Record Productivity and Unprecedented Molecular Weight for Ring-Opening Copolymerization of Epoxides and Cyclic Anhydrides Enabled by Organoboron Catalysts

Producing polyesters with high molecular weight (M-n) through ring-opening copolymerization (ROCOP) of epoxides with cyclic anhydrides remains a major challenge. Herein, we communicate a metal-free, highly active, and high thermoresistance system for the ROCOP of epoxides with cyclic anhydrides to prepare polyesters (13 examples). The organoboron catalysts can endure a reaction temperature as high as 180 degrees C for the ROCOP of cyclohexane oxide (CHO) with phthalic anhydride (PA) without the observation of any side reactions. The average M-n of the produced poly(CHO-alt-PA) climbed to 94.5 kDa with low polydispersity (D = 1.19). Furthermore, an unprecedented turnover number of 9900, equivalent to an efficiency of 7.4 kg of polyester/g of catalyst, was achieved at a feed ratio of CHO/PA/catalyst = 20000:10000:1 at 150 degrees C. Kinetic studies, crystal structure analysis, B-11 NMR spectra, and DFT calculations provided mechanistic justification for the effectiveness of the catalyst system.