Effects of thermal treatment on properties and higher order structure of poly(3-alkylthiophene) and their relaxation behavior

Summary form only given. Effects of thermal treatment on electrical and optical properties and higher order structure of poly(3-alkylthiophene) film and their relaxation behaviour have been studied. Conductivity of poly(3-dodecylthiophene) film decreased remarkably after thermal treatment at temperature below 120 /spl deg/C, though the ESR spin density and the band gap energy evaluated from both photoluminescence and visible absorption spectra did not change. The orthorhombic lattice structure of poly(3-dodecylthiophene) was found to elongate perpendicularly to the conjugation plane of the main chain. After the heat treatment, clear relaxation was observed in both conductivity and the lattice structure. These results suggest that changes in probability of carrier hopping between main chains result in changes in conductivity upon thermal treatment and relaxation. FT-IR measurements indicated that conformational isomerization of side alkyl chain upon thermal treatment results in larger content of the Gauche form conformation in the side chain even after the cooling down to the room temperature. During thermal relaxation of lattice structure and conductivity, slow relaxation of conformation of side alkyl chain was also observed. Correlation between content of Gauche conformation in the side chain and lattice parameters was discussed as an origin of the unique change in conductivity.