From Virginia Tech
Chemists increase conductivity of fuel cell materials (Blacksburg, Va., Aug. 29, 2001) -- At the heart of modern fuel cells are proton exchange membrane (PEM), through which hydrogen protons pass to meet oxygen and generate electrochemical energy. PEM polymer molecules consist of two components, the most critical of which is an ion conductor. Virginia Tech researchers may have determined how to increase the proportion of ion-conducting material without weakening the co-polymer.
The research will be presented at the 222nd national meeting of the American Chemical Society on Aug. 26-30 in Chicago.
Co-polymer structure can be either random or block. Random copolymers have short, alternating sequences of the monomers (A-B-A-B-A-B), which tends to average the behavior of the components, explains James E. McGrath, university distinguished professor at Virginia Tech and leader of the fuel cell materials research group.
The molecules of block-copolymers consist of 5 or 10 segments of one monomer and then 5 or 10 segments of the second monomer (AAAAA-BBBBB-AAAAA-BBBBB…). "With block copolymers, you get contributions from both components that are not a simple averaging," says McGrath.
"We are trying to see if we can fool mother nature. It appears that constructing block copolymers will allow us to control the conductivity and morphology of the material -- to increase the conductive monomer without weakening the total polymer strength."
Ordinarily, when the conducting monomer exceeds 50 percent of the copolymer, water uptake reduces the polymer to a highly swollen gel. Research is being presented for the first time that demonstrates a block copolymer with lower water uptake with good proton conductivity compared with a random copolymer of the same composition.
The paper, "Synthesis of polyarlylene ether block copolymers containing sulfonate groups ( PMSE 309)," will be presented Wednesday, Aug. 29, at 1:35 p.m. at McCormick Place South, Room S104B, Level 1, by Virginia Tech postdoctoral associate Feng Wang. Co-authors are postdoctoral associate Yuseung Kim, Ph.D. chemical engineering student Mike Hickner, Tom A. Zawodzinski of Los Alamos National Laboratory, and chemistry professor McGrath.
The research is sponsored by the Office of Naval Research.
Contact for more information:
James E. McGrath, University Distinguished Professor & Ethyl Corp Chair of Chemistry