2007 Annual Report
1a.Objectives (from AD-416)
The goal of this research is to develop new biobased materials from starch and new fundamental knowledge of their properties. Objectives of this work fall into three topic areas: materials development, molecular modeling and simulations, and analysis techniques.
1b.Approach (from AD-416)
Develop new biobased materials from starches with novel properties, utilizing the inherent properties of starch so that it is an active component rather than a low cost, biodegradable filler. Develop molecular modeling tools for use in rational design approaches. Develop novel sophisticated instrumental analytical techniques to characterize the structures and properties of multicomponent biobased materials.
Significant progress was made in our program to determine the molecular structural parameters for interactions between carbohydrates and water. Using advanced computational methods (including density functional ab initio molecular dynamics using a dielectic cavity method), we studied hundreds of conformations of glucose, maltose, maltotriose, and maltotetrose. Our analysis of maltose has led to a deeper understanding of its complex solution conformation, which appears to possibly have some "kink" structure in addition to the normal conformations. These intriguing questions are being examined further by ab initio molecular dynamics calculations, designed to provide an answer that aligns all the data into an integrated scheme. In related work, we mapped the energy, dipole moment, and selected internal coordinates of alpha-maltose while varying the two glycosidic bonds. This is the first published density functional theory paper in which maps of bond angles and dihedral angles were shown to change as a function of the glycosidic bonds variance. We continued work on modeling large amylose fragments with explicit water molecules (corresponding to a moisture content of 15%). Our molecular modeling results provide fundamental knowledge of carbohydrate-water interactions, and are laying the groundwork needed to provide improved understanding of carbohydrate-based biomaterials and feedstocks. This research addresses National Program 306, Quality and Utilization of Agricultural Products, Problem 2a. New Product Technology.
Building on our previous results, we have developed new starch-based films which shrink at high relative humidity. We demonstrated that various types of starches and plasticizers could be used, in addition to initial results with cationic waxy maize starch and urea. It was shown that glycerol - a byproduct of biodiesel production - functions as well as urea as a plasticizer. Analysis of shrinkage results taken at different relative humidities showed that results for a range of starch-polymer-plasticizer combinations could be reduced to a single shrinkage-relative humidity curve. This analysis allows prediction and control of shrinkage properties based on composition, which is essential for developing new uses for starch-based biomaterials. Temperature-sensitive starch-based hydrogels were developed. The hydrogels displayed volume shrinkage of up to 80% above a certain critical temperature. In addition, the hydrogels changed from translucent to opaque as the critical temperature was exceeded. The optical transition occurred over a period of several seconds, while the volume shrinkage took up to several hours to complete. Starch-based materials with controllable and tunable properties provide new opportunities for biobased materials derived from agricultural products. This research addresses National Program 306, Quality and Utilization of Agricultural Products, Problem Statement 2c. New and Improved Processes and Feedstocks.
Oriented amylose/starch films. There has been considerable interest recently in developing starch-based fibers and films for use as biodegradable packaging and hygiene products. Such biobased products are desirable since they are made from a renewable, agricultural commodity produced in the U.S. (corn) rather than imported oil. However, starch-based materials are typically brittle and rather water sensitive. This research has demonstrated that stretching amylose films (the linear polymeric component of starch), so that the molecules are pointed in one direction (oriented) gives films that are much stronger and more flexible. An easy optical method to assess the degree of orientation was also developed. In addition, it was found that treating the starch films under hot, humid conditions gives much improved water resistance. These results should help companies and university scientists develop new starch-based materials for disposable consumer products. This work was carried out in support of ARS National Program 306, Quality and Utilization of Agricultural Products and addresses Problem Statement 2c. New and Improved Processes and Feedstocks.
5.Significant Activities that Support Special Target Populations
|Number of non-peer reviewed presentations and proceedings||1|
Finkenstadt, V.L., Liu, L.S., Willett, J.L. 2006. Preparation of poly(lactic acid) and sugar beet pulp green composites. Polymers and the Environment.
Finkenstadt, V.L., Willett, J.L. 2006. Characterization of functionalized electroactive biopolymers. American Chemical Society Symposium Series. p.256-261.
Schnupf, U., Willett, J.L., Bosma, W.B., Momany, F.A. 2006. DFT study of Alpha- and BETA-allopyranose at the B3LYP/6-311++G* level of theory. Carbohydrate Research. 342:196-216.