Preparation of starch 2-hydroxy-3-mercaptopropyl ethers and their use in graft polymerizations
1978
Trimnell, D. | Stout, E.I. | Doane, W.M. | Russell, C.R.
In the reported experiments, starch 2-hydroxy-3-mercaptopropyl ethers of degree of substitution (DS) up to 0. 34 were prepared as follows: starch was reacted with epichlorohydrin to give 3-chloro-2-hydroxypropyl ethers which were treated with thiosulfate to displace chloride ion followed by reduction of the resulting thiol-sulfonates with sodium borohydride. These mercapto ethers formed graft copolymers with acrylonitrile, styrene, acrylic acid, and dimethylaminoethyl methacrylate (DMAEMA) under hydrogen peroxide initiation. The resulting graft copolymers, after treatment with sodium borohydride to regenerate thiol groups from disulfides formed by peroxide oxidation, could then be reacted with additional monomer and peroxide to increase add-on of the synthetic moiety. Graft copolymers containing about 60% polyacrylonitrile or 70% polystyrene were thus obtained. Graft copolymers prepared from acrylic acid and DMAEMA precipitated near the iso-electric point upon neutralizing their acidic or basic solutions.
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