Perspective: Comments on “Polymerization by oxidative coupling. II. Oxidation of 2,6-disubstituted phenols,” by Allan S. Hay,J. Polym. Sci., 58, 581 (1962)

Abstract

The discovery that high molecular weight polymers could be prepared by oxidative coupling reactions has opened up many routes to new classes of polymers and led to new major industrial processes. The initial work by Allan S. Hay grew from work at the General Electric Research Laboratory on metal catalyzed oxidation of simple organic materials, such as xylenes, to produce phthalic acids for alkyd resins. Among other substrates examined were phenols, thiophenols, and amines. The observation that a highly selective polymerization reaction could be achieved by blocking reactive sites in the ortho positions of phenol with methyl groups spurred an extensive research program on oxidative coupling.' From this work came knowledge of the poly-1,4-phenylene ether structure of the polymers from 2,6-disubstituted phenols, the scope of the reaction, the mechanism of the polymerization, and the determination of the physical properties of the polymeric products.2The polymerization process for the conversion of 2.6-dimethylphenol to poly(2,6-dimethyl-l,4-phenylene oxide) (PPO" resin) was sufficiently straightforward to be commercially attractive, and efforts were made to scale up and optimize the process. However, an unusual characteristic of the polymer was its high glass transition temperature of -208OC, which meant high processing temperatures would be required for commercial utilization. Under these conditions, polymer degradation via oxidation and thermal side reactions became an issue. The problem was overcome by the discovery that PPO resin formed homogeneous blends with polystyrene3 and