Tunable volume memory poly(acrylic acid sodium) hydrogel by metal ionsd

In this paper, the volume memory effect of poly(acrylic acid sodium) (PAAS) in different salt solutions, such as Na 2 SO 4 , MgSO 4 , Al 2 (SO[Formula: see text], is investigated. The degree of shrinkage and shrinkage rate is related to the valence of metal ions and the ionic strength of a salt solution. Multivalent ions can chelate with carboxyl groups of PAAS and form a second network in the covalently cross-linked PAAS. The metal–ligand coordination as a physical network significantly increases the ultimate compressive stress, compressive modulus, and fracture strain of the hydrogel. The ultimate compressive stress of the hydrogel chelated by Mg[Formula: see text] ions increases from 35 KPa to 24.1 MPa, an increase of nearly 690 times.