine ligands, copper precursors, and solvent composition on copper-catalyzed oxidative coupling of 2,6-dimethylphenol was investigated. The most efficient catalytic reaction was conducted with CuCl2-di-tert-butylemylenediarnine (Dt-BEDA) complex in anisole or toluene with alcohol cosolvent. Slight structural changes in the N-substituent, backbone, or coordination atom of the ligand significantly dropped catalytic activities, leading to a low polymer yield. Alcohol cosolvent was necessary to synthesize a polymer of high molecular weight (M_n>10,000) with the copper(II) catalyst in toluene. With increasing alcohol ratios, the isolated yields and M_n values of the resulting polymers gradually decreased. However, the use of sterically bulky t-butanol produced polymers of the desired molecular weight ranges with low polydispersity indexes (PDI, <2) and without a significant drop in isolated yield.