Although several organocatalysts have been reported for the efficient ring-opening alternating copolymerization (ROAC) of epoxides and cyclic anhydrides, the low catalytic activity still remains as a problem. Thus, there is still a motivation to develop new simple and high active organocatalysts. In this contribution, an organic cyclic trimeric phosphazene base (CTPB) is used as catalyst in combination with different ureas for the ROAC of phthalic anhydride with a variety of epoxides. The CTPB/urea binary catalysts exhibit high catalytic activities, producing perfectly alternating polyesters without formation of ether linkages. Polyesters with diverse structures, well-defined chain-ends, as well as low dispersities are successfully obtained.

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