A method for synthesizing a novel thermosetting poly(2-allyl-6-methylphenol-co-2,6-dimethylphenol) (Allyl-PPE) with a narrow molecular weight distribution (MWD) has been developed. Allyl-PPE was prepared by a pyridine/copper(I) chloride-catalyzed oxidative coupling polymerization of 2- allyl-6-methylphenol (10 mol %) with 2,6-dimethylphenol (90 mol %), using large amounts of pyridine. Allyl-PPE with a narrow MWD showed a lower dielectric constant (epsilon') and dielectric loss tangent (tan delta) than copolymers with a broad MWD.