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The oxyanionic ring‐opening polymerization of propylene oxide (PO) from an exogenous alcohol activated with benign (complexed) metal‐alkali carboxylates is described. The equimolar mixture of potassium acetate (KOAc) and 18‐crown‐6 ether (18C6) is demonstrated to be the complex of choice for preparing poly(propylene oxide) (PPO) in a controlled manner. In the presence of 18C6/KOAc, hydrogen‐bonded alcohols act as soft nucleophiles promoting the PO SN2 process at room temperature and in solvent‐free conditions while drastically limiting the occurrence of parasitic hydrogen abstraction generally observed during the anionic ROP of PO. The resulting PPO displays predictable and unprecedented molar masses (up to 20 kg mol−1) with low dispersities (ĐM < 1.1), rendering the 18C6/KOAc complex the most performing activator for the oxyanionic polymerization of PO reported to date. Preliminary studies on the preparation of block and statistical copolyethers are also reported. [ABSTRACT FROM AUTHOR]

Controlled Oxyanionic Polymerization of Propylene Oxide: Unlocking the Molecular-Weight Limitation by a Soft Nucleophilic Catalysis In its presence, alcohols act as soft nucleophiles promoting a perfectly controlled oxyanionic polymerization at room temperature and in bulk leading to polymers displaying predictable and unprecedented molar masses. B Front Cover b : Article 2200424 by Olivier Coulembier and co-workers reveals that an equimolar mixture of potassium acetate and 18-crown-6 ether is highly effective for controlling the polymerization of propylene oxide. [Extracted from the article]