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

Abstract

Producing polyesters with high molecular weight (Mn) 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 °C for the ROCOP of cyclohexane oxide (CHO) with phthalic anhydride (PA) without the observation of any side reactions. The average Mn of the produced poly(CHO‐alt‐PA) climbed to 94.5 kDa with low polydispersity (Ð=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 °C. Kinetic studies, crystal structure analysis, 11B NMR spectra, and DFT calculations provided mechanistic justification for the effectiveness of the catalyst system.

Heterodinuclear Mg(II)M(II) (M=Cr, Mn, Fe, Co, Ni, Cu and Zn) Complexes for the Ring Opening Copolymerization of Carbon Dioxide/Epoxide and Anhydride/Epoxide

“…In comparison, organocatalyst systems show lower activities, with typical TOF values being below 300 h −1 but may have advantages in terms of ease of use/commercial availability. For example, catalysts based on bases like t BuP 1 (TOF=48 h −1 , 100 °C), [57] BEt 3 /DBU (TOF=27 h −1 , 60 °C), [58] BPh 3 /PPNCl (TOF=200 h −1 , 0.2 mol %, 130 °C) [59] or (9‐BBN)B‐(C 4 H 10 )‐NMe 2 n Bu (TOF=258 h −1 , 0.25 mol%, 120 °C) [60] …”

“…For example, catalysts based on bases like t BuP 1 (TOF = 48 h À 1 , 100 °C), [57] BEt 3 /DBU (TOF = 27 h À 1 , 60 °C), [58] BPh 3 /PPNCl (TOF = 200 h À 1 , 0.2 mol %, 130 °C) [59] or (9-BBN)B-(C 4 H 10 )-NMe 2n Bu (TOF = 258 h À 1 , 0.25 mol%, 120 °C). [60] Since 5 shows the best performances of the series, its rate law was investigated for the ring opening copolymerization of anhydride/epoxide. Polymerizations were monitored using in situ infrared spectroscopy, following the stretching frequencies for anhydride (1820 cm À 1 ) and polyester (1784 cm À 1 ).…”

Construction of triblock copolyesters via one-step switchable terpolymerization of epoxides, phthalic anhydride and ε-caprolactone using dual urea/organic base catalysts

“…Therefore, it is always desired to develop advanced metal-free, simple, and greener catalysts toward switchable polymerization. 25–30…”

Chemically recyclable polymer materials: polymerization and depolymerization cycles

“…81 Ring-opening copolymerization (ROCOP) of epoxides and anhydrides is an alternative way to form polyesters, and since epoxides and anhydrides can be regenerated, it is possible to produce sustainable materials. [82][83][84][85] However, there is no reported case of this kind of material recycling to recover the corresponding epoxide monomers. Very recently, Kerton reported an aryl borane (BPh 3 )-based catalytic system which showed the power to polymerize epoxides, anhydrides and CO 2 , resulting in perfectly alternating block copolymers such as poly(CHO/PAH-alt-CHO/CO 2 ) (Scheme 7).…”