The ring-opening polymerizations (ROPs) of epsilon-caprolactone (epsilon-CL) and L-lactide (LLA) have been studied using the organocatalysts of diphenyl phosphate (DPP) and 4-dimethylaminopyridine (DMAP). The dual activation property of DPP and the bifunctional activation property of DPP/DMAP were confirmed by the NMR measurement for epsilon-CL and its chain-end model of poly(epsilon-caprolactone) and for LLA and its chain-end model of poly(L-lactide) (PLLA), respectively. The molar ratio of DPP/DMAP was optimized as 1/2 for the ROP of LLA leading to the well-defined PLLA, such as the molecular weight determined from H-1 NMR measurement of 19,200 g mol(-1) and the narrow polydispersity of 1.10. Additionally, functional initiators were utilized for producing the end-functionalized PLLAs. The DPP-catalyzed ROPs of epsilon-CL and its analogue cyclic monomers and then the DPP/DMAP-catalyzed ROP of LLA produced block copolymers. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1047-1054