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.