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Posted: September 16, 2009
Researcher proposes to shrink ionic liquid polymers to nanoscale
(Nanowerk News) Scientists throughout the world are exploring the use of liquid salts in a variety of electrochemical devices that could some day lead to more robust lithium ion batteries, fuel cells, organic cells and other novel applications.
Rochester Institute of Technology scientist Tom Smith is experimenting with synthesizing liquid salts into a gel. He recently received an EAGER (EArly-concept Grants for Exploratory Research) grant from the National Science Foundation to create an entirely new material—a polymer, or a plastic, from ionic liquid monomers—that will confine charge-carrying ions in a gelled, pseudo-liquid state.
Smith will bypass the loss of conductivity that results from tethering free-moving ions by incorporating the gelatinous ionic-liquid polymer into composite materials at nanoscopic dimensions.
"There are some reports indicating that if you reduce the dimensionality of a system of ions, the conductivity goes up," says Smith, professor of chemistry and microsystems at RIT, who was recently selected as a member of the American Chemical Society's inaugural class of fellows. "We're talking 200 angstroms or 20 nanometers small—about 4,000 times smaller than the diameter of a human hair. How these polymer chains are distributed in the composite and how the ions associated with them move can be different."
Smith is trying to tap the amazing conductivity of room temperature ionic liquids—a unique class of salts that exist in a liquid state over a wide temperature range, extending from room temperature to well below zero, and exhibit high ionic conductivity, nonvolatility, and nonflammability.
"I see them being useful in capacitors for energy storage, and for better organic solar cells," he adds. "Right now solar cells are made of silicon. They're relatively expensive. I see the possibility that these materials might be of use in those areas. We're going to explore that possibility."
Once contained in nanostructured, film-forming polymers, room temperature ionic liquids will enable scientists to do certain things that cannot be done with any other material, Smith says.
"Room temperature ionic liquids that are stable in the air were first created in 1992, so they're fairly new," Smith says. "If you're dealing with liquids, you have to contain them. We'd like to have the properties of an ionic liquid in a state that's not liquid."
Nanomaterials derived from ionic liquid polymers have not been synthesized prior to Smith's current experimental study.
"The material we're working on is very hard to make, mostly because it will polymerize spontaneously before you want it to," Smith says. "And to synthesize a dissymmetric ion, necessary in the formation of salts that are liquid at room temperature, requires chemical reactions that have several steps—and steps that are not necessarily easy to carry out."
Students contributing to Smith's study include graduate researcher Darren Smith and, during the past summer, Darius Wynn, an undergraduate student studying electrical engineering in RIT's College of Applied Science and Technology. High school student Jaquest Wilson-MacDonald, from Wilson Magnet High School in the Rochester Central School District, also worked on the project this summer. Wynn was supported by the NSF's Louis Stokes Alliances for Minority Participation Program. Wilson-MacDonald participated as part of the ACS' Project SEED Summer Research Internship Program for Economically Disadvantaged High School Students.
"In addition to the potential to impact technological applications where one might want to use an ionic liquid, the research is a great vehicle for teaching concepts to our students and having them think in revolutionary ways," Smith says.
Smith expects to add three more graduate students to his synthetic chemistry laboratory during the next two years.