Cross-linked copolymers of acrylamide (AAm) with N-[3-(dimethyl amine)propyl]methacrylamide (NDAPM) were prepared by solution free radical polymerization at different feed molar ratios. In this reaction, ammonium persulfate (APS) and N,N´-methylene-bis-acrylamide (MBA) were used as initiator and cross-linking reagents respectively. The effects of reaction parameters, including the concentration of crosslinking reagent and initiator, the monomer concentration, pH, temperature, the various salt solutions, and solvent polarity, on the water absorption have been investigated. The results indicate that the copolymers obtained are stimuli-responsive hydrogels that change their volume and elasticity in depending on the properties of the liquid phase