Mutsumasa Kyotani

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.

Helical polyacetylene synthesized under chiral nematic liquid crystals

Abstract We synthesized helical polyacetylene films under asymmetric and anisotropic reaction field consisting of chiral nematic (N * ) liquid crystals. A series of axially chiral binaphthols and chiral phenylcyclohexyl derivatives were used as chiral dopants to induce N * liquid crystals. Acetylene polymerizations were carried out with Ti(O- n -Bu) 4 -Et 3 Al under N * reaction field. Measurements of SEM and CD spectra showed that the polyacetylene films are composed of clockwise or counter-clockwise helical structures not only in fibril but also in each polyene chain. By virtue of its high electrical conductivity of 1.51.8 x 103 S/cm after iodine doping, the helical polyacetylene might serve as a molecular solenoid based on conducting polymer. The helicity of the present film also suggests a feasibility of second-order nonlinear optical material.

Hierarchically Controlled Helical Graphite Films Prepared from Iodine-Doped Helical Polyacetylene Films Using Morphology-Retaining Carbonization

One-handed helical graphite films with a hierarchically controlled morphology were prepared from iodine-doped helical polyacetylene (H-PA) films using the recently developed morphology-retaining carbonization method. Results from scanning electron microscopy indicate that the hierarchical helical morphology of the H-PA film remains unchanged even after carbonization at 800 °C. The weight loss of the film due to carbonization was very small; only 10-29% of the weight of the film before doping was lost. Furthermore, the graphite film prepared by subsequent heating at 2600 °C retained the same morphology as that of the original H-PA film and that of the helical carbon film prepared at 800 °C. The screwed direction, twisted degree, and vertical or horizontal alignment of the helical graphite film were well controlled by changing the helical sense, helical pitch, and orientation state of the chiral nematic liquid crystal (N*-LC) used as an asymmetric LC reaction field. X-ray diffraction and Raman scattering measurements showed that graphitic crystallization proceeds in the carbon film during heat treatment at 2600 °C. Transmission electron microscopy measurements indicate that ultrasonication of the helical graphite film in ethanol for several hours gives rise to a single helical graphite fibril. The profound potentiality of the present graphite films is exemplified in their electrical properties. The horizontally aligned helical graphite film exhibits an enhancement in electrical conductivity and an evolution of electrical anisotropy in which conductivity parallel to the helical axis of the fibril bundle is higher than that perpendicular to the axis.

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.

Synthesis of vertically aligned polyacetylene thin films in homeotropic liquid crystal solvents

Abstract Vertically aligned polyacetylene thin films were synthesized in homeotropic nematic liquid crystal (LC) solvents, in which the homeotropic orientation of an LC, 4-( trans -4- n -pentylcyclohexyl)hexyloxybenzene, is strengthened by addition of newly synthesized LCs having two mesogenic cores, 1,6-bis-[(4- trans - n -pentylcyclohexyl)phenoxy]hexane or 1,8-bis-[(4- trans - n -pentylcyclohexyl)phenoxy]octane. Vertically aligned helical polyacetylene thin films were synthesized by adding a chiral dopant into the same LC solvent in order to induce chiral nematic phase with homeotropic orientation.

Entanglement-free fibrils of aligned polyacetylene films that produce single nanofibers

An aligned polyacetylene (PA) film was synthesized in a macroscopically-aligned nematic liquid crystal (N-LC) solvent using a gravity-flow method. Long and single nanofibers of less than 100 nm in radius were successfully prepared by ultrasonication of the aligned PA film immersed in ethanol. The usual PA film was synthesized in an isotropic solvent, such as toluene, only yielding short and non-dispersed fibers after the ultrasonication due to the entangled fibril morphology. Entanglement-free fibrils of the aligned PA were well-separated into single fibrils through ultrasonication, even without a surfactant.

Horizontally and vertically aligned helical conjugated polymers: Comprehensive formation mechanisms of helical fibrillar morphologies in orientation-controlled asymmetric reaction fields consisting of chiral nematic liquid crystals

Orientation-controlled asymmetric reaction fields consisting of chiral nematic liquid crystals (N*-LCs) were comprehensively studied to elucidate the formation mechanisms of horizontally and vertically aligned helical polyacetylenes (H-PAs). The alignment of the N*-LC was controlled by tuning the concentration of a chiral molecule added as a chiral dopant to a parent nematic LC and/or by using a rod-like molecule used as a vertical orientation inducer. It was found that the horizontal N*-LC gives rise to horizontally aligned H-PAs, and the vertical N*-LC consisting of two types of multilayered arrangements provides U- and V-shaped fibrillar morphologies of vertically aligned H-PAs. The observed formation mechanisms are useful for understanding asymmetric polymerisations of helical conjugated polymers prepared in chiral nematic or cholesteric liquid crystal reaction fields.

Synthesis of well-controlled helical polyacetylene films using chiral nematic liquid crystals

Abstract Helical polyacetylene recently developed is anticipated to show novel electromagnetic and optical properties. We have synthesized for the first time helical polyacetylene films with left- and right-handed screw structures under chiral nematic reaction field. We discuss the influence of the chiral nematic reaction field on film properties, morphology, crystal structure, electrical conductivity, and optical activity. The films are characterized with scanning electron microscopy (SEM), X-ray diffraction analysis, the four-probe method and circular dichroism (CD) spectroscopy.

Thermal behavior, morphology, and mechanical properties of blend strands consisting of poly(ethylene terephthalate) and semiaromatic liquid crystalline polymer

Polymer blends of poly(ethylene terephthalate) (PET) and a liquid crystalline polymer (LCP) [random copolymers of the poly(ethylene telephthalate) and poly(hydroxybenzoic acid)] were prepared by using a twin-screw extruder. Strands were extruded from a capillary die. Extruded strands were stretched in an oven at 80°C. DSC and SEM were employed to investigate the structural properties of the strands. Mechanical properties of the strands were evaluated by a sonic propagation method. DSC investigation suggested that LCP phases may act as a nucleating agent of PET and the orientation-induced crystallization of PET was accelerated by the presence of LCP. An SEM micrograph shows that the LCP phases formed finely spherical domains with a diameter of 0.1-1.0 μm in the PET matrix and large parts of LCP spherical droplets were deformed to fibrils. In the case of unstretched strands, sonic moduli increased linearly with increasing LCP content, because PET was reinforced by LCP fibrils as in the case of glass fiber-reinforced PET. The degree of crystallization of PET also increased with increasing LCP contents. In the case of stretched strands, sonic moduli increased with an increasing stretching ratio due to the orientation-induced crystallization of PET. A larger increasing of the sonic modulus was shown in LCP-containing strands in the regions of a low stretching ratio (1-5), since the orientation-induced crystallization of PET was accelerated by the presence of LCP phases.

Synthesis and properties of helical polyacetylene

Abstract We have synthesized for the first time helical polyacetylene [(CH) x ] with leftand right-handed screwstructures under chiral nematic reaction field. We discuss the influence of the chiral nematic reaction field on film properties, morphology, crystal structure, electrical conductivity, and optical activity. These properties are characterized by scanning electron microscopy (SEM), X-ray diffraction, the four-probe method and circular dichroism (CD) spectroscopy.