Heat capacity, electron paramagnetic resonance, and dc conductivity investigations of dispersed polyaniline and poly(ethylene dioxythiophene)

Dispersible polyaniline (PANI) exhibits a dc conductivity σ ≈ 0.1 S/cm when it's doped with poly(styrene sulfonic acid) (PSS) such that the number of sulfate ions per two-ring PANI unit (y) is 2. On increasing the dopant amount to y = 12 the conductivity σ drops to 10−5 S/cm. The EPR magnetic susceptibility results on these samples give nearly the same density of states at the Fermi level N(EF) ≈ 0.65 states/eV 2-rings. With y′ defined as the number of sulfate groups per three-ring PEDOT unit, PSS doping of poly(ethylene dioxythiophene) (PEDOT) gives σ ≈ 10−1 S/cm at y′ = 5.7 and σ ≈ 10−5 S/cm at y′ = 45.9. Like PANI, N(EF) ≈ 0.55 states/eV 3-rings is same at both the doping levels. The EPR linewidth for these samples in the less conducting state is found to be large compared with the mote conducting state, although the overall temperature dependence in the two states is qualitatively the same. These results are consistent with the inhomogeneous disorder models.