Effects of ligand and cosolvent on oxidative coupling polymerization of 2,6-dimethylphenol catalyzed by chelating amine-copper(II) complexes

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 CuCl 2 -di- tert -butylethylenediamine (D t -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 with the copper(II) catalyst in toluene. With increasing alcohol ratios, the isolated yields and 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,