Free radical polymerization of DMAAm (dimethylacrylamide)-co-PEG diacrylate in a semi-frozen aqueous solution was studied using H-1 NMR, which enables to monitor the non-frozen water as well as the reaction of monomers over time. It was possible to confirm the presence of a heterogeneous system with a liquid phase where the monomers were concentrated and the reaction proceeded. The resulting macroporous polymeric structure with dense pore walls was confirmed using scanning electron microscopy (SEM). (C) 2008 Elsevier Ltd. All rights reserved.