The polyamide 1 (PA1) containing the highest density of hydrogen bond and dipole was synthesized using carbon dioxide (CO2) and urea as raw materials under supercritical CO2 condition through environment-friendly method. Three kinds of molecular weights of PA1 were prepared in this study to satisfy different application areas. The chemical structures of PA1 were characterized comprehensively by means of H-1 and C-13 NMR, Fourier transform infrared spectroscopy, elements analysis, intrinsic viscosity, and wide angle X-ray diffraction. The thermal properties and glass transition temperature were measured by thermogravimetric analysis (TGA) and differential scanning calorimetry. The obtained products had intrinsic average molecular weights ranging from 1.29 x 10(3) to 1.29 x 10(4). And the thermal stability and glass transition temperature increased with the increasing of molecular weight. TGA results indicated that the temperatures of 5% and 10% weight loss were 378 and 395 degrees C, respectively and the maximum decomposition temperatures for the two stages were 416 and 457 degrees C for the highest molecular weight product. The PA1, a new family member of polyamides, was a potential multifunctional material and found applications as high-performance material. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 853-859