PEG/Y(OAr)3 system only contains sole bifunctional active species to synthesize copolymer of CL with PEG (poly(CL-b-PEG-b-CL)).

• PEG/Y(OAr)3引发体系中只有一种活性中心,可以制备CL和PEG的poly(CL-b--PEG-b-CL)三嵌段共聚物。