Shuzo Aoki

Electrical conductivity of drawn polythiophene films

Abstract We have investigated the electrical conductivity of drawn polythiophene films doped under various conditions. By vapour-phase iodine doping at 25 °C, a drawn film shows an increase in conductivity to a value greater than 150 S/cm, whereas an undrawn film has a conductivity of 60 S/cm. The conductivity of the drawn film increases with increasing dopant concentration and reaches the extremely large value of 1 kS/cm for a film heavily doped at higher temperature. A metal-like temperature dependence of the d.c. conductivity between 120 °C and 50 °C is observed in such a drawn and heavily-doped film.

Solvent effect on electrochemical polymerization of aromatic compounds

Abstract The effects of the electrolytic conditions on the outcome of the electrochemical polymerization of pyrrole, thiophene and benzene were investigated. The solvent nucleophilicity, represented by the donor number, was found to affect the selectivity of the film formation. These solvent effects were explained in terms of the radical cation character of the intermediate and were quite similar to that of cationic polymerization of vinyl monomers. The solvent polarity, defined by the RPM value, was related to the current density during the reaction.

Crystal Structure of Drawn Polythiophene Film

Abstract The crystallographic structure of the drawn polythiophene film prepared electrochemically was investigated by a wide angle x-ray diffraction. The film showed the distinguishable pattern. The results obtained indicated the crystal structure of an orthorhombic unit cell with lattice constants a = 10.8 A, b = 4.74 A and c = 7.56 A, which was very different from that proposed for the chemically prepared polythiophene powder.

Electrical conductivity of elongated polypyrrole film

The mechanical and electrical properties of elongated polypyrrole film have been investigated. The maximum elongation ratio of electrochemically prepared polypyrrole film increased on decreasing the elongation speed and reached 0.55. The simultaneous measurement of tensile stress and electrical resistance of the film during elongation has also been carried out. The approximately constant resistivity of the film by weight or volume was observed during measurement at slow elongation speeds; this provides evidence that the polypyrrole is a low-dimensional conductor. The electrical conductivity of the elongated and relaxed films increased in proportion to the square of the elongation ratio. The films with an elongation ratio of over 0.25 exhibited anisotropy in the conductivity.

Temperature dependence of mechanical properties of electrochemically prepared polypyrole film

Abstract The mechanical and thermal properties of an electrochemically prepared polypyrrole film are studied. The Youngs modulus of this film decreases slightly below 140 °C and steeply above 140 °C, while the tensile strength decreases linearly with increasing temperature. The inflection point of the Youngs modulus exists at around 140 °C, which coincides with the temperature at the main peak of the temperature variation of the mechanical loss factor, tan σ. It seems that the main peak of tan σ results from the glass transition of this polymer. The film has a very high thermal diffusivity constant of 0.028 cm 2 /s at room temperature.