Imide units are incorporated into thermoplastic and solvent-based polyurethane (PU) chains to improve the thermal stability of PU. However, these poly(urethane-imide) (PUI) materials have poor processablity and suffer from solvent emission. To prepare easily processable and environmentally friendly PUI products, some waterborne PUIs are synthesized using a prepolymer process. A series of PUI dispersions will, 25 wt % solid content, viscosities of 7.5-11.5 cps, and particle sizes of 63-207 nm was prepared. The composition-property relationship of PUIs, including the solubility behavior of PUI cast films, and their thermal and mechanical properties were established. The solvent resistance and tensile strength of PUI film increased with the number of imide groups. All PUIs exhibited improved thermal stability but not char yield as the temperature increased. The inclusion of a little imide increased the decomposition temperature of PUI while maintaining the elasticity of the polymer, revealing successful translation of PUI into the water-based form. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 517-524, 2009