Abstract
New hydrogels were synthesized by cross-linking poly(allylamine) (PAA) with carbon disulfide (CS2) in an aqueous basic medium. Studies on the effects of various bases revealed that potassium hydroxide most effectively prompted the cross-linking reaction, affording transparent hydrogels having thiourea-type closs-linking points and residual amino groups in the side chains. Swelling behavior of the obtained hydrogels was investigated as a function of pH and CS2 concentration. The swelling behavior of the PAA hydrogels showed the characteristic pH-dependence of amino groups, i. e., the degree of swelling increased with decreasing pH. At any pH, the degree of swelling increased with decreasing amount of CS2 used, indicating that the cross-link density could be controlled by the feed amount of CS2. Further, the PAA gels could adsorb noble metal ions [Au (III), Pt (IV), and Pd (II)] efficiently owing to the high affinity of the thiourea cross-links and amino groups to heavy metal ions.
