Polyacrylamide-starch graft copolymers

Superabsorbent polymers are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a polyacrylic acid, sodium salt (sometimes referred to as cross-linked sodium polyacrylate). Some of the polymers include polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxy-methyl-cellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, and starch grafted copolymer of polyacrylonitrile to name a few. The latter is one of the oldest SAP forms created. 

Acrylamide graft copolymers such as those with starch (qv)(131), dextran (132), and lignin (qv) (133), have been studied to try to reduce copolymer costs. A general disadvantage of acrylamide copolymers is greater cost compared to partially hydroly2ed polyacrylamides. 

Both starch-g-PAN and starch-g-polyacrylamide were prepared by cobalt-60 initiation, since acrylamide does not graft efficiently in the presence of ceric ammonium nitrate (16). Both graft copolymers were irradiated with ultrasound to give totally soluble products the ultrasonic treatment of starch-g-PAN was carried out in DMSO, while that of starch-g-polyacrylamide was run in water. 

A similar procedure was used to prepare starch-j -polyacrylamlde, and 15 g of acrylamide (97%, Polysciences) was used In the polymerization. After irradiation, the reaction mass was extracted several times with water to remove ungrafted polyacrylamide, and the graft copolymer was washed with ethanol and vacuum dried at 60°C. Weight percent polyacrylamide in the graft copolymer (% add-on) was 35%, based on the weight gain of starch. 

Finkenstadt VL, Willett JL. 2005. Reactive extrusion of starch-polyacrylamide graft copolymers Effects of monomer/starch ratio and moisture content. Macromol Chem Phys 206 1648-1652. 

Different types of floeculants can be prepared by aminomethylation the amino-methyl derivatives of polyacrylamide represent the most widely adopted class of compounds, which includes high-molecular-weight floeculants (502, 517 in Table 38, 562 in Table 40), and has been widely patented. The large amount of research on these pnxlucts is concerned, in particular, with is(x lcctric points, the content of functionalized co-units, the extent of amido groups hydrolysis, and the use of copolymcrs. -"- Applications of acrylamide copolymers grafted onto starch or other polysaccharides arc also considered. ... 

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