Biobased Plastic Flexes its Muscle

Electroactive polymers—plastics that expand or contract when stimulated by electricity—can now be made from plants rather than petrochemicals, according to Agricultural Research Service (ARS) scientists in Peoria, Ill.

There is now significant interest in the possible use of electroactive polymers in many industrial and biomedical applications, from light-emitting diodes and controlled-release devices to artificial muscles and environmental sensors. The material is typically petroleum-based, but ARS researchers Victoria Finkenstadt and J.L. Willett showed that plant polysaccharides like starch can work just as well.

Use of the polysaccharides in certain types of conductive polymers could leapfrog some of the pitfalls associated with using petroleum feedstocks, such as U.S. reliance on foreign suppliers, according to Finkenstadt, a chemist, and Willett, a supervisory chemical engineer with ARS' National Center for Agricultural Utilization Research in Peoria.

There, in the Plant Polymer Research Unit, the scientists created biobased polymers that bend and contract slightly when pulsed with electricity. In nature, many polysaccharides are natural insulators, meaning they obstruct the flow of electricity. However, the Peoria team devised a process for overcoming this so that the biopolymers conduct electricity at levels similar to synthetic products.

Cornstarch is an ideal starter material because it is inexpensive—about 20 cents a pound—and plentiful. In 2004, U.S. farmers planted nearly 81 million acres of corn and harvested approximately 12 billion bushels. (One bushel yields an average of 32 pounds of cornstarch.) By comparison, one of the synthetic polymers the scientists used, polyaniline emeraldine, costs $58 a gram.

One potential use for the biopolymers is in recharging of lithium batteries. Petroleum-based gels are now used, but Finkenstadt wants to find out whether the biobased polymers could shorten the recharging time, or hold the charge longer.

Read more about the work in the December 2005 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.