A novel water-soluble polymer was prepared by binary copolymerization and sulfomethylation using acrylamide (AM) and N-phenylmaleimide (N-PMI) as raw materials under mild conditions. Several factors were investigated and optimized conditions were confirmed in the copolymerization and sulfomethylation. It was found that the sulfonates copolymer was afforded with up to 60% retention rate of the apparent viscosity at 85 degrees C; 30.4 mPa s apparent viscosity under 500 s-1 shear rate with 5.028 min; 3.3 times relativity viscosity (compared with polyacrylamides) was obtained in 80 g/L NaCl brine; up to 9.5% enhance oil recovery in presence of 5000 ppm NaCl brine by core flood tests; and it was also found that the polymer 4a, which combine with 10 wt % of KCl or NaCl brine could significantly affect the crystalline interspace of sodium montmorillonite (from 18.9 to 15.3 angstrom). (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012