Spin susceptibility and its relationship to structure in perchlorate doped polyacetylene in the intermediate dopant-concentration region

We present the results of ESR, thermoelectric power, and resistivity measurements for perchlorate doped polyacetylene. An anomaly similar to a spin-gap was observed in the spin susceptibility in the intermediate dopant-concentration region. Since a corresponding anomaly was not observed in the thermoelectric power, the comparison leads us to conclude that the anomaly is associated with spin–charge separation, in relation to the formation of charged soliton-like carrier, as a result of phase separation. The resistivity data show a decreasing tendency in the activation energy on the low-temperature side of the transition, suggesting a change in carrier transport. The absence of similar data in previous reports is discussed in terms of structural difference in polyacetylene chains. The low-temperature heat capacity measurement carried out as a function of the dopant-concentration revealed that the chain arrangement to form channels to accommodate the dopants is almost formed at the initiation of doping.