CHANGE IN CRYSTAL-STRUCTURE OF POLY(3-ALKYLTHIOPHENE) UPON DOPING

Crystal structures of poly(3-alkylthiophene) having various kinds of the side chain length (-CnH2n+1) ranging from 4 to 18 have been studied by X-ray diffraction measurement in the neutral and in the doped states. Dependence of the lattice parameters of orthorhombic lattice of P3AT was clarified. The lattice parameters were also varied upon electrochemical doping, indicating incorporation of the dopant anions into the crystal region of poly(3-alkylthiophene). Anomalous decrease in parameter b was observed upon doping, contrary to increase in parameter a. The position and the orientation of the dopant ion within the orthorhombic lattice were also discussed.