Hydrophobic porous copolymer resins based on divinylbenzene (DVB) and acrylonitrile (AN) could be prepared as directly swellable in water by using purified DVB (98.8%) and technical DVB (79.3%) in the presence of 1,2-dichloroethane as porogen. Compared with the resins based on DVB and methyl acrylate (MA/DVB resins), the AN/DVB resins thus obtained are water-swellable over a wider range of copolymer compositions, and the swelling ability of the AN/DVB resins in water was further confirmed by investigating the water-swelling behavior of the AN/DVB resins undergoing solvent treatment. The copolymer composition (AN and DVB contents) of the resins and the property of the porogen affect the water-swellable behavior of the AN/DVB resins profoundly. The results in this paper provide additional evidence to support the hypothesis that the swelling ability of a hydrophobic porous copolymer in water originates from the existence of the inner stresses in the strained polymer network of the resins and the weak interaction between polymer and water that is negligible in the case of a conventional hydrophobic polymer. (C) 2004 Wiley Periodicals