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United States Department of Agriculture

Agricultural Research Service


item Cao, Xingxiang
item Sessa, David
item Willett, Julious - J L

Submitted to: Macromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/1999
Publication Date: 2/15/2000
Citation: N/A

Interpretive Summary: Of the approximately eight billion pounds of various starches produced annually, about six billion pounds were used for industrial purposes. The replacement of certain petroleum products with starch-based products has spurred an intense research activity toward an increased usage of starch as a renewable industrial raw material. Blending of starch with other components requires a fundamental knowledge of its molecular structure. Static and dynamic light scattering techniques were used to study the solution properties of corn amylose. Our findings are basic and necessary to affect complex formation between corn amylose and other biodegradable molecules for the development of biodegradable polymers for packaging and mulch products.

Technical Abstract: Static and dynamic light scattering techniques were used to study the solution properties of corn amylose in N,N-dimethylacetamide with 3% (w/v) LiCl. Static properties show three distinguishable regions, which are designated as the dilute, the semidilute, and the concentrated regimes. The concentrations at which these transitions occur are designated as the overlap concentration c* and the semidilute concentrated transition concentration c**. Two master curves are used successfully to fit the static data in the dilute and semidilute regimes. Dynamic data show that at c < c*, a single diffusion motion representing the translational diffusion of the amylose macromolecule is present in the solution. At c > c*, two dynamic motions are observed: a fast diffusion representing the cooperative diffusion, and a slow one representing the cluster diffusion. The slow diffusion motion is found to follow the "stretched exponential" diffusion law. The fast diffusion motion is found to have two distinguishable concentration dependence patterns: its concentration dependence at c > c** is stronger than that at c < c**. The relative amounts of these two modes are also analyzed in terms of their concentration dependence.

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