A method of making a polyether polymer comprises reacting a salt of a dihydroxy-substituted aromatic hydrocarbon with a substituted aromatic compound of formula (I) Z(A1-X1)2   (I) in the presence of a catalyst to form an intermediate polymer having endgroups, wherein the molar ratio of the salt of a dihydroxy-substituted aromatic hydrocarbon to the substituted aromatic compound is less than 1, Z is an activating radical, A1 is an aromatic radical and X1 is fluoro, chloro, bromo or nitro; determining the additional amount of the salt of a dihydroxy-substituted aromatic hydrocarbon needed to form a final polyether polymer with a predetermined molecular weight and adding the additional amount of the salt of a dihydroxy-substituted aromatic hydrocarbon to the intermediate polymer.