Ac conductivity of poly(N-methylpyrrole)

The dielectric constant epsilon'(omega) of lightly doped poly(N-methylpyrrole) films have been investigated in the temperature range 77-350 K and in the frequency range 100 Hz-1 MHz. In the low-temperature region the measured a.c. conductivity can be described by the relation sigma(omega) = A omega(s), where the exponent s is found to be less than unity. At high temperatures the conductivity remains strongly frequency dependent but the dependence becomes weak at low frequencies. The temperature and frequency dependences of a.c. conductivity sigma(omega) can be qualitatively explained by the contributions from two mechanisms, one giving rise to a broad dielectric loss peak having a distribution of relaxation times, and the other giving a linear dependence of conductivity on frequency.