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

A sodium starch sulfate- based superabsorbent was synthesized to improve wa ter and saline absorbencies. A sodium starch sulfate with high degree of su bstitution was synthesized by the reaction of starch gelatinized with dimet hyl acetamide (DMAc)/ lithium chloride (LiCl) and a dimethyl formamide-sulf ur trioxide (DMF-SO,) complex. The sodium starch sulfate was then graft-pol ymerized with acrylonitrile and the nitrile groups of the sodium starch sul fate-g-polyacrylonitrile were converted to a mixture of hydrophilic carboxa mide and carboxylate groups by alkaline hydrolysis. The hydrolyzed sodium s tarch sulfate-g-polyacrylonitrile copolymer exhibited improved water and sa line absorbencies compared with that of existing starch-based superabsorben ts, resulting from the presence of sulfate groups. The maximum water and sa line absorbencies of the sodium starch sulfate-based superabsorbent were 15 10 and 126.4 g/g, respectively. (C) 2000 John Wiley & Sons, Inc.