Dielectric Relaxation of Polyacrylonitrile in Its Pristine and Cyclized Stage

The dielectric behavior of polyacrylonitrile (PAN) in its pristine and cyclized stages was investigated. A PAN homopolymer displays a strong secondary relaxation at an activation energy of E a = 111 kJ/mol in the pristine stage and a weak relaxation at E a = 48 kJ/mol in the cyclized stage. By contrast, a PAN copolymer with itaconic acid, which is used in carbon fiber production, displays a strong secondary relaxation at E a = 134 kJ/mol in the pristine stage and two relaxations with activation energies of E a = 24 kJ/mol for the lower frequency relaxation and E a = 9 kJ/mol for the higher frequency relaxation. No relaxations were found for either polymer in the aromatized stage. The relaxation spectra were interpretated in terms of the Havriliak−Negami (HN) function.