A new aliphatic poly(propylene-co-gamma-butyrolactone carbonate) (PPCG) was successfully synthesized through the copolymerization of carbon dioxide, propylene oxide (PO), and gamma-butyrolactone (GBL). GBL was inserted into the backbone of PO-CO2. The glass transition of PPCG was as high as 16 degrees C, far higher than that (-1.5 degrees C) of poly(propylene carbonate) (PPC). The decomposition temperatures of PPCG and PPC were only slightly different. Because of the existence of the GBL ester unit, PPCG had stronger degradability than PPC in a pH 7.4 phosphate-buffered solution. However, when the PO/GBL ratio increased beyond 5:2, the excessive amount of GBL was not added to the polymerization. PPCG and PPC microcapsules were prepared by the water-in-oil-in-water multiple-emulsion method. Glucose was encapsulated. The PPCG microcapsules, about 2 mu m in diameter, had smooth and spherical surfaces. The glucose release test revealed that the glucose release speed of the PPCG-glucose microcapsules was more than eight times faster than that of the PPC-glucose microcapsules in a pH 7.4 phosphate-buffered solution. (c) 2005 Wiley Periodicals, Inc.