Researchers describe how to put the 'nano' in synthetic polymers

Geoffrey Hutchison, right, a Cornell postdoctoral associate with the Cornell Center for Materials Research (CCMR), talks about his research poster with Nathaniel Brese, who received his Ph.D. in chemistry from Cornell 1994 and now is a research fellow at Rohm & Haas Electronic Materials on Long Island. The research described in the poster, on the "Molecular Electronics of Metal Coordination Oligomers," was developed with graduate students Samuel Flores-Torres, Jing Jin, Daniel Blasini and with Héctor Abruña, Cornell's Emile M. Chamot Professor of Chemistry and Chemical Biology. Poster presentations in Statler Hall, May 24, were part of the CCMR Polymer Outreach Program's annual symposium. Frank DiMeo/University Photography

By Tom Oberst

Polymers are old news. Indeed, DNA, which is one type of naturally occurring polymer, has been around since the formation of life itself. The first synthetic polymers date to 1839 when a bankrupt hardware merchant from Philadelphia named Charles Goodyear heated a mixture of sulfur and natural rubber on a stove. The science of synthetic polymers was developed in the 1920s, and by the mid-1940s scientists had invented polystyrene, polyvinyl chloride, low-density polyethylene, polyacrylates and glass-fiber reinforced polyesters, to name just a few man-made polymers. The world of "plastics" had been born.

But that was more than 50 years ago. Can polymers still be that exciting? To answer this question more than 100 researchers from academia, industry (General Electric and Clariant Corp.) and government (U.S. Office of Naval Research) attended the Cornell Center for Materials Research (CCMR) Polymer Outreach Program's (POP) 15th annual symposium, May 24, on campus. They gathered in Alice Statler Auditorium of Statler Hall to hear experts talk about the latest advances in synthetic polymer science. The most important of these advances may be "nanocomposite polymers," polymers that are doped with nanometer-sized particles (a millionth of a millimeter) to achieve properties superior to conventional polymers.

Polymers display an amazing range of material properties, and the processes by which synthetic polymers are manufactured -- which can include heat, pressure, the presence of catalysts or the addition of additives to create "composites" -- allow precise control over the nature of these properties. Polymers can be tailored to be hard, soft, light, heavy, chemically resistant, heat resistant, flame resistant or to have an affinity for water. Tires, shampoo, couch cushions and sandwich bags are all made of polymers.

Emmanuel Giannelis, the Walter R. Read Professor of Engineering, discussed his research into new nanocomposite polymers with unexpected and unique properties. Toughness, which is a measure of a material's ability to absorb stress without fracturing, is usually improved when the material has a high elasticity and is not very stiff. And, vice versa, a material with a high stiffness usually fractures more easily and thus has a lower toughness. Giannelis, however, has discovered that the addition of nanoparticles to certain polymers can improve both the stiffness and toughness of the polymers, simultaneously.

"To me that is quite remarkable ... because of the interesting possibilities that these new materials may be offering," said Giannelis. One material created by his research group, he said, is able to stretch up to 250 percent of its original length without fracturing and at the same time increase in stiffness.

Other speakers at the symposium included graduate student Rafael Herrera, who is working with Giannelis on improving fuel cells using nanocomposite polymers. A fuel cell is a type of battery that converts hydrogen into electrical energy with few emissions and no moving parts. Herrera has found that fuel cell efficiency can be improved by adding nanoparticles, which increase conduction in the cell. The research is sponsored by the Department of Energy-funded Cornell Fuel Cell Institute.