The relationship between electrical transport property and microscopic mole
cular motion in poly(3-octylthiophene) (POT) was investigated. We observed
the temperature gradient of thermoelectric power S(T) changes at around 220
K and 250K in POTs doped with ClO4- or FeCl4-. NMR results show that the ob
served anomaly in S(T) is closely related to the molecular motion of side c
hain, which might affect the scattering process of conduction electrons.