Resumen de JCE Classroom Activity Connections:: NaCl or CaCl2, Smart Polymer Gel Tells More
Yueh-Huey Chen, Jia Ying Lin, Yu Chen Wang, Jing Fun Yaung
This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl2 (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl2 both collapse the swollen polymer gels. The gel contracted by NaCl reswells in deionized water, but that contracted by CaCl2 does not reswell. The CaCl2 contracted gel is subsequently immersed in concentrated NaCl solution to reverse the ion exchange. The Ca2+ ions in the contracted gel are released, and Na+ ions are redistributed in the polymer network. The ion-exchange cycle is accomplished and the water-absorbing ability of the gel is recovered. Other compound pairs of monovalent versus polyvalent metal ions involving LiCl, NaCl, KCl, CaCl2, BaCl2, and ZnCl2 give similar results.
