C13solid-state NMR study of polyacenic materials

A ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ high-resolution solid-state NMR study has been performed with respect to polyacenic materials which were prepared by pyrolytic treatment of phenolformaldehyde resin under different temperatures. A Knight shift was observed in the samples treated at temperatures higher than 640 °C which show rather high electrical conductivities. The material was found to be composed of electrically high- and low-conductive parts, the content of the former increasing as the pyrolytic temperature is raised. The path of conduction carriers is concluded to lie on the outer edge of metallic islands consisting of condensed aromatic rings.