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In this study, we design various bi- and trimetallic CoIII complexes as catalysts for the ring-opening copolymerization of phthalic anhydride or CO2 (A) with terminal epoxides (B). A trimetallic catalyst with flexible linking groups prefers consecutive epoxide insertion and the formation of ABn ether sequences. Sequence-controlled polymers with evenly distributed backbone ether groups are produced with a broad substrate scope, resulting in a single-glass transition and tunable properties. This new class of polymers featuring controlled ABn sequences cannot be obtained using traditional catalysts, which tend to favor alternating AB structures. Further, copolymer chains possessing both alternating AB and nonalternating ABn structures could have potential applications as miscibility-promoting agents in mixed polyether/polyester systems.
Cui et al. (Thu,) studied this question.