Location: Plant Polymer Research2013 Annual Report
1a. Objectives (from AD-416):
The long-term objective of this project is to develop processes to enhance the conversion of cereal crops and residues into value added polymers, demonstrate the useful properties and applications of these biobased materials, reduce dependence on petroleum and increase utilization of environmentally friendly renewable resources. Objective 1: Develop technologies that enable commercially viable products composed of lipid and amylose or modified starch complexes with novel micro- and nano-sized spherulitic morphologies; Objective 2: Develop reactive extrusion-based technologies that enable commercially viable graft co-polymers from starches and lignocellulosics; Objective 3: Develop novel chemical and thermal processes that enable the commercially viable production of derivatives of starches, lignins, and lignocellulosics; Objective 4: Develop novel biocatalytic processes to produce commercially viable derivatives of starches, lignins, and/or lignocellulosics.
1b. Approach (from AD-416):
New biobased products and sustainable processing technologies are needed to replace industrial and consumer products made from petroleum based feedstocks. This project focuses on making polymeric materials with a variety of useful applications from starch and associated low cost coproducts of corn processing and harvesting. In order to accomplish this, modified biopolymers with new or improved properties need to be prepared and processing technologies which are more efficient, i.e. use safer or less solvent, are faster, have more complete reaction and fewer byproducts need to be developed. Specific objectives for this project include: 1) prepare novel spherulitic starch-polymer composites via jet-cooking; 2) prepare starch graft copolymers with controlled structure by reactive extrusion and evaluate applications; 3) prepare modified starches, celluloses and lignins with novel structures via processing with ionic liquids, microwaves and autoclave heating; and 4) prepare new starch and lignin graft copolymers as well as polyglutamic acid and polyhydroxyalkanoates by enzymatic and microbial catalysis. Overall, this research will lead to biobased polymer products which will have new or improved properties, have lower cost, are more environmentally friendly and thus will be more acceptable to consumer markets.
3. Progress Report:
A detailed study of the acetylation of starch in four ionic liquids was conducted. All four ionic liquids were found to be acceptable with respect to the acetylation reaction. An advantage to this route is that pyridine was found to be unnecessary for the reaction to proceed. It was also discovered that starch could readily react with two identified anhydrides in ionic liquids to give the corresponding derivatives. The products were anionic and might be useful as anionic polysaccharides. Amylose inclusion complexes were prepared by jet-cooking mixtures of high amylose corn starch and 1-hexadecylamine (HDA) or its hydrochloric acid (HC1) salt. Water insoluble spherulites were formed from the amylose-HDA complex and were similar to those prepared from palmitic acid. Aqueous solutions of a cationic amylose complex were obtained when the HCl salt of HDA was used. These starch-HDA salts functioned as flocculating agents, suggesting their use in water purification and as retention aids in papermaking. Starch-polyglutamic acid (PGA) graft copolymers have been produced. PGA was prepared from low cost corn condensed distillers solubles and distillers dry grains and solubles. The impact of pH and temperature on production and structure of PGA was evaluated. The rheological and flocculation properties as well as water solubility/absorption index of the starch-PGA graft are being conducted. The study of starch-poly(methyl acrylate) graft copolymers prepared from jet-cooked aqueous dispersions of amylose-oleic acid spherulites has been expanded to include aqueous spherulite dispersions in which un-complexed, water soluble amylopectin was removed by water extraction. Spherulite-reinforced plastics with good tensile properties were obtained from these graft copolymers by extrusion processing. Nano-particles of lignin were prepared using a high temperature and pressure homogenizer. Impact of temperature, pressure, and time on lignin particles were tested and will be evaluated using transmitted electronic microscopy, scanning electronic microscopy, and light scattering. The viscoelastic properties of starch-polyacrylamide graft co-polymers prepared from water (few long branches) and dimethyl sulfoxide (many short branches) was evaluated. These co-polymers can swell water at room temperature and form gels. These two starch graft co-polymers exhibited different behaviors under shear. These two different starch graft copolymers can be good candidates for wound-healing gel, drug delivery material, and cosmetic cream according to their different properties. It was determined that microwave processing could replace jet cooking to prepare starch-palmitic acid spherulites in similar yield. The steam jet cooking process is more robust, however if only small quantities of spherulites are needed, then microwave processing has value.
1. Production of improved polymers through use of starch. Starch has been used in polymer formulations historically where it acts as inexpensive filler. Unfortunately the physical properties of a polymer typically deteriorate upon the incorporation of starch. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, have determined that by attaching polymers to the surface of starch particles, the starch graft polymer has improved properties. The starch particles were formed as hollow spheres using techniques developed by ARS and then polymers are attached to the surface of the spheres. The polymer chosen is typically gummy with poor properties. By attaching the polymer to the starch, this gummy polymer is turned into a higher melting polymer composite that is on the order of 50% starch. The starch containing polymer has strength and elongation that are competitive with polyethylene, providing companies with a product that utilizes inexpensive renewable filler that can replace polymers used petroleum based chemicals.
2. New process for producing alkyl celluloses are commercial products used as thickeners in food and non-food products. These materials are typically made in an alcohol solution where the reaction can take many hours. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, Illinois, have found an alternative, simplified synthesis of alkyl cellulose. By changing the solvent from alcohol to water (at high pH) and heating in a microwave, the reaction time is greatly reduced. Given that alcohol is a flammable material, this process is safer than the traditional route. Overall reaction time is less than 30 minutes with yield of product varying between 54 and 87%. The number of alkyl groups on the cellulose is similar to that made using traditional routes. The product of this research is competitive with industrial products in terms of composition and was made in less time using a safer procedure.
3. Improved complexing agents capable of delivering or trapping unwanted compounds. ARS Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research (NCAUR) in Peoria, Illinois, developed a microwave-assisted method to modify starch derived cyclodextrins. Cyclodextrins are compounds shaped like a bowl. In the cavity of the bowl, these compounds may either trap unwanted chemicals or deliver desirable ones. The solubility of cyclodextrins often limits their applications. The solubility can be improved through chemical modification. Through the use of microwave techniques, the desired chemical modification was complete in 3-10 minutes (a >10x reduction) with improved yield relative to conventional heating. The modified cyclodextrins were not soluble in water but were soluble in organic solvents. By altering the chemical reaction, cyclodextrin products could be obtained that were insoluble in all solvents. Films were produced using these materials that can remove specific organic molecules through the formation of cyclodextrin complexes. Companies interested in producing products that remove undesirable materials from process streams, toxic compounds from the environment, or encapsulation of fragrance molecules will benefit trough the development of this technology based on renewable cyclodextrins.Fanta, G.F., Kenar, J.A., Felker, F.C., Byars, J.A. 2013. Preparation of starch-stabilized silver nanoparticles from amylose-sodium palmitate inclusion complexes. Carbohydrate Polymers. 92(1):260-268.