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To synthesize high molecular weight poly(phenolic ester) via a living ring‐opening polymerization (ROP) of cyclic phenolic ester monomers remains a critical challenge due to serious transesterification and back‐biting reactions. Both phenolic ester bonds in monomer and polymer chains are highly active, and it is difficult so far to distinguish them. In this work, an unprecedented selectively bifunctional catalytic system of tetra‐n‐butylammonium chloride (TBACl) was discovered to mediate the syntheses of high molecular weight salicylic acid‐based copolyesters via a living ROP of salicylate cyclic esters (for poly(salicylic methyl glycolide) (PSMG), Mn=361.8 kg/mol, Ð<1.30). Compared to previous catalysis systems, the side reactions were suppressed remarkably in this catalysis system because phenolic ester bond in monomer can be selectively cleaved over that in polymer chains during ROP progress. Mechanistic studies reveal that the halide anion and alkyl‐quaternaryammonium cation work synergistically, where the alkyl‐quaternaryammonium cation moiety interacts with the carbonyl group of substrates via non‐classical hydrogen bonding. Moreover, these salicylic acid‐based copolyesters can be recycled to dimeric monomer under solution condition, and can be recycled to original monomeric monomers without catalyst under sublimation condition. [ABSTRACT FROM AUTHOR]

To develop bench‐stable and nontoxic catalysts for the ring‐opening polymerization (ROP) of lactides is of importance with the aim of reducing costs in industrial production. Although, recently, some potassium complexes have been reported for the living polymerization of rac‐lactide (rac‐LA), the moisture sensitivities of these complexes prevent their further applications in the mild polymerization condition. In this work, three bench‐stable potassium phenolates as isoselective catalysts for the ROP of rac‐LA were reported, and the moisture stability of these complexes does not inhibit their high activity under mild conditions even in the presence of trace water (2.0 equivalent relative to the catalysts) or unpurified solvents. The controllable polymerization reactions can afford polylactides with desirable molecular weights, which can be high up to Mn = 80.0 kg/mol at an anhydrous condition and Mn = 54.3 kg/mol in presence of trace water. A best isoselectivity of Pm = 0.83 also can be achieved in this system at −70°C. [ABSTRACT FROM AUTHOR]