Abstract: The graft copolymer of starch-sulfomethylated polyacrylamide(S-g-SPAM) was prepared by the sulfomethylation of graft copolyrner of starch-poly-acrylamide (S-g-PAM) with paraformaldehyde and sodium sulfite. The structure of the sul-fomethylated copolytner was identified by IR.The effects of their molecular structure on flocculation of Kaolin suspension were studied. The results are as follows.(1) The ability of flocculation of S-g-SPAMis better than that of S-g-PAM, HP AM, and much better than that of PAM.(2) S-g-SPAMshowed that the ability increases with increased molecular weight of grafted polymer.(3) Amid-degree of sulfomethylation (30%) is effective for Kaolin suspension.The rheological behaviour of S-g-SPAM aqueous solution showed pseudoplastic flow in the range of concentration of 0.1-1.0%. The metal ions (such as Na⁺, Mg²⁺, Ca²⁺) cause reduction in apparent viscosity (η_α), the order of influence is as follows:Na⁺<Mg²⁺<Ca²⁺.

Key words: Graft copolymer, Sulfomethylation, Flocculation