Masaharu Fujii

Fractal character of DC trees in polymethylmethacrylate

The fractal dimensions of DC trees in polymethylmethacrylate have been investigated using the self-correlation function. The fractal-established range is proportional to the tree length for both positive and negative polarities of the applied voltage. For positive polarity, the fractal dimension increases with increasing inception voltage and saturates at 1.5 to 1.6. For negative polarity, the fractal dimension is nearly constant, approximately=1.5, as a function of voltage. >

Fractal Structure of Electrochemically Polymerized Polypyrrole and Growth Process as Function of Monomer Concentration, Electrolyte Concentration and Applied Voltage

By the electrochemical method in the needle-circle electrode configuration, polypyrrole has been found to grow with two kinds of growth patterns; three-dimensional and two-dimensional growth patterns depending on the polymerization conditions such as condition of electrolyte and monomer and applied voltage. The conditions of pattern formation are found to be classified into three regions, 3-D growth, 2-D growth and 3-D+2-D growth regions. Three-dimensional growth model has been proposed from the growth condition. Influence of protuberance at the surface on the growth pattern by the electrochemical polymerization has been taken into consideration for the understanding of the patterns. The pattern of 3-D growth has been found to be fractal in the small scale region using the density correlation function.

Measurement of Nonsymmetrical Electric Field Vector Distribution in Nitrobenzene Using Electrooptic Method

The three-dimensional nonuniform electric field vector distribution was measured in a nonsymmetrical electrode system using the Kerr electrooptic effect with the reconstruction technique modified by computed tomography (CT). The intensity of the light transmitted through a dielectric liquid in nonuniform field was detected at many points on one plane. It was found that the nonuniform electric field in the liquid can be measured three-dimensionally and visualized.

Observation of Electrochemical Polymerization Pattern of Conducting Polymer and Its Interpretation by Fractal Dimension

Characteristic growth patterns of conducting polymers prepared by the electrochemical polymerization method have been found to be strongly dependent on the polymerization conditions and undergo dramatic change during their growth. In polypyrrole, three types of growth one-, two- and three-dimensional growth, have been observed depending on the condition. These are discussed in terms of fractal dimension.

Anomalous Temperature Dependence of Electrical Conductivity in Polythiophene Derivatives Substituted with Long Alkyl Chain

The electrical conductivity of poly(3-alkylthiophene)s such as poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-octylthiophene), poly(3-decylthiophene) and poly(3-dodecylthiophene) increases with increasing temperature. However, after attaining a maximum value, it decreases with further temperature increases. Hysteresis has also been observed in the temperature dependence of conductivity during heating and cooling cycles. This anomaly is interpreted in terms of the strong influence of molecular conformation change on carrier scattering.

Neuron-type polypyrrole device prepared by electrochemical polymerization method and its properties

Abstract Conducting polymer, polypyrrole, with a neuron-like pattern has been prepared electrochemically using a needle-to-circle electrode on a glass substrate or a PET film. Two neuron-type conducting polymer has been connected and thus a neural network-type conducting polymer has been made. This neuron-type device has a characteristic of learning or memory effect.

Kerr Effect for Three-Dimensional Electric Fields

An optical method using the Kerr effect is useful to measure electric fields in dielectric liquids without disturbing the field. A conventional relation of the Kerr effect cannot be applied to the measurement of a three-dimensional field, the direction of which is not always perpendicular to an incident light. We have derived the relation of the Kerr effect which can be applied to three-dimensional measurement and confirmed it experimentally.

Two-Dimensional Kerr Electrooptic Measurement of Nonuniform Electric Fields by CT Method

It is very difficult to measure nonuniform electric field distributions in insulators. The optical measurements of the electric field were investigated in nitrobenzene using the Kerr effect. A sphere-to-sphere electrode or a sphere-to-plane electrode system was used to produce the nonuniform electric field. A rectangular test cell was made of teflon with two glass windows. A He-Ne laser was used for a light source. The intensity of the light transmitted through the cell was measured with a photodiode. The two-dimensional electric field distribution expressed in absolute value was reconstructed by the computed tomography (CT) method. The measured electric fields were compared with the theoretical one and good agreement was obtained.

Two-dimensional growth of polypyrrole with a fractal pattern and dependence of pattern on polymerization condition

Polypyrrole with a fractal pattern has been prepared by electrochemical polymerization method with the needle-circle electrode configuration in electrolyte solution of acetonitrile containing sodium p-toluenesulfonate and monomer. Under certain polymerization conditions, the polypyrrole has been polymerized not only on the needle but also on the bottom surface of the cell and has grown to the circle electrode with branching. The growth patterns on the cell are classified into three types: broad leaf-like, DLA-like and needle-like patterns. The patterns depend on the polymerization conditions such as applied voltage and concentrations of electrolyte and monomer. The patterns can be controlled by the polymerization conditions. A neural network pattern has been synthesized by changing the condition during the polymerization. The fractal dimension of the pattern has been calculated from the self-correlation function, which is obtained using a fast Fourier transform technique.

Electrochemical growth of poly(3-dodecylthiophene) and its interpretation as a fractal

Poly(3-dodecylthiophene) with a fractal pattern has been prepared by an electrochemical method on the surface of a solution. The fractal dimension has been calculated by four methods. At an applied voltage of about 10 V, the fractal dimension indicates a maximum value of 1.79. The growth rate in the radial direction has a maximum value at about 7.5 V and the conductivity in the iodine doped state is a maximum for the sample prepared at a voltage of about 15 V in accordance with the voltage dependence of fractal dimension. Although the conducting polymer is usually doped by the counter-ion, BF4-, in polymerisation an undoped region has been observed in the branches of the conducting polymer at high voltage. The time dependence of the fractal dimension has been calculated and the rise time has been found to depend on the applied voltage. By short circuiting the electrode after the polymerisation, the undoped region in the branch has proceeded concentrically from the tip of the growth to the needle electrode.