A lot of polymeric hydrogels undergo volume changes in response to external stimuli such as pH

temperature

electric field and light.These intelligent hydrogels have been used for the preparation of a wide variety of devices

for instance

immobilized enzyme

recyclable absorbents and controlled drug release.However

most of the hydrogels studied previously are responsive to only one kind of stimulus.But for some situations

responsiveness to several stimuli

such as temperature and pH

may be requied.We wish to report here the synthesis of a new intelligent hydrogel which can response to temperature and pH at the same time.Poly (acrylic acid_-co-(acrylonitrile) Hydrogels were synthesized.The Temperatura and pH sensitivities of these hydrogels were studied.The swelling ratio(SR) of hydrogels at various pH values is different.In water medium

SR of hydrogels at elevated temperature(62℃) is increased with the prolongation of time.However

this phenomenon is not so obvious in weak alkaline and acidic solutions.