Polymer monoliths with highly developed porous structure have been successfully synthesized by polymerization of 1-vinyl-2-pyrrolidone with trimethylolpropane trimethacrylate and divinylbenzene. During the copolymerization, the mixtures of toluene/n-dodecane and toluene/decan-1-ol were used as pore-forming diluents. The thermodynamic quality of the porogen mixtures strongly influences the process of the pore formation. By changing the ratio of non-solvating and solvating diluents, monoliths with surface area from 57 to 650 m2 g−1 and pore diameters from 4 to 51 nm were prepared. Thermal properties of the obtained materials were investigated by the means of thermogravimetry and differential scanning calorimetry. It was found that they do not depend on the diluent composition but are determined by the type of cross-linker used in the synthesis.