Semi-interpenetrating polymer networks (IPNs) have been prepared from polyurethane anionomers and poly(vinyl chloride) using sequential polymerization technique. These IPNs were compression molded and obtained as tough films. The hydrogen bonding interaction, glass transition temperature, and thermal stabilities were discussed based on Fourier-transform infrared spectrophotometer, differential scanning calorimetry, and thermogravimetric analysis. Morphology of the IPNs was characterized by scanning electron microscope and it reveals the formation of compatible IPNs. Tensile strength and hardness increase with increasing NCO/OH ratio and ionic content of the polyurethane. (C) 2004 Wiley Periodicals, Inc.