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.