A number of semi-interpenetrating polymer networks (IPNs) based on linear poly (vinyl chloride-co-vinyl acetate) and poly(alkyl methacrylates) were synthesized. The semi-IPNs were found to be transparent, high strength materials. The IPNs show only one glass-transition temperature and it is dependent on the composition as studied by differential scanning calorimetry and dynamic mechanical analysis. These IPNs are also characterized by high tan delta values. The tensile strength of the IPNs were found to be higher compared to the starting polymers. In order to compare the properties of these IPNs with the corresponding homopolymers and blends, the latter were synthesized and the properties were studied.