Superabsorbent hydrogels from poly(aspartic acid) with salt-, temperature- and pH-responsiveness properties

Polyaspartic acid (PAsp) resin was synthesized by polysuccinimide (PSI), through chemical cross-linking using the cross-linking agent (diamine). The effects of reaction variables, such as PSI concentration and terminal pH on the water absorbent capacity have been studied. These phenomena were discussed according to structural parameters, which were confirmed by SEM. Water absorbencies were compared for the hydrogels at terminal pH 8 and 10. The water absorbent capacity enhanced with increasing terminal pH and decreasing PSI concentration. The swelling/deswelling kinetics of the super-absorbent hydrogels was investigated as well. It is found that the hydrogels showed ampholytic and reversible pH-responsiveness properties. The variational water absorbencies were attributed to swelling theory based on the hydrogel physical and chemical structure. The swelling was also extremely sensitive to the temperature, ionic strength and cationic kind. The reversible pH-responsiveness, salt- and temperature-sensitivity of the hydrogels make this intelligentized polymer had wider applications.