Poly(dimethyl trimethylene carbonate) (PDTC) and poly(trimethylene carbonate) (PTMC) were synthesized by ring-opening polymerization (ROP) of dimethly trimethylene carbonate (DTC) and trimethylene carbonate (TMC) in the presence of five kinds of natural amino acids (L-alanine, L-valine, L-leucine, L-proline, and L-phenylalanine). PDTCs with number-average molecular weight (M-n) from 6700 to 18,900 g/mol and PTMCs with M-n from 7200 to 17,800 g/mol were obtained at a feed ratio of [monomefl/[L-phenylalanine] ranging from 50 to 200. The results of H-1 nuclear magnetic resonance and titration proved amino acid connecting onto the polymer backbone. (c) 2007 Wiley Periodicals, Inc.