Process for the preparation of polyphenylene oxides with hydrolytically stable copper catalysts

A process for formation of a polyphenylene oxide having the formula ##STR5## where R and R' are lower primary alkyl and n is a number representing the average degree of polymerization and is at least 100 which comprises:

• oxidatively coupling the corresponding monohydric phenol with an oxygen-containing gas under polymer-forming reaction conditions in a liquid reaction mixture which is essentially free of ammonium ion and in which the phenol is soluble
• in the presence of a copper-amine complex soluble in the reaction mixture comprising
• a. copper ion
• b. bromide ion
• c. a diamine having the formula
• R.sub.b HN--R.sub.a --NHR.sub.c
• where R.sub.a is C.sub.2-4 -alkylene or C.sub.3-7 -cycloalkylene and R.sub.b and R.sub.c are isopropyl or C.sub.4-8 -tertiary alkyl, including cycloalkyl, in which only the .alpha.-carbon atom has no hydrogens, there being at least two and no more than three carbon atoms separating the two nitrogen atoms
• d. a tertiary amine which is N-methylpyrrolidine, triethylenediamine or a trialkylamine wherein at least two of the alkyl groups are methyl and the third is C.sub.1-8 primary or C.sub.3-8 secondary alkyl,
• wherein, the molar ratio of (b) to (a) is at least 2, the molar ratio of (c) to (a) is at least 1 and the ratio of equivalents of (d) to moles of (a) is at least 6.