Interpenetrating networks (IPNs) of polybutadiene-based polyurethane (PU) and poly(methyl methacrylate) (PMMA) were synthesized. The effect of the incorporation of 2% glycidyl methacrylate (GUA) and 2-hydroxyethyl methacrylate (2-HEMA) on the thermal, mechanical, and morphological properties of IPNs was investigated, Both 2-HEMA and GMa led to improvements in these properties. However, 2-HEMA-containing IPNs showed somewhat better tensile strength, elongation, and damping characteristics. The morphology of IPNs containing 2-HEMA showed better mixing of the components. The improvement in the properties was observed for up to 40% PMMA in the IPNs. Differential scanning calorimetry thermograms showed the presence of three glass transitions. The third glass-transition temperature was explained by possible grafting of methyl methacrylate onto PU.