A series of metallopolymers (CuMP) were prepared from a MDI-based polyesterurethane and copper ions as chloride by using different initial molar ratios urethane groups/copper ions ranging from 180:1 to 12:1. CuMP and the parent polymer (PU) were analyzed by atomic absorption spectrometry (AAS), ultraviolet and visible (UV-vis) absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetry (TGA) and tensile testing. The copper ions form coordination complexes with the nitrogen atoms of the urethane groups, the intermolecular complexation resulting in the crosslinking of the hard segments; as a consequence, the destruction of the original hydrogen bonding and crystallinity of the hard-segment domains takes place. The differences in viscoelastic and mechanical behaviors shown by CuMP in comparison with PU (higher soft-segment glass transition, storage modulus and tensile strength, and lower elongation at break) reveal the reinforcing effect of copper ions on the polymer matrix. CuMP compared with PU exhibit lower initial thermal stability, the final stage of their thermal decomposition process is catalyzed, whereas the intermediate decomposition products are more thermally stable. The implications and mechanisms behind these observations are discussed. (c) 2007 Elsevier Ltd. All rights reserved.