The hydrolysis, sulfonation and crosslinking modification of a poly(styrene-co-acrylonitrile) copolymer in one step was studied. An extremely vigorous process has been developed for the preparation of a series of hydrophilic gels bearing strongly and weakly acidic groups on the same polymer backbone. The products were characterized using infra-red spectra, scanning electron microscopy, elemental analysis and titrimetric determination of the strongly and weakly acidic groups. Kinetic data and swelling measurements in aqueous media were also performed. A fully transformable hydrogel was obtained from a series of macronet products having different degrees of crosslinking. This irreversible gel-solution transition was recorded within 15 weeks, a fact that indicates that these polymers may have specific applications in fields where separation media are required. or as transformable soil conditioners.