The possibility to obtain biodegradable high molecular weight aliphatic polycarbonates from trimethylene carbonate (TMC) and 2,2-dimethyltrimethylene carbonate (DTC) monomers with designed composition of comonomeric units was presented. Zinc(II) acetylacetonate monohydrate was used as a catalyst. A detailed analysis of copolymer chain structure was performed by means of high resolution 13C-NMR spectroscopy. The equations for calculation of characteristic parameters of copolymer chain such as average length of blocks, randomization and transesterification coefficients were shown. The copolymerization reactivity ratios were determined (rTMC = 1.17 ± 0.20 and rDTC= 0.42 ± 0.09). Significant differences in the reactivity of comonomers and the low transesterification result in gradient chain microstructure. The synthesized copolymer containing about 80 mol % of DTC units is a semicrystalline material with good mechanical properties, allowing for application of this material in the formation of bioresorbable flexible implants or scaffolds. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40037.