A series of water soluble terpolymer (P3A) acrylamide/2-acrylamido-2-methyl propanesulfonate/acrylic acid (AM/AMPS/AA) with high molecular weight was obtained by partial hydrolysis from the corresponding (AM/AMPS) copolymers (P2A).The structure and composition of polymers prepared were characterized by potentiometric titration and 13C-NMR spectroscopy.The results obtained show that in the given experimental conditions the AMPS units of polymers (P2A) are stable enough in the hydrolysis process

while the acrylamide groups transform into acrylic acid smoothly.In all cases of various copolymers (P2A)the amide hydrolysis obeys an auto-retarded kinetic model due to the electrostatic repulsion between anionic groups and OH- ions.Finally the hydrolysis reaction rtends to a conversion limit

and the residual AM units is around 30mol%.The relationships between the intrinsic viscosity and compositions of various terpolymers(P3A)were also studied in detail.