In this work microphase separation in ideal interpenetrating networks as well as its influence on the mechanical properties of the networks has been studied. Structures with long-range order in such networks have not been found to be formed; the reason for this is apparently the weak bonding (physical entanglements) between the subnetworks. The dynamics of the relaxation of interpenetrating networks with highly incompatible subnetworks has been studied and it has been found that the slow rearrangement of phase boundaries during the stretching process has a significant influence on it. Using the analysis of subchains conformations, it has been found that the increase in the stiffness of interpenetrating networks with incompatible subchains occurs due to the irregular tension of subchains related to the presence of big aggregates in the system.