Controlled Ring-Opening Polymerization of Epoxides Catalyzed by Metal-Free Phosphazenium Salts (P 5 + ): Using Carboxylic Acid as an Initiator to Prepare Esterified Polyethers

作者：Xiaoyu Liu, Chunhuan Jiang, Chuanli Ren, Zhibo Li · 发表于：ACS Applied Polymer Materials · 年份：2023 · DOI：10.1021/acsapm.3c02477 · 被引用次数：14 · 研究领域：Carbon dioxide utilization in catalysis、biodegradable polymer synthesis and properties、Organometallic Complex Synthesis and Catalysis

The applications of functional polyether materials include surfactants, lubricants, pharmaceuticals, and fundamental components in polyurethane products. The ring-opening polymerization (ROP) using carboxylic acid as an initiator offers enhanced pathways for synthesizing α,ω-heterobifunctional polyethers with cleavable or modifiable α-end junctions. The primary challenge lies in achieving a compatible balance between high efficiency and precise control over polymerization, as the ester groups generated during initiation steps may not tolerate highly basic catalysts. Herein, we present metal-free phosphazenium salts, namely, tetrakis [tris(dimethylamino) phosphoranylidenamino] phosphonium carboxylates (P 5 + RCOO – ), as catalysts for the carboxylic acid-initiated ROP of epoxides. Promoted by the appropriate basicity of P 5 + RCOO – and electrostatic effects of loose cation–anion pairs, the P 5 + RCOO – catalysts display high efficiency and controlled/living behavior even with a low catalyst loading. Moreover, the catalysts can be easily scaled up to the kilogram scale through simple procedures. Our strategy has successfully provided well-defined α-(carboxylic ester)-ω-hydroxy polyethers (PPO, PEO, and PBO) with controlled molecular weight, low dispersity, and high end-group fidelity. The effectiveness of the catalyst system is supported by kinetic investigations, 1 H NMR and size exclusion chromatography (SEC) spectra, and matrix-assisted laser desorption/ionization time-of-f...