Metal‐Free Synthesis of α,ω‐Dihydroxy Low‐Molecular‐Weight Poly(2,6‐Dimethyl‐1,4‐Phenylene Oxide) via Amine‐Catalyzed Redistribution

ABSTRACT Although poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is a promising dielectric material, the conventionally produced PPO inevitably contains Cu(I) residues, which constrain its dielectric performances. In this work, a fully metal‐free route to prepare α,ω‐dihydroxy low‐molecular‐weight PPO (PPO‐OH) was developed via the redistribution of metal‐free PPO (MF‐PPO, M n = 4.5 × 10 3 , PDI = 1.60, hydroxyl value = 17.7 mg KOH g −1 ) that was previously synthesized by our group. In the redistribution process, N ‐methylbenzylamine catalyst enables efficient activation of dissolved O 2 , promoting controlled backbone scission and dihydroxyl end‐group transformation, affording MF‐PPO‐OH with M n of 1.5 × 10 3 , narrow dispersity (PDI = 1.35), and the hydroxyl value up to 80.7 mg KOH g −1 . The obtained MF‐PPO‐OH maintains high thermal stability ( T d10% > 395°C) and exhibits a reduced glass transition temperature ( T g = 130°C). Notably, the MF‐PPO‐OH sample displays a dielectric constant ( D k ) of 1.84 and a dielectric loss ( D f ) of 8.91 × 10 −4 at 1.0 GHz, which are significantly lower than those of commercial PPO ( D k = 2.45, D f = 3.16 × 10 −3 ). This study demonstrates that the aromatic amine‐assisted redistribution enables precise molecular weight control and efficient hydroxyl functionalization, providing a metal‐free redistribution route for tailoring PPO dielectric performances.