Miao, Zhihui, Faith J. Scott, Johan Van Tol, Russel Bowers, Adam S. Veige, and Frederic Mentink-Vigier. “Soliton Based Dynamic Nuclear Polarization: An Unexpected Overhauser Effect in Cyclic Polyacetylene at High Field and Room Temperature,” December 26, 2023.
https://doi.org/10.26434/chemrxiv-2023-txxmf.
Polyacetylene, a versatile material with an electrical conductivity that can span seven orders of magnitude, is the prototypical conductive polymer. In this letter, we report an unexpected and unprecedented Overhauser Effect that increases with temperature, observed under high magnetic field of 14.1 T, in both linear and cyclic polyacetylene. Significant NMR signal enhancements ranging from 24 to 45 are obtained. The heightened sensitivity enabled the characterization of chain defects at natural abundance. The absence of end methyl group carbon-13 signals provides proof of the closed-loop molecular structure of the cyclic polyacetylene. This efficiency of the soliton based Overhauser Effect DNP mechanism at high temperature and high field holds promise for applications and extension to other conductive polymer systems.