A series of polyurethane (PU)/poly(vinylidene chloride) (PVDC) interpenetrating polymer networks (IPNs) were synthesized through variations in the amounts of the prepolyurethane and vinylidene chloride monomer via sequential polymerization (80/20, 60/40, 50/50, 40/60, 30/70, and 20/80 PU/PVDC). The physicomechanical and optical properties of the IPNs were investigated. Thermo-gravimetric analysis (TGA) studies of the IPNs were performed to establish their thermal stability. TGA thermo-grams showed that the thermal degradation of the IPNs proceeded in three steps. Microcrystalline parameters, such as the crystal size and lattice disorder, of the PU/PVDC IPNs were estimated with wide-angle X-ray scattering. (c) 2006 Wiley Periodicals, Inc.