Ester-type photosensitive polyimide precursor with low thermal expansion coefficient

For an ester-type photosensitive polyimide precursor of low thermal expansion coefficient, the oxygen concentration in the curing process and the molecular weight of the polyimide precursor were found to control the properties of the polyimide. The effects of these factors on the thermal expansion coefficient, tensile strength, and modulus of polyimide film were investigated. Based on these results, a photosensitive polyimide with low thermal expansion coefficient, called the PIMEL TL-series, was developed. Crack and delamination free multilayers were successfully achieved using this newly developed product.     

ATR-FTIR and SEM Gradient Study of Poly(2-ethylhexyl acrylate)/Poly (vinylidene fluoride-co-hexafluoro acetone) Blends

The segregation structure and the gradient structure of poly(2-ethylhexylacrylate) (P2-EHA)/poly(vinylidene fluoride-co-hexafluoro acetone) [P(VDF-HFA)] blends were confirmed by ATR-FTIR and SEM. For the P2-EHA/P(VDF-HFA) (50/50) blend, the P(VDF-HFA) and P2-EHA layers were observed at the free surface side and bottom side, respectively. The gradient structure was obtained for the P2-EHA/P(VDF-HFA) (30/70) blend. The domain morphology of a cross section of the P2-EHA/P(VDF-HFA) (50/50) blend was dramatically changed by the thickness of the blend film. Finally, we propose that the segregation structure and gradient structure formed in P2-EHA/ P(VDF-HFA) blends were caused by surface tension difference, rate of phase separation, rate of solvent evaporation, and molecular weight difference.     

Free Volume of cis-1,4 polyisoprene/polybutadiene blends

Summary The number and radius of molecular order free space present in polybutadiene (PBD)/polyisoprene (PIP) blend were observed by positron life-time measurement, and apparent free volume fraction was estimated. The changes in the number and radius of the free space were not represented to be a linear function of blend composition. The apparent free volume fraction increased by mixing PBD with PIP and was approximated by a concave curve depicted against blend composition, even though the excess volume of mixing was proved to be negative. The change in the apparent free volume fraction was related to the variation of thermal expansion coefficient on blend composition. Received: 21 July 2000/Revised version: 21 August 2000/ Accepted: 24 August 2000     

Photocatalytic decomposition of NO on titanium oxide thin film photocatalysts prepared by an ionized cluster beam technique

Transparent TiO₂ thin film photocatalysts were prepared on transparent porous Vycor glass (PVG) by an ionized cluster beam (ICB) method. The UV‐VIS absorption spectra of these films show specific interference fringes, indicating that uniform and transparent TiO₂ thin films are formed. The results of XRD measurements indicate that these TiO₂ thin films consist of both anatase and rutile structures. UV light (λ > 270 nm) irradiation of these TiO₂ thin films in the presence of NO led to the photocatalytic decomposition of NO into N₂, O₂ and N₂O. The reactivity of these TiO₂ thin films for the photocatalytic decomposition of NO is strongly dependent on the film thickness, i.e., the thinner the TiO₂ thin films, the higher the reactivity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigations on the photoluminescence properties of Mo-MCM-41 and the photocatalytic decomposition of NO in the presence of CO

The photocatalytic decomposition of NO into N₂ and CO₂ on Mo-MCM-41 was found to proceed efficiently in the presence of CO. In situ photoluminescence measurements demonstrated that this reaction proceeds in a redox cycle between alternating Mo⁶⁺ and Mo⁴⁺ ions. The yields of N₂ formation in the photocatalytic reaction correspond with the yields of the photoluminescence of the tetrahedrally coordinated Mo oxide species, indicating that the charge transfer excited triplet state of the tetrahedral Mo oxide species plays a significant role in this reaction, leading to the formation of N₂ and CO₂ with a good stoichiometry. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photocatalytic decomposition of NO on Ti-HMS mesoporous zeolite catalysts

Titanium oxide species were loaded within the framework of mesoporous materials (Ti-HMS) by hydrothermal synthesis. These Ti-HMS exhibited high and unique photocatalytic reactivity for the decomposition of NO into N₂ and O₂ at 275 K. In situ diffuse reflectance absorption and XRD investigations indicated that the titanium oxide species were dispersed well within the zeolite framework and isolated in tetrahedral coordination with low Ti content. This revised version was published online in July 2006 with corrections to the Cover Date.     

The flame‐retardant polyester fiber: Improvement of hydrolysis resistance

As far as the flame‐retardant polyester fibers are concerned, the copolymerization of phosphorus retardants is the most common method. But a serious problem is that the phosphorus‐containing polymer is easily hydrolyzed. We investigated the flame retardancy and the hydrolysis properties of two poly(ethylene terephthalate) (PET) fibers, one with a phosphorus compound as a side chain (side‐chain type: HEIM® Toyobo Co., Ltd.), and one with a phosphorus compound inserted in the polymer backbone (main‐chain type). Both types had almost the same properties of fibers and flame retardancy, but the main‐chain type was hydrolyzed about two times faster than the side‐chain type, and led to a decrease of toughness immediately. This difference of hydrolysis properties between main‐chain type and side‐chain type depends on whether a phosphonate ester bond is placed in the polymer backbone or the pendant site. In the case of the main‐chain type, the scission of the polymer backbone chain occurs by hydrolysis of phosphonate ester bonds; however, in the case of the side‐chain type, this does not occur. These results demonstrate that the flame‐retardant polyester fiber with the side‐chain type modifier gives sufficient flame retardancy and excellent hydrolysis resistance. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1134–1138, 2000     

The design of Ti-, V-, Cr-oxide single-site catalysts within zeolite frameworks and their photocatalytic reactivity for the decomposition of undesirable molecules—The role of their excited states and reaction mechanisms

Transition metal oxides (Ti, V, Mo, Cr, etc.) incorporated within the framework of zeolites were found to exhibit high and unique photocatalytic reactivity as single-site heterogeneous catalysts for various reactions such as the decomposition of NOx (NO, N₂O) into N₂ and O₂, the reduction of CO₂ with H₂O to produce CH₄ and CH₃OH, the preferential oxidation of CO in the presence of H₂ (PROX), the partial oxidation of various hydrocarbons with O₂ or NO or N₂O and the epoxidation and metathesis reaction of alkenes. In situ spectroscopic investigations of these photofunctional systems applying photoluminescence, XAFS (XANES and FT-EXAFS), ESR and FT-IR revealed that the photo-excited states of the transition metal oxides play a vital role in the photocatalytic reactions. The high photocatalytic efficiency and selectivity of these single-site catalysts for significant reactions, which could not be observed with semiconducting bulk photocatalysts, were found to depend strongly on the unique and isolated local structure of the catalysts constructed within the restricted framework structure of the zeolites.     

Carbonization properties of partially hydrogenated aromatic compounds—I: Carbonization of partially hydrogenated pyrene prepared by Birch reduction

The carbonization properties of pyrene hydrogenated by Birch reduction to a variable extent were studied at 600°C under atmospheric pressure, in order to examine the influence of partial hydrogenation on the carbonization reactivity. Pyrene, which did not yield any coke, produced coke with flow texture after partial hydrogenation. Carbon yield of partially hydrogenated pyrene sharply depended on the hydrogenation extent. The intermediate stage of the carbonization pursued by hot-stage microscopy followed the steps of nucleation, growth and coalescence of anisotropic sphere. Considerable fluidity was observed at the final stage of mesophase development prior to the complete solidification where the benzene insoluble content exceeded 90%. The carbonization mechanism was discussed from the view of the polymerization of hydrogenated pyrene in relation with its structure.     

Butylamination of 1-aminohalogeno-anthraquinones promoted by metal ions

The butylamination of 1-aminohalogenoanthraquinones was promoted by both copper and cobalt ions. In the presence of cobalt(ii) chloride the butylamination of 1-amino-4-bromo-(2b) or 1-amino-2,4-dibromo-anthraquinone(2j) proceeded smoothly even at ambient temperature to give the corresponding butylaminated products. It is proposed that the formation of a metal complex(1), in which the 1-aminoanthraquinone moiety coordinates with the metal ion, facilitates the amination.