Biphasic coupling polymerization of 2,6-dimethylphenol using surface-active copper complex catalysts

Coupling polymerization of 2,6-dimethylphenol to poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was carried out in an 1:1 aqueous-chloroform biphasic mixture using Cu-surface active ligand complex catalysts. Bidentate ligands were superior to monodentate ligands in promoting the oxidative coupling possibly due to their higher surface-activity and ability to form a binuclear complex with two metal ions. In particular, N,N-dibutylethylenediamine complex of copper gave the highest reaction rates and produced a polymer with an average molecular weight of 48,000 in a 95% yield. Spontaneous phase separation induced by the surface-active ligand made it possible to recover the catalyst complex segregated at the middle emulsion layer in a compact form. Biphasic reaction with a suitable surface-active ligand was found to be more effective than homogeneous counterpart to promote the oxidative coupling reaction and was more favorable for forming higher molecular weight polymer products. (C) 1999 Elsevier Science B.V. All rights reserved.