The regio-controlled oxidative coupling polymerization of 2,5-dimethylphenol using CuCl with 2-substituted pyridine ligands was investigated under an oxygen atmosphere. By increasing the bulkiness of the substituents of the pyridine, a higher molecular weight polymer was obtained with a good yield. CuCl with 2-phenylpyridine or 2-(p-tolyl)pyridine ligand yielded the corresponding poly(2,5-dimethyl-1,4-phenylene ether) polymer, which shows a melting temperature of around 310 degrees C. XRD indicated that these are semicrystalline polymers having a degree of crystallization of up to 42%.