Polyphenylene Oxides by Oxidative Polymerization of Phenols

In 1955, Terent ev and Mogilyanskii reported the catalytic oxidative coupling of aniline to azobenzene with a yield of 88%, mediated by copper chloride in pyridine (which acts as both a metal ligand and solvent) in the presence of molecular oxygen [1]. This system was subsequently used for the generation of various conjugated and nonconjugated main-chain aromatic azo polymers from primary aromatic diamines [2]. In contrast, the use of CUCI-O2 with phenol produces tars [3] as a result of the inherent properties of this reactant. Indeed, while the metal salt produces iV-centered aniline radicals that dimerize to form azobenzene 

4- phenylene ethers by thermal decomposition of the corresponding benzene- 

4- diazooxides however, this method only functioned with limited success. Concurrently, Stafiin and Price, inspired by an earlier work reported by Hunter and Morse [8], developed a procedure to produce poly-2,6-dimethyl-l,4-phenylene ether via displacement of the bromine in 4-bromo-2,6-dimethylphenol, but with low molecular weights [9]. 

In 1959, Hay and coworkers described the first efficient route for the production of high-molecular-weight poly-2,6-disubstituted-l,4-phenylene ethers [10]. For instance, the reaction of 2,6-dimethylphenol (DMP) in the presence 

Liquid Phase Aerobic Oxidation Catalysis Industrial Applications and Academic Perspectives, 

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