Synthesis and absorbency of a superabsorbent from sodium starch sulfate-g-polyacrylonitrile

A sodium starch sulfate–based superabsorbent was synthesized to improve water and saline absorbencies. A sodium starch sulfate with high degree of substitution was synthesized by the reaction of starch gelatinized with dimethyl acetamide (DMAc)/lithium chloride (LiCl) and a dimethyl formamide–sulfur trioxide (DMF–SO3) complex. The sodium starch sulfate was then graft-polymerized with acrylonitrile and the nitrile groups of the sodium starch sulfate-g-polyacrylonitrile were converted to a mixture of hydrophilic carboxamide and carboxylate groups by alkaline hydrolysis. The hydrolyzed sodium starch sulfate-g-polyacrylonitrile copolymer exhibited improved water and saline absorbencies compared with that of existing starch-based superabsorbents, resulting from the presence of sulfate groups. The maximum water and saline absorbencies of the sodium starch sulfate–based superabsorbent were 1510 and 126.4 g/g, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1423–1430, 2001