Synthesis of glycerol-based (co)polyethers via ring-opening polymerization of glycidyl butyrate catalyzed by a one-component phosphonium tetraborane Lewis pair

Abstract

Linear polyglycerol (linPGC)-based functionalized polyethers exhibit superior water solubility and biocompatibility compared to traditional polyethylene glycol (PEG). However, their efficient and straightforward synthesis remains a significant challenge. Herein, we report a one-component phosphonium tetraborane Lewis pair (P4B-Br) obtained via a three-step synthesis and demonstrate that P4B-Br enables the ring-opening polymerization (ROP) of commercially available (R)-(−)-glycidyl butyrate (RGB) at room temperature with a turnover number (TON) of 200, yielding α-Br/ω-OH and α-OH/ω-OH terminated poly(glycidyl butyrate) (PRGB). Kinetic studies reveal a pseudo-zero-order dependence on the monomer concentration and a first-order dependence on the catalyst concentration. An intramolecular synergistic catalysis mode is proposed. The deprotection of PRGB via alcoholysis releases pendant hydroxyl groups to form linPGC. Furthermore, RGB can be copolymerized with propylene oxide (PO), 1,2-butylene oxide (BO), allyl glycidyl ether (AGE), and tert-butyl glycidyl ether (t-BGE) to prepare linPGC-based functionalized polyethers with diverse sequence structures. This work provides a practical approach for obtaining various linPGC derivatives.