Polymorpholine-2,5-dione-block-polylactide (PMD-b-PLA) was synthesized via two-step anionic ring-opening polymerization at room temperature. First step of ring-opening polymerization was the ring-opening of morpholine-2,5-dione (MD). It was carried out in an airtight and dry polymerization tube using potassium ethoxide/THF (0.2M/L) as an initiator for 90 mm. Then lactide was ring-opened in THE solution by the potassium alcoholate of PMD. From the FTIR of the copolymer, we can find all the peaks in PLA and PMD. The H-1-NMR of copolymer gave us a proof to the principle of the anionic ring-opening polymerization and the traction of PMD in the copolymer was calculated as 86.3%. DSC analysis of copolymer indicated that it was a copolymer with one T-g (63.6 degrees C) and two T(m)s (155.6 and 171.4 degrees C) instead of a mixture of PMD and PLA. The yields of the PMD and the copolymer were 32 and 26%, respectively. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2005-2008, 2010