Akira Kaito

Helical Carbon and Graphitic Films Prepared from Iodine-Doped Helical Polyacetylene Film Using Morphology-Retaining Carbonization

In this communication, we report a novel preparation of the helical carbon nanofibril-fabricated thin film from the iodine-doped filmy helical polyacetylene through a carbonization process. Carbonization of the helical polyacetylene films by way of iodine doping is found to afford carbon and graphitic films completely preserving morphologies and even helical nanofibril structures.

Oriented thin films of conjugated polymers : polysilanes and polyphenylenes

Abstract In this paper, preparation of uniaxially oriented films of conjugated polymers, polysilanes and poly(p-phenylenes) (PPP) is investigated. Highly oriented thin films of poly(dimethylsilane) (PDMS) were prepared by the friction transfer method. The properties of PDMS films strongly depend on the preparation temperature. At a temperature higher than 210°C, uniform ultrathin films with extremely high orientation were obtained. It is considered that the friction transfer is related to the disorder (hexagonal) phase of PDMS. Other polysilanes, such as poly(diethylsilane) (PDES), poly(di-n-hexylsilane) (PDHS), poly(di-n-butylsilane) and poly(methylphenylsilane) also afforded oriented films by the same method. Oriented films of PPP were prepared by the friction transfer method. The thin films of the polymers were characterized mainly by ultraviolet absorption spectroscopy. The friction-transferred PDMS and PPP had abilities of orienting other materials. The films of polysilanes, such as PDHS, which were cast on the oriented PDMS from solution, were oriented along the PDMS chain direction. Oriented films of some oligophenylenes were obtained by vapor deposition or cast on the friction-transferred PPP. When the friction-transferred PPP film was immersed into the reaction mixture, a newly oriented PPP film were polymerized on the friction-transferred PPP films.

Highly oriented films of poly(dimethylsilylene) by friction deposition

Highly oriented films of poly(dimethylsilylene) on smooth substrates such as glass and quartz plates were prepared by the friction deposition technique. The structure of the oriented film was characterized by polarized optical microscopy, transmission electron microscopy and polarized ultraviolet absorption spectroscopy. The polymer backbone in the film was parallel to the sliding direction. The orientation was confirmed to be dependent on the temperature of substrates during deposition.

Infrared dichroism and visible-ultraviolet dichroism studies on roller-drawn polypropylene and polyethylene sheets

Abstract The crystal and amorphous orientation functions of polypropylene (PP) and high-density polyethylene (HDPE) sheets, stretched by the roller-drawing technique, were measured by means of infrared dichroism and visible-ultraviolet dichroism. The molecular chains in the crystalline and amorphous regions lined up parallel to the draw direction in the roller-drawing process. At higher draw ratio (λ > 7–13), the crystal orientation function approached a constant value, whereas the amorphous orientation function increased monotonically with draw ratio. Film tilting measurements revealed that the deviation from symmetric uniaxial orientation was small for the roller-drawn HDPE and PP sheets. In the case of HDPE, the fraction of—GTTG—,—4TG—, and—GG—sequences decreased, and that of the trans-rich sequences increased in the roller-drawing process. These changes were interpreted in terms of the Peterlin model. The orientation function calculated from visible-ultraviolet dichroism decreased greatly with decreas...

Mechanical and structural properties of extruded strands of blends containing a liquid-crystalline polyester with poly(ethylene terephthalate)

Abstract Mechanical and structural properties of extruded strands of blends of a liquid-crystalline copolyester (LCP), containing p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, with poly(ethylene terephthalate) (PET) were investigated using tensile testing, X-ray diffraction measurements and scanning electron microscopic observation. The extruded strands of the blends consist of a crystalline and oriented LCP phase and an amorphous and unoriented PET phase. The tensile modulus increases almost linearly with increasing LCP content for the strands of the blends of more than 10% LCP content. The LCP component hardly contributes to the improvement of the mechanical tensile properties for the strands of the blends of less than 5% LCP content. The LCP phase tends to form fibrous structures, which orient almost parallel to the direction of extrusion in the blend strands. The fibrils of the LCP component become longer and thinner with increasing extension draw ratio of the blend strands. A relationship between the mechanical tensile properties and the morphology of the LCP phase in the blend strands was discussed.

LCAO MO SCFπ-electron calculations on the magnetic circular dichroism of porphin, protoporphyrin, and porphyrin a

The transition energies, the oscillator strengths, and the A/D values of porphin, protoporphyrin, and porphyrin a were calculated within the framework of the Pariser -Parr-Pople approximation. The calculated values are in reasonable agreement with the experimental data obtained from the absorption and magnetic circular dichroism spectra of metal porphin, low-spin ferrous protoheme, and low-spin ferrous heme a. The magnetic circular dichroism of the Q and Soret bands in the heme a and the protoheme was analysed in terms of an “apparent” A term which originates from the magnetic mixing between the components of the nearly degenerate excited state.

Oriented Films of Poly(p-Phenylene) by Friction-Deposition and Oriented Growth in Polymerization

Abstract Oriented films of poly(p-phenylene) (PPP) were prepared by two methods. One was the friction-deposition technique, in which sliding the solid PPP on the substrate at a controlled temperature afforded a highly oriented film on the surface. In another method, when the friction-deposited film was immersed into the reaction mixture, benzene was polymerized into the oriented PPP film on the friction-deposited substrate. Both oriented films of PPP were characterized by electron microscope and polarized spectroscopic methods.

Oriented films of insoluble polymers by the friction technique

Abstract Highly-oriented films of insoluble polymers, such as poly(dimethylsilylene) and poly(p-phenylene), on smooth substrates were prepared by the friction deposition technique. The structures of films were characterizedby polarized light microscopy, transmission electron microscopy, and polarized ultraviolet-visible light absorption spectroscopy to confirm the uni-directional molecular orientation. Especially, polarized fluorescence spectroscopy revealed highly-polarized photoluminescence from the oriented films.

Hole transport properties of self-organized oligosilane films in a polycrystalline and a mesophase

Carrier transport properties of self-organized oligosilane films were investigated by the time- of-flight transient photocurrent technique in a polycrystalline (C) and a smectic B (S B ) phase. In both phases, a multi-layer structure with a same spacing (24.5 A) was found and clear non-dispersive photocurrent waveforms were observed. Hole mobility in the C phase abruptly decreased at a phase transition to the S B phase.

Molecular orientation dependent photoconductivity of liquid crystalline oligosilanes

Abstract Polysilanes are known to be promising hole transport materials among conducting polymers. Their structure can be better controlled by using single dispersed oligomers. Recently an oligosilane (Me(SiMe 2 ) 10 Me) is found to show a mesophase (S B ). In the mesophase, we have observed unusual negative temperature dependence of photocurrent. This can be explained by temperature dependent molecular orientation, which has been confirmed by polarized UV absorption spectroscopy.