A method of: providing a solution of a dichloroaromatic compound having an electron-withdrawing group bound to each aromatic ring containing one of the chloride groups; an excess of a dihydroxyaromatic compound; an organic transition metal complex or a transition metal salt; a base; and a solvent; and heating the solution to a temperature at which the dichloroaromatic compound and the dihydroxyaromatic compound react to form an aromatic ether oligomer that is a dihydroxy-terminated compound or a dimetallic salt thereof. Water formed during the heating is concurrently distilled from the solution. A method of curing a phthalonitrile monomer in the presence of an acid and a curing agent to form a phthalonitrile thermoset.