Temperature-sensitive polyzwitterionic gels

An abrupt change in the polyzwitterionic swelling ratio as a function of th e temperature, sodium chloride concentration and chemical crosslinking dens ity is established. These results are reasonably explained by the model pre suming zwitterionic cluster formation in the segments between the chemical junction points. The zwitter-ionic clusters, produced at low chemical cross linking density only, act as temperature- and salt concentration-dependent physical junction points. An irreversible temperature-stimulated swelling-s hrinking behaviour of the polyzwitter-ionic hydrogels (swelling ratio-tempe rature hysteresis loop) at low chemical cross-linking density is also obser ved and analysed.