The objects of this study are highly crosslinked networks. The base-catalyzed Michael reaction of beta-ketoesters with vinyl groups of the pentaerythritol tetra-acrylate (PETA) was used for a step grow formation of the crosslinked polymer in dark. The nonreacted vinyl groups and vinyl monomer were built up to the network structure by photopolymerization in the second step of synthesis. An analysis of crosslinked polymers shows that the long spacer between beta-ketoester groups in propylenglycol-425-diacetoacetate (PGDAA) favors an extent of reaction compared to pentaerythritol tetrakis (acetoacetate) (PETAA). The excess of vinyl monomers added to polymerization batch functions in the first step of the synthesis as a reactive solvent [triethylene glycol dimethacrylate (TEGDMA); PETA]. The dissolution of reactants has a positive effect on homogeneity, conversion, and crosslink density of prepared networks. The consumption of reactive groups in a course of the network formation, the crosslink density, and dynamic mechanical properties of the prepared networks were determined from Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), sol-gel analysis, dynamic testing, and stress-strain dependencies. The dynamic testing indicates that the networks synthesized in two steps from batches containing an excess of vinyl monomer consist from two highly crosslinked phases interpenetrating each other.