Response characteristics of the ionic superabsorbent hydrogel

Influence of properties of the solution on the swelling ratios of the CMCTS-g-PAA and CMCTS-g-(PAANa-co-PVP) ionic superabsorbent hydrogels, which were prepared through modification of carboxymethyl chitosan, was studied. The phase transition of the hydrogel can be observed if the volume fraction of alcohol (ψ) in the alcohol/water mixture is increased. The volume phase transition points of the hydrogels are decreased as increasing of the polarity of the segments in the structure of the hydrogel. The exclusion between the -COO^- is decreased as increasing of the content of the alcohol, with which the polarity is low, and the swelling of the polymer is slow-down. Response of the hydrogels to the ion strength was also studied. The 1/S value is found to be directly proportional to Q^5/3 at high 1/S value. On the contrary, the linear correlation between the Q^5/3 and 1/S is disappeared if the ion concentration was high. The swelling ratio of the hydrogel is also influenced greatly by the pH value of the absorbed solution. The maximum swelling ratio can be reached around the pH value between 6 and 7.