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United States Department of Agriculture

Agricultural Research Service

Research Project: ADVANCED STARCH-BASED MATERIALS FOR NON-FOOD APPLICATIONS

Location: Plant Polymer Research

2006 Annual Report


1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
This research project will generate new uses for cereal grains and co-products by discovery and development of value added biomaterials, and is part of ARS National Program 306, Quality and Utilization of Agricultural Products. The economic viability of U.S. farmers is threatened by low commodity prices due to domestic and foreign production in excess of current demand. There is a growing demand for biobased materials to replace petroleum-based plastics. Starch and fibers derived from corn or wheat have potential to fill a large part of the approximately 70 billion lb/yr U.S. market for synthetic thermoplastics. To develop starch-based materials with functional properties, it is critical to better understand how starch interacts with other polymers and how these interactions can be modified and optimized. Development of new starch-based materials will increase market opportunities for biobased products and enhance the economic viability of U.S. agriculture.

The development of new, higher value products from cereal grains and co-products would boost farm income and help ensure that farmers remain competitive worldwide. Improved processes would reduce environmental impact of production of biobased materials. Market penetration of 1% of the current thermoplastics market in the U.S. would translate into approximately 700 million lbs/yr of biobased materials. If these new materials were 80% by weight starch, new markets would be created for approximately 100,000 acres of corn. Reduced environmental impact of solid waste disposal would provide significant positive societal impact. Improved methods of analysis of complex multicomponent systems will benefit other researchers in this broad field of study.

Potential products of this research include materials for applications such as disposable films, absorbents, adhesives, sensors, and materials responsive to changes in humidity, temperature, or pH. New fundamental knowledge of the interactions of starch with water and other additives will provide the basis for rational design of biobased materials.

Customers of this research project include scientists and engineers in academic and government labs who conduct research in carbohydrate biobased materials. Companies who develop, manufacture, or use biobased materials will also be customers of this research. Growers and grower organizations will benefit from increased markets for their products, and ultimately consumers will benefit from increased environmental benefits of biobased materials.


2.List by year the currently approved milestones (indicators of research progress)
FY 2005 1.1 Prepare and characterize conductive blends; demonstrate critical formulation variables. 1.2 Graft copolymer film study; initiate responsive material study; demonstrate critical variables controlling shrinkage. 1.3 Prepare and characterize oriented films. 1.4 Produce particles using dialysis method; demonstrate critical variables controlling particle size. Determine enzyme/acid treatments to weaken granules. Optimize viscosity ratios of starch and PLA (poly(lactic acid). 2.1 DFT (density functional theory) studies of glucose, maltose, cellobiose with 1-5 water molecules. 2.2 DP (degree of polymerizaton)30 periodic box study; Tg (glass transition) and crosslinking. 2.3 Complete prelimiary periodic box study. 2.4 Complete mannose/allose structure; begin glucose/water. 3 Infrared and thermodynamic analyses to identify and quantify individual components and their interactions.

FY 2006 1.1 Prepare and characterize graft copolymers; demonstrate efficacy of anti-corrosion materials. 1.2 Complete film study; begin larger cross-sections; develop cost estimates of film technology; demonstrate temperature-sensitive response materials. 1.3 Examine alternate orientation techniques; initiate epitaxy work. 1.4 Optimize solvents and membrane to control particle size; develop cost estimates of solvent process. Ball mill treated starches into nanoparticle; develop cost estimates of milling process. Optimize extrusion parameters; develop cost estimates of extrusion process. 2.1 Glucose trimers and water; glucose with 10 water molecules. 2.2 DP100 periodic box study; include epimers. 2.3 Determine structure to fit Xray data; complete study (final milestone for 2.3). 2.4 Complete galactose/Idose structure; increase number of water with glucose. 3 Utilize infrared spectra to characterize intermolecular interaction and hydrogen bonding between components.

FY 2007 1.1 Doping of graft copolymers. Transfer anti-corrosion technology; develop cost estimates of selected materials. 1.2 Alternate monomers for grafting; complete thicker cross-sections; demonstrate pH responsive modulated materials. 1.3 Prepare oriented films by extrusion and characterize properties; develop cost estimates of selected film formulations. 1.4 Characterize particles in solution; measure particle uptake of various chemicals for controlled release. Characterize ageing properties and demonstrate particle size effects; use materials based on optimized conditions. 2.1 Epimer solvation; larger glucose oligomers. 2.2 Metal ion effects on water diffusion and conduction band. 2.4 Complete analog study; begin twisted boat solvation. 3 IR (infrared) method for determination of concentrations of individual polymers. Develop chemometric models for infrared analysis of intermolecular interactions in multicomponent biopolymer materials.

FY 2008 & FY 2009 (Milestones overlap since original Project Plan milestones were written in 15-month intervals, not by FY). 1.1 Scale-up of processing in pilot plant for targeted materials. 1.2 Technology transfer of SM (shape memory) materials; complete pH sensitive materials; develop cost estimate of selected responsive materials. 1.3 Complete epitaxy work; pursue technology transfer. 1.4 Demonstrate uptake and release properties. Complete controlled release study; technology transfer efforts. Characterize ageing properties and demonstrate particle size effects; use materials based on optimized conditions. 2.1 Vibration and NMR (nuclear magnetic resonance) shifts; complete glucose study. 2.2 Complete metal ion study. 2.3 Determine vibrational frequencies and NMR shifts. 3 Develop mathematical models to extract structure-property relationships in multicomponent biopolymers and optimize formulation parameters.


4a.List the single most significant research accomplishment during FY 2006.
ORIENTED STARCH FILMS. Starch films are normally rather brittle and water sensitive and this limits the usefulness of starch as a material. One route to improve flexibility of starch films is by orientation. Oriented starch films were prepared by stretching high amylose starch triacetate films in hot glycerol followed by deacetylation. Elongations to break increased with draw ratio, reaching values of 20-30% (vs. 7% for undrawn) while tensile strength and modulus did not change. Flexible, oriented starch films and fibers may be of interest for a number of packaging and personal care applications. 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.


4b.List other significant research accomplishment(s), if any.
These accomplishments were 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.

RESPONSIVE STARCH COPOLYMER FILMS. New advanced technologies are needed to provide expanded commercial opportunities for biobased materials. Graft copolymers of starch and poly(methyl acrylate)(PMA) were prepared and converted into films by extrusion. When exposed to relative humidities exceeding approximately 70%, these films shrink in a controllable and predictable manner depending on the composition. Critical variables controlling shrinkage were identified. These results demonstrate that new advanced materials with novel properties can be prepared using starch.

COMPUTER MODELING OF BETA-CELLOBIOSE USING IMPLICIT AND EXPLICIT SOLVENT MODELS. Recent theoretical and experimental evidence confirmed that the most stable form of the solvated cellobiose molecule is more stable than the most stable vacuum conformer. This solvent-induced conformational change arises primarily from strong hydrogen-bonding interactions with a water molecule situated between the two rings, with hydrogen bonds to both rings. Density function theory (DFT) calculations on cellobiose and cellobiose water complexes and with COSMO (software), a polarized continuum model for solvation, were used to examine the role water plays in this solvent-induced conformational change. This work showed that 3-4 explicit water molecules were required for the syn form to be fully stabilized relative to the anti form, the COSMO results were inconclusive. The importance of this work relates to the native cellulose structures and the ability to solvate cellulose (i.e. preference for nonaqueous solvents) by energetically favoring the anti or puckered form thus disrupting the crystal lattice. One of the hurdles that must be overcome in converting cellulose to alcohol is that of dissolving or disrupting the cellulose matrix prior to enzymatic digestion. This work was carried out in collaboration with Dr. Wayne Bosma of Bradley University. Dr. Bosma was a resident in our laboratory during the 2005-2006 year on sabbatical leave.

STARCH/PLA BLENDS WITH DISPERSED MORPHOLOGY. Results demonstrated that the viscosity of poly(lactic acid)(PLA) when extruded at 160 deg C was almost identical to that of thermoplastic starch containing 15% moisture. The viscosity vs shear rate curve of PLA and starch at 15% moisture almost overlay. This means that when compounding PLA and 15% moisture starch at 160 deg C their viscosity ratio will be close to one. According to models of immiscible blends, a fine dispersion of starch in a matrix PLA is possible; this should improve the tensile properties of starch filled PLA composites.

CHARACTERIZATION OF BIOBLENDS. Bioblends are composites of at least one biodegradable polymer with non-biodegradable polymers. Successful development of bioblends requires that the biodegradable polymers be compatible with other component polymers. The compatibility of polymers in bioblends was characterized to evaluate the degree of intermolecular interactions between the component polymers. The degree of interaction in blends of polycaprolactone (PCL) and polystyrene (PS) was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared photoacoustic spectrometry (FTIR-PAS). The DSC studies showed that some parameters favored partial miscibility of PS in PCL, while others favored immiscibility. The TGA studies indicated that incorporation of PCL in PS results in thermal destabilization of PCL/PS bioblends. The FTIR-PAS spectral evidence suggested the presence of intermolecular bond interactions between PCL and PS. A conventional equation was modified to better predict the Tg of binary bioblends from the Tg's of the two component polymers. Results computed with the new equation from DSC data were consistent with, and therefore support, the results of TGA and FTIR-PAS analyses of PCL/PS bioblends. The new equation may have potential to corroborate or confirm FTIR-PAS spectral evidence of intermolecular interactions between polymers in binary bioblends.


4c.List significant activities that support special target populations.
None.


4d.Progress report.
FY 2006 research progress on this project is addressed in questions 4a and 4b. Our ability to perform sophisticated computer simulations has been enhanced by the addition of a 16-processor, 64 bit word computer. This computer has increased the delivery of computational output and allowed larger molecular systems to be studied.


5.Describe the major accomplishments to date and their predicted or actual impact.
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.

STARCH NANOPARTICLES. Use of starch in many material applications is limited by the inherent size of starch granules. Therefore, the development of starch nanoparticles is an area of active interest. Cornstarch was dissolved in water-dimethyl sulfoxide solvents and dialyzed against pure ethanol. The starch particles generated by this method had particle sizes ranging from 200 nanometers to 1 micron. For comparison, native corn starch granules are typically 10 microns or larger in size. Drying methods directly affected particle size. Particles that were air dried had the largest size whereas particles that were critical point dried while still in an ethanol suspension had the smallest size. Producing nano-particle starch will open new markets for starch by imparting novel properties not attainable with larger-particle starch.

SPECTROSCOPY OF WHEAT GLUTEN. Wheat gluten was modified to add value by improving its viscoelasticity and other food end-use properties. In collaboration with Dr. Abdellatif Mohamed (CPF - Cereal Products & Food Science Research) to improve the properties of wheat protein, the effects of the enzymatic crosslinking upon native wheat gluten were examined by Modulated Differential Scanning Calorimetry (MDSC) and Fourier Transform Infrared Spectroscopy (FTIR). An FTIR spectroscopic method was devised to obtain evidence of molecular interaction between the gluten protein and the TRIS buffer used in the crosslinking reaction. It is well known that FTIR spectra of proteins are sensitive to their molecular conformations and environments. Therefore, FTIR spectroscopy of the crosslinked gluten in TRIS buffer provided definitive evidence that gluten-TRIS hydrogen bonding likely occurs at their molecular interface in aqueous systems and thus plays an important role in enzymatic crosslinking reactions. These MDSC and FTIR methods, especially when combined with potential spectral deconvolution strategies, have applications for distinguishing between levels of crosslinking in wheat gluten for studies in flour and dough rheology.

MOLECULAR MODELING OF CARBOHYDRATE-WATER INTERACTIONS. Since all natural carbohydrates (such as starch and cellulose) exist in the presence of water, successful computer modeling requires accurate methods of incorporating water. Various models of glucose (the structural building block of starch and cellulose) with water were simulated at a high level of theory. These structural studies of solvated carbohydrates are the first detailed examinations which describe how water changes conformational preferences, or shape, in amylose- and cellulose-like compounds. This work has great potential for improving our understanding of these biobased materials, with the goal of improved properties for commercial utility.

ELECTROACTIVE BIOPLASTICS. Thermoplastic starch-carbon black blends with up to 40% by weight carbon black prepared by extrusion. Films were evaluated for their electrical conductivity and mechanical properties. Conductivity increased with increasing carbon black up to an optimum level after which it decreased. Strength and stiffness increased with increasing carbon black content while extensibility decreased. The materials retained their conductance values after 21 days of ageing. Strength and stiffness increased significantly with ageing time. These results demonstrate that starch-based materials with useful levels of conductivity and mechanical properties can be easily prepared using conventional techniques. This information is useful to other researchers developing biobased materials.

RESPONSIVE STARCH COPOLYMER FILMS. Successful development of new markets for biobased materials requires materials with novel properties. Starch graft copolymers, in which a synthetic polymer is chemically bonded to starch, were prepared and evaluated for use as responsive ("smart") materials. Initial results indicated that these starch-based materials respond to changes in relative humidity or temperature by changing shape. The responses are due to the starch component. These studies provide the basis for future work in this area, and suggest new opportunities for starch-based materials.

Customers for this research include companies involved in making biobased products for applications such as disposable packaging, personal hygiene products, and edible films. This research will lead to greater understanding of structure-property relationships and the effects of composition and processing parameters. New knowledge created using chemometrics for characterization molecular modeling to predict property differences will enable the design of new biobased materials with predicted properties. Ultimately this research will lead to new materials with improved properties, and expanded uses of corn and other grains.


6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
Technology transfer activities have focused on publishing and presentations of research results at meetings and conferences. Initial discussions have been held with potential commercial partners interested in the oriented starch film and electroactive materials.


7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Electroactive Bioplastics Flex Their Industrial Muscle. Agricultural Research Magazine, December 2005.

Bioplastics Becoming A New Solution. Feedstuffs, page 21, April 3, 2006.


Review Publications
Schnupf, U., Willett, J.L., Momany, F.A. 2006. DFT study of carbohydrates: A comparison between the epimers of glucose [abstract]. Midwest Chemistry Conference. n.10.

Finkenstadt, V.L. 2005. Biopolymers as electroactive bioplastics [abstract]. American Association of Cereal Chemists. p.54.

Finkenstadt, V.L. 2005. Electroactive biomaterials composed from natural polymers [abstract]. American Association of Cereal Chemists. p.170.

Momany, F.A., Willett, J.L., Bosma, W. 2005. Calculations to determine the experimental conformation of a cyclic insect pheromone using a novel multi-faceted ab initio approach [abstract]. American Chemical Society. Paper No. 98.

Bosma, W., Appell, M.D., Willett, J.L., Momany, F.A. 2005. Stepwise hydration of a disaccharide: DFT calculations of structural and energetic changes as 1 to 4 water molecules are added to b-cellobiose [abstract]. American Chemical Society. Paper No.94.

Finkenstadt, V.L., Willett, J.L. 2005. Mechanical and electrical properties of starch composites using carbon black as a conductive filler [abstract]. American Chemical Society. Paper No.81.

Finkenstadt, V.L., Willett, J.L. 2005. Mechanical and electrical properties of thermoplastic starch composites using carbon black as a conductive filler [abstract]. Proceedings of UJNR Food & Agricultural Panel. p.106.

Momany, F.A., Willett, J.L., Appell, M.D., Bosma, W. 2005. DFT studies of hydrated carbohydrates:explicit water molecule around glucose and cellobiose geometry optimized at B3lYP/6-311++G** [abstract]. CD-ROM. International Chemical Congress of Pacific Basin.

Schnupf, U., Willett, J.L., Momany, F.A. 2006. Solvation studies by DFT of carbohydrates: A/B-anomeric ratios of epimers of glucose using a continuum-solvation model (cosmo) [abstract]. American Chemical Society. n.130.

Finkenstadt, V.L., Cermak, S.C., Willett, J.L. 2006. Preparation and characterization of poly(lactic acid) green composites using agricultural co-products as fillers [abstract]. American Chemical Society. n.10.

Bosma, W., Schnupf, U., Willett, J.L., Momany, F.A. 2006. Computer modeling of b-cellobiose in a solvent environment: DFT calculations using implicit and explicit solvent models [abstract]. American Chemical Society. n.16.

Momany, F.A., Willett, J.L. 2006. Molecular dynamics simulations of a cyclic-DP-240 amylose fragment: glass transition temperature study [abstract]. 37th Great Lakes Regional Meeting. p.173.

Finkenstadt, V.L. 2006. Poly(lactic acid): A biodegradable commodity plastic [abstract]. BioEnvironmental 2006 Meeting. p.20.

Finkenstadt, V.L., Liu, L.S., Liu, C., Cermak, S.C., Evangelista, R.L., Hojillaevangelist, M.P., Willett, J.L. 2006. Green composites using poly(lactic acid) and agricultural co-products [abstract]. Green Chemistry and Engineering Conference. p.64. n.190.

Finkenstadt, V.L., Willett, J.L. 2004. Preparation and characterization of functionalized electroactive biopolymers. Polymer Networks. p.367-371.

Momany, F.A., Appell, M.D., Willett, J.L., Schnupf, U., Bosma, W.B. 2006. DFT study of A- and B-D-galactopyranose at the B3lYP/6-311++G** level of theory. Carbohydrate Research. p.525-537.

Bosma, W.B., Bartelt, R.J., Momany, F.A. 2006. Determination of the preferred conformation of the bicyclic Galerucella pheromone using density functional theory optimization and calculations of chemical shifts. Journal of Organic Chemistry. 71(13):4748-4758.

Last Modified: 4/18/2014
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