Helical peptide structure improves conductivity and stability of solid electrolytes
ORAL
Abstract
Polymers electrolytes with adding salt or tethered ions on the backbone have been studied for decades with random coil backbones. The role of a helical secondary structure on ionic conductivity has not been investigated for solvent-free systems. Cationic polypeptides with ammonium groups were prepared with either random coil or helical secondary structure using monomers with different chirality but the same polymer chemistry. The degree of polymerization was controlled from N= 50 – 1000, and longer helices lead to higher conductivity. The random coil peptide analogues show substantially lower conductivity and are consistent with prior works. This is attributed to the role of the macrodipole along the helix which grows with backbone length and substantially increases the dielectric constant. X-ray scattering a more intense ion-ion correlation peak with longer helical peptides and are more pronounced than for random coils. The helix is stable in the solid state based on circular dichroism and FTIR up to at least 200 °C. The hydrogen bonding of the helix also imparts thermal and electrochemical stability, while allowing for facile dissolution back to monomer in acid. Peptide electrolytes demonstrate the important role of secondary structure on conductivity and stability.
*This work is partially supported by the United States National Science Foundation (NSF CHE 17-09820 to J.C. and CHE 19-05097 to J.C. and P.V.B. for peptide synthesis, and DMR-1751291 to C.M.E. for polymerized ionic liquid physics). The work is also partially supported by the US Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering under award #DE-SC0020858 (ionic conductivity and dielectric measurements). The authors acknowledge the facility and instrumental support from the Materials Research Laboratory, the SCS NMR Laboratory, Beckman Institute, University of Illinois Urbana-Champaign. Specifically, the Q-Tof Ultima mass spectrometer was purchased in part with a grant from the National Science Foundation, Division of Biological Infrastructure (DBI-0100085).
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Publication:Published paper: Helical peptide structure improves conductivity and stability of solid electrolytes
