Oxidative coupling polymerization of 2,6-dimethylphenol catalysed by copper(II) complexes of n-methylimidazole

✍ Scribed by Wei Chen; Ger Challa

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 448 KB
• Volume: 26
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(90)90030-8

✦ Synopsis

The oxidative coupling polymerization of 2,6-dimethylphenol (DMP) catalysed by copper(II) complexes of N-methylimidazole in toluene/iso-propanol (13/2v/v) or 1,2-dichlorobenzene/methanol (ODCB/MeOH) (13/2 v/v) was investigated. EPR spectra of these complexes indicated that the complex had a mononuclear structure in solution for higher ligand/copper ratios. The mononuclear complex was found to be a more active catalyst for the reaction and more favourable for poly(2,6-dimethyl-1,4-phenyleneoxide) (PPO) formation than dinuclear complexes. A main role of hydroxide appears to be to give more reactive phenolate anions from DMP. In toluene/iso-propanol, Michaelis-Menten kinetics were observed for the reaction under standard conditions with k 2 = 0.15 sec -t and K~ ~ = 9.1 dm 3. mol -t. Also, a better catalytic specificity for PPO formation and a higher molar mass of PPO (~n = 78,300) were obtained in toluene/iso-propanol than in ODCB/MeOH. At reaction temperatures of 5-25 ° in toluene/iso-propanol, a yield of only 0.8-1.0% of the side product DPQ was achieved by adding the DMP solution slowly to the reacting system.