Thermal transformation of local to extended electronic states in polymers

Electron-energy-loss spectroscopy is used to show the nature of electronic states accompanying structural changes induced by thermal treatment of polyacrylonitrile. At moderate temperatures both localized and delocalized $\pi$-electron systems are produced, while at higher temperatures, below the graphitization onset, delocalized states similar to those in graphite appear. Models often used to explain the transport properties of heat treated polymers are spectroscopically confirmed.