Tetrabutylammonium Halides as Selectively Bifunctional Catalysts Enabling the Syntheses of Recyclable High Molecular Weight Salicylic Acid‐Based Copolyesters

Abstract

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, Ɖ < 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.

Torsional Strain Enabled Ring‐Opening Polymerization towards Axially Chiral Semiaromatic Polyesters with Chemical Recyclability

“…[23,24] The introduction of benzo-fused structures to ɛ-caprolactone contributed to enhance its depolymerizability, manifesting the feasibility of chemical recycling to monomer. Representative examples including DHB-(2,3-dihydro-5H-1,4benzodioxepin), [23,[25][26][27][28] BDXO-(3,4-dihydro-2H-benzo[b]- [1,4]dioxepin-2-one), [29] and BDPO-(5H-1,4-benzodioxepin-3(2H)-one) [30,31] based monomers and salicylic methyl glycolide (SMG) [32,33] were reported to accomplish completely reversible polymerization and depolymerization process via the manipulation of the reaction conditions. Meanwhile, these benzo-fused polyester products with diverse function-ality and tacticity were disclosed to perform distinct thermal and mechanical properties.…”