Submitted to: Polymers and the Environment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/11/2009
Publication Date: 9/20/2009
Citation: Willett, J.L., Finkenstadt, V.L. 2009. Comparison of Cationic and Unmodified Starches in Reactive Extrusion of Starch-Polyacrylamide Graft Copolymers. Polymers and the Environment. 17(1):248-253. Interpretive Summary: These results demonstrate the potential of producing new biobased materials by taking advantage of the natural properties of starch. SGPs (starch graft copolymers) are chemically bonded blends of starch and other polymers which have improved properties compared to physical blends of the same components. Potential applications for SGPs include superabsorbents, hydrogels, responsive materials, and controlled release matrice, all materials currently produced from petrochemicals. In this research, we showed how the use of commercially available cationic (positively-charged) starches can control the properties of starch graft copolymers (SGPs) for specific range of use materials. This process addresses the growing need to develop functional biobased materials which provide new markets for agricultural products and reduce dependence on nonrenewable resources.
Technical Abstract: Graft copolymers of starch and polyacrylamide (PAAm) were prepared using reactive extrusion in a corotating twin screw extruder. The effect of cationic starch modification was examined using unmodified and cationic dent starch (approximately 23% amylose) and waxy maize starch (approximately 2% amylose). For a fixed acrylamide/starch feed ratio, conversion, graft content, and grafting efficiency were essentially unaffected by starch type or modification. Cationic starch graft copolymers generally had lower molecular weight PAAm grafts compared to the unmodified starch, whereas amylose content had little or no significant effect. In addition, the frequency of grafting was higher with cationic starch. These results indicate that cationic modification of starch enhances formation of grafting sites, resulting in graft copolymers with more grafts of lower molecular compared to unmodified starch. Cationic modification may therefore be a way to tailor the properties of starch-PAAm graft copolymers.