Ion responsiveness of polyacrylamide/sodium alginate (PAM/SA) shape memory hydrogel.

Polyacrylamide/sodium alginate (PAM/SA) hydrogel was prepared from sodium alginate (SA) and acrylamide (AM) by covalently cross-linking. Temporary shape double network PAM/SA hydrogels were obtained by ionic cross-linking formed by complexation of SA and six metal cations (Fe³⁺, Cu²⁺, Ag⁺, Ca²⁺, Ni²⁺, and Co²⁺), among the PAM/SA—Fe³⁺ hydrogels has the best shape fixity ratio (83%). When the hydrogel is placed in different recovery liquids (sodium citrate, EDTA, sulfuric acid, and potassium carbonate), the shape recovery ratio (98.9%) is the best in sodium citrate solution, and the recovery time (182 s) of the hydrogel is the shortest. In general, Fe³⁺, Cu²⁺, and Ag⁺ are suitable for the construction of ionic-shape memory hydrogels. The PAM/SA hydrogels also exhibited excellent adjustable mechanical properties by changing metal cations and soaking time. The strategy could broaden the construction of ion-responsive shape-memory hydrogels. [ABSTRACT FROM AUTHOR]