Using Vinyl Cyclicsiloxane as a Scaffold to Prepare Tetraborane Lewis Acid as a Synergistic Catalyst for the Ring-Opening Polymerization of Epoxides

The development of efficient metal-free catalyst systems for the ring-opening polymerization (ROP) of epoxides is essential for producing functional polyethers with controlled molecular weights, low dispersity, and precise main-chain sequences. In this study, we present a binary system comprising tetravinyltetramethylcyclotetrasiloxane-based tetraboranes (V4B) as the catalyst and tetrabutyl ammonium succinic salt (TBASA) as the initiator for the ROP of epoxides to precisely synthesize polyethers. The binary V4B/TBASA system demonstrates high activity (TOF = 1500 h^–1 per borane) under mild conditions, enabling polyethers with predictable molecular weights and moderate dispersity (D̵ = 1.32). Notably, this binary system exhibits living polymerization characteristics, allowing the preparation of multiblock polyethers. Kinetic studies and density functional theory (DFT) calculations suggested that a synergistic intramolecular PO activation from symmetric tetraborane centers with suitably spatial proximity was critical for the high activity of V4B as compared to the triborane substituted counterpart. This work provides valuable insights into designing advanced multiborane catalysts for highly efficient and precise polymerization processes.