Interpenetrating polymer networks (IPNs) with a controlled degree of microphase separation were synthesized from a poly(ether urethane) (PUR) and poly(ethyl methacrylate) (PEMA). The influence of the crosslink density of both networks was investigated in the 70 : 30 PUR/PEMA IPN. The extent of damping was evaluated by dynamic mechanical thermal analysis. Mechanical properties were studied using tensile testing and hardness measurements. Control of crosslinking was successful in tailoring the damping profile. Higher crosslinking in the first-formed network (polyurethane) seemed to increase slightly the area under the linear loss modulus curve, LA, whereas no influence was obvious when changing the crosslink density in the second network. TGA studies revealed improved thermal properties for the IPNs with a higher crosslink density in the PUR network. TEM micrographs confirmed a finer morphology for the materials with a higher crosslink density in the PUR, whereas increasing the crosslink density in the PEMA network resulted in a decrease of phase mixing.