Abstract Large pore volume and pore size ranges were achieved in 2-hydroxyethyl methacrylate (HEMA)/ethylene glycol dimethylacrylate (EGDMA) copolymers prepared by microsyneretic phase separation in free-radical copolymerization of comonomers in the presence of a tenfold volume of porogenic solvents. A mixture of methanol, i.e. good swelling solvent for poly(HEMA), and tetrahydrofuran, i.e. good swelling solvent for poly(EGDMA), was used as porogens. The morphology of the as-prepared copolymers was assessed in their native, expanded state using inverse steric exclusion chromatography (ISEC), which enabled to get a much better insight into the mechanism of pore formation than a conventional approach based on the evaluation of the morphology of dried materials. Two porosity levels with distinct pore volumes and sizes could be distinguished depending on the crosslinking degree and the MeOH/THF ratio. Their formation could be explained by a two-step syneretic phase separation during the free-radical copolymerization, namely χ-induced syneresis for the larger pore sizes and ν-induced syneresis for the smaller pore sizes Due to their high crosslink density, the porosity of the resulting polymers do not rely on swelling, and it was virtually independent on the nature of surrounding solvent.