Taiyo Yoshioka

DYEING BEHAVIOR OF HIGH-SPEED SPUN POLY(ETHYLENE TEREPHTHALATE) FIBERS IN SUPERCRITICAL CARBON DIOXIDE

The dyeing behaviors for several types of high-speed and normal speed spun poly (ethylene terephthalate) fibers were compared in supercritical CO2 fluid. At lower temperature and pressure, the high-speed spun fibers, which had inherently larger crystallite sizes and lower birefringence, showed a larger dye uptake than the other fibers. However, when the supercritical conditions were elevated to 125°C and 230 bar, the dye uptake of both types increased markedly and the difference in dye uptake between the fibers became small. This suggests that the swelling of fibers in supercritical CO2 fluid exceeded a certain degree and then the diffusion of dye molecules was promoted. The swelling also promoted the rearrangement of molecular chains and permitting cold crystallization to occur. The modification of fiber structure through the dyeing in supercritical CO2 fluid was serious especially for the fibers whose inherent structure was not so well developed.

Electron microscopy and diffraction of radiation-sensitive nanostructured materials

Soft matter research of natural organic and synthetic nanomaterials is an area in nanoscience and technology that has been growing particularly quickly in recent years. The materials under investigation are sensitive to high‐energy electrons. Any structure characterization using electron microscopy thus requires special care. First, we illustrated this on naturally grown nanotubes observed by normal and cryogenic scanning electron microscopy. Second, we studied the ordering and orientation of the mesophase in template‐grown nanotubes and nanorods containing discotic liquid crystals without and with doping, as desired. For these studies, we mainly used transmission electron diffraction and microscopy at low‐dose conditions, high‐efficiency image acquisition, and cryoprotection of the structures at liquid helium temperature. Additional analytical information was obtained by electron energy filtering observations.

Morphology of high-speed spun poly(ethylene-2,6-naphthalene dicarboxylate) fiber and its structural changes by the treatment in supercritical carbon dioxide fluid

An alkaline etching for high-speed spun poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) fibers revealed that these fibers have a well-developed fibrillar structure. From a comparison between the morphologies for PEN and poly(ethylene terephthalate) (PET) fibers, the high-speed spinning technique is useful to develop the fibrillar structure in both fibers. Treatment with supercritical carbon dioxide fluid promoted local rotation of the molecular chains for PEN and caused the crystal transition from β- to α-form more markedly as compared with the pressurized hot water treatment.

Transmission Electron Microscopic Investigation of the Morphology of High-Speed Spun Poly(Ethylene Terephthalate) Fibers

Permanganic etching was performed on high-speed spun (HSS) and regular fibers of poly(ethylene terephthalate) (PET), and their surface morphologies were investigated via the two-stage carbon replica method using a transmission electron microscope (TEM). The HSS PET fibers, with disordered amorphous regions, showed peculiar surface morphology; many small warts corresponding to the pits of etched disordered amorphous regions were observed. Such unevenness, however, was hardly observed on the surface of the permanganic-etched regular PET fibers, with well-oriented amorphous regions, or on the surface of alkali-etched HSS PET fibers. The permanganic etchant removed the disordered amorphous regions more preferentially compared with the alkali etchant.

Transformation of Coiled α-Helices into Cross-β-Sheets Superstructure

The fibrous silk produced by bees, wasps, ants, or hornets is known to form a four-strand α-helical coiled coil superstructure. We have succeeded in showing the formation of this coiled coil structure not only in natural fibers, but also in artificial films made of regenerated silk of the hornet Vespa simillima xanthoptera using wide- and small-angle X-ray scatterings and polarized Fourier transform infrared spectroscopy. On the basis of time-resolved simultaneous synchrotron X-ray scattering observations for in situ monitoring of the structural changes in regenerated silk material during tensile deformation, we have shown that the application of tensile force under appropriate conditions induces a transition from the coiled α-helices to a cross-β-sheet superstructure. The four-stranded tertiary superstructure remains unchanged during this process. It has also been shown that the amorphous protein chains in the regenerated silk material are transformed into conventional β-sheet arrangements with varying orientation.

Composite structure of liquid crystal/polymer nanotubes revealed by high-angle annular dark-field scanning transmission electron microscopy.

We have applied high-angle annular dark-field microscopy to the characterization of the structure of template-grown nanotubes composed of a polymer and a discotic liquid crystalline material. Selective staining of the liquid crystal phase with ruthenium tetroxide was used to develop adequate Z-contrast that allows us to distinguish between the two phases. At appropriate staining conditions, we could clearly visualize, in the annular dark-field mode, a 5-15-nm thin liquid crystalline layer precipitated on the inner surface of the polymer tubes. Cryo-electron diffraction has shown high alignment of the discotic columns within the layer parallel to the tube axis. However, although the polymer/liquid crystal phase separation is almost complete, the wetting behavior of the polymer in relation to the template appears to be sensitively influenced by kinetic factors.

Compatibility Evaluation of Non-Woven Sheet Composite of Silk Fibroin and Polyurethane in the Wet State

SF/polyurethane composite non-woven sheet was fabricated to evaluate the cardiovascular tissue engineering materials in the wet state. The compatibility and microstructure analyses were carried out on the fabricated SF/polyurethane composite non-woven sheet by thermal analysis and solid-state NMR analysis in the wet state. To evaluate the modulus of elasticity, a tensile test was performed and supported with dynamic viscoelasticity and mechanical analysis. Results showed that SF/polyurethane composites form domains within the non-woven sheet and are in a finely dispersed state while maintaining their structures at a scale of several tens of nm. Moreover, an increase of the loss tangent with low elastic modulus proved that a micromolecular interaction occurs between silk fibroin (SF) and polyurethane molecules.

Evaluation as Biomaterials of Silk Fibroin Degummed by Different Method

要 旨 本研究では生きた蚕から直接取り出した絹糸腺 フィブロイン (SGF)と精練糸を再溶解・凍結乾燥して得た スポンジ状の再生フィブロイン (RSF)の二種類のフィブロ インから,エレクトロスピニング法によりナノファイバー 不織布を作製し,構造,力学特性,組織学的特性の評価を 行った.固体NMRを用いた構造評価では二種類の不織布の 二次構造に大きな差異はみられなかったが,水中での引張 試験では SGFの方がRSFと比較し,破断強度やヤング率の 値が高いことが示された.この力学特性の違いは,RSFの 精練時に起こる分子量低下により,RSFの分子どうしのか らみ合いが SGFより少ないことに起因すると考えられる. 組織学的評価では,SGF不織布がマウスの皮下移植後 4週間で石灰化しないこと,多核巨細胞の貪食により緩やかに分解され ていることが確認された.In vitro試験では,マクロファージによる炎症性が各フィブロインで同程度であることが示された.

Stacked-Lamellar Structure in High-Speed Spun PET Fibers as Revealed by TEM

Morphological study of high-speed spun poly(ethylene terephthalate) (HSS-PET) fibers spun at 6 km/min was performed by a combination of alkaline etching, surface replica method, and transmission electron microscopy. In the two-stage replica of the alkaline-etched fiber, the stacked-lamella-like structure was observed, in which lamella-like striations were stacked in a direction leaning at about 40° away from the fiber axis. The spacing between the adjacent striations, namely the lamellar periodicity, was measured to be 10–30 nm. We have proposed that the stacked-lamellar structure, which is mainly composed of mosaic lamellar crystals and has the extended-chain crystals connecting the adjacently stacked lamellae, is an appropriate model for the fiber structure of HSS-PET fibers.

TEM observation of crystalline morphology of a novel cyclic compound, 1,3,5,7-tetraoxacyclononan

1,3,5,7-Tetraoxacyclononan (TOCN) was crystallized by cooling down to -20°C and then examined by transmission electron microscopy (TEM) at about -70°C with a cryo-transfer specimen holder. Long rodlike crystals and short lath-like ones of TOCN were recognized, and most of the rodlike ones were too thick for TEM observation. Some of fine tips of the rodlike crystals and most of the lath-like ones were, however, thin enough to take their selected-area electron diffraction patterns which showed that each of the crystals is highly crystalline like a single crystal (or like a twin crystal whose twin plane is parallel to the long axis of the crystal). Together with these rodlike and lath-like crystals, ill-formed crystalline aggregates of TOCN were also recognized.