Kazuo Ikezaki

Thermally stimulated currents from corona‐charged polypropylene films: A thermal effect of vacuum deposition of metallic electrodes

It is demonstrated that the thermally stimulated currents (TSC) from positively or negatively corona‐charged polypropylene strongly depend on the order of the following two processes: a process of vacuum deposition of Al electrodes on the sample polymer and a process of heat‐treatment of the polymer. Observed results are explained by a thermal effect which is introduced during the vacuum deposition of metallic electrodes. This thermal effect of the vacuum deposition of metallic electrodes is the largest for Al and the smallest for Bi among Al, Au, Ag, and Bi. Observed TSC spectra have three peaks at about 68, 142, and above 147 °C for positively charged samples and four peaks at about 48, 90, 142, and above 147 °C for negatively charged samples, respectively. Origins of these TSC peaks are discussed in some detail.

Wire bonding over insulating substrates by electropolymerization of polypyrrole using a scanning micro-needle

Abstract Electrically conducting wires 10–200 μm in diameter were controllably formed over electrically insulating substrates by electropolymerization of a conducting polymer using a scanning micro-needle. The conductivity of the wire was estimated from the I-V characteristics to be about 0.5–200 S cm −1 which is not inferior to the reported conductivity of an electrochemically polymerized polypyrrole (PPy) film. Wires were formed like bridges between two conducting electrodes over glass substrates. This technique can be used for wire bonding of elements or electrodes.

A method for detection and visualization of charge trapping sites in amorphous parts in crystalline polymers

A simple method was proposed to detect charge traps in amorphous regions of crystalline polymers. The proposed method is a combination of two experiments: observation of thermally stimulated current spectra and visualization of charged areas for sample polymers with and without organic solvent vapor induced charge decay. By this method charge traps in spherulitic PP were directly related to its higher order structure. The shallow traps in the spherulitic PP preferentially exist in the amorphous regions of interfacial and peripheral parts of PP spherulites, while the deep traps in the crystalline regions at the central parts of the spherulites.

Drawing and annealing effects on thermally stimulated currents in polypropylene films

Thermally stimulated currents (TSCs) were examined in a temperature range from room temperature to 170 °C for positively corona‐charged polypropylene films which were, before charging, uniaxially cold drawn to different drawing ratios D up to 3.5 or were annealed at different annealing temperatures Ta after drawn to D=3. Two main TSC bands P+1 and P+2 were observed around 60 and 140 °C, respectively. The peak temperature of P+1 strongly depended on D and Ta: It shifted toward higher temperature by drawing while it turned to shift toward lower temperature by annealing.

CHARGE STABILITY OF TPX FILM ELECTRETS

Abstract Charge stability of poly (4-methyl-1-pentane) (TPX) film electrets was evaluated by observing their isothermal surface potential decay under various environmental conditions. Observed results were compared with those of polypropylene and polyethylene electrets. TPX electrets were extremely stable in humid atmosphere, while they rapidly decayed when exposed to acetone or cyclohexane vapours. For TPX electrets exposed to acetone vapour, temporary decrease and recovery in the surface potential were found. These phenomena were explained in terms of a screening effect of acetone molecules on the trapped charges in the electrets.

Charge Trapping Sites in Spherulitic Polypropylene

Charged areas of spherulitic polypropylene (PP) samples were visualized by a simple technique of attaching oppositely charged fine dye particles. A combination of this visualization technique and thermally stimulated current (TSC) spectroscopy was applied to identify the regions where shallow and deep charge traps exist densely in positively corona-charged spherulitic PP. The shallow and deep traps in the PP sample are directly related to its two TSC bands, BL and BH, appearing at temperatures around 60°C and above 100°C, respectively. From visualized charge patterns of the PP samples with and without thermal cleaning of the BL band, it was found that the shallow traps mainly exist in the boundaries and the peripheral regions of spherulites while the deep traps are located in the central parts. Furthermore, the relative numbers of the shallow and the deep traps in the PP spherulites were estimated and found to depend on spherulite size: the ratio of shallow to deep traps decreased from 60/40 for 130–190 µm spherulites to 43/57 for 320–400 µm spherulites.

Formation of electrically conducting polypyrrole fine lines in arachidic acid Langmuir-Blodgett films

A new method is proposed for preparing electrically conducting fine lines in Langmuir-Blodgett films: during transference of arachidic acid L film containing pyrrole monomers to an indium-tin-oxide (ITO)-coated glass substrate, a voltage was applied between the ITO and the platinum counterelectrode dipped in the water subphase. From microscopic observations and conductivity measurements, it was confirmed that conducting filaments of polypyrrole were formed by this new method along the contact line between the substrate and the water surface by electrochemical polymerization of pyrrole monomers in an arachidic L film.

Thermally stimulated currents from positively corona‐charged polypropylene films

Thermally stimulated currents from positively corona‐charged polypropylene films which were heat treated at various temperatures have been studied in the temperature range 20–165 °C. Three peaks are observed in the TSC spectra. Intensities of these peaks strongly depend on the thermal history of the sample films. A thermal effect of the TSC, which has been introduced during vacuum deposition of metallic electrodes on the sample films, is demonstrated. Observed results suggest that the electrical trap properties in polypropylene depend on the fine structure of the polymer.

Molecular sifter using space controlled Langmuir-Blodgett films by fullerene molecules

Abstract We have found that the intermolecular spacing of an arachidic acid (C 20 ) Langmuir–Blodgett (LB) film can be controlled by introducing a variable amount of spacer molecules such as fullerene (C 60 ) into the film. Using this characteristic, several kinds of mixed LB films, composed of C 20 and C 60 , were prepared and the adsorption characteristics of gas molecules, namely phytoncid (e.g. limonene, α -pinene), to these films were studied using a quartz crystal microbalance. The dependence of the amount of the gas adsorbed on the number of layers reveal that the permeability of the gas molecules into the LB films remarkably increases with an increase of the intermolecular spacing of LB films. Gas molecules with different sizes or structures were sifted by using C 60 containing LB films. This characteristic of the LB films containing C 60 can be applied to a novel gas sensor with a molecular sifter function.

2-D lattice constant control in lb films containing pyrrole

Abstract Pyrrole (Py) was used as a spacer molecule and we studied the structural phase transition of two-dimensional (2-D) crystal latti ce of the arachidic acid (C 20 ) Langmuir-Blodgett films using atomic force microscopy. It was found that when quantity of Py in the Langmuir-Blodgett film is increased, the molecular occupation area of C 20 molecules increased and that the crystal lattice changed as follows : “oblique → hexagonal → rectangular”. These structural phase transitions were compared with the computer simulation using 3-D model of the molecules by molecular mechanics.