Hydrogels based on n-alkyl methacrylate esters(n-AMA)

acrylic acid and acrylamide cross-linked with 4

4′-di(methacryloylmino)azobenzene were preparared

and their deswelling kinetics was studied．The hydrogels swellon at pH values of 7.4 and 8.0 were transferred into buffered solutions at pH2.2 and pH4.0 respectively．The processes of deswelling appear in both cases：The first is that hydrogels deswelled immediately after the immersion of the swollen hydrogels into the lower pH of buffered solutions；the other is that hydrogels proceeded a short time swelling before deswelling．For the former the reciprocal of the average rate of deswelling [t/(Ht-H0)] has an excellent linear correlation with the time of deswelling．For latter the reciprocal of square root of water uptake in unit time [(t／Ht)1/2] has an excellent linear correlation with the time of deswelling．