Masafumi Yamato

Magnetic orientation of poly(ethylene-2,6-naphthalate)

A new finding is reported of the magnetic orientation of poly(ethylene-2,6-naphthalate) (PEN) near its melting point, evidenced by X-ray analyses and magnetic birefringence measurements. Since PEN does not exhibit features characteristic of liquid-crystalline polymers under a polarization microscope, the magnetic orientation was unexpected. The orientation is probably due to some ordered structure susceptible to a magnetic field, but the detail of the structure is not fully understood at present.

Magnetic Alignment in Solid State and Temperature Hysteresis in Aqueous Tetrahydrofuran Solution for Tetrathiafulvaleno[18]annulenes

Tris(tetrathiafulvaleno)dodecadehydro[18]annulene-hexaesters have a multi-functionality that is very sensitive to small differences in the ester side-chain. Self-aggregation of the [18]annulenes in amphiphilic media such as THF-H(2)O (v/v, 1:1) either produce a fibrous structure or result in temperature hysteresis of the color and (1)H NMR signals. This temperature hysteresis in solution is due to both strong self-aggregation behavior and unique cluster formation in a binary solution of THF and water.

Determination of Anisotropic Diamagnetic Susceptibility of Polymeric Fibers Suspended in Liquid

Anisotropic diamagnetic susceptibilities of polymeric fibers in liquid suspensions determined by means of the method proposed recently by us were compared with those obtained by other methods including superconducting quantum interference device (SQUID) and magnetic torque meter. Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers and carbon fibers (CF) were used for the measurements. Both fibers exhibited positive diamagnetic anisotropy, i.e., χa≡χ//-χ⊥>0, where the parallel direction is taken as the fiber axis. The values of anisotropic susceptibilities determined by these three different methods were in good agreement with each other, demonstrating the usefulness of the proposed method for the measurement of a single fiber.

Birefringence of silica hydrogels prepared under high magnetic fields reinvestigated

Birefringence is an indicator of structural anisotropy of materials. We measured the birefringence of Pb(II)-doped silica hydrogels prepared under a high magnetic field of various strengths. Because the silica is diamagnetic, one does not expect the structural anisotropy induced by a magnetic field. In previous work [Mori A, Kaito T, Furukawa H 2008 Mater. Lett. 62 3459-3461], we prepared samples in cylindrical cells made of borosilicate glass and obtained a preliminary result indicating a negative birefringence for samples prepared at 5T with the direction of the magnetic field being the optic axis. We have measured the birefringence of Pn(II)-doped silica hydrogels prepared in square cross-sectional cells made of quartz and reverted the previous conclusion. Interestingly, the magnetic-influenced silica hydrogels measured have been classified into four classes: two positive birefringent ones, no birefringent one, and negative birefringent one. Proportionality between birefringence and the strength of magnetic field is seen for the former two.

Effect of a magnetic field on surface structure of the electrode modified with aromatic polymer

abstract An electrode (platinum) was modified with poly (o-phenylenediamine) (PoPD) by electrochemical polymerization in the magnetic field (6T) and without the magnetic field (OT). The modified electrode (PoPD/Pt) surface was investigated using AFM. It was found that the flatness of the modified electrode surfaces was dependent on magnetic field direction. For electrode setup (1), a flat surface is observed. In case (2), the modified surface is very rough. The image of the electrode surface prepared with no magnetic field is the intermediate one between cases (1) and (2).

Magnetic field effects on surface morphology and oxidation-reduction process of polymers prepared by electropolymerization

Abstract The purpose of this paper is intended to study the effect of a magnetic field on electrochemical reactions without the MHD effect. We observed the effect of a magnetic field on the wavelengths (λ max ) of UV-VIS spectra for maximum absorption and the cyclic voltammograms of polypyrrole and poly( o -phenylenediamine) films prepared electrochemistry in a magnetic field. λ max of the polypyrrole films prepared at 6T shifted to longer wavelength, while we could not observed the effect of a magnetic field on λ max of poly( o -phenylenediamine) films. The peaks of redox potential at the curves of cyclic voltammogram for polypyrrole films shifted to lower potential.

Stimuli-responsive hydroxyapatite liquid crystal with macroscopically controllable ordering and magneto-optical functions

Liquid crystals are mostly formed by self-assembly of organic molecules. In contrast, inorganic materials available as liquid crystals are limited. Here we report the development of liquid-crystalline (LC) hydroxyapatite (HAp), which is an environmentally friendly and biocompatible biomineral. Its alignment behavior, magneto-optical properties, and atomic-scale structures are described. We successfully induce LC properties into aqueous colloidal dispersions of rod-shaped HAp by controlling the morphology of the material using acidic macromolecules. These LC HAp nanorod materials are macroscopically oriented in response to external magnetic fields and mechanical forces. We achieve magnetic modulation of the optical transmission by dynamic control of the LC order. Atomic-scale observations using transmission electron microscopy show the self-organized inorganic/organic hybrid structures of mesogenic nanorods. HAp liquid crystals have potential as bio-friendly functional materials because of their facile preparation, the bio-friendliness of HAp, and the stimuli-responsive properties of these colloidal ordered fluids.Liquid crystals comprising inorganic species are far less common than their organic-based counterparts. Here, the authors report a magneto-optically responsive liquid crystal based on nanorods of the biomineral hydroxyapatite, representing a new type of biologically-based, dynamic inorganic material.

Magnetic alignment of poly(ethylene terephthalate) in molten state

The magnetic alignment of poly(ethylene terephthalate) in molten state was studied by in-situ birefringence measurement in a magnetic field. The melting point of the sample determined by DSC was 253°C. We observed the increase of birefringence in a molten state at temperatures between 254°Cand 260°C in the magnetic filed (10T). The dependence of the apparent rate of orientation on the annealing time was attributed to the increase in the viscosity due to the structure formation under the lower supercooling condition. The time at which the transmitting light became a maximum increased with the increase in the melting temperature. These results suggested that the residual structure of crystal, which can be aligned magnetically, existed in the molten state and the volume fraction of the residual structure was reduced with increase in the melting temperature.

Study of Sorbed Water on a Trifunctional Epoxy Resin.

三官能エポキシ樹脂は耐熱性に優れた樹脂である. しかし従来からある二官能樹脂より吸湿量が多いため, 絶縁性が劣るという欠点がある. 本研究は吸湿性の改良のための基礎研究で, 近赤外線分光および固体高分解能 13C NMRと 1H NMRの測定を行い, 三官能エポキシ樹脂に収着された水分子が樹脂の中でどのような状態で存在しているのかを考察することを目的とした. 吸湿試料の近赤外線スペクトルから乾燥試料のスペクトルを差し引いた差スペクトル (6300～7600cm-1) は精度良く四成分に分けることができた. 観察される波数位置から収着水の大部分は疎水性ポリマーのPETと同様な状態にあり, 一部の収着水は親水性ポリマーのNylon6の極性基に強く吸着された水分子に近い状態にあることが分かった. また, 固体高分解能 13C NMRよりこの樹脂の吸着サイトはカルポニル基であると推測された. 1H NMRの測定結果から緩和時間の異なる2種類の収着水の存在が示唆され, この結果は近赤外分光の測定結果を支持するものであった.

Study on Dielectric .BETA. Relaxation Process of Aromatic Ester Ether Copolymer.

芳香族高分子のβ緩和の機構を明らかにするため, ポリエチレン-1, 2-ジフェノキシエタン-p, p″-ジカルボキシレート (PEBC) の誘電的β緩和を測定した. PEBCはポリエチレンテレフタレート (PET) に相当するエステル部分を持つ, 芳香族エステルエーテルコポリマーである. PEBCのスペクトルからPETのスペクトルを差し引くことにより得られた差スペクトルは, 損失極大周波数がPETよりも高く, さらに見かけの活性化エネルギーはPETより小さかった. これらのことから, 差スペクトルはPEBCのエーテル部分に起因していると考えられる. っまり, PEBCのβ緩和はエステル基とエーテル基を含む部分の二っの緩和の和で表されることを示している. これは, 芳香族ポリエステルのβ分散に起因する分子運動が, 芳香環に挟まれた屈曲性の高い分子鎖部分の運動であるという先の報告を支持するものである.