EFFECTS OF DOPING ON THE CRYSTAL-STRUCTURE OF POLY(3-ALKYLTHIOPHENE)

The changes in the crystal structure of poly(3-alkylthiophene)s resulting from doping have been studied by X-ray diffraction measurements of electrochemically doped poly(3-alkylthiophene) films. The lattice parameter a, which corresponds to the distance between main chains along the side alkyl chain, increases upon doping, while the lattice parameter b, which corresponds to the distance between neighbouring conjugation planes, decreases slightly upon doping. The variation in the lattice parameters depends on the size of dopant ion and alkyl chain length. The dopant ion incorporated into the crystal structure of poly(3-alkylthiophene)s has been found to be located in a hexahedral (cuboidal) vacant space in the crystal lattice.