Fast‐swelling Superabsorbent Hydrogels from Poly(2‐hydroxy ethyl acrylate‐co‐sodium acrylate) Grafted on Starch

Fast‐swelling highly porous superabsorbent hydrogels were synthesized through a rapid radical polymerization under normal atmospheric conditions. To synthesize a biopolymer‐based superabsorbent hydrogel, 2‐hydroxyethyl acrylate (HEA) and sodium acrylate (AANa) were grafted on the starch backbone in an aqueous solution. The graft copolymerization reaction was carried out in the presence of ammonium persulfate (APS) as an initiator and N,N' ‐methylenebisacrylamide (MBA) as a crosslinker in a homogeneous medium. The chemical structure of the hydrogels was confirmed by FT‐IR spectroscopy and thermogravimetric analysis (TGA). The morphology of the samples was examined by scanning electron microscopy (SEM). The results indicated that with increasing the amount of sodium acrylate both swelling capacity and swelling under load (AUL) were increased. Preliminary swelling and deswelling behaviors of the hydrogels were also studied. The effects of pH and inorganic salt on the swelling behavior of the hydrogels were investigated as well.