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Volume 63, Issue 11
Displaying 1-7 of 7 articles from this issue
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Review Articles
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Tetsuo ASAKURA, Yasumoto NAKAZAWA2006 Volume 63 Issue 11 Pages 707-719
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSSolid state NMR has been successfully used for structural determination of silk fibroins whose single crystals are difficult to prepare. The structure of the crystalline region of silk fibroin from the domesticated silkworm, Bombyx mori, before spinning (Silk I) in the solid state was first determined. For the purpose, several stable-isotope labeled model peptides, (AG)15, were synthesized. Then, several solid state NMR methods; quantitative use of the conformation-dependent 13C CP/MAS chemical shifts, 13C two-dimensional solid-state spin-diffusion NMR and rotational echo double resonance techniques, were used for the structural analysis. The heterogeneous structure of the same silk fibroin after spinning (Silk II) has been also determined with solid state NMR. The structural change from Silk I to Silk II was reproduced using molecular dynamics simulation by considering several external forces applied to the silk fibroin in the silkworm. The structural analyses of Samia cynthia ricini silk fibroin and spider silks have also been reviewed. Finally, designs of new silk-like materials based on these structural information and their productions with Escherichia coli were described.View full abstractDownload PDF (1423K)
Original Papers
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Daisuke SUGAWARA, Hidekazu TAKEYAMA, Takao IIJIMA, Toshiyuki OYAMA, Ma ...2006 Volume 63 Issue 11 Pages 720-726
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSThe modification of acid anhydride-cured epoxy resin with poly[poly(N-phenylmaleimide-alt-styrene)-block-polyoxyethylene] (PMSE) prepared by in situ polymerization was carried out in order to increase the toughness of the cured epoxy resin without loss of flexural strength. The modification with PMSE resulted in microscopic two-phase morphology with PMSE-rich spherical particles dispersed in the epoxy-rich matrix. The introduction of polyoxyethylene segments into the modifier brought about the increased interfacial interaction between the epoxy matrix and the modifier, thereby increasing the fracture toughness of the modified resin by 180%, compared with the unmodified resin, with substantial retention of flexural strength. The addition of a small amount of divinylbenzene to the in situ polymerization system induced the formation of IPN structures at the interface between the matrix and the modifier, resulting in the increased fracture toughness. The flexural modulus and glass transition temperature of the modified epoxy resin were comparable to those of the unmodified resin.View full abstractDownload PDF (496K) -
Kenzo YADA, Sakie TANAKA, Hiroki IKAKE, Shigeru SHIMIZU, Kimio KURITA2006 Volume 63 Issue 11 Pages 727-736
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSSome transparent hybrid materials were prepared with poly(propylene glycol) (PPG) (Mn=1000, 2000, 3000) and titanium tetraisopropoxide (TiOPr) by the sol-gel process. The hybrid films exhibited high transparency in a visible light region and the film containing 10 wt% TiOPr cut UV-rays below 320 nm. The refractive index linearly increased and the Abbe number decreased with increasing volume fraction of titania. The refractive index increased with increasing Mn of PPG when the titania content is constant. The tensile strength of the hybrids is improved and the strain is decreased with increasing TiOPr content. The dynamic viscoelastic properties and small-angle X-ray scattering suggested that the inorganic domains consisting of titania and silica were formed and that the size of the domains became larger and the PPG segments were more restricted and the storage modulus at the rubbery-plateau region increased with increasing TiOPr. The increase in Mn of PPG increases the amount of titania per ethoxysilyl end groups of PPG when the TiOPr content is constant and the domain size thus becomes larger.View full abstractDownload PDF (411K) -
Yusuke WATANABE, Mitsuru TANAHASHI, Kunihiko TAKEDA2006 Volume 63 Issue 11 Pages 737-744
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSThe dispersion of silica particles with hydrophilic surfaces into hydrophobic polymeric materials without any hydrophobic treatment has been investigated by the direct melt-compounding method. Loose agglomerates of silica fine particles with controlled mechanical strength were prepared from an aqueous colloidal silica solution. The shear stress acting on polyethylene-polyvinylalcohol random copolymer, polycarbonate, polystyrene, and polyfluoroethyene polymer melts was evaluated as a function of the melt-compounding condition. The shear stress was maximized in order to disintegrate the loose silica agglomerates and simultaneously disperse the primary silica particles in the polymer. For all the polymer matrices selected in the present study, well-dispersed silica particles were observed in the composites. This is in contrast to the conventional knowledge that particle dispersion largely depends on the compatibility of particles with the polymer matrix.View full abstractDownload PDF (733K) -
Masashi HATANAKA, Makoto HOSHI, Ryuichi SHIBA2006 Volume 63 Issue 11 Pages 745-752
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSWe synthesized functional resins which adsorb various metals using amidinourea (AU) as a metal complexing agent. We synthesized a novel vinyl monomer N,N,N'-trimethyl-N'-(4-vinylbenzyl)cyanoguanidine (TMVBCG) and polymerized it with divinylbenzene (DVB) and styrene. The copolymers were hydrated to obtain resins having AU moieties as pendant metal-capturing sites. The efficiencies of adsorption of various metal ions (Cu2+, Zn2+, Ni2+, Co2+, and Cd2+) were quantitatively determined by ion chromatography. The efficiency of Cu2+ adsorption was as good as that of a typical chelate resin having sodium iminodiacetate. We found that these resins possess higher efficiencies of Cu2+ desorption than that of the chelate resin. The coordination structures in the AU resins are discussed.View full abstractDownload PDF (630K) -
Mitsuhiro SHIBATA, Masamichi KURIBAYASHI2006 Volume 63 Issue 11 Pages 753-758
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSBlends of poly (ethylene glycol) diacrylate (PGDAc) and pentaerythritol ethoxylate tetraacrylate (PETAc) containing cobalt (II) chloride and photoinitiators were cast on a glass substrate and photocured. The glass transition temperature of the cured films, measured by dynamic viscoelastic measurements, increased with increasing tetrafunctional PETAc content. When the cured films that had been peeled from the glass substrate were reduced with aqueous sodium borohydride, the surface of the PGDAc/PETAc 100/0—60/40 films was successfully metallized. However, the films with PETAc content more than 40 wt% could not be metallized. The surface resistance of the metallized film increased with increasing PETAc content, and the film surface in contact with the glass substrate showed higher surface resistance than that at the air side. The electron probe microanalysis (EPMA) revealed that the migration of cobalt ions toward the film surface became more difficult with increasing PETAc content. The X-ray photoelectron spectroscopy (XPS) analysis in the depth direction of the metallized film by argon ion beam etching revealed that the cobalt layer generated at the glass side of the film contained more polymer component than that at the air side.View full abstractDownload PDF (299K) -
Tomohiro OHKAWA, Masao MORI, Tomoyuki ISHIKAWA, Kunihiko TAKEDA2006 Volume 63 Issue 11 Pages 759-765
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSThe polymerization reaction of polyetherketone (PEK) was studied. The relative rate of the polymerization of PEK in a solution after adding potassium carbonate was higher than that observed during the 4-fluoro-4'-hydroxylbenzophenone (FHB) polymerization based on the degree of polymerization as well as the molecular weight. The rate in the solid state, where the diffusion constants are much lower, was almost the same under the higher equivalent concentration of the potassium. The rate of the molecular weight increases in the case of the polymerization using PEK seemed to be higher than the polymerization rate using a monomer. The rates were 7.1 to 33.5 × 10-3 L · mol-1 · s-1 in the solid phase polymerization and the activation energy was 25.6 kJ · mol-1. Results suggested that the polymerization of PEK in the solution was limited by the diffusion constant. Therefore, the higher rate of the PEK polymerization in the solution is due to the higher activities on the polymers and the additives in the nano-sized reaction region.View full abstractDownload PDF (646K)
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