Iodine-initiated,solid-state copolymerization of tetraoxane with 1,3-dioxolane in the presence of methylal. II. Properties of copolymer obtained by beaker-scale copolymerization

In order to elucidate the copolymerization mechanism, the properties of the copolymer obtained by the iodine-initiated copolymerization of the tetraoxane–1,3-dioxolane–methylal system have been studied using gas chromatography, microscopy, scanning electron microscopy, differential scanning calorimetry, and gel permeation chromatography. From the behavior of the thermal stability and gas chromatography of the reaction mixture, it was found that reactivity of 1,3-dioxolane with active center is larger than that of tetraoxane, i.e., more than 90% 1,3-dioxolane is consumed at an early stage of the polymerization. The results obtained by microscopy, DSC, and GPC of the copolymer suggested that the copolymerization proceeds from the surface to the center of the tetraoxane crystal as if it were a core model. It was also suggested that the heterogeniety in copolymer properties can be explained not only by heterogeneous dispersion of 1,3-dioxolane in tetraoxane crystal, but also by the difference of reactivity of 1,3-dioxolane with the active center.     

Permeative separation of metal ions through the polymer membrane containing gluconate group

Summary The adsorption and permeation of metal ion mixtures were examined for the membrane of poly(3-O-vinylbenzyl gluconate-co-acrylonitrile). The membrane is found to be effective for permeative separation of metal ions. For the Cu/Cd combination, especially, Cu ion was selectively adsorbed and permeated in a neutral aqueous solution. The high selectivity and the high permeation rate are discussed in connection with the chelate formation and the hydrophilicity of ion channel.     

Thermal Stability of Hexaaluminate Film Coated on SiC Substrate for High-Temperature Catalytic Application

A coating of barium hexaaluminate (Ba_0.75Al_11.0O_17.25) on an α-SiC substrate and the thermal stability of the formed film were investigated for a high-temperature catalytic application. The film prepared by sol coating consisted of BaAl₂Si₂O₈ and α-Al₂O₃ phases and always contained many cracks or exfoliations after heating at 1200C. A hexaaluminate porous film was successfully formed by slurry coating without void formation at the interface between the film and the substrate and exfoliation due to the formation of the intermediate layer after heating at 1200°C. The microstructure of the film remained unchanged, even after heating at 1300°C.     

Hydrogel of biodegradable cellulose derivatives. I. Radiation‐induced crosslinking of CMC

Radiation crosslinking of carboxymethylcellulose (CMC) with a degree of substitution (DS) from 0.7 to 2.2 was the subject of the current investigation. CMC was irradiated in solid‐state and aqueous solutions at various irradiation doses. The DS and the concentration of the aqueous solution had a remarkable affect on the crosslinking of CMC. Irradiation of CMC, even with a high DS, 2.2 in solid state, and a low DS, 0.7 in 10% aqueous solution, resulted in degradation. However, it was found that irradiation of CMC with a relatively high DS, 1.32, led to crosslinking in a 5% aqueous solution, and 20% CMC gave the highest gel fraction. CMC with a DS of 2.2 induced higher crosslinking than that with a DS of 1.32 at lower doses with the same concentration. Hence, it was apparent that a high DS and a high concentration in an aqueous solution were favorable for high crosslinking of CMC. It is assumed that high radiation crosslinking of CMC was induced by the increased mobility of its molecules in water and by the formation of CMC radicals from the abstraction of H atoms from macromolecules in the intermediate products of water radiolysis. A preliminary biodegradation study confirmed that crosslinked CMC hydrogel can be digested by a cellulase enzyme. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 278–283, 2000     

Effect of metallic wire inserted in nozzle in high-speed melt spinning of poly(ethylene terephthalate)

High-speed melt spinning of poly(ethylene terephthalate) was performed using a spinning nozzle with an inserted metallic wire of various lengths (0, 8, 30, and 45 mm). The molecular orientation of as-spun fibers increased with the increase in the wire length at all the take-up velocities examined. Along with the enhanced molecular orientation, the longer wire length led to the starting of orientation-induced crystallization at lower take-up velocities. The structure of crystallized fibers obtained at low speeds can be characterized by high crystallinity and relatively low molecular orientation. From the on-line measurement of the diameter and temperature profiles of the spin line with the 30-mm metallic wire, it was revealed that the spin-line had a maximum diameter of about 6 mm at the wire end. The spin-line temperature at this position was about 190°C. The solidification of the spin-line occurred at positions much closer to the spinneret in comparison with ordinary high-speed spinning. These results show that high-speed spinning with a wire inserted in the nozzle corresponds to a spinning process operated at extremely low extrusion temperature using a nozzle with an extremely large diameter. From the starting of orientation-induced crystallization at lower levels of birefringence in comparison with ordinary high-speed spinning, the alteration of the inherent fiber structure that cannot be represented by birefringence was also suggested. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 665–674, 1998     

A new class of transparent polymeric materials. III. Miscible blends of poly(N-methylmaleimide-alt-isobutene) with poly(acrylonitrile-co-styrene) and the properties of the blends

The blend miscibility of poly(N-methylmaleimide-alt-isobutene) [poly-(MeMI-IB)] with poly(acrylonitrile-co-styrene) (SAN) was investigated by means of measurement of the glass transition temperature of the blends. Poly(MeMI-IB) was found to be miscible with SAN of a specific range of acrylonitrile (AN) contents in the copolymer to produce transparent moldings. The refractive index changed from 1.58 to 1.53 and the dispersion decreased with increasing the amount of poly(MeMI-IB) in the blends. The stress optical coefficient of poly(MeMI-IB) was found to be reduced by the blending of SAN. The glass transition temperature, flexural modulus, and surface hardness of the blends increased with an increase in the amount of poly(MeMI-IB) in the blend. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 925–929, 1997     

Mechanisms of tubulin modification by phosphatidylcholine hydroperoxides

The interaction of lipid peroxides with cellular proteins has been postulated to contribute to cellular aging. A potential target for such effects is tubulin, the building block of microtubules. We examined the concentration-dependent effects of phosphatidylcholine hydroperoxides on the ability of tubulin to polymerize into microtubules. The results demonstrated that even very low concentrations of peroxides were sufficient to interfere with the tubulin and, therefore, the microtubule function. Decreased tubulin activity (as measured by tubulin GTPase activity) showed correlation with the modification of methionine and cysteine in tubulin and a change in the tubulin conformational state as indicated by fluorescence and ultraviolet spectroscopic measurements. As no effect on electric conductivity was observed, indicating that modulation of ionic binding was not involved, the interaction mechanism may be a hydrophobic one.     

Oxygen Uptake and Release Mechanism of Lithium Manganese Ferrite in the Low Temperature Range of 573–773 K

Oxygen uptake and release of (Li,Mn) ferrite [LMF; (Li_0.60Mn_1.20Fe_1.20)_1−δO₄; δ= 0.007 to 0.033] was investigated concerning the relations between redox reactions of ferrite and cation migration. Mössbauer spectroscopy and X-ray diffractometry showed that some of the Li⁺ and Fe³⁺ ions migrated from the A sites to the B sites of the spinel-type structure and Mn⁴⁺ ions migrated from the B sites to the A sites during oxygen uptake at 573 K. The cation-deficient LMF formed by the oxygen uptake released oxygen molecules in He gas only at 660 K. The cation migration during the oxygen release was in the opposite direction of the movement during oxygen uptake at 573 K.     

Optical Amplification at 1.3 μm in a Praseodymium-Doped Sulfide-Glass Fiber

Praseodymium-doped glasses were prepared in the Ga-Na-S (GNS) system and their optical properties were studied. A single-mode fiber with an attenuation loss of 1.2 dB/m at a wavelength of 1.31 μm was fabricated using an extrusion method, and the amplification characteristics were measured in the bidirectional pumping configuration. We demonstrated a gain coefficient of 0.81 dB/mW at a wavelength of 1.34 μm, which is the highest we have ever reported, and achieved a net gain of 32 dB for a pump power of 90 mW. Highly efficient optical amplification at a wavelength of 1.3 μm was demonstrated in the praseodymium-doped GNS fiber.     

Magnetic properties of metal layer deposited by reduction of metal ions contained in polymer with applying magnetic field

Metal layer was deposited by the reduction of NiCl₂ and CoCl₂ in polyacrylonitrile film after applying an external magnetic field in directions parallel and perpendicular to the surface of the film; the magnetic properties of the metal-deposited film were investigated. When the parallel magnetic field was applied, the values of coercivity (H_c), remanent flux density (B_r) and maximum flux density (B_s) increased regardless of the composition of the metal ions, compared with the case without the application of the magnetic field. From the scanning electron micrographs and X-ray diffraction analyses, it was shown that the growth of crystalline orientation in the deposited metals was enhanced by applying a parallel magnetic field.